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Preview: Advanced Materials for Optics and Electronics

Advanced Functional Materials

Wiley Online Library : Advanced Functional Materials

Published: 2017-11-01T00:00:00-05:00


Poly(arylene piperidinium) Hydroxide Ion Exchange Membranes: Synthesis, Alkaline Stability, and Conductivity


A series of poly(arylene piperidinium)s (PAPipQs) devoid of any alkali-sensitive aryl ether bonds or benzylic sites are prepared and studied as anion exchange membranes (AEMs) for alkaline fuel cells. First, the excellent alkaline stability of the model compound 4,4-diarylpiperidinium is confirmed. Medium molecular weight poly(arylene piperidine)s are then synthesized in polycondensations of N-methyl-4-piperidone and either bi- or terphenyl via superelectrophilic activation in triflic acid. Film-forming PAPipQs are subsequently prepared in Menshutkin reactions with methyl, butyl, hexyl, and octyl halides, respectively. AEMs based on poly(terphenyl dimethylpiperidinium) show the best performance with no structural degradation detectable by 1H NMR spectroscopy after storage in 2 m aq. NaOH at 60 °C after 15 d, and a mere 5% ionic loss at 90 °C. In the fully hydrated state these AEMs reach an OH− conductivity of 89 S cm−1 at 80 °C. The presence of longer pendant N-alkyl chains (butyl to octyl) is found to significantly promote Hofmann ring-opening elimination reactions and the degradation rate increases with increasing alkyl chain length. The results of the present study demonstrate that PAPipQs are efficiently prepared from readily available monomers and show excellent alkaline stability and OH− conductivity when devoid of pendant N-alkyl chains. Hydroxide ion conducting polymer membranes are an emerging group of materials, which potentially enables non-noble metal catalysis in fuel cells. Here, poly(arylene piperidinium)s are prepared in straightforward polycondensations using inexpensive building blocks. After judicious macromolecular design, these polymers constitute a new class of durable and high-performing membranes, devoid of base-sensitive diaryl ether bonds and benzylic hydrogens.

Brilliant Pitaya-Type Silica Colloids with Central–Radial and High-Density Quantum Dots Incorporation for Ultrasensitive Fluorescence Immunoassays


Creating secondary nanostructures from fundamental building blocks with simultaneous high loading capacity and well-controlled size/uniformity, is highly desired for nanoscale synergism and integration of functional units. Here a novel strategy is reported for hydrophobic quantum dots (QDs) assembley with porous templates, to form pitaya-type fluorescent silica colloids with densely packed and intact QDs throughout the silica matrix. The mercapto-terminated dendritic silica spheres with highly accessible central–radial pores and metal-affinity interior surface, are adopted as a powerful absorbent host for direct immobilization of QDs from organic phase with high loading capacity. The alkylsilane mediated silica encapsulation prevents QDs' optical degradation induced by ligand exchange and favors the homogeneous silica shell formation. These multiple QD embedded silica spheres exhibit good compatibility for different colored QDs with well-preserved fluorescence, high colloidal/optical stability, and versatile surface functionality. It is demonstrated that after integration with a lateral flow strip platform, these silica colloids provide an ultrasensitive, specific, and robust immunoassay for C-reaction protein in clinical samples as promising fluorescent reporters. The central–radial incorporation of quantum dots (QDs) with high packing density into mercapto-terminated dendritic silica templates, generates homogeneous and intact QDs-in-silica structures, after organosilica/silica bilayer encapsulation. The high brightness of accumulated fluorophores in single spheres and excellent stability enables an ultrasensitive, specific, and robust immunoassay of C-reaction protein in complex biological samples, using a lateral flow strip platform.

React-on-Demand (RoD) Fabrication of Highly Conductive Metal–Polymer Hybrid Structure for Flexible Electronics via One-Step Direct Writing or Printing


As a fast prototyping technique, direct writing of flexible electronics is gaining popularity for its low-cost, simplicity, ultrahigh portability, and ease of use. However, the latest handwritten circuits reported either have relative low conductivity or require additional post-treatment, keeping this emerging technology away from end-users. Here, a one-step react-on-demand (RoD) method for fabricating flexible circuits with ultralow sheet resistance, enhanced safety, and durability is proposed. With the special functionalized substrate, a real-time 3D synthesis of silver plates in microscale is triggered on-demand right beneath the tip in the water-swelled polyvinyl alcohol (PVA) coating, forming a 3D metal–polymer hybrid structure of ≈7 µm with one single stroke. The as-fabricated silver traces show an enhanced durability and ultralow sheet resistance down to 4 mΩ sq−1 which is by far the lowest sheet resistance reported in literatures achieved by direct writing. Meanwhile, PVA seal small particles inside the film, adding additional safety to this technology. Since neither nanomaterials nor a harsh fabrication environment are required, the proposed method remains low cost, user friendly, and accessible to end users. With little effort, the RoD approach can be extended to various printing systems, offering a particle-free, sintering-free solution for high-resolution, high-speed production of flexible electronics. A one-step react-on-demand approach for cost-effective fabrication of high-performance flexible circuits is demonstrated. With the special functionalized substrate, the real-time 3D synthesis of silver plates is triggered on-demand right beneath the tip and printhead, forming a 3D metal–polymer hybrid structure with ultralow sheet resistance down to 4 mΩ sq−1.

Continuous Melt-Drawing of Highly Aligned Flexible and Stretchable Semiconducting Microfibers for Organic Electronics


A scalable and green approach to manufacture semiconducting microfibers from polymer melts has been demonstrated. The polymer chains are highly aligned along the microfiber's long axis direction and exhibit highly anisotropic optical properties. In addition, the polymer microfibers show good flexibility and stretchability with a yield point around 10% under a reversible stress and can be stretched up to 180% without breaking. These features are desired for future flexible, stretchable, and conformable electronics. The origin of this stretchability is studied with diketopyrrolopyrrole derivatives using different conjugation break spacers and side chains. In addition, stretchable conducting microfibers can be obtained by doping with FeCl3, which are further evaluated as organic conductors and source/drain electrodes in organic field-effect transistors. Highly aligned flexible and stretchable microfibers are manufactured by continuously drawing from semiconducting polymer melts, which exhibit highly anisotropic optical and electronic properties. The polymer microfibers have a yield point around 10% under reversible stress and can be stretched up to 180% without breaking. After doped by FeCl3, the polymer microfibers can be also used as stretchable conducting fibers and electrodes, and show great potential in organic electronics.

Memristor with Ag-Cluster-Doped TiO2 Films as Artificial Synapse for Neuroinspired Computing


Memristor, based on the principle of biological synapse, is recognized as one of the key devices in confronting the bottleneck of classical von Neumann computers. However, conventional memristors are difficult to continuously adjust the conduction and dutifully mimic the biosynapse function. Here, TiO2 films with self-assembled Ag nanoclusters implemented by gradient Ag dopant are employed to achieve enhanced memristor performance. The memristors exhibit gradual both potentiating and depressing conduction under positive and negative pulse trains, which can fully emulate excitation and inhibition of biosynapse. Moreover, comprehensive biosynaptic functions and plasticity, including the transition from short-term memory to long-term memory, long-term potentiation and depression, spike-timing-dependent plasticity, and paired-pulse facilitation, are implemented with the fabricated memristors in this work. The applied pulses with a width of hundreds of nanoseconds timescale are beneficial to realize fast learning and computing. High-resolution transmission electron microscopy observations clearly demonstrate that Ag clusters redistribute to form Ag conductive filaments between Ag and Pt electrode under electrical field at ON-state device. The experimental data confirm that the oxides doped with Ag clusters have the potential for mimicking biosynaptic behavior, which is essential for the further creation of artificial neural systems. TiO2 films doped with nanoscale Ag cluster serve as memristor medium, and the device exhibits excellent memory and plasticity characteristics to mimic synaptic behavior essential for the further creation of artificial neural systems. The tunneling gap variation between Ag clusters is presented to be responsible for the memristor mechanism according to the conduction transport analysis.

Large-Scale and Washable Smart Textiles Based on Triboelectric Nanogenerator Arrays for Self-Powered Sleeping Monitoring


Sleeping disorder is a major health threatening in high-pace modern society. Characterizing sleep behavior with pressure-sensitive, simple fabrication, and decent washability still remains a challenge and highly desired. Here, a pressure-sensitive, large-scale, and washable smart textile is reported based on triboelectric nanogenerator (TENG) array as bedsheet for real-time and self-powered sleep behavior monitoring. Fabricated by conductive fibers and elastomeric materials with a wave structure, the TENG units exhibit desirable features including high sensitivity, fast response time, durability, and water resistance, and are interconnected together, forming a pressure sensor array. Furthermore, highly integrated data acquisition, processing, and wireless transmission system is established and equipped with the sensor array to realize real-time sleep behavior monitoring and sleep quality evaluation. Moreover, the smart textile can further serve as a self-powered warning system in the case of an aged nonhospitalized patients falling down from the bed, which will immediately inform the medical staff. This work not only paves a new way for real-time noninvasive sleep monitoring, but also presents a new perspective for the practical applications of remote clinical medical service. A large-scale and washable smart textile based on a triboelectric nanogenerator array as bedsheet is demonstrated for self-powered sleep behavior monitoring, which can detect and record the person's sleeping behavior in real-time manner. Based on the acquired sleep-behavioral data, the sleep quality report will be generated for further health evaluation or illness diagnosis.

Restoration of Impact Damage in Polymers via a Hybrid Microcapsule–Microvascular Self-Healing System


A hybrid microcapsule–microvascular system is introduced to regenerate the multiscale damage that results from impact puncture of vascularized polymeric sheets. Microvascular delivery of a two-stage healing agent restores lost damage volume (puncture) to recover impact energy absorption, while embedded microcapsules heal microcracks to facilitate sealing. Modulation of the mechanical properties (1.4 GPa to 1.1 MPa stiffness) of the healing agent after curing is achieved by selection of compatible reactive acrylate monomers. Specimens are punctured and the impacted hole and surrounding damaged volume is restored by delivering the two-stage healing agents to the site of damage via a microvascular network. Rapid gelling of two-stage healing agents enables their retention in the damage region, while subsequent polymerization recovers structural performance. Impact recovery efficiency is assessed in terms of energy absorption, comparing reimpacted specimens to the initial impact. Recovery of impact energy absorption as high as 100% is observed for the optimal specimen design. Specimens are tested for sealing under static pressurization to monitoring leakage through the restored damage. A hybrid system incorporating both microvascular delivery of the two-stage healing agents and microcapsules containing solvated epoxy enables sealing of 100% of specimens. A hybrid system incorporates both microcapsules and microvascular delivery for the restoration of impact puncture damage. Multiscale damage is addressed by multiple healing modes: two-stage healing agents delivered through a dual microvascular network restore lost material volume in order to recover impact energy absorption, while embedded microcapsules heal radiating microcracks to facilitate sealing and recovery of barrier properties.

Designing a High-Performance Lithium–Sulfur Batteries Based on Layered Double Hydroxides–Carbon Nanotubes Composite Cathode and a Dual-Functional Graphene–Polypropylene–Al2O3 Separator


Designing an optimum cell configuration that can deliver high capacity, fast charge–discharge capability, and good cycle retention is imperative for developing a high-performance lithium–sulfur battery. Herein, a novel lithium–sulfur cell design is proposed, which consists of sulfur and magnesium–aluminum-layered double hydroxides (MgAl-LDH)–carbon nanotubes (CNTs) composite cathode with a modified polymer separator produced by dual side coating approaches (one side: graphene and the other side: aluminum oxides). The composite cathode functions as a combined electrocatalyst and polysulfide scavenger, greatly improving the reaction kinetics and stabilizing the Coulombic efficiency upon cycling. The modified separator enhances further Li+-ion or electron transport and prevents undesirable contact between the cathode and dendritic lithium on the anode. The proposed lithium–sulfur cell fabricated with the as-prepared composite cathode and modified separator exhibits a high initial discharge capacity of 1375 mA h g−1 at 0.1 C rate, excellent cycling stability during 200 cycles at 1 C rate, and superior rate capability up to 5 C rate, even with high sulfur loading of 4.0 mg cm−2. In addition, the findings that found in postmortem chracterization of cathode, separator, and Li metal anode from cycled cell help in identifying the reason for its subsequent degradation upon cycling in Li–S cells. The enhanced lithium–sulfur cell design including a MgAl-LDH@CNT-S composite cathode and a DF-GPA separator is proposed. By improving lithium–sulfur redox reactions and minimizing the risk of internal short circuit, this cell configuration enables to yield superior rate capability up to 5 C rate and excellent long-term cycling stability even with high sulfur loading in the electrode of 4.0 mg cm−2.

Novel Eco-Friendly Starch Paper for Use in Flexible, Transparent, and Disposable Organic Electronics


An eco-friendly biodegradable starch paper is introduced for use in next-generation disposable organic electronics without the need for a planarizing layer. The starch papers are formed by starch gelatinization using a very small amount of 0.5 wt% polyvinyl alcohol (PVA), a polymer that bound to the starch, and 5 wt% of a crosslinker that bound to the PVA to improve mechanical properties. This process minimizes the additions of synthetic materials. The resultant starch paper provides a remarkable mechanical strength and stability under repeated movements. Robustness tests using various chemical solvents are conducted by immersing the starch paper for 6 h. Excellent nonpolar solvent stabilities are observed. They are important for the manufacture of organic electronics that use nonpolar solution processes. The applicability of the starch paper as a flexible substrate is tested by fabricating flexible organic transistors using pentacene, dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene, and poly(dimethyl-triarylamine) using both vacuum and solution processes. Electrically well-behaved device performances are identified. Finally, the eco-friendly biodegradability is verified by subjecting the starch paper to complete degradation by fungi in fishbowl water over 24 d. These developments illuminate new research areas in the field of biodegradable green electronics, enabling the development of extremely low-cost electronics. Eco-friendly biodegradable starch paper for disposable organic electronics is developed that does not require a planarizing layer. This paper applied by starch gelatinization provides a remarkable mechanical strength and chemical robustness in variety of nonpolar solvents, indicating the possibility as a flexible substrate. Finally, biodegradability of the starch paper is verified by the complete decomposition by fungi over 24 d.

Baby Diaper-Inspired Construction of 3D Porous Composites for Long-Term Lithium-Ion Batteries


In this paper, by using the superabsorbent polymers (SAPs) from baby diaper, the 3D porous composites decorated with NiO and Ni nanoparticles (NNSCs) have been prepared via a facile dissolving-freeze drying and subsequent annealing reactions. The porous carbon matrix (PCM) derived from the SAPs also provides a continuous highly conductive network to facilitate the fast charge transfer and form a stable solid electrolyte interface film. Furthermore, NNSC can exhibit the high specific capacity and excellent cycle performance as anode materials for lithium-ion batteries. And more importantly, employing the PCM derived from baby diaper offers a green approach for other energy storage materials. A porous network decorated with NiO nanoparticles is prepared by using the superabsorbent polymers from fresh baby diapers via a facile annealing reaction. The composite exhibits high specific capacity and excellent cycle performance as anode materials for lithium-ion batteries.

Porous Hydrogel Encapsulated Photonic Barcodes for Multiplex MicroRNA Quantification


The development of a highly sensitive platform for multiplex circulating microRNAs (miRNAs) detection is important for clinical diagnosis. Here, a new type of porous hydrogel encapsulated photonic crystal (PhC) barcodes is presented with integrated rolling circle amplification (RCA) strategy for multiplex miRNA quantification. As the surrounding porous hydrogel shells of the PhC barcodes are interconnected inverse opal structure with hydrophilic scaffolds, they can provide homogeneous water surrounding for the miRNA targets reaction and RCA. The encapsulated PhC cores of the barcodes can offer stable diffraction peaks for encoding different miRNAs and their RCAs during the detection. By integrating the advantages of PhC barcodes and RCA, it is demonstrated that the technology shows acceptable accuracy and detection reproducibility for the rapid quantification of low-abundance miRNAs, with the limits of detection of 20 fM. Thus, the proposed porous hydrogel encapsulated PhC barcodes provide a new platform for the multiplex quantification of low-abundance targets for practical applications. Porous hydrogel encapsulated photonic crystal (PhC) barcodes with integrated rolling circle amplification strategy are developed for multiplex microRNA (miRNA) quantification. The hydrogel shells provide a homogeneous aqueous environment for miRNA hybridization and rolling circle amplification, while the PhC cores offer stable diffraction peaks for encoding different miRNAs.

Ultrafine Nickel-Nanoparticle-Enabled SiO2 Hierarchical Hollow Spheres for High-Performance Lithium Storage


The high theoretical capacity and natural abundance of SiO2 make it a promising high-capacity anode material for lithium-ion batteries. However, its widespread application is significantly hampered by the intrinsic poor electronic conductivity and drastic volume variation. Herein, a unique hollow structured Ni/SiO2 nanocomposite constructed by ultrafine Ni nanoparticle (≈3 nm) functionalized SiO2 nanosheets is designed. The Ni nanoparticles boost not only the electronic conductivity but also the electrochemical activity of SiO2 effectively. Meanwhile, the hollow cavity provides sufficient free space to accommodate the volume change of SiO2 during repeated lithiation/delithiation; the nanosheet building blocks reduce the diffusion lengths of lithium ions. Due to the synergistic effect between Ni and SiO2, the Ni/SiO2 composite delivers a high reversible capacity of 676 mA h g−1 at 0.1 A g−1. At a high current density of 10 A g−1, a capacity of 337 mA h g−1 can be retained after 1000 cycles. Ultrafine nickel-nanoparticle-functionalized SiO2 hierarchical hollow spheres are synthesized via an in situ reduction approach. The resultant Ni/SiO2 hierarchical hollow spheres manifest high reversible capacity (676 mA h g−1 at 0.1 A g−1), excellent rate capability, and outstanding cyclability (337 mA h g−1 after 1000 cycles at 10 A g−1).

Light-Responsive Ion-Redistribution-Induced Resistive Switching in Hybrid Perovskite Schottky Junctions


Hybrid Perovskites have emerged as a class of highly versatile functional materials with applications in solar cells, photodetectors, transistors, and lasers. Recently, there have also been reports on perovskite-based resistive switching (RS) memories, but there remain open questions regarding device stability and switching mechanism. Here, an RS memory based on a high-quality capacitor structure made of an MAPbBr3 (CH3NH3PbBr3) perovskite layer sandwiched between Au and indium tin oxide (ITO) electrodes is reported. Such perovskite devices exhibit reliable RS with an ON/OFF ratio greater than 103, endurance over 103 cycles, and a retention time of 104 s. The analysis suggests that the RS operation hinges on the migration of charged ions, most likely MA vacancies, which reversibly modifies the perovskite bulk transport and the Schottky barrier at the MAPbBr3/ITO interface. Such perovskite memory devices can also be fabricated on flexible polyethylene terephthalate substrates with high bendability and reliability. Furthermore, it is found that reference devices made of another hybrid perovskite MAPbI3 consistently exhibit filament-type switching behavior. This work elucidates the important role of processing-dependent defects in the charge transport of hybrid perovskites and provides insights on the ion-redistribution-based RS in perovskite memory devices. An interface-based hybrid perovskite-based resistive switching (RS) memory device is fabricated and characterized. Because of the elements gradient distribution and movable ionic charges in the perovskite film, the Schottky junction at the MAPbBr3/ITO interface can be reliably modulated, directly giving rise to RS with good endurance and data retention.

Memristive Logic-in-Memory Integrated Circuits for Energy-Efficient Flexible Electronics


A memristive nonvolatile logic-in-memory circuit can provide a novel energy-efficient computing architecture for battery-powered flexible electronics. However, the cell-to-cell interference existing in the memristor crossbar array impedes both the reading process and parallel computing. Here, it is demonstrated that integration of an amorphous In-Zn-Sn-O (a-IZTO) semiconductor-based selector (1S) device and a poly(1,3,5-trivinyl-1,3,5-trimethyl cyclotrisiloxane) (pV3D3)-based memristor (1M) on a flexible substrate can overcome these problems. The developed a-IZTO-based selector device, having a Pd/a-IZTO/Pd structure, exhibits nonlinear current–voltage (I–V) characteristics with outstanding stability against electrical and mechanical stresses. Its underlying conduction mechanism is systematically determined via the temperature-dependent I–V characteristics. The flexible one-selector−one-memristor (1S–1M) array exhibits reliable electrical characteristics and significant leakage current suppression. Furthermore, single-instruction multiple-data (SIMD), the foundation of parallel computing, is successfully implemented by performing NOT and NOR gates over multiple rows within the 1S–1M array. The results presented here will pave the way for development of a flexible nonvolatile logic-in-memory circuit for energy-efficient flexible electronics. Parallel computing of flexible nonvolatile logic-in-memory circuits enabling normally off computing can be implemented using an integrated circuit of one-selector-one memristor (1S–1M) on a plastic substrate. The 1S–1M integrated circuits successfully mitigate sneaky current existing inherently on the memristor crossbar array, achieving a maximum array size of more than 1 Mbit as well as parallel logic operations on a plastic substrate.

Solvothermal Synthesis of Alloyed PtNi Colloidal Nanocrystal Clusters (CNCs) with Enhanced Catalytic Activity for Methanol Oxidation


Colloidal nanocrystal clusters (CNCs), which are composed of many nanocrystal subunits, have attracted intensive attention because they can possess not only the properties of each single subunit but also the collective properties and novel functionalities resulting from the ensembles. However, to date, the successful preparation of metal CNCs has rarely been reported. In this work, a simple one-pot solvothermal method is developed to prepare PtNi-alloyed CNCs with homogeneous distribution of Pt and Ni elements, porous feature, and interconnected steady framework. The PtNi CNCs are composed of many PtNi nanocrystals with size around 7–8 nm. Their growth mechanism is proposed through a systematic study. Thanks to the unique structure, the as-prepared PtNi CNCs show better catalytic performance in methanol oxidation reaction than that of PtNi nanocrystals and Pt/C catalysts. This work is important because it not only provides a new method for the preparation of metal CNCs with desired morphology and properties, but also paves the way for practical applications of metal nanoparticles. Alloyed PtNi colloidal cluster nanocrystals (CNCs) are successfully prepared through a solvothermal approach. The CNCs are composed of many PtNi nanocrystals with size ≈7–8 nm and do possess homogeneously distributed Pt and Ni elements, a porous structure, and an interconnected steady framework. The product shows better catalytic performance in methanol oxidation reaction than that of PtNi nanocrystals and Pt/C catalysts.

Gold Nanoparticles Sliding on Recyclable Nanohoodoos—Engineered for Surface-Enhanced Raman Spectroscopy


Robust, macroscopically uniform, and highly sensitive substrates for surface-enhanced Raman spectroscopy (SERS) are fabricated using wafer-scale block copolymer lithography. The substrate consists of gold nanoparticles that can slide and aggregate on dense and recyclable alumina/silicon nanohoodoos. Hot-spot engineering is conducted to maximize the SERS performance of the substrate. The substrate demonstrates remarkably large surface-averaged SERS enhancements, greater than 107 (>108 in hot spots), with unrivalled macroscopic signal uniformity as characterized by a coefficient of variation of only 6% across 4 cm. After SERS analyses, the nanohoodoos can be recycled by complete removal of gold via a one-step, simple, and robust wet etching process without compromising performance. After eight times of recycling, the substrate still exhibits identical SERS performance in comparison to a new substrate. The macroscopic uniformity combined with recyclability at conserved high performance is expected to contribute significantly on the overall competitivity of the substrates. These findings show that the gold nanoparticles sliding on recyclable nanohoodoo substrate is a very strong candidate for obtaining cost-effective, high-quality, and reliable SERS spectra, facilitating a wide and simple use of SERS for both laboratorial and commercial applications. Cheap, robust, macroscopically uniform, and highly efficient substrates for surface-enhanced Raman spectroscopy (SERS) are fabricated using block copolymer lithography. A nanohoodoo template in the substrate is recyclable after SERS analyses via a simple wet chemistry process. The renovated substrate exhibits reproducibly low SERS backgrounds and identical SERS performance, in comparison to a new substrate.

Thermodynamic Activation of Charge Transfer in Anionic Redox Process for Li-Ion Batteries


Anionic redox processes are vital to realize high capacity in lithium-rich electrodes of lithium-ion batteries. However, the activation mechanism of these processes remains ambiguous, hampering further implementation in new electrode design. This study demonstrates that the electrochemical activity of inert cubic-Li2TiO3 is triggered by Fe3+ substitution, to afford considerable oxygen redox activity. Coupled with first principles calculations, it is found that electron holes tend to be selectively generated on oxygen ions bonded to Fe rather than Ti. Subsequently, a thermodynamic threshold is unravelled dictated by the relative values of the Coulomb and exchange interactions (U) and charge-transfer energy (Δ) for the anionic redox electron-transfer process, which is further verified by extension to inactive layered Li2TiS3, in which the sulfur redox process is activated by Co substitution to form Li1.2Ti0.6Co0.2S2. This work establishes general guidance for the design of high-capacity electrodes utilizing anionic redox processes. The charge transfer process of anionic redox processes is thermodynamically dictated by the relative values of the Coulomb and exchange interactions (U) and charge-transfer energy (Δ), as experimentally validated by the activation of oxygen and sulfur redox in Li1.2Ti0.4Fe0.4O2 and Li1.2Ti0.6Co0.2S2, respectively. This work establishes general guidance for the design of high-capacity electrodes utilizing anionic redox processes.

Colorectal Cancer Diagnosis Using Enzyme-Sensitive Ratiometric Fluorescence Dye and Antibody–Quantum Dot Conjugates for Multiplexed Detection


A rapid and accurate molecular fluorescence imaging technique will greatly reduce cancer mortality by overcoming the detection limit of the naked eye in colonoscopy. Two imaging probes are reported that can be co-used for colonoscopic diagnosis: a fluorescent molecular probe, cresyl violet–glutamic acid derivative, that ratiometrically switches between two fluorescent colors in response to the enzyme activity of λ-glutamyltranspeptidase and an antibody quantum dot probe that is a conjugate of biocompatible AgInS2 quantum dot with matrix metalloproteinase 14 antibodies. Validity of the probes is confirmed using human colon cancer cell lines, ex vivo mouse model tissues, and patient tumor colon tissues in which the tumor lesions are well-visualized in less than five minutes. Co-application of the two probes onto fresh colon tissues affords accurate visualization of carcinomas and also hyperplasia and adenoma regions. Fresh human colon adenoma tissues are also valuated, where the two probes show complementary diagnoses of cancer. Two-photon microscopy shows the time-dependent depth profiles of the two probes. Both rapidly permeate and populate most at 10–20 µm from the surface. Extensive toxicity studies are performed for the two probes at cellular level and also at the organ level using a small animal model. A ratiometric fluorescent probe that responds to the λ-glutamyltranspeptidase activity is developed and co-used with an antibody–quantum dot conjugate probe, which demonstrates the potential for endoscopic early colon cancer diagnosis by multiplexed and complementary detection of colorectal tumors and precancerous regions such as adenoma and hyperplasia.

Single Crystal Microwires of p-DTS(FBTTh2)2 and Their Use in the Fabrication of Field-Effect Transistors and Photodetectors


Single crystal microwires of a well-studied organic semiconductor used in organic solar cells, namely p-DTS(FBTTh2)2, are prepared via a self-assembly method in solution. The high level of intermolecular organization in the single crystals facilitates migration of charges, relative to solution-processed films, and provides insight into the intrinsic charge transport properties of p-DTS(FBTTh2)2. Field-effect transistors based on the microwires can achieve hole mobilities on the order of ≈1.8 cm2 V−1 s−1. Furthermore, these microwires show photoresponsive electrical characteristics and can act as photoswitches, with switch ratios over 1000. These experimental results are interpreted using theoretical simulations using an atomistic density functional theory approach. Based on the lattice organization, intermolecular couplings and reorganization energies are calculated, and hole mobilities for comparison with experimental measurements are further estimated. These results demonstrate a unique example of the optoelectronic applications of p-DTS(FBTTh2)2 microwires. Crystalline microwires of p-DTS(FBTTh2)2 are fabricated via solution-phase self-assembly. Such wires exhibit good charge mobility and highly photosensitive response characteristics. Furthermore, these experimental results are interpreted and rationalized using theoretical simulations.

An Ultrathin Flexible 2D Membrane Based on Single-Walled Nanotube–MoS2 Hybrid Film for High-Performance Solar Steam Generation


Solar steam generation is achieved by localized heating system using various floating photothermal materials. However, the steam generation efficiency is hindered by the difficulty in obtaining a photothermal material with ultrathin structure yet sufficient solar spectrum absorption capability. Herein, for the first time, an ultrathin 2D porous photothermal film based on MoS2 nanosheets and single-walled nanotube (SWNT) films is prepared. The as-prepared SWNT–MoS2 film exhibits an absorption of more than 82% over the whole solar spectrum range even with an ultrathin thickness of ≈120 nm. Moreover, the SWNT–MoS2 film floating on the water surface can generate a sharp temperature gradient due to the localized heat confinement effect. Meanwhile, the ultrathin and porous structure effectively facilitates the fast water vapor escaping, consequently an impressively high evaporation efficiency of 91.5% is achieved. Additionally, the superior mechanical strength of the SWNT–MoS2 film enables the film to be reused for atleast 20 solar illumination cycles and maintains stable water productivity as well as high salt rejection performance. This rational designed hybrid architecture provides a novel strategy for constructing 2D-based nanomaterials for solar energy harvesting, chemical separation, and related technologies. To address the difficulties in obtaining photothermal materials with ultrathin structure yet sufficient solar spectrum absorption capability, an ultrathin and self-floating SWNT–MoS2 hybrid film is designed. As an interfacial heating membrane, this SWNT–MoS2 film shows enhanced steam generation efficiency and superior recycle stability due to the ultrathin and porous structure as well as high mechanical strength.

Combination of Hybrid CVD and Cation Exchange for Upscaling Cs-Substituted Mixed Cation Perovskite Solar Cells with High Efficiency and Stability


Mixed cation hybrid perovskites such as CsxFA1−xPbI3 are promising materials for solar cell applications, due to their excellent photoelectronic properties and improved stability. Although power conversion efficiencies (PCEs) as high as 18.16% have been reported, devices are mostly processed by the anti-solvent method, which is difficult for further scaling-up. Here, a method to fabricate CsxFA1−xPbI3 by performing Cs cation exchange on hybrid chemical vapor deposition grown FAPbI3 with the Cs+ ratio adjustable from 0 to 24% is reported. The champion perovskite module based on Cs0.07FA0.93PbI3 with an active area of 12.0 cm2 shows a module PCE of 14.6% and PCE loss/area of 0.17% cm−2, demonstrating the significant advantage of this method toward scaling-up. This in-depth study shows that when the perovskite films prepared by this method contain 6.6% Cs+ in bulk and 15.0% at the surface, that is, Cs0.07FA0.93PbI3, solar cell devices show not only significantly increased PCEs but also substantially improved stability, due to favorable energy level alignment with TiO2 electron transport layer and spiro-MeOTAD hole transport layer, increased grain size, and improved perovskite phase stability. Cs-substituted mixed perovskite modules are prepared by a new developed large-area-compatible method combining hybrid chemical vapor deposition and cation exchange. Power conversion efficiency (PCE) as high as 14.6% is achieved, benefiting from the large-area film uniformity on macroscopic and microscopic scales. In-depth study shows that 7% Cs+ in CsxFA1−xPbI3 is the optimal ratio for achieving best device PCE and longest lifetime.

Kinetically Controlled Coprecipitation for General Fast Synthesis of Sandwiched Metal Hydroxide Nanosheets/Graphene Composites toward Efficient Water Splitting


The development of cost-effective and applicable strategies for producing efficient oxygen evolution reaction (OER) electrocatalysts is crucial to advance electrochemical water splitting. Herein, a kinetically controlled room-temperature coprecipitation is developed as a general strategy to produce a variety of sandwich-type metal hydroxide/graphene composites. Specifically, well-defined α-phase nickel cobalt hydroxide nanosheets are vertically assembled on the entire graphene surface (NiCo-HS@G) to provide plenty of accessible active sites and enable facile gas escaping. The tight contact between NiCo-HS and graphene promises effective electron transfer and remarkable durability. It is discovered that Ni doping adjusts the nanosheet morphology to augment active sites and effectively modulates the electronic structure of Co center to favor the adsorption of oxygen species. Consequently, NiCo-HS@G exhibits superior electrocatalytic activity and durability for OER with a very low overpotential of 259 mV at 10 mA cm−2. Furthermore, a practical water electrolyzer demonstrates a small cell voltage of 1.51 V to stably achieve the current density of 10 mA cm−2, and 1.68 V to 50 mA cm−2. Such superior electrocatalytic performance indicates that this facile and manageable strategy with low energy consumption may open up opportunities for the cost-effective mass production of various metal hydroxides/graphene nanocomposites with desirable morphology and competing performance for diverse applications. Kinetically controlled coprecipitation strategy is developed as a general cost-effective strategy to prepare sandwiched metal hydroxide/graphene nanocomposites. Nickel cobalt hydroxide nanosheets vertically assembled on graphene exhibit superior electrocatalytic activity and durability for oxygen evolution reaction, which enables the developed strategy to mass produce a variety of hydroxide/graphene nanocomposites for diverse energy applications.

A Cocatalytic Electron-Transfer Cascade Site-Selectively Placed on TiO2 Nanotubes Yields Enhanced Photocatalytic H2 Evolution


Separation and transfer of photogenerated charge carriers are key elements in designing photocatalysts. TiO2 in numerous geometries has been for many years the most studied photocatalyst. To overcome kinetic limitations and achieve swift charge transfer, TiO2 has been widely investigated with cocatalysts that are commonly randomly placed nanoparticles on a TiO2 surface. The poor control over cocatalyst placement in powder technology approaches can drastically hamper the photocatalytic efficiencies. Here in contrast it is shown that the site-selective placement of suitable charge-separation and charge-transfer cocatalysts on a defined TiO2 nanotube morphology can provide an enhancement of the photocatalytic reactivity. A TiO2–WO3–Au electron-transfer cascade photocatalyst is designed with nanoscale precision for H2 production on TiO2 nanotube arrays. Key aspects in the construction are the placement of the WO3/Au element at the nanotube top by site-selective deposition and self-ordered thermal dewetting of Au. In the ideal configuration, WO3 acts as a buffer layer for TiO2 conduction band electrons, allowing for their efficient transfer to the Au nanoparticles and then to a suitable environment for H2 generation, while TiO2 holes due to intrinsic upward band bending in the nanotube walls and short diffusion length undergo a facilitated transfer to the electrolyte where oxidation of hole-scavenger molecules takes place. These photocatalytic structures can achieve H2 generation rates significantly higher than any individual cocatalyst–TiO2 combination, including a classic noble metal–TiO2 configuration. A geometrically highly defined synergistic photocatalytic platform is designed based on TiO2 nanotubes. A key element is an electron-transfer cascade from TiO2 to a WO3 junction and onward to an Au mediator placed at the tube mouth. Essential is the well-defined tube geometry and the TiO2–WO3–Au architecture. WO3 acts as a buffer layer, transferring electrons photogenerated in TiO2 to the Au nanoparticles for H2 generation.

High-Performance Ultrathin Flexible Solid-State Supercapacitors Based on Solution Processable Mo1.33C MXene and PEDOT:PSS


MXenes, a young family of 2D transition metal carbides/nitrides, show great potential in electrochemical energy storage applications. Herein, a high performance ultrathin flexible solid-state supercapacitor is demonstrated based on a Mo1.33C MXene with vacancy ordering in an aligned layer structure MXene/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS) composite film posttreated with concentrated H2SO4. The flexible solid-state supercapacitor delivers a maximum capacitance of 568 F cm−3, an ultrahigh energy density of 33.2 mWh cm−3 and a power density of 19 470 mW cm−3. The Mo1.33C MXene/PEDOT:PSS composite film shows a reduction in resistance upon H2SO4 treatment, a higher capacitance (1310 F cm−3) and improved rate capabilities than both pristine Mo1.33C MXene and the nontreated Mo1.33C/PEDOT:PSS composite films. The enhanced capacitance and stability are attributed to the synergistic effect of increased interlayer spacing between Mo1.33C MXene layers due to insertion of conductive PEDOT, and surface redox processes of the PEDOT and the MXene. A MXene-based solution processable flexible solid-state supercapacitor with high performance is developed from a MXene/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS) composite film. After posttreatment with concentrated H2SO4, the PEDOT nanofiber network is aligned between the MXene sheets, leading to highly improved flexibility and, most importantly, improved capacitances (1310 F cm−3), rate-capabilities, and stability.

Biphase Cobalt–Manganese Oxide with High Capacity and Rate Performance for Aqueous Sodium-Ion Electrochemical Energy Storage


Manganese-based metal oxide electrode materials are of great importance in electrochemical energy storage for their favorable redox behavior, low cost, and environmental friendliness. However, their storage capacity and cycle life in aqueous Na-ion electrolytes is not satisfactory. Herein, the development of a biphase cobalt–manganese oxide (CoMnO) nanostructured electrode material is reported, comprised of a layered MnO2⋅H2O birnessite phase and a (Co0.83Mn0.13Va0.04)tetra(Co0.38Mn1.62)octaO3.72 (Va: vacancy; tetra: tetrahedral sites; octa: octahedral sites) spinel phase, verified by neutron total scattering and pair distribution function analyses. The biphase CoMnO material demonstrates an excellent storage capacity toward Na-ions in an aqueous electrolyte (121 mA h g−1 at a scan rate of 1 mV s−1 in the half-cell and 81 mA h g−1 at a current density of 2 A g−1 after 5000 cycles in full-cells), as well as high rate performance (57 mA h g−1 a rate of 360 C). Electrokinetic analysis and in situ X-ray diffraction measurements further confirm that the synergistic interaction between the spinel and layered phases, as well as the vacancy of the tetrahedral sites of spinel phase, contribute to the improved capacity and rate performance of the CoMnO material by facilitating both diffusion-limited redox and capacitive charge storage processes. In situ X-ray diffraction characterizations of biphase CoMnO material are conducted during electrochemical charge (oxidation) and discharge (reduction) processes, the structure evolution of CoMnO results from Na-ion intercalation and/or deintercalation for aqueous energy storage and is verified by the variations of the lattice constants or layered spacing of a Co1.21Mn1.75O3.72 spinel phase and a MnO2 layered birnessite phase.

Comment on “Structural and Electrical Properties of Atomic Layer Deposited Al-Doped ZnO Films”


In a recent report, Lee et al. have proposed an “effective field model” for extrinsic doping to explain the electrical properties of Al-doped zinc oxide (ZnO) films grown by atomic layer deposition (ALD). They have introduced the doping model by considering the layered structure of the ALD-grown films as observed in the transmission electron microscopy measurements. However, in the present comment, we have demonstrated that the suggested doping model is misleading in which physically inconsistent assumptions are considered throughout. Herein, a reasonable interpretation of the electrical properties and doping mechanism of the ALD-grown films by taking into consideration the theoretical formulations of the disordered electronic system is suggested.

Oriented Multiwalled Organic–Co(OH)2 Nanotubes for Energy Storage


In energy storage materials, large surface areas and oriented structures are key architecture design features for improving performance through enhanced electrolyte access and efficient electron conduction pathways. Layered hydroxides provide a tunable materials platform with opportunities for achieving such nanostructures via bottom-up syntheses. These nanostructures, however, can degrade in the presence of the alkaline electrolytes required for their redox-based energy storage. A layered Co(OH)2–organic hybrid material that forms a hierarchical structure consisting of micrometer-long, 30 nm diameter tubes with concentric curved layers of Co(OH)2 and 1-pyrenebutyric acid is reported. The nanotubular structure offers high surface area as well as macroscopic orientation perpendicular to the substrate for efficient electron transfer. Using a comparison with flat films of the same composition, it is demonstrated that the superior performance of the nanotubular films is the result of a large accessible surface area for redox activity. It is found that the organic molecules used to template nanotubular growth also impart stability to the hybrid when present in the alkaline environments necessary for redox function. A layered Co(OH)2–organic hybrid material consisting of multiwalled nanotubes with preferred alignment is electrodeposited on conductive substrates for use as energy storage electrodes. The molecular structure of the organic component determines the morphology of the hybrid material and its resulting electrochemical performance. The same organic molecules used to template nanotubular growth enhance the hybrid material's stability when present in alkaline electrolytes.

Analysis of Optical Losses in a Photoelectrochemical Cell: A Tool for Precise Absorptance Estimation


Optical losses in a photoelectrochemical (PEC) cell account for a substantial part of solar-to-hydrogen conversion losses, but limited attention is paid to the detailed investigation of optical losses in PEC cells. In this work, an optical model of combined coherent and incoherent light propagation in all layers of the PEC cell based on spectroscopic measurements is presented. Specifically, photoelectrodes using transparent conductive substrates such as F:SnO2 coated with thin absorber films are focused. The optical model is verified for hematite photoanodes fabricated by atomic layer deposition and successfully used to determine wavelength-dependent reflection, transmission, layer absorptances, and charge generation rates. Furthermore, the calculated absorptances enable 20–30% more accurate calculations of the absorbed photon-to-current efficiency of PEC cells. Our optical model is a powerful tool for the optimization of the optical performance of PEC cells focusing on single absorber or tandem configurations and represents a cornerstone of a complete (optical and electrical) model for PEC water splitting cells. An in-depth analysis of wavelength-dependent optical losses for a photoelectrochemical water splitting cell based on a transparent conducting substrate is presented. Specifically, ultrathin films with a thickness comparable to the roughness of the substrate are described conveniently with the graded layer approach. Our validated model enables extraction of absorptance and absorbed photon-to-current efficiency of the photoabsorber with improved accuracy over established methods.

A Unique Disintegration–Reassembly Route to Mesoporous Titania Nanocrystalline Hollow Spheres with Enhanced Photocatalytic Activity


A novel disintegration–reassembly route is reported for the synthesis of mesoporous TiO2 nanocrystalline hollow spheres with controlled crystallinity and enhanced photocatalytic activity. In this unique synthesis strategy, it is demonstrated that sol–gel-derived mesoporous TiO2 colloidal spheres can be disintegrated into discrete small nanoparticles that are uniformly embedded in the polymer (polystyrene, PS) matrix by surface-induced photocatalytic polymerization. Subsequent reassembly of these TiO2 nanoparticles can be induced by an annealing process after further coating of a resorcinol–formaldehyde (RF) resin, which forms self-supported hollow spheres of TiO2 at the PS/RF interface. The abundant phenolic groups on the RF resin serve as anchoring sites for the TiO2 nanoparticles, thus enable the reassembly of the TiO2 nanoparticles and prevent their sintering during the thermal crystallization process. This unique disintegration–reassembly process leads to the formation of self-supported TiO2 hollow spheres with relatively large surface area, high crystallinity, and superior photocatalytic activity in dye degradation under UV light irradiation. A novel disintegration–reassembly route is devised to synthesize mesoporous titania nanocrystalline shells starting from titania spheres. The resulting titania hollow spheres show high crystallinity, small grain size, and large surface area, which account for their superior photocatalytic activity in dye degradation under UV light irradiation, benchmarking against commercial P25.

Tailoring Hybrid Layered Double Hydroxides for the Development of Innovative Applications


Hybrid materials based on layered double hydroxides (LDHs) exhibit great potential in diverse fields such as health care, polymer composites, environment, catalysis, and energy generation. Indeed, the compositional flexibility and the scalability of LDH structures, their low cost, and their ease of synthesis have made hybrid LDHs extremely attractive for constructing smart and high-performance multifunctional materials. This review provides a comprehensive and critical overview of the current research on multifunctional hybrid LDHs. Organic–inorganic hybrid LDHs, intercalated and surface-immobilized structures, are both specifically addressed. The new trends and strategies for hybrid LDH synthesis are first described, and then the potential of the latest hybrid LDHs, polymer LDH nanocomposites, and LDH bio-nanocomposites are presented. Significant achievements published from ≈2010, including authors' results, which employ hybrid LDH assemblies in materials science, medicine, polymer nanocomposites, cement chemistry, and environmental technologies, are specifically addressed. It is concluded with remarks on present challenges and future prospects. The concept of multifunctionality has exploded in materials science during the last decade, and this trend also applies to hybrid layered double hydroxides (LDHs). In this Feature Article, after a survey of the diverse approaches to hybrid LDH synthesis, significant achievements based on the use of hybrid LDH assemblies in materials science, medicine, polymer nanocomposites, cement chemistry, and environmental technologies are specifically addressed.

Surfactant-Free β-Galactosidase Micromotors for “On-The-Move” Lactose Hydrolysis


Surfactant-free β-galactosidase micromotors are explored here as moving biocatalyst for highly efficient lactose hydrolysis from raw milk. The coupling of the hydrolytic properties of such enzyme with the efficient movement of carbon nanotube tubular micromotors results in nearly 100% lactose hydrolysis and two fold removal efficiency as compared with static conditions and with free enzyme. The incorporation of an inner Ni layer allows its reusability to operate in batch mode. The rough micromotor surface area allows the immobilization of a high loading of β-galactosidase and results in an increase in the enzyme affinity toward lactose. The new micromotor concept opens new avenues for the use of micromotors as moving immobilized biocatalyst to improve the technological process not only in food industry but also in other fields. β-galactosidase functionalized micromotors are used as moving microcatalysts for highly efficient lactose hydrolysis. Dynamic micromotor movement results in quantitative lactose removal in 25 min. The incorporation of an inner Ni layer allows for its reusability to operate in batch mode. The concept opens new avenues for the use of micromotors to improve the biotechnological process in the alimentary industry.

The Meeting Point of Carbonaceous Materials and Clays: Toward a New Generation of Functional Composites


Carbon and clays are worldwide-spread natural resources known and used for centuries by humans. In spite of their differences, both have been combined to produce diverse types of functional materials, from conventional pencil cores to advanced hybrid composites. The presence of highly conductive graphene and/or carbon nanotubes allows for their use in applications ranging from elements of electrochemical devices to additives for polymer nanocomposites, pollution adsorbents, or active catalysts. Both top-down and bottom-up strategies can be applied to conveniently assemble carbon and clay counterparts. Moreover, such synthetic strategies can be tailored to produce adequate nanostructured materials and/or associate other species. This critical review presents the latest advances on this topic, addressing aspects related to the possibility to produce hybrid materials based on their functionalization capacity. Carbon and clays are abundant natural resources that can be combined to produce functional materials from conventional pencil cores to advanced hybrid composites. Top-down and bottom-up strategies are suitable to conveniently assemble carbon and clay counterparts, whose functionalization capacity can be exploited to produce tailored hybrid materials for applications in energy, environmental remediation, nanocomposites, and catalysis.

Ultra-Broadband Wide-Angle Terahertz Absorption Properties of 3D Graphene Foam


As a next generation of detection technology, terahertz technology is very promising. In this work, a highly efficient terahertz wave absorber based on 3D graphene foam (3DG) is first reported. Excellent terahertz absorption property at frequency ranging from 0.1 to 1.2 THz is obtained owing to faint surface reflection and enormous internal absorption. By precise control of the constant properties for 3DG, the reflection loss (RL) value of 19 dB is acquired and the qualified frequency bandwidth (with RL value over 10 dB) covers 95% of the entire measured bandwidth at normal incidence, which far surpasses most reported materials. More importantly, the terahertz absorption performance of 3DG enhances obviously with increasing the incidence while majority of materials become invalid at oblique incidence, instead. At the incidence of 45°, the maximum RL value increases 50% from 19 to 28.6 dB and the qualified frequency bandwidth covers 100% of the measured bandwidth. After considering all core indicators involving density, qualified bandwidth, and RL values, the specific average terahertz absorption (SATA) property is investigated. The SATA value of 3DG is over 3000 times higher than those of other materials in open literatures. The absorption performance of 3D graphene foam (3DG) is measured in the terahertz time-domain spectroscopy. The porous structure reduces surface reflection and the incident radiation quickly attenuates. Therefore, 3DG possesses the high reflection loss of −19 dB at 0.88 THz at normal incidence and −28.6 dB at 0.64 THz at oblique incidence and the qualified frequency bandwidth covers 100% of the measured bandwidth.

Dynamically Gas-Phase Switchable Super(de)wetting States by Reversible Amphiphilic Functionalization: A Powerful Approach for Smart Fluid Gating Membranes


In nature, cellular membranes perform critical functions such as endocytosis and exocytosis through smart fluid gating processes mediated by nonspecific amphiphilic interactions. Despite considerable progress, artificial fluid gating membranes still rely on laborious stimuli-responsive mechanisms and triggering systems. In this study, a room temperature gas-phase approach is presented for dynamically switching a porous material from a superhydrophobic to a superhydrophilic wetting state and back. This is realized by the reversible attachment of bipolar amphiphiles, which promote surface wetting. Application of this reversible amphiphilic functionalization to an impermeable nanofibrous membrane induces a temporary state of superhydrophilicity resulting in its pressure-less permeation. This mechanism allows for rapid smart fluid gating processes that can be triggered at room temperature by variations in the environment of the membrane. Owing to the universal adsorption of volatile amphiphiles on surfaces, this approach is applicable to a broad range of materials and geometries enabling facile fabrication of valve-less flow systems, fluid-erasable microfluidic arrays, and sophisticated microfluidic designs. Inspired by the spontaneous self-­assembly of simple amphiphilic hydro­carbons, a reversible amphiphilic functionalization concept for porous hierarchical material is presented. The gas-phase tuning of wettability for membranes is demonstrated, achieving cycles of superhydrophilicity and near-superhydrophobicity. Potential of the concept is showcased through valve-less fluid-gating and erasable microfluidic templates.

Conductive Nanocrystalline Niobium Carbide as High-Efficiency Polysulfides Tamer for Lithium-Sulfur Batteries


Rational design of functional interlayer is highly significant in pursuit of high-performance Li-S batteries. Herein, a nanocrystalline niobium carbide (NbC) is developed via a facile and scalable autoclave technology, which is, for the first time, employed as the advanced interlayer material for Li-S batteries. Combining the merits of strong polysulfides (PS) anchoring with high electric conductivity, the NbC-coated membrane enables efficiently tamed PS shuttling and fast sulfur electrochemistry, achieving outstanding cyclability with negligible capacity fading rate of 0.037% cycle−1 over 1500 cycles, superb rate capability up to 5 C, high areal capacity of 3.6 mA h cm−2 under raised sulfur loading, and reliable operation even in soft-package cells. This work offers a facile and effective method of promoting Li-S batteries for practical application. Nanocrystalline niobium carbide (NbC), combining the merits of strong polysulfides anchoring with high electric conductivity, is prepared via scalable autoclave technology. The application of a NbC-coated membrane enables prolonged lifespan and excellent rate capability for both thin and thick cathodes in coin cells, and reliable operation even in soft-package cells.

Self-Established Rapid Magnesiation/De-Magnesiation Pathways in Binary Selenium–Copper Mixtures with Significantly Enhanced Mg-Ion Storage Reversibility


Rechargeable magnesium/sulfur (Mg/S) and magnesium/selenium (Mg/Se) batteries are characterized by high energy density, inherent safety, and economical effectiveness, and therefore, are of great scientific and technological interest. However, elusive challenges, including the limited charge storage capacity, low Coulombic efficiency, and short cycle life, have been encountered due to the sluggish electrochemical kinetics and severe shuttles of ploysulfides (polyselenide). Taking selenium as model paradigm, a new and reliable Mg-Se chemistry is proposed through designing binary selenium-copper (Se-Cu) cathodes. An intriguing effect of Cu powders on the electrochemical reaction pathways of the active Se microparticles is revealed in a way of forming Cu3Se2 intermediates, which induces an unconventional yet reversible two-stage magnesiation mechanism: Mg-ions first insert into Cu3Se2 phases; in a second step Cu-ions in the Mg2xCu3Se2 lattice exchange with Mg-ions. As expected, binary Se-Cu electrodes show significantly improved reversibility and elongated cycle life. More bracingly, Se/C nanostructures fabricated by facile blade coating Se nanorodes onto copper foils exhibit high output power and capacity (696.0 mAh g−1 at 67.9 mA g−1), which outperforms all previously reported Mg/Se batteries. This work envisions a facile and reliable strategy to achieve better reversibility and long-term durability of selenium (sulfur) electrodes. Binary microsized Se-Cu electrodes show an unconventional yet reversible process occurring in a way of two-stage magnesiation mechanism: one step is the Mg-ions inserting into the Cu3Se2 phases; in the second step Cu-ions in the Mg2xCu3Se2 lattice exchange with Mg-ions forming the final products of MgSe nanoparticles and metallic Cu nanowires, resulting in excellent Mg-ion storage properties.

Wearable, Healable, and Adhesive Epidermal Sensors Assembled from Mussel-Inspired Conductive Hybrid Hydrogel Framework


Healable, adhesive, wearable, and soft human-motion sensors for ultrasensitive human–machine interaction and healthcare monitoring are successfully assembled from conductive and human-friendly hybrid hydrogels with reliable self-healing capability and robust self-adhesiveness. The conductive, healable, and self-adhesive hybrid network hydrogels are prepared from the delicate conformal coating of conductive functionalized single-wall carbon nanotube (FSWCNT) networks by dynamic supramolecular cross-linking among FSWCNT, biocompatible polyvinyl alcohol, and polydopamine. They exhibit fast self-healing ability (within 2 s), high self-healing efficiency (99%), and robust adhesiveness, and can be assembled as healable, adhesive, and soft human-motion sensors with tunable conducting channels of pores for ions and framework for electrons for real time and accurate detection of both large-scale and tiny human activities (including bending and relaxing of fingers, walking, chewing, and pulse). Furthermore, the soft human-motion sensors can be enabled to wirelessly monitor the human activities by coupling to a wireless transmitter. Additionally, the in vitro cytotoxicity results suggest that the hydrogels show no cytotoxicity and can facilitate cell attachment and proliferation. Thus, the healable, adhesive, wearable, and soft human-motion sensors have promising potential in various wearable, wireless, and soft electronics for human–machine interfaces, human activity monitoring, personal healthcare diagnosis, and therapy. Flexible, wearable, healable, and adhesive soft strain sensors are successfully developed from a conductive and biocompatible hybrid hydrogel framework for ultrasensitive human–machine interaction and healthcare monitoring. They exhibit fast self-healing ability (within 2 s), highly self-healing efficiency (99%), robust self-adhesiveness, and a tunable conducting framework for real-time, wireless, and accurate detection in human–machine interfaces, human activity monitoring, personal healthcare diagnosis, and therapy.

High-Performance Triboelectric Nanogenerators Based on Electrospun Polyvinylidene Fluoride–Silver Nanowire Composite Nanofibers


The preparation of ferroelectric polymer–metallic nanowire composite nanofiber triboelectric layers is described for use in high-performance triboelectric nanogenerators (TENGs). The electrospun polyvinylidene fluoride (PVDF)–silver nanowire (AgNW) composite and nylon nanofibers are utilized in the TENGs as the top and bottom triboelectric layers, respectively. The electrospinning process facilitates uniaxial stretching of the polymer chains, which enhances the formation of the highly oriented crystalline β-phase that forms the most polar crystalline phase of PVDF. The addition of AgNWs further promotes the β-phase crystal formation by introducing electrostatic interactions between the surface charges of the nanowires and the dipoles of the PVDF chains. The extent of β-phase formation and the resulting variations in the surface charge potential upon the addition of nanowires are systematically analyzed using X-ray diffraction (XRD) and Kelvin probe force microscopy techniques. The ability of trapping the induced tribocharges increases upon the addition of nanowires to the PVDF matrix. The enhanced surface charge potential and the charge trapping capabilities of the PVDF–AgNW composite nanofibers significantly enhance the TENG output performances. Finally, the mechanical stability of the electrospun nanofibers is dramatically enhanced while maintaining the TENG performances by applying thermal welding near the melting temperature of PVDF. High-performance triboelectric nanogenerators (TENG) are successfully demonstrated using electrospun polyvinylidene fluoride (PVDF)–silver nanowire (AgNW) composite nanofibers. It is found that an electrospinning process and the addition of AgNWs to the PVDF promote the effective formation of the polar crystalline β-phase. The enhanced surface charge potential and charge trapping properties of the PVDF–AgNW composite nanofibers significantly enhance the TENG performances.

Electromagnetic Shielding Hybrid Nanogenerator for Health Monitoring and Protection


Nowadays, mankind faces increasingly energy crisis and electromagnetic radiation pollution. An energy harvester with function of protecting human health from electromagnetic radiation is a desirable solution to this problem. Here, a stretchable electromagnetic shielding hybrid nanogenerator (ES-HNG) is reported which can not only scavenge thermal and mechanical energy from living environment but also protect and monitor human health. The ES-HNG is capable of transforming mechanical and thermal energy to electricity based on triboelectric, piezoelectric, and pyroelectric effects. To be devised as a computer keyboard cover, ES-HNG takes about 200 s to charge a capacitor to 3 V by typing. The stored energy can drive the portable devices successfully. Besides, the ES-HNG eliminates electromagnetic radiation of computer completely due to its unique electromagnetic shielding property. A large range of electromagnetic wave (frequency is between 0 and 1.5 GHz) is shielded more than 99.9978% by the ES-HNG. Moreover, the ES-HNG is able to monitor human health by attaching it on human abdomen to be a self-powered sensor. This work opens up a new prospect of harvesting energy effectively as well as protecting/monitoring human health from electromagnetic radiation surroundings. An electromagnetic shielding hybrid nanogenerator (ES-HNG) is fabricated by integrating triboelectric nanogenerator and pyroelectric-piezoelectric nanogenerators. The ES-HNG is capable of harvesting thermal and mechanical energies from ambient environment, monitoring, and protecting human health from electromagnetic radiation.

Flexible Graphene Solution-Gated Field-Effect Transistors: Efficient Transducers for Micro-Electrocorticography


Brain–computer interfaces and neural prostheses based on the detection of electrocorticography (ECoG) signals are rapidly growing fields of research. Several technologies are currently competing to be the first to reach the market; however, none of them fulfill yet all the requirements of the ideal interface with neurons. Thanks to its biocompatibility, low dimensionality, mechanical flexibility, and electronic properties, graphene is one of the most promising material candidates for neural interfacing. After discussing the operation of graphene solution-gated field-effect transistors (SGFET) and characterizing their performance in saline solution, it is reported here that this technology is suitable for μ-ECoG recordings through studies of spontaneous slow-wave activity, sensory-evoked responses on the visual and auditory cortices, and synchronous activity in a rat model of epilepsy. An in-depth comparison of the signal-to-noise ratio of graphene SGFETs with that of platinum black electrodes confirms that graphene SGFET technology is approaching the performance of state-of-the art neural technologies. Flexible graphene solution-gated field-effect transistors are proposed as a new advanced technology for neural recordings thanks to the outstanding properties of single-layer graphene. In this paper, the key concepts of this technology are discussed and its perfect suitability for μ-ECoG applications is shown by demonstrating the recording of sensory-evoked potential as well as synchronous activity.

High-Efficient Clearable Nanoparticles for Multi-Modal Imaging and Image-Guided Cancer Therapy


Renal-clearable nanoparticles have made it possible to overcome the toxicity by nonspecific accumulation in healthy tissues/organs due to their highly efficient clearance characteristics. However, their tumor uptake is relatively low due to the short blood circulation time and rapid body elimination. Here, this problem is addressed by developing renal-clearable nanoparticles by controlled coating of sub-6 nm CuS nanodots (CuSNDs) on doxorubicin ladened mesoporous silica nanoparticles (pore size ≈6 nm) for multimodal application. High tumor uptake of the as-synthesized nanoparticles (abbreviated as MDNs) is achieved due to the longer blood circulation time. The MDNs also show excellent performance in bimodal imaging. Moreover, the MDNs demonstrated a photothermally sensitive drug release and pronounced synergetic effects of chemo-photothermal therapy, which were confirmed by two different tumor models in vivo. A novel key feature of the proposed synthesis is the use of renal-clearable CuSNDs and biodegradable mesoporous silica nanoparticles which also are renal-clearable after degradation. Therefore, the MDNs would be rapidly degraded and excreted in a reasonable period in living body and avoid long-term toxicity. Such biodegradable and clearable single-compartment theranostic agents applicable in highly integrated multimodal imaging and multiple therapeutic functions may have substantial potentials in clinical practice. Highly efficient clearable theranostic ultrasmall CuS nanodots@mesoporous silica nanoparticles with high tumor uptake are synthesized, and demonstrated to be capable for positron emission tomography/photoacoustic bimodal imaging, imaging-guided effective combined chemo-photothermal therapy, and high-efficient body clearance.

A Multifunctional Polymeric Periodontal Membrane with Osteogenic and Antibacterial Characteristics


Periodontitis is a prevalent chronic, destructive inflammatory disease affecting tooth-supporting tissues in humans. Guided tissue regeneration strategies are widely utilized for periodontal tissue regeneration generally by using a periodontal membrane. The main role of these membranes is to establish a mechanical barrier that prevents the apical migration of the gingival epithelium and hence allowing the growth of periodontal ligament and bone tissue to selectively repopulate the root surface. Currently available membranes have limited bioactivity and regeneration potential. To address such challenges, an osteoconductive, antibacterial, and flexible poly(caprolactone) (PCL) composite membrane containing zinc oxide (ZnO) nanoparticles is developed. The membranes are fabricated through electrospinning of PCL and ZnO particles. The physical properties, mechanical characteristics, and in vitro degradation of the engineered membrane are studied in detail. Also, the osteoconductivity and antibacterial properties of the developed membrane are analyzed in vitro. Moreover, the functionality of the membrane is evaluated with a rat periodontal defect model. The results confirmed that the engineered membrane exerts both osteoconductive and antibacterial properties, demonstrating its great potential for periodontal tissue engineering. An osteoconductive, antibacterial, and flexible poly(caprolactone) composite membrane containing zinc oxide (ZnO) nanoparticles is developed through electrospinning for periodontal tissue engineering. The osteoconductivity and antibacterial properties of the developed membrane are analyzed in vitro. Moreover, the functionality of the membrane is evaluated with a rat periodontal defect model.

Multifunctional AIEgens: Ready Synthesis, Tunable Emission, Mechanochromism, Mitochondrial, and Bacterial Imaging


Luminogens with aggregation-induced emission characteristics (AIEgens) are intriguing due to its rapid expansion in various high-tech applications. However, there is still in high demand on the development of novel AIEgens with easy preparation and functionalization, stable structures, tunable emissions, and high quantum efficiency. In this contribution, three AIEgens based on diphenyl isoquinolinium (IQ) derivatives are reported. They can be facilely synthesized and possess high structural stability, favorable visible light excitation, large Stokes shifts, high quantum yields, tunable colors, and sufficient two-photon absorption of near-infrared light. Importantly, they exhibit multifunctionalities. They exhibit mechanochromic property, making them capable to be applied for rewritable papers. They can also be applied in mitochondrial imaging with high specificity, cell permeability, brightness, biocompatibility, and photostability. They are promising for the applications in evaluation of mitochondrial membrane potential and image-guided cancer cell ablation. Last, they are able to stain bacteria in a wash-free manner. All these intriguing results suggest such readily accessible and multifunctional diphenyl IQ-based AIEgens provide a new platform for construction of advanced materials for practical applications. Based on diphenyl isoquinolinium structure, readily accessible multifunctional AIEgens are developed for mechanochromic materials, mitochondrial, and bacterial imaging probes, providing a new platform for construction of advanced materials for practical applications.

Thermosensitive, Stretchable, and Piezoelectric Substrate for Generation of Myogenic Cell Sheet Fragments from Human Mesenchymal Stem Cells for Skeletal Muscle Regeneration


In a native muscle microenvironment, electrical and mechanical stimuli exist in the form of action potentials and muscle contraction. Here, a cell culture system is developed that can mimic the in vivo microenvironment and provide these stimuli to cultured cells, and it is tested whether the stimulation can promote myogenic differentiation of human umbilical cord blood mesenchymal stem cells (hUCBMSCs). A thermosensitive, stretchable, and piezoelectric substrate (TSPS) is fabricated by polydimethylsiloxane spin-coating of aligned ZnO nanorods and subsequent poly(N-isopropylacrylamide) grafting on the polydimethylsiloxane surface. Pulsatile mechanoelectrical cues are provided to hUCBMSCs cultured on the TSPS by subjecting the TSPS to cyclic stretching and bending, resulting in significant promotion of myogenic differentiation of hUCBMSCs as well as intracellular signaling related to the differentiation. After differentiation ex vivo, the cells are detached from the TSPS in the form of cell sheet fragments. Injection of the cell sheet fragments of differentiated cells into injured mouse skeletal muscle shows improved cell retention and muscle regeneration as compared to injection of either undifferentiated cells or differentiated dissociated cells. This system may serve as a tool for research on the electrical and mechanical regulation of stem cells and may be used to potentiate stem cell therapies. Thermosensitive, stretchable, and piezoelectric substrates can mimic the skeletal muscle microenvironment by providing pulsatile mechanoelectric cues to human umbilical cord blood mesenchymal stem cells (hUCBMSCs). Electrical and mechanical stimulations induce skeletal muscle differentiation of hUCBMSCs, and the differentiated cell sheet fragments are a good source of cell therapy to treat skeletal muscle diseases.

Hydrogen Bonding Directed Colloidal Self-Assembly of Nanoparticles into 2D Crystals, Capsids, and Supracolloidal Assemblies


Self-assembly of colloidal building blocks, like metal nanoparticles, is a rapidly progressing research area toward new functional materials. However, in-depth control of the colloidal self-assembly and especially hierarchical self-assembly is difficult due to challenges in controlling the size dispersities, shape/morphology, directionalities, and aggregation tendencies. Using either polydispersed or narrow-size dispersed nanoparticles, considerable progress has been achieved over the past few years. However, absolutely monodisperse nanoparticles could allow new options for rational designs of self-assemblies. Therein, atomically precise monolayer protected nanoclusters (d < 3 nm) have recently been synthesized with well-defined metal cores and surface ligands. Their dispersion behavior is commonly tuned by surfactant-like ligands. Beyond that, this study deals with approaches based on ligand-driven supramolecular interactions and colloidal monodispersity until atomic precision to tune the colloidal self-assembly and hierarchy from nanoscale to mesoscopic scale. Therein colloidal packing to self-assembled 2D crystals and closed virus capsid-inspired shells provide relevant research goals due to ever increasing potential of 2D materials and encapsulation. This study addresses the hydrogen bonding (H-bonding) directed self-assembly of atomically precise gold and silver nanoparticles and narrow size dispersed cobalt nanoparticles to free-standing 2D colloidal nanosheets, nanowire assemblies, capsid-like colloidal closed shells, as well as higher order structures. Unforeseen colloidal self-assemblies, hierarchies, and related functions are expected upon control of the polydispersity of nanoparticles with atomic precision and by using functional ligands incorporating supramolecular motifs, beyond surfactants. This study describes 2D colloidal crystals, composite bilayers, spherical-, ellipsoidal-, and rod-like capsids with potential applications in, e.g., colloidal encapsulation and as porous supracolloidal materials.

Functional Defective Metal-Organic Coordinated Network of Mesostructured Nanoframes for Enhanced Electrocatalysis


Although defects are traditionally perceived as undesired feature, the prevalence of tenacious low-coordinated defects can instead give rise to desirable functionalities. Here, a spontaneous etching of mesostructured crystal, cyanide-bridged cobalt-iron (CN-CoFe) organometallic hybrid into atomically crafted open framework that is populated with erosion-tolerant high surface energy defects is presented. Unprecedently, the distinct mechanistic etching pathway dictated by the mesostructured assembly, bulk defects, and strong intercoordinated cyanide-bridged hybrid mediates not only formation of excess low-coordinated defects but also more importantly stabilizes them against prevailing dissolution and migration issues. Clearly, the heteropolynuclear cyanide bonded inorganic mesostructured clusters sanction the restructuring of a new breed of stable organometallic polymorph with 3D accessible structure enclosed by electrochemical active atomic stepped edges and high index facets. The exceptional electrocatalysis performance supports the assertion that defective mesostructured polymorph offers a new material paradigm to synthetically tailor the elementary building block constituents toward functional materials. A spontaneous etching of mesostructured nanocubes readily transforms cyanide-bridged cobalt-iron (CN-CoFe) organometallic hybrids into atomically crafted nanoframes. The strong intercoordinated cyanide-bridged hybrid facilitates the formation of abundant low-coordinated defects and stabilizes them against dissolution/migration issues. The synthetically tailorable atomic bonding and crystal structure hybrid polymorphs exhibit outstanding electrochemical active and stable structure.

Photoacoustic Imaging of Embryonic Stem Cell-Derived Cardiomyocytes in Living Hearts with Ultrasensitive Semiconducting Polymer Nanoparticles


Human embryonic stem cell-derived cardiomyocytes (hESC-CMs) have become promising tools to repair injured hearts. To achieve optimal outcomes, advanced molecular imaging methods are essential to accurately track these transplanted cells in the heart. In this study, it is demonstrated for the first time that a class of photoacoustic nanoparticles (PANPs) incorporating semiconducting polymers (SPs) as contrast agents can be used in the photoacoustic imaging (PAI) of transplanted hESC-CMs in living mouse hearts. This is achieved by virtue of two benefits of PANPs. First, strong photoacoustic (PA) signals and specific spectral features of SPs allow PAI to sensitively detect and distinguish a small number of PANP-labeled cells (2000) from background tissues. Second, the PANPs show a high efficiency for hESC-CM labeling without adverse effects on cell structure, function, and gene expression. Assisted by ultrasound imaging, the delivery and engraftment of hESC-CMs in living mouse hearts can be assessed by PANP-based PAI with high spatial resolution (≈100 µm). In summary, this study explores and validates a novel application of SPs as a PA contrast agent to track labeled cells with high sensitivity and accuracy in vivo, highlighting the advantages of integrating PAI and PANPs to advance cardiac regenerative therapies. Ultrasensitive semiconducting polymer nanoparticles (SPNs) for photoacoustic (PA) imaging of transplantation and engraftment of human embryonic stem cell-derived cardiomyocytes (hESC-CMs) are developed. The SPNs have strong and stable PA signals as well as a specific PA spectrum, which facilitate real-time monitoring of delivery and localization of hESC-CMs in mouse hearts for cardiac regenerative therapy.

Probing the Dynamic Nature of Self-Assembling Cyclic Peptide–Polymer Nanotubes in Solution and in Mammalian Cells


Self-assembling cyclic peptide–polymer nanotubes have emerged as a fascinating supramolecular system, well suited for a diverse range of biomedical applications. Due to their well-defined diameter, tunable peptide anatomy, and ability to disassemble in situ, they have been investigated as promising materials for numerous applications including biosensors, antimicrobials, and drug delivery. Despite this continuous effort, the underlying mechanisms of assembly and disassembly are still not fully understood. In particular, the exchange of units between individual assembled nanotubes has been overlooked so far, despite its knowledge being essential for understanding their behavior in different environments. To investigate the dynamic nature of these systems, cyclic peptide–polymer nanotubes are synthesized, conjugated with complementary dyes, which undergo a Förster resonance energy transfer (FRET) in close proximity. Model conjugates enable to demonstrate not only that their self-assembly is highly dynamic and not kinetically trapped, but also that the self-assembly of the conjugates is strongly influenced by both solvent and concentration. Additionally, the versatility of the FRET system allows studying the dynamic exchange of these systems in mammalian cells in vitro using confocal microscopy, demonstrating the exchange of subunits between assembled nanotubes in the highly complex environment of a cell. Dynamically exchanging supramolecular polymers observe via FRET. Self-assembling cyclic peptide–polymer nanotubes are widely studied for their biological applications, and show dynamic behavior in a range of different environments proven by FRET; mixing takes place not only in various solvents, but also in the complex environment within a cells.

Highly Condensed Boron Cage Cluster Anions in 2D Carrier and Its Enhanced Antitumor Efficiency for Boron Neutron Capture Therapy


An attempt is made to apply layered double hydroxide (LDH) as a boron delivery carrier for boron neutron capture therapy (BNCT), which needs a sufficient amount of boron in tumor cells for its successful administration. To meet this requirement, a nanohybrid (BSH-LDH), mercaptoundecahydro-closo-dodecaborate (BSH) anionic molecules in LDH, is developed as a boron delivery system. The cellular boron content upon permeation of BSH-LDH nanoparticles (42.4 µg 10B 10−6 cells) in U87 glioblastoma cell line is found to be ≈2000 times larger than the minimum boron requirement (≈0.02 µg 10B 10−6 cells) for BNCT and also orders of magnitude higher than the previous results (0.2–1.5 µg 10B 10−6 cells) by those applied with other targeting strategies, and eventually results in excellent neutron capture efficiency even under such low dose (30 µg 10B mL−1) and weak irradiation (1 × 1012 n cm−2 corresponding to 20 min) condition. According to the biodistribution studies in xenograft mice model, the tumor-to-blood ratio of BSH in the BSH-LDH-treated-group is found to be 4.4-fold higher than that in the intact BSH treated one in 2 h after drug treatment. The present BNCT combined with boron delivery system provides a promising integrative therapeutic platform for cancer treatment. Developing a novel boron neutron capture therapy-drug delivery system based on the mercaptoundecahydro-closo-dodecaborate-layered double hydroxide nanohybrid system is quite successful, which greatly enhance the boron delivery to cancer cells, and thereby resulting in effective cell destruction even after irradiation of such a low neutron flux (1 × 1012 n cm−2). This result can eventually be very helpful in the radiation administration for cancer patients.

Construction of a Biomimetic Magnetosome and Its Application as a SiRNA Carrier for High-Performance Anticancer Therapy


Precisely delivering siRNA to its target site in cancer cells is a high-demanding but challenging task. Herein, a biomimetic magnetosome is developed using magnetic nanocluster (MNC) as the core and Arg–Gly–Asp (RGD) decorated macrophage membrane as the cloak, which is achieved via a combination of MNC synthesis, azide-membrane engineering, electrical assembly, and click chemistry. Such a feature-packed magnetosome enables us to gain the success of high-performance siRNA delivery through superior stealth effect, magnetic resonance imaging, magnetic accumulation, RGD targeting, and favorable cytoplasm trafficking. As a result, target gene expression can be significantly suppressed and tumor growth is effectively inhibited, while the systemic toxicity is not notable. These results together vote the biomimetic magnetosome as a promising siRNA delivery system for anticancer therapy. A biomimetic magnetosome is developed using magnetic nanocluster as the core and Arg–Gly–Asp (RGD) decorated macrophage membrane as the cloak for siRNA delivery to cancer cells. The superior stealth effect, magnetic accumulation, RGD targeting, MR imaging, and favorable cytoplasm trafficking are demonstrated. The target gene expression is significantly suppressed, and significantly inhibited tumor growth is achieved with few side effects.

Unusual Twisting Phonons and Breathing Modes in Tube-Terminated Phosphorene Nanoribbons and Their Effects on Thermal Conductivity


By studying tube-terminated phosphorene nanoribbons (PNRs), it is found that unusual phonon and thermal properties can emerge from topologically new edges. The lattice dynamics calculations show that in tube-terminated PNRs, the breaking of rotation symmetry suppresses the degeneracy of phonon modes, causing the emergence of twisting mode. An anomalous change of an out-of-plane acoustic mode to breathing modes with nonzero energy at the center of Brillouin zone occurs when the phosphorene sheet is converted into a tube-terminated PNR. These unusual twisting and breathing modes provide a larger phase space for scattering phonons, thus explaining the low thermal conductivity of tube-terminated PNRs revealed by molecular dynamics calculations. Due to the change in the stress field distribution caused by the tube edge, a nearly strain-independent thermal conductivity in tube-terminated PNRs is observed, which is in contrast to the apparent enhancement of thermal conductivity in pristine and dimer-terminated PNRs under tensile strain. The work reveals intriguing phononic and thermal behaviors of tube-terminated 2D materials. Unusual phonon and thermal properties are observed for tube-terminated phosphorene nanoribbons. Converting the phosphorene sheet into a tube-edged phosphorene nanoribbon breaks the rotation symmetry. The degeneracy of phonon modes is suppressed, causing the emergence of a twisting mode and an anomalous change of the out-of-plane acoustic mode to breathing modes with nonzero energy at the center of Brillouin zone occurs.

High Seebeck Coefficient in Mixtures of Conjugated Polymers


A universal method to obtain record-high electronic Seebeck coefficients is demonstrated while preserving reasonable conductivities in doped blends of organic semiconductors through rational design of the density of states (DOSs). A polymer semiconductor with a shallow highest occupied molecular orbital (HOMO) level-poly(3-hexylthiophene) (P3HT) is mixed with materials with a deeper HOMO (PTB7, TQ1) to form binary blends of the type P3HTx:B1-x (0 ≤ x ≤ 1) that is p-type doped by F4TCNQ. For B = PTB7, a Seebeck coefficient S = 1100 µV K−1 with conductivity σ = 0.3 S m−1 at x = 0.10 is achieved, while for B = TQ1, S = 2000 µV K−1 and σ = 0.03 S m−1 at x = 0.05 is found. Kinetic Monte Carlo simulations with parameters based on experiments show good agreement with the experimental results, confirming the intended mechanism. The simulations are used to derive a design rule for parameter tuning. These results can become relevant for low-power, low-cost applications like (providing power to) autonomous sensors, in which a high Seebeck coefficient translates directly to a proportionally reduced number of legs in the thermogenerator, and hence in reduced fabrication cost and complexity. Record-high Seebeck coefficients are achieved for p-type-doped blends of common conjugated polymers. The method used is based on a rational design of the density of states, such that the characteristic hop occurs from the compound with the shallower HOMO to the compound with the deeper HOMO.

Investigation of the High Electron Affinity Molecular Dopant F6-TCNNQ for Hole-Transport Materials


2,2′-(perfluoronaphthalene-2,6-diylidene)dimalononitrile (F6-TCNNQ) is investigated as a molecular p-type dopant in two hole-transport materials, 2,2′,7,7′-tetrakis(N,N-diphenylamino)-9,9-spirobifluorene (Spiro-TAD) and tris(4-carbazoyl-9-ylphenyl)amine (TCTA). The electron affinity of F6-TCNNQ is determined to be 5.60 eV, one of the strongest organic molecular oxidizing agents used to date in organic electronics. p-Doping is found to be effective in Spiro-TAD (ionization energy = 5.46 eV) but not in TCTA (ionization energy = 5.85 eV). Optical absorption measurements demonstrate that charge transfer is the predominant doping mechanism in Spiro-TAD:F6-TCNNQ. The host–dopant interaction also leads to a significant alteration of the host film morphology. Finally, transport measurements done on Spiro-TAD:F6-TCNNQ as a function of dopant concentration and temperature, and using a highly doped contact layer to ensure negligible hole injection barrier, lead to an accurate measurement of the film conductivity and hole-hopping activation energy. 2,2′-(perfluoronaphthalene-2,6-diylidene)dimalononitrile (F6-TCNNQ) is investigated as p-dopant in two hole-transport materials (HTMs). Ultrathin, heavily doped 2,2′,7,7′-tetrakis(N,N-diphenylamino)-9,9-spirobifluorene (Spiro-TAD) injection layers are implemented to ensure a negligible hole injection barrier in transport measurements, allowing accurate determination of conductivity and carrier hopping activation energy in HTMs such as Spiro-TAD.

Spatially Configuring Wrinkle Pattern and Multiscale Surface Evolution with Structural Confinement


Surface elastic instabilities, such as wrinkling and creasing, can enable a convenient strategy to impart reversible patterned topography to a surface. Here the classic system of a stiff layer on a soft substrate is focused, which famously produces parallel harmonic wrinkles at modest uniaxial compression that period-double repeatedly at higher compressions and ultimately evolve into deep folds and creases. By introducing micrometer-scale planar Bravais lattice holes to spatially pattern the substrate, these instabilities are guided into a wide variety of different patterns, including wrinkling in parallel bands and star shape bands, and radically reduce the threshold compression. The experimental patterns and thresholds are enabled to understand by considering a simple plane-strain model for the patterned substrate-deformation, decorated by wrinkling on the stiff surface layer. The experiments also show localized wrinkle-crease transitions at modest compression, yielding a hierarchical surface with different generations of instability mixed together. By varying the geometrical inputs, control over the stepwise evolution of surface morphologies is demonstrated. These results demonstrate considerable control over both the patterns and threshold of the surface elastic instabilities, and have relevance to many emerging applications of morphing surfaces, including in wearable/flexible electronics, biomedical systems, and optical devices. Taking advantage of patterning lattice holes on an elastic bilayer, the formation of versatile wrinkle patterns that selectively cover the substrate and provide controllable evolution of the instability morphology is demonstrated to achieve a hierarchical surface. This provides insight into the formation and evolution of elastic instabilities on complex surfaces.

Liquid-Tin-Assisted Molten Salt Electrodeposition of Photoresponsive n-Type Silicon Films


Production of silicon film directly by electrodeposition from molten salt would have utility in the manufacturing of photovoltaic and optoelectronic devices owing to the simplicity of the process and the attendant low capital and operating costs. Here, dense and uniform polycrystalline silicon films (thickness up to 60 µm) are electrodeposited on graphite sheet substrates at 650 °C from molten KCl–KF-1 mol% K2SiF6 salt containing 0.020–0.035 wt% tin. The growth of such high-quality tin-doped silicon films is attributable to the mediation effect of tin in the molten salt electrolyte. A four-step mechanism is proposed for the generation of the films: nucleation, island formation, island aggregation, and film formation. The electrodeposited tin-doped silicon film exhibits n-type semiconductor behavior. In liquid junction photoelectrochemical measurement, this material generates a photocurrent about 38–44% that of a commercial n-type Si wafer. Dense and uniform polycrystalline silicon films (thickness up to 60 µm) were successfully electrodeposited on graphite from molten KCl-KF-1 mol% K2SiF6 containing a tiny amount of tin which promotes the growth of n-type material. In the photoelectrochemical measurement this tin-doped Si film generates a photocurrent about 38–44% that of a commercial n-type Si wafer.

Photoswitchable Nanomaterials Based on Hierarchically Organized Siloxane Oligomers


Materials with highly ordered molecular arrangements have the capacity to display unique properties derived from their nanoscale structure. Here, the synthesis and characterization of azobenzene (AZO)-functionalized siloxane oligomers of discrete length that form photoswitchable supramolecular materials are described. Specifically, synergy between phase segregation and azobenzene crystallization leads to the self-assembly of an exfoliated 2D crystal that becomes isotropic upon photoisomerization with UV light. Consequently, the material undergoes a rapid athermal solid-to-liquid transition which can be reversed using blue light due to the unexpectedly fast 2D crystallization that is facilitated by phase segregation. In contrast, enabling telechelic supramolecular polymerization through hydrogen bonding inhibits azobenzene crystallization, and nanostructured pastes with well-ordered morphologies are obtained based on phase segregation alone, thus demonstrating block copolymer-like behavior. Therefore, by tailoring the balance of self-assembly forces in the azobenzene-functionalized siloxane oligomers, fast and reversible phase-changing materials can be engineered with various mechanical properties for applications in photolithography or switchable adhesion to lubricant properties. Azobenzene-functionalized siloxane oligomers self-assemble into supramolecular materials with well-ordered nanostructure and highly organized molecular arrangement. Photoisomerization with UV and visible wavelengths alter molecular organization, resulting in materials with rapid and reversible athermal phase transitions. Furthermore, by varying the synergy between phase segregation and azobenzene crystallization, material properties can be tailored for applications in photoswitchable adhesion and photolithography.

Reversible Switching of Spiropyran Molecules in Direct Contact With a Bi(111) Single Crystal Surface


Photochromic molecular switches immobilized by direct contact with surfaces typically show only weak response to optical excitation, which often is not reversible. In contrast, here, it is shown that a complete and reversible ring-opening and ring-closing reaction of submonolayers of spironaphthopyran on the Bi(111) surface is possible. The ring opening to the merocyanine isomer is initiated by ultraviolet light. Switching occurs in a two-step process, in which after optical excitation, an energy barrier needs to be overcome to convert to the merocyanine form. This leads to a strong temperature dependence of the conversion efficiency. Switching of the merocyanine isomer back to the closed form is achieved by a temperature increase. Thus, the process can be repeated in a fully reversible manner, in contrast to previously studied nitrospiropyran molecules on surfaces. This is attributed to the destabilization of the merocyanine isomer by the electron-donating nature of the naphtho group and the reduced van der Waals interaction of the Bi(111) surface. The result shows that molecules designed for switching in solutions need to be modified to function in direct contact with a surface. Reversible on-surface switching of spiropyran (SP) is achieved using a weakly interacting substrate and choosing a SP derivative such that the modification of the energetics in the adsorbed state is taken into account. The ring-opening reaction is induced by UV light. By an increase of temperature, the open merocyanine isomer is converted back to the closed SP form.

Photoelectrochemically Active and Environmentally Stable CsPbBr3/TiO2 Core/Shell Nanocrystals


Inherent poor stability of perovskite nanocrystals (NCs) is the main impediment preventing broad applications of the materials. Here, TiO2 shell coated CsPbBr3 core/shell NCs are synthesized through the encapsulation of colloidal CsPbBr3 NCs with titanium precursor, followed by calcination at 300 °C. The nearly monodispersed CsPbBr3/TiO2 core/shell NCs show excellent water stability for at least three months with the size, structure, morphology, and optical properties remaining identical, which represent the most water-stable inorganic shell passivated perovskite NCs reported to date. In addition, TiO2 shell coating can effectively suppress anion exchange and photodegradation, therefore dramatically improving the chemical stability and photostability of the core CsPbBr3 NCs. More importantly, photoluminescence and (photo)electrochemical characterizations exhibit increased charge separation efficiency due to the electrical conductivity of the TiO2 shell, hence leading to an improved photoelectric activity in water. This study opens new possibilities for optoelectronic and photocatalytic applications of perovskites-based NCs in aqueous phase. TiO2 shell coated CsPbBr3 core/shell nanocrystals are successfully constructed, resulting in excellent water, photo and thermal stability. TiO2 shell coating effectively increases charge separation efficiency, hence leading to an improved photoelectric activity in water.

A Multiparameter pH-Sensitive Nanodevice Based on Plasmonic Nanopores


With controllable mass transfer and special optical properties, plasmonic nanopores may be applied as a nanodevice and possibly create a new generation of single molecule detection technique based on plasmon-enhanced spectra. In the present study, gold nanoparticles self-assemble into a gold porous sphere (GPS) on the tip of a glass nanopipette with the help of i-motif DNA thiolated by both ends as linker molecules. The gaps among neighboring gold nanoparticles are considered as plasmonic nanopores. The size of the formed nanopores can be tuned by the folded–unfolded conformational change of i-motif DNA upon pH adjustment from 4.5 to 7.0. Based on its tunable structural property, the GPS shows reversible changes in ionic current, potential, and surface-enhanced Raman scattering signal. The GPS is further used to probe regional pH in single cells. The successful application of GPS in multiparameter pH probing and single cell analysis suggests that the new physical properties of the self-assembled plasmonic nanopores can be used for fabricating multiple types of nanodevices and nanosensors. Plasmonic nanopores are developed by assembling gold nanoparticles into a gold porous sphere (GPS) on the tip of a glass nanopipette using i-motif DNA as linker molecules. The GPS with clear ionic current rectification, potential response, and strong surface-enhanced Raman scattering properties is used as a multiparameter pH-sensitive nanodevice and successfully applied in probing the regional pH in single cells.

Photosensitizers for Two-Photon Excited Photodynamic Therapy


Photodynamic therapy (PDT) is a noninvasive protocol for the treatment of various cancers and nonmalignant diseases. Light, oxygen, and photosensitizer (PS) are the essential three elements in a typical PDT process. Currently, there are two major barriers limiting the further development of PDT. One issue is limited tissue penetration, and the other is the lack of high-performance PSs. Therefore, the newly emerging two-photon excited PDT (2PE-PDT) has attracted considerable attention in recent years due to its advantages such as a higher spatial resolution and a greater penetration depth. In this review, focus is on (i) the principle of 2PE-PDT, (ii) the progression of PSs for 2PE-PDT, and (iii) the potential indications and future directions in this field. Two-photon excited photodynamic therapy (2PE-PDT) has attracted considerable attention in recent years due to its advantages such as a greater tissue penetration depth and a higher spatial selectivity, which can promote the development of PDT in clinic. This review introduces the principle of 2PE-PDT, the progression of photosensitizers, and potential indications and future directions for this newly emerging branch of PDT.

Cancer Therapy: Dual-Targeting to Cancer Cells and M2 Macrophages via Biomimetic Delivery of Mannosylated Albumin Nanoparticles for Drug-Resistant Cancer Therapy (Adv. Funct. Mater. 44/2017)


A complicated mechanistic interaction exists between cancer cells and tumor microenvironments. In article number 1700403, Yongzhuo Huang and co-workers describe a “one-stone-two-birds” strategy, which uses a mannosylated albumin nanoparticulate co-delivery system to dual-target cancer cells and M2 macrophages via the pathways of both mannose receptors and the albumin-binding protein SPARC. This results in M2 macrophage modulation and enhanced cytotoxicity.

Lithium–Sulfur Batteries: The Fusion of Imidazolium-Based Ionic Polymer and Carbon Nanotubes: One Type of New Heteroatom-Doped Carbon Precursors for High-Performance Lithium–Sulfur Batteries (Adv. Funct. Mater. 44/2017)


A heteroatom-doped carbon material for high-performance lithium–sulfur batteries is reported in article number 1703936 by Xiaoju Li, Ruihu Wang, and co-workers. The integration of main-chain imidazolium-based ionic polymer and carbon nanotubes (CNTs) yields porous materials. They can serve as an effective sulfur host, and both the electrical conductivity from CNTs and polysulfide entrapping ability from the heteroatom-doped carbons are inherited and strengthened.

Cancer Therapy: Photo-Induced Charge-Variable Conjugated Polyelectrolyte Brushes Encapsulating Upconversion Nanoparticles for Promoted siRNA Release and Collaborative Photodynamic Therapy under NIR Light Irradiation (Adv. Funct. Mater. 44/2017)


In article number 1702592 Quli Fan and co-workers report a photo-induced charge-variable cationic conjugated polyelectrolyte brush encapsulating upconversion nanoparticles (UCNP@CCPEB) for siRNA release and collaborative photodynamic therapy under near-IR light irradiation. With good stability and excellent siRNA-loading capacity, UCNP@CCPEB exhibits good 1O2 production and facilitate siRNA release under 980 nm irradiation, enabling highly effective collaborative tumor therapy in vitro and in vivo.

Actuators: Electrically and Sunlight-Driven Actuator with Versatile Biomimetic Motions Based on Rolled Carbon Nanotube Bilayer Composite (Adv. Funct. Mater. 44/2017)


Inspired by the common flicking finger motion, Ying Hu, Jiaqin Liu, Wei Chen, and co-workers describe in article number 1704388 a novel soft jumping robot based on the rolled carbon nanotube/polymer bilayer actuator with the two ends serving as thumb and middle finger, respectively. Upon light irradiation, this soft robot can jump up, accompanied by somersaults in the air, due to the energy accumulation and instantaneous release.

Masthead: (Adv. Funct. Mater. 44/2017)


Contents: (Adv. Funct. Mater. 44/2017)


Syntheses and Energy Storage Applications of MxSy (M = Cu, Ag, Au) and Their Composites: Rechargeable Batteries and Supercapacitors


The development of novel materials to improve energy storage efficiencies is essential to satisfy ever-increasing energy demands. MxSy (M = Cu, Ag, Au) and their composites offer opportunities and enormous prospects in energy storage due to their extraordinary electrochemical properties, which promote promising energy storage characteristics in terms of stability, energy and power density, lifetime, etc. Recent developments of MxSy (M = Cu, Ag, Au) and their composites with various morphologies have received considerable attention. Multidimensional morphologies of MxSy (M = Cu, Ag, Au) and their composites have enriched charge-storage and electron-transport abilities. This review provides a detailed account of the synthetic strategies based on sulfur sources (i.e., inorganic sulfur sources, organosulfur sources, and other sulfur sources), which dictate the morphologies of nanosized MxSy (M = Cu, Ag, Au) and their composites. Notably, nanostructured silver sulfide can be prepared from the bulk to nanoscale. Moreover, the electrochemical applications of these materials for lithium-ion batteries, sodium-ion batteries, lithium-sulfur batteries, and supercapacitors are summarized. Finally, future perspectives on the development challenges and major opportunities for MxSy (M = Cu, Ag, Au) and their composites, which must be overcome to achieve further improvements in electrochemical performance are outlined. Recent developments and challenges of MxSy (M = Cu, Ag, Au) and their composites with a focus on synthetic methods and their electrochemical applications, including lithium-ion batteries, sodium-ion batteries, lithium-sulfur batteries, and supercapacitors have been reported. The relationships between their morphologies and electrochemical performances are comprehensively summarized and evaluations are given in this review.

Multifunctional Mo–N/C@MoS2 Electrocatalysts for HER, OER, ORR, and Zn–Air Batteries


Replacement of noble-metal platinum catalysts with cheaper, operationally stable, and highly efficient electrocatalysts holds huge potential for large-scale implementation of clean energy devices. Metal–organic frameworks (MOFs) and metal dichalcogenides (MDs) offer rich platforms for design of highly active electrocatalysts owing to their flexibility, ultrahigh surface area, hierarchical pore structures, and high catalytic activity. Herein, an advanced electrocatalyst based on a vertically aligned MoS2 nanosheet encapsulated Mo–N/C framework with interfacial Mo–N coupling centers is reported. The hybrid structure exhibits robust multifunctional electrocatalytic activity and stability toward the hydrogen evolution reaction, oxygen evolution reaction, and oxygen reduction reaction. Interestingly, it further displays high-performance of Zn–air batteries as a cathode electrocatalyst with a high power density of ≈196.4 mW cm−2 and a voltaic efficiency of ≈63 % at 5 mA cm−2, as well as excellent cycling stability even after 48 h at 25 mA cm−2. Such outstanding electrocatalytic properties stem from the synergistic effect of the distinct chemical composition, the unique three-phase active sites, and the hierarchical pore framework for fast mass transport. This work is expected to inspire the design of advanced and performance-oriented MOF/MD hybrid-based electrocatalysts for wider application in electrochemical energy devices. An advanced electrocatalyst is designed based on a vertically-aligned MoS2 nanosheet encapsulated Mo–N/C framework with Mo–N coupling centers at the interface. The hybrid electrocatalyst exhibits high multifunctional activity and stability toward the hydrogen evolution reaction, oxygen evolution reaction, and oxygen reduction reaction, as well as high Zn–air battery performance.

Dual-Targeting to Cancer Cells and M2 Macrophages via Biomimetic Delivery of Mannosylated Albumin Nanoparticles for Drug-Resistant Cancer Therapy


Multidrug resistance (MDR) is an issue that is not only related to cancer cells but also associated with the tumor microenvironments. MDR involves the complicated cancer cellular events and the crosstalk between cancer cells and their surroundings. Ideally, an effective system against MDR cancer should take dual action on both cancer cells and tumor microenvironments. The authors find that both the drug-resistant colon cancer cells and the protumor M2 macrophages highly express two nutrient transporters, i.e., secreted protein acidic and rich in cysteine (SPARC) and mannose receptors (MR). By targeting SPARC and MR, a system can act on both cancer cells and M2 macrophages. Herein the authors develop a mannosylated albumin nanoparticles with coencapsulation of different drugs, i.e., disulfiram/copper complex (DSF/Cu) and regorafenib (Rego). The results show that combination therapy of DSF/Cu and Rego efficiently inhibits the growth of drug-resistant colon tumor, and the combination has not been reported yet for use in anticancer treatment. The system significantly improves the treatment outcomes in the animal model bearing drug-resistant tumors. The therapeutic mechanisms involve enhanced apoptosis, upregulation of intracellular ROS, anti-angiogenesis, and tumor-associated macrophage “re-education.” This strategy is characterized by dual targeting to and the simultaneous action on cancer cells and M2 macrophages, with biomimetic codelivery of a novel drug combination. Multidrug resistance (MDR) is a complex of various events involving not only the cancer cells but also their surroundings (tumor microenvironments). The authors develop the “one stone two birds” strategy to overcome MDR by using a mannosylated albumin nanoparticulate codelivery system to dual-target the cancer cells and M2 macrophages, both of which overexpress mannose receptors and the albumin-binding protein—secreted protein acidic and rich in cysteine.

The Fusion of Imidazolium-Based Ionic Polymer and Carbon Nanotubes: One Type of New Heteroatom-Doped Carbon Precursors for High-Performance Lithium–Sulfur Batteries


Rational design of sulfur host materials with high electrical conductivity and strong polysulfides (PS) confinement is indispensable for high-performance lithium–sulfur (Li–S) batteries. This study presents one type of new polymer material based on main-chain imidazolium-based ionic polymer (ImIP) and carbon nanotubes (CNTs); the polymer composites can serve as a precursor of CNT/NPC-300, in which close coverage and seamless junction of CNTs by N-doped porous carbon (NPC) form a 3D conductive network. CNT/NPC-300 inherits and strengthens the advantages of both high electrical conductivity from CNTs and strong PS entrapping ability from NPC. Benefiting from the improved attributes, the CNT/NPC-300-57S electrode shows much higher reversible capacity, rate capability, and cycling stability than NPC-57S and CNTs-56S. The initial discharge capacity of 1065 mA h g−1 is achieved at 0.5 C with the capacity retention of 817 mA h g−1 over 300 cycles. Importantly, when counter bromide anion in the composite of CNTs and ImIP is metathesized to bis(trifluoromethane sulfonimide), heteroatom sulfur is cooperatively incorporated into the carbon hosts, and the surface area is increased with the promotion of micropore formation, thus further improving electrochemical performance. This provides a new method for optimizing porous properties and dopant components of the cathode materials in Li–S batteries. The integration of main-chain imidazolium-based ionic polymer and carbon nanotubes (CNTs) generates one type of new 3D conductive carbon material for high-performance Li–S batteries. The close coverage and seamless junction of CNTs by N-doped porous carbon (NPC) result in inheritance and improvement of high electrical conductivity from CNTs and strong polysulfides entrapping ability from NPC.

The Effects of Crystallinity on Charge Transport and the Structure of Sequentially Processed F4TCNQ-Doped Conjugated Polymer Films


The properties of molecularly doped films of conjugated polymers are explored as the crystallinity of the polymer is systematically varied. Solution sequential processing (SqP) was used to introduce 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) into poly(3-hexylthiophene-2,5-diyl) (P3HT) while preserving the pristine polymer's degree of crystallinity. X-ray data suggest that F4TCNQ anions reside primarily in the amorphous regions of the film as well as in the P3HT lamellae between the side chains, but do not π-stack within the polymer crystallites. Optical spectroscopy shows that the polaron absorption redshifts with increasing polymer crystallinity and increases in cross section. Theoretical modeling suggests that the polaron spectrum is inhomogeneously broadened by the presence of the anions, which reside on average 6–8 Å from the polymer backbone. Electrical measurements show that the conductivity of P3HT films doped by F4TCNQ via SqP can be improved by increasing the polymer crystallinity. AC magnetic field Hall measurements show that the increased conductivity results from improved mobility of the carriers with increasing crystallinity, reaching over 0.1 cm2 V−1 s−1 in the most crystalline P3HT samples. Temperature-dependent conductivity measurements show that polaron mobility in SqP-doped P3HT is still dominated by hopping transport, but that more crystalline samples are on the edge of a transition to diffusive transport at room temperature. This study sequentially dopes conjugated polymer films with controlled crystallinity, finding that dopants do not π-stack with the polymer chains. The most crystalline films show the highest carrier mobilities and a redshifted absorption with increased cross section due to enhanced polaron delocalization.

Thermoelectric Polymer Aerogels for Pressure–Temperature Sensing Applications


The evolution of the society is characterized by an increasing flow of information from things to the internet. Sensors have become the cornerstone of the internet-of-everything as they track various parameters in the society and send them to the cloud for analysis, forecast, or learning. With the many parameters to sense, sensors are becoming complex and difficult to manufacture. To reduce the complexity of manufacturing, one can instead create advanced functional materials that react to multiple stimuli. To this end, conducting polymer aerogels are promising materials as they combine elasticity and sensitivity to pressure and temperature. However, the challenge is to read independently pressure and temperature output signals without cross-talk. Here, a strategy to fully decouple temperature and pressure reading in a dual-parameter sensor based on thermoelectric polymer aerogels is demonstrated. It is found that aerogels made of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) can display properties of semiconductors lying at the transition between insulator and semimetal upon exposure to high boiling point polar solvents, such as dimethylsulfoxide (DMSO). Importantly, because of the temperature-independent charge transport observed for DMSO-treated PEDOT-based aerogel, a decoupled pressure and temperature sensing can be achieved without cross-talk in the dual-parameter sensor devices. A dual-parameter sensor based on thermoelectric polymer aerogel with fully decoupled temperature and pressure sensing capability is successfully developed and characterized. This is achieved by finely tuning the transport properties of the conducting aerogels with exposure to the vapor of high boiling point polar solvents, such as dimethyl sulfoxide (DMSO). Pressure sensitivity is also improved by DMSO treatment.

Photo-Induced Charge-Variable Conjugated Polyelectrolyte Brushes Encapsulating Upconversion Nanoparticles for Promoted siRNA Release and Collaborative Photodynamic Therapy under NIR Light Irradiation


Combination of photodynamic therapy (PDT) with small interfering RNA (siRNA) therapy has become a major strategy in cancer treatment for enhancing anticancer efficacy. However, developing nanoplatform that can promote siRNA release and collaborate with efficient PDT under NIR light irradiation is still a big challenge. Photo-induced charge-variable conjugated polyelectrolyte brushes encapsulating upconversion nanoparticles (UCNP@CCPEB) as an efficient nanoplatform are reported. Cationic conjugated polyelectrolyte brush (CCPEB) is synthesized through quaternary ammoniation of N-functionalized polyfluorene brush by photodegradable 2-nitrobenzyl-2-bromoacetate. CCPEB with abundant positive charges and intrinsic photosensitizer (PS) performance is good for integrating siRNA carrier and PS into one molecule. The obtained CCPEB next encapsulates upconversion nanoparticle for realizing its NIR light excitation. Agarose gel electrophoresis experiments show that UCNP@CCPEB present good stability and excellent siRNA-loading capacity (1 mol UCNP@CCPEB to at least 32.5 mol siRNA). Under 980 nm light irradiation, UCNP@CCPEB exhibit efficient single oxygen production for PDT. Concurrently, the photoresponsive cationic side-chain of CCPEB turns into zwitterionic chain and thus accelerates its siRNA release to 80%. In vitro and in vivo experiments show that the successful A549 tumor suppression is achieved by UCNP@CCPEB/siPlk1 complex under 980 irradiation. It is envisioned that UCNP@CCPEB can serve as an efficient platform for combining various phototherapies together. Photo-induced charge-variable conjugated polyelectrolyte brushes encapsulating upconversion nanoparticle (UCNP@CCPEB) is fabricated for promoted small interfering RNA (siRNA) release and collaborative photodynamic therapy under NIR light irradiation. UCNP@CCPEB with good stability and excellent siRNA-loading capacity exhibit good 1O2 production and promote siRNA release under 980 nm irradiation which induces highly effective collaborative tumor therapy in vitro and in vivo.

Electrically and Sunlight-Driven Actuator with Versatile Biomimetic Motions Based on Rolled Carbon Nanotube Bilayer Composite


Designing multistimuli responsive soft actuators which can mimic advanced and sophisticated biological movements through simple configuration is highly demanded for the biomimetic robotics application. Here, inspired by the human's flick finger behavior which can release large force output, a soft jumping robot mimicking the gymnast's somersault is designed based on the rolled carbon nanotube/polymer bilayer composite actuator. This new type of rolled bilayer actuator with tubular shape is fabricated and shows electrically and sunlight-induced actuation with remarkable performances including ultralarge deformation from tubular to flat (angel change >200° or curvature >2 cm−1), fast response (<5 s), and low actuation voltage (≤10 V). Besides jumping, the uniquely reversible rolling–unrolling actuation can lead to other smart soft robots with versatile complex biomimetic motions, including light-induced tumbler with cyclic wobbling, electrically/light-induced crawling-type walking robots and grippers, electrically induced mouth movement, and ambient-sunlight-induced blooming of a biomimetic flower. These results open the way for using one simple type of actuator structure for the construction of various soft robots and devices toward practical biomimetic applications. Electrically and sunlight-driven carbon nanotube bilayer actuators with tubular structure are fabricated, exhibiting fast and large deformation from tubular to almost flat. Inspired by flicking finger motion, this tubular actuator is used to construct a jumping robot, showing somersaults in the air. Moreover, various soft biomimetic devices including a crawling-type robot, a mechanical gripper, and sunlight-induced flower are also constructed.

Direct Laser Writing of Superhydrophobic PDMS Elastomers for Controllable Manipulation via Marangoni Effect


Direct light-to-work conversion enables manipulating remote devices in a contactless, controllable, and continuous manner. Although some pioneering works have already proven the feasibility of controlling devices through light-irradiation-induced surface tension gradients, challenges remain, including the flexible integration of efficient photothermal materials, multifunctional structure design, and fluidic drag reduction. This paper reports a facile one-step method for preparing light-driven floating devices with functional surfaces for both light absorption and drag reduction. The direct laser writing technique is employed for both arbitrary patterning and surface modification. By integrating the functional layer at the desired position or by designing asymmetric structures, three typical light-driven floating devices with fast linear or rotational motions are demonstrated. Furthermore, these devices can be driven by a variety of light sources including sunlight, a filament lamp, or laser beams. The approach provides a simple, green, and cost-effective strategy for building functional floating devices and smart light-driven actuators. A facile fabrication of superhydrophobic polydimethylsiloxane (PDMS) elastomers structures that permit controllable manipulation via Marangoni effectthat permit controllable manipulation via Marangoni effect is reported here. Direct laser writing technology is employed to apply a light absorbing and superhydrophobic layer on the PDMS surface. By integrating the functional layer at the desired position or by designing asymmetric structures, typical light-driven devices with fast linear or rotational motions are demonstrated.

Bioinspired Adhesive Hydrogels Tackified by Nucleobases


Bioinspired strategies for designing hydrogels with excellent adhesive performance have drawn much attention in biomedical applications. Here, bioinspired adhesive hydrogels tackified by independent nucleobase (adenine, thymine, guanine, cytosine, and uracil) from DNA and RNA are successfully explored. The nucleobase-tackified hydrogels exhibit an excellent adhesive behavior for not only various solid substrates (polytetrafluoroethylene, plastics, rubbers, glasses, metals, and woods) but also biological tissues consisting of heart, liver, spleen, lung, kidney, bone, and muscle. The maximum adhesion strength of A-, T-, G-, C-, and U-tackified hydrogels on the aluminum alloy surface is 780, 166, 250, 227, and 433 N m−1, respectively, superior to that of pure PAAm hydrogels (40 N m−1) after adhesive time of 10 min. It is anticipated that bioinspired hydrogels will play a significant role in the applications of wound dressing, medical electrodes, tissue adhesives, and portable equipment. Moreover, the bioinspired nucleobase-tackified strategy would open a novel avenue for designing the next generation of soft and adhesive materials. In the current investigation, bioinspired adhesive hydrogels tackified by independent nucleobase (adenine, thymine, guanine, cytosine, and uracil) from DNA and RNA are successfully explored. The nucleobase-tackified hydrogels exhibit an excellent adhesive behavior for various solid substrates and biological tissues. It is anticipated that the bioinspired nucleobase-tackified strategy will open a novel avenue for designing the next generation of soft materials with adhesive behavior.

Eradication of Multidrug-Resistant Staphylococcal Infections by Light-Activatable Micellar Nanocarriers in a Murine Model


Bacterial infections are mostly due to bacteria in their biofilm mode-of-growth, making them recalcitrant to antibiotic penetration. In addition, the number of bacterial strains intrinsically resistant to available antibiotics is alarmingly growing. This study reports that micellar nanocarriers with a poly(ethylene glycol) shell fully penetrate staphylococcal biofilms due to their biological invisibility. However, when the shell is complemented with poly(β-amino ester), these mixed-shell micelles become positively charged in the low pH environment of a biofilm, allowing not only their penetration but also their accumulation in biofilms without being washed out, as do single-shell micelles lacking the pH-adaptive feature. Accordingly, bacterial killing of multidrug resistant staphylococcal biofilms exposed to protoporphyrin IX-loaded mixed-shell micelles and after light-activation is superior compared with single-shell micelles. Subcutaneous infections in mice, induced with vancomycin-resistant, bioluminescent staphylococci can be eradicated by daily injection of photoactivatable protoporphyrin IX-loaded, mixed-shell micelles in the bloodstream and light-activation at the infected site. Micelles, which are not degraded by bacterial enzymes in the biofilm, are degraded in the liver and spleen and cleared from the body through the kidneys. Thus, adaptive micellar nanocarriers loaded with light-activatable antimicrobials constitute a much-needed alternative to current antibiotic therapies. Photodynamic treatment with protoporphyrin IX-loaded micelles is successful in eradicating a subcutaneous, multidrug-resistant infection in mice, while unused micelles are demonstrated to be cleared from the blood circuation.

Super Bulk and Interfacial Toughness of Physically Crosslinked Double-Network Hydrogels


Conventional design wisdom prevents both bulk and interfacial toughness to be presented in the same hydrogel, because the bulk properties of hydrogels are usually different from the interfacial properties of the same hydrogels on solid surfaces. Here, a fully-physically-linked agar (the first network)/poly(N-hydroxyethyl acrylamide) (pHEAA, the second network), where both networks are physically crosslinked via hydrogen bonds, is designed and synthesized. Bulk agar/pHEAA hydrogels exhibit high mechanical properties (2.6 MPa tensile stress, 8.0 tensile strain, 8000 J m−2 tearing energy, 1.62 MJ m−3 energy dissipation), high self-recovery without any external stimuli (62%/30% toughness/stiffness recovery), and self-healing property. More impressively, without any surface modification, agar/pHEAA hydrogels can be easily and physically anchored onto different nonporous solid substrates of glass, titanium, aluminum, and ceramics to produce superadhesive hydrogel–solid interfaces (i.e., high interfacial toughness of 2000–7000 J m−2). Comparison of as-prepared and swollen gels in water and hydrogen-bond-breaking solvents reveals that strong bulk toughness provides a structural basis for strong interfacial toughness, and both high toughness mainly stem from cooperative hydrogen bonds between and within two networks and between two networks and solid substrates. This work demonstrates a new gel system to achieve superhigh bulk and interfacial toughness on nonporous solid surfaces. A newly developed agar/poly(N-hydroxyethyl acrylamide) double network hydrogel enables mechanically strong and self-recovery properties. The resulting hydrogels exhibit superior strength and toughness both in bulk and at the interface, making them promising hydrogels for applications requiring both toughness and adhesive properties.

Metal-Ion (Fe, V, Co, and Ni)-Doped MnO2 Ultrathin Nanosheets Supported on Carbon Fiber Paper for the Oxygen Evolution Reaction


Manganese dioxides (MnO2) are considered one of the most attractive materials as an oxygen evolution reaction (OER) electrode due to its low cost, natural abundance, easy synthesis, and environmental friendliness. Here, metal-ion (Fe, V, Co, and Ni)-doped MnO2 ultrathin nanosheets electrodeposited on carbon fiber paper (CFP) are fabricated using a facile anodic co-electrodeposition method. A high density of nanoclusters is observed on the surface of the carbon fibers consisting of doped MnO2 ultrathin nanosheets with an approximate thickness of 5 nm. It is confirmed that the metal ions (Fe, V, Co, and Ni) are doped into MnO2, improving the conductivity of MnO2. The doped MnO2 ultrathin nanosheet/CFP and the IrO2/CFP composite electrodes for OER achieve a low overpotential of 390 and 245 mV to reach 10 mA cm−2 in 1 m KOH, respectively. The potential of the doped composite electrode for long-term OER at a constant current density of 20 mA cm−2 is much lower than that of the pure MnO2 composite electrode. Metal-ion (Fe, V, Co, and Ni)-doped MnO2 ultrathin nanosheets with an approximate thickness of 5 nm are formed on the carbon fibers using a facile anodic co-electrodeposition method. The doping of metal ions and ultrathin nanostructure play an important role in improving the electrocatalytic activities and stabilities of the composite electrode for the oxygen evolution reaction.

Ice-Templated Protein Nanoridges Induce Bone Tissue Formation


Little is known about the role of biocompatible protein nanoridges in directing stem cell fate and tissue regeneration due to the difficulty in forming protein nanoridges. Here an ice-templating approach is proposed to produce semi-parallel pure silk protein nanoridges. The key to this approach is that water droplets formed in the protein films are frozen into ice crystals (removed later by sublimation), pushing the surrounding protein molecules to be assembled into nanoridges. Unlike the flat protein films, the unique protein nanoridges can induce the differentiation of human mesenchymal stem cells (MSCs) into osteoblasts without any additional inducers, as well as the formation of bone tissue in a subcutaneous rat model even when not seeded with MSCs. Moreover, the nanoridged films induce less inflammatory infiltration than the flat films in vivo. This work indicates that decorating biomaterials surfaces with protein nanoridges can enhance bone tissue formation in bone repair. Semi-parallel nanoridges made of silk protein can induce the differentiation of human mesenchymal stem cells into osteoblasts without any additional inducers and further induce the formation of bone tissue in a rat model.

pH-Sensitive Dissociable Nanoscale Coordination Polymers with Drug Loading for Synergistically Enhanced Chemoradiotherapy


Although various types of radiosensitizers based on nanoparticles are explored to enhance radiotherapy via different mechanisms, nanoscale radiosensitizers with full biodegradability, sensitive responsiveness to the tumor microenvironment, as well as the ability to greatly amplify radiation-induced tumor destruction are still demanded. Herein, this study designs nanoscale coordination polymers (NCPs) based on acidic sensitive linker and high Z number element hafnium (Hf) ions. Chloro(triphenylphosphine)gold(I) (TPPGC), a chemotherapeutic drug, is successfully loaded into those NCPs after they are coated with polyethylene glycol (PEG). Owing to the acid-triggered cleavage of the organic linker, such formed NCP-PEG/TPPGC nanoparticles would be dissociated under reduced pH within the tumor, leading to the release of TPPGC to induce mitochondrial damage and arrest the cell cycle of tumor cells into the radiosensitive phase (G1). Meanwhile, Hf ions are able to act as radiosensitizers by absorbing X-ray and depositing radiation energy within tumors. With efficient tumor accumulation after intravenous injection, NCP-PEG/TPPGC offers remarkable synergistic therapeutic outcome in chemoradiotherapy without appreciable toxic side effect. This work thus presents a biodegradable nano-radiosensitizer with in vivo tumor-specific decomposition/drug release profiles and great efficacy in chemoradiotherapy of cancer. In this work, a new type nanoscale coordination polymer (NCP) is designed based on a pH-sensitive linker and high Z element hafnium (Hf) ions. After loading with a chemotherapy drug, Chloro(triphenylphosphine)gold(I), such drug-loaded NCP nanoparticles can be degraded to release chemotherapeutics under reduced pH within the tumor, and in the meanwhile act as a radiosensitizer to achieve synergistically enhanced chemoradiotherapy.

A Specific Groove Pattern Can Effectively Induce Osteoblast Differentiation


Little is known about the principles of surface structure design for orthopedic and dental implants. To find topographical groove patterns that could enhance osteoblast differentiation according to cell type, groove patterns are fabricated with ridges (0.35−7 µm) and grooves (0.65−6 µm) of various widths and explored their mechanisms in improving osteoblast differentiation. This study finds that a groove pattern enhancing osteoblast differentiation is associated with the ability of the cell to extend its length and that it is able to overcome the inhibition of osteoblast differentiation that takes place under inflammatory conditions. The groove pattern suppresses the generation of reactive oxygen species, a reaction that is increased in inflammatory conditions. It also modulates the expression of osteogenic factors according to differentiation time. Importantly, specific groove patterns AZ-2 and AZ-4, with ridge width of 2 µm and groove width of 2 or 4 µm, respectively, effectively promote bone regeneration in critical-sized calvarial defects without additional factors. This knowledge of groove patterns can be applied to the development of orthopedic and dental devices. A groove pattern enhancing osteoblast differentiation is associated with the ability of the cell to extend its length and that it is able to overcome the inhibition of osteoblast differentiation and effectively promotes bone regeneration in calvarial defects. This knowledge of groove patterns can be applied to the development of orthopedic and dental devices.

Ordered Superparticles with an Enhanced Photoelectric Effect by Sub-Nanometer Interparticle Distance


As the development in self-assembly of nanoparticles, a main question is directed to whether the supercrystalline structure can facilitate generation of collective properties, such as coupling between adjacent nanocrystals or delocalization of exciton to achieve band-like electronic transport in a 3D assembly. The nanocrystal surfaces are generally passivated by insulating organic ligands, which block electronic communication of neighboring building blocks in nanoparticle assemblies. Ligand removal or exchange is an operable strategy for promoting electron transfer, but usually changes the surface states, resulting in performance alteration or uncontrollable aggregation. Here, 3D, supercompact superparticles with well-defined superlattice domains through a thermally controlled emulsion-based self-assembly method is fabricated. The interparticle spacing in the superparticles shrinks to ≈0.3 nm because organic ligands lie prone on the nanoparticle surface, which are sufficient to overcome the electron transfer barrier. The ordered and compressed superstructures promote coupling and electronic energy transfer between CdSSe quantum dots (QDs). Therefore, the acquired QD superparticles exhibit different optical properties and enhanced photoelectric activity compared to individual QDs. Ordered quantum dot (QD) superparticles with a compressed supercrystalline domain are fabricated through a thermally controlled emulsification process. The interparticle distances are shrunk down to the lattice constant of the QDs by prostrating ligands, which promotes coupling and electronic energy transfer between QDs. The acquired QD superparticles, exhibiting unique optical and photoelectric properties, can be applied in photodegradation and solar-driven photocatalytic processes.

Multifunctional Glyco-Nanofibers: siRNA Induced Supermolecular Assembly for Codelivery In Vivo


Targeted codelivery and controlled release of drug/siRNA (small interfering RNA) in a safe and effective vehicle hold great promises for overcoming drug resistance and optimal efficacy in cancer treatment; however, rational design and preparation of such vehicles remain a critical challenge. Thus, glyco-nanofibers (GNFs) are fabricated via supermolecular assembly of polyanionic siRNA and cationic vesicles to simultaneously deliver siRNA and doxorubicin hydrochloride (DOX) in vitro and in vivo. The vesicles are created through self-assembly of a positively charged amphiphilic lactose derivative featuring a lactose moiety and a ferrocenium unit on either end of the molecule. The GNFs display excellent biocompatibility, enhanced cell-penetrating ability, and hepatoma targetability. The high transport efficiency of siRNA, effective gene silencing ability, and enhanced cytotoxicity to HepG2 cells of GNFs loaded with DOX are observed in vitro. Furthermore, in vivo experiments show reduced systemic toxicity and enhanced therapeutic efficacy of DOX to both HepG2 and HepG2/ADR subcutaneous tumor-bearing nude mice. This work proves the electrostatic self-assembly between cationic carbohydrates and polyanionic siRNA to be a convenient and effective strategy to fabricate a single vehicle for safe and effective codelivery of drug/siRNA, which can be used to combine chemo- and gene-therapy against cancers and other diseases. Glyco-nanofibers (GNFs) are synthesized via supermolecular assembly of polyanionic small interfering RNA (siRNA) and cationic vesicles assembled by an amphiphilic lactose derivative capped with cationic ferrocenium. The obtained GNFs display excellent biocompatibility, enhanced cell-penetrating ability, and hepatoma targetability, enabling highly efficient codelivery of drug/siRNA to reduc[...]

Selective Dispersion of Large-Diameter Semiconducting Carbon Nanotubes by Functionalized Conjugated Dendritic Oligothiophenes for Use in Printed Thin Film Transistors


Selective dispersion of semiconducting single walled carbon nanotubes (s-SWCNTs) by conjugated polymer wrapping is recognized as the most promising scalable method for s-SWCNT separation. Despite a number of linear conjugated polymers being reported for use in s-SWCNT separation, these linear polymers suffer batch-to-batch variation for their undefined molecular structure. Here, it is reported that conjugated dendritic oligothiophenes with multiple diketopyrrolopyrrole groups at the periphery have the capability of selectively dispersing large diameter s-SWCNTs with high dispersion efficiency and certain chiral selectivity. Printed top-gated thin film transistors using the dendrimer sorted s-SWCNTs show high charge carrier mobility of up to 57 cm2 V−1 s−1 and on/off ratios of ≈106 with high reproducibility, which is ascribed to the defined and monodispersed molecular structure of dendrimers. Moreover, owing to the multiple peripheral anchoring groups of these dendritic molecules, these dendrimer-s-SWCNT dispersions display excellent stability. The current work proves that dendritic molecules are excellent dispersion reagents for s-SWCNT separation. Diketopyrrolopyrrole-functionalized conjugated dendrons and dendrimers with 3D hyperbranched structure are a new class of materials for use in single walled carbon nanotubes (SWCNT) selective sorting. It is reported that the devices based on these conjugated dendrimer wrapped s-SWCNT can achieve high charge carrier mobility of up to 57 cm2 V−1 s−1, and with high on/off ratios of ≈106.