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Journal of Nanomaterials



The latest articles from Hindawi



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Surface Modification of Sodium Montmorillonite Nanoclay by Plasma Polymerization and Its Effect on the Properties of Polystyrene Nanocomposites

Mon, 23 Apr 2018 00:00:00 +0000

Sodium montmorillonite nanoclay (Na+-MMT) was modified by plasma polymerization with methyl methacrylate (MMA) and styrene (St) as monomers and was denominated as Na+-MMT/MMA and Na+-MMT/St, respectively. This plasma modified nanoclay was used as reinforcement for polystyrene (PS) nanocomposites that were prepared by melt mixing. Pristine and modified Na+-MMT nanoclay were analyzed by the dispersion in various solvents, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The results confirmed a change in hydrophilicity of the modified Na+-MMT, as well as the presence of a polymeric material over its surface. The pristine PS/Na+-MMT and modified PS/Na+-MMT/MMA and PS/Na+-MMT/St nanocomposites were studied with X-ray diffraction (XRD), differential scanning calorimetry (DSC), and TGA, as well as mechanical properties. It was found that the PS/Na+-MMT/St nanocomposites presented better thermal properties and an improvement in Young’s modulus (YM) in compared to PS/Na+-MMT/MMA nanocomposites.



Boron-Doped Carbon Nano-/Microballs from Orthoboric Acid-Starch: Preparation, Characterization, and Lithium Ion Storage Properties

Mon, 23 Apr 2018 00:00:00 +0000

A boron-doped carbon nano-/microballs (BC) was successfully obtained via a two-step procedure including hydrothermal reaction (180°C) and carbonization (800°C) with cheap starch and H3BO3 as the carbon and boron source. As a new kind of boron-doped carbon, BC contained 2.03 at% B-content and presented the morphology as almost perfect nano-/microballs with different sizes ranging from 500 nm to 5 μm. Besides that, due to the electron deficient boron, BC was explored as anode material and presented good lithium storage performance. At a current density of 0.2 C, the first reversible specific discharge capacity of BC electrode reached as high as 964.2 mAh g–1 and kept at 699 mAh g–1 till the 11th cycle. BC also exhibited good cycle ability with a specific capacity of 356 mAh g–1 after 79 cycles at a current density of 0.5 C. This work proved to be an effective approach for boron-doped carbon nanostructures which has potential usage for lithium storage material.



Covalent Surface Functionalization of Boron Nitride Nanotubes Fabricated with Diazonium Salt

Wed, 18 Apr 2018 00:00:00 +0000

The chemical inertness and poor wetting properties of boron nitride nanotubes (BNNTs) hindered their applications. In this work, BNNTs have been functionalized with aniline groups by reacting with diazonium salt and the graft content of aniline component was calculated as high as 71.4 wt.%. The chemical structure, composition, and morphology of functionalized BNNTs were carefully characterized to illustrate the modification. The anilinocarbocation generated by decomposition of diazonium salt reacted not only with NH2 sites, but also with B-OH sites on the surface of BNNTs. Meanwhile, the reaction applied a hot strong acid environment, which would help to open parts of B-N bonds to produce more reactive sites and enrich the functional groups grafted on the surface of BNNTs. Consequently, the functionalized BNNTs exhibited significantly improved dispersion stability in chloroform compared with pristine BNNTs. Amino surface functionalization of BNNTs offered more possibilities for surface chemical design of boron nitride and its practical application.



Electrochemical Determination of Paracetamol Using Fe3O4/Reduced Graphene-Oxide-Based Electrode

Tue, 17 Apr 2018 00:00:00 +0000

The synthesis of magnetic iron oxide/reduced graphene oxide (Fe3O4/rGO) and its application to the electrochemical determination of paracetamol using Fe3O4/rGO modified electrode were demonstrated. The obtained materials were characterized by means of X-ray diffraction (XRD), nitrogen adsorption/desorption isotherms, X-ray photoelectron spectroscopy (XPS), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FTIR), and magnetic measurement. The results showed that Fe3O4/rGO composite exhibited high specific surface area, and its morphology consists of very fine spherical particles of Fe3O4 in nanoscales. Fe3O4/rGO was used as an electrode modifier for the determination of paracetamol by differential pulse-anodic stripping voltammetry (DP-ASV). The preparation of Fe3O4/rGO-based electrode and some factors affecting voltammetric responses were investigated. The results showed that Fe3O4/rGO is a potential electrode modifier for paracetamol detection by DP-ASV with a low limit of detection. The interfering effect of uric acid, ascorbic acid, and dopamine on the current response of paracetamol has been reported. The repeatability, reproducibility, linear range, and limit of detection were also addressed. The proposed method could be applied to the real samples with satisfactory results.



Surface Disinfections: Present and Future

Mon, 16 Apr 2018 09:19:02 +0000

The propagation of antibiotic resistance increases the chances of major infections for patients during hospitalization and the spread of health related diseases. Therefore finding new and effective solutions to prevent the proliferation of pathogenic microorganisms is critical, in order to protect hospital environment, such as the surfaces of biomedical devices. Modern nanotechnology has proven to be an effective countermeasure to tackle the threat of infections. On this note, recent scientific breakthroughs have demonstrated that antimicrobial nanomaterials are effective in preventing pathogens from developing resistance. Despite the ability to destroy a great deal of bacteria and control the outbreak of infections, nanomaterials present many other advantages. Moreover, it is unlikely for nanomaterials to develop resistance due to their multiple and simultaneous bactericidal mechanisms. In recent years, science has explored more complex antimicrobial coatings and nanomaterials based on graphene have shown great potential in antibacterial treatment. The purpose of this article is to deepen the discussion on the threat of infections related to surface disinfection and to assess the state of the art and potential solutions, with specific focus on disinfection procedures using nanomaterials.



Electronic Pulses from Pulsed Field Emission of CNT Cathodes

Mon, 16 Apr 2018 00:00:00 +0000

We presented a demonstration of infrared laser irradiated field emission electronic pulse based on carbon nanotube (CNT) cathodes. Electronic pulses greatly depended on pulsed infrared laser and were almost synchronous with laser pulses. We have designed a pulsed field emission cathode based on CNTs and investigated correlation between electronic pulse and laser pulse, acquiring the shortest width of electronic pulses about 50 ms and turn-on field less than 0.14 V/μm. Besides, we have studied the thermal effect on the pulsed field emission of CNT cathodes caused by laser heating. Interestingly, the thermal effect has caused an enhancement of emission current but resulted in a waveform distortion on short electronic pulses. The application of laser pulses on CNT cathodes would extend conventional electron sources to a pulsed electron source and offered a possibility of pulsed field emission. These results were encouraging us to prepare further studies of ultrafast electronic pulses for high-frequency electron sources.



Preparation and Characterization of Nanoporous Sodium Carboxymethyl Cellulose Hydrogel Beads

Sun, 15 Apr 2018 00:00:00 +0000

A series of nanoporous sodium carboxymethyl cellulose (NaCMC) hydrogel beads were prepared using FeCl3 ionic crosslinker by changing polymer and crosslinker percentages (%). Characteristics of the hydrogels were investigated by gel content, swelling test, degradation test, Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR), Scanning Electron Microscope/Energy Dispersive X-ray Analysis (SEM/EDX), and Atomic Force Microscopy (AFM). Swelling experiments were studied by changing time, temperature, and pH. The swelling percentage (%) regularly decreased with increasing the amounts of polymer and crosslinker, in contrast with gel content results. NaCMC hydrogels were found to be sensitive to pH variations. The degradation test showed that hydrogels had good stability and their degradation period varied from 30 to 36 days. According to SEM analysis, NaCMC hydrogels had mostly nanoporous structure. The average granule and pore sizes of the least swollen NaCMC-12 hydrogel were found to be  nm and  nm. The elemental compositions of hydrogels were determined with EDX. The minimum average surface roughness () and root mean square roughness () parameters were found to be  nm and  nm for NaCMC-12 hydrogels by AFM. Due to their good morphologies, stabilities, and swelling behaviors, NaCMC hydrogels can be suitable for biomaterial applications.



Efficient Delivery of Therapeutic siRNA with Nanoparticles Induces Apoptosis in Prostate Cancer Cells

Sun, 15 Apr 2018 00:00:00 +0000

Gene silencing using small interfering RNA (siRNA) has shown significant potential in the treatment of cancer. Herein, we developed the lipid-polymer hybrid nanoparticles (PEG-LP/siRNA NPs) for siRNA delivery. The cell viability assay indicated that PEG-LP/siRNA NPs had negligible cell cytotoxicity. The cellular uptake efficiency of PEG-LP/siRNA NPs measured by flow cytometry was up to 94.4%. Importantly, in vitro gene knockdown experiments demonstrated that PEG-LP/siJnk-1 NPs could significantly downregulate the expression of Jnk-1 at both the mRNA and protein levels in DU145 cells. Gene knockdown of Jnk-1 could activate apoptosis in part by the mitochondrial pathway in DU145 cells. Moreover, the PEG-LP/siJnk-1 NPs could inhibit tumor growth in a DU145 xenograft murine model, suggesting its therapeutic promise in cancer therapy.



Fabrication and Investigation of 26NCA Films Exhibiting Tunable Blue Fluorescence Based on LVPVDM

Sun, 15 Apr 2018 00:00:00 +0000

The development of metallic fluorescent materials, π-conjugated molecular systems with high-efficiency generation of blue light, and new ways to fabricate metallic/organic luminescent materials plays an important role in the fields of large-scale flat panel displays and soft optical devices. Herein, different fluorescent films have been fabricated by low vacuum physical vapor deposition method (LVPVDM), including single/two-component films. Compared with raw materials, all films show novel fluorescent behaviors, which means potential application in the fields of multicolor luminescence and thickness-optical response sensors. Meanwhile, the speculation is demonstrated in many ways that the maximum emission () at 406 nm and 426 nm of pristine 2,6-naphthalenedicarboxylic acid (26NCA) is caused by the crystal structure, while the shoulder peak at 445 nm is caused by the self-structure of 26NCA molecule. Significantly, this speculation may afford new insight into the relationship between not only crystal structure and luminescence, but also molecular self-structure and luminescence, which means a new strategy to tune the fluorescent behaviors based on molecular self-structure by LVPVDM. Therefore, this work provides a facile way to fabricate single/multicomponent metallic/organic film materials with tunable blue luminescence properties, which have potential application in the fields of next generation of photofunctional materials.



Enhanced Electrical Insulation and Heat Transfer Performance of Vegetable Oil Based Nanofluids

Sun, 15 Apr 2018 00:00:00 +0000

Nanoparticles enhance the electrical insulation and thermal properties of vegetable oil, and such improvements are desirable for its application as an alternative to traditional insulating oil for power transformers. However, the traditional method of insulating nanofluids typically achieves high electrical insulation but low thermal conductivity. This work reports an environmentally friendly vegetable oil using exfoliated hexagonal boron nitride (h-BN) showing high thermal conductivity and high electrical insulation. Stable nanofluids were prepared by liquid exfoliation of h-BN in isopropyl alcohol. With 0.1 vol.% of the nano-oil, the AC breakdown voltage increased by 18% at 25°C and 15% at 90°C. Both the positive and negative lightning impulse breakdown voltages of the nano-oil were also enhanced compared with those of the pure oil. Moreover, the thermal conductivity of the nano-oil increased by 11.9% at 25°C and 14% at 90°C. Given its high thermal conductivity, the nano-oil exhibited faster heating and cooling effects than the pure oil. Nano-oils with an electric field (either DC or AC) displayed a faster thermal response than that without an electric field. The reason is that h-BN is oriented under the electric field and formed a thermal network to increase the heat transfer.



Effects of Nanoimprinted Structures on the Performance of Organic Solar Cells

Wed, 11 Apr 2018 06:26:28 +0000

The effect of nanoimprinted structures on the performance of organic bulk heterojunction solar cells was investigated. The nanostructures were formed over the active layer employing the soft lithographic technique. The measured incident photon-to-current efficiency revealed that the nanostructured morphology over the active layer can efficiently enhance both light harvesting and charge carrier collection due to improvement of the absorption of incident light and the buried nanostructured cathode, respectively. The devices prepared with the imprinted nanostructures exhibited significantly higher power conversion efficiencies as compared to those of the control cells.



Nano-HNS Particles: Mechanochemical Preparation and Properties Investigation

Wed, 11 Apr 2018 00:00:00 +0000

Nano-2,2′,4,4′,6,6′-hexanitrostilbene (HNS) particles were successfully prepared by a mechanochemical (i.e., high energy milling) process without an organic solvent, which can be viewed as a green technology. The particle size, morphology, specific area, crystal phase, thermal decomposition properties, impact sensitivity, and short duration shock initiation sensitivity were characterized and tested. The diameter of milling HNS is about 89.2 nm with a narrow size distribution and without agglomeration of particles. The formation mechanism of nano-HNS can be viewed as the transformation from thin HNS sheets with a one-dimensional nanostructure to three-dimensional nanoparticles. The nano-HNS particles present a much higher and lower impact sensitivity than purified HNS, revealing the outstanding safety properties. From the results of the short duration shock initiation sensitivity, 50% and 100% initiation voltages are decreased compared with those of HNS-IV, indicating the higher initiation sensitivity.



Vibration Analysis of Bilayered Graphene Sheets for Building Materials in Thermal Environments Based on the Element-Free Method

Wed, 11 Apr 2018 00:00:00 +0000

Graphene sheets are widely applied due to their unique and highly valuable properties, such as energy conservation materials in buildings. In this paper, we investigate the vibration behavior of double layer graphene sheets (DLGSs) in thermal environments which helps probe into the mechanism of energy conservation of graphene sheets in building materials. The nonlocal elastic theory and classical plate theory (CLPT) are used to derive the governing equations. The element-free method is employed to analyze the vibration behaviors of DLGSs embedded in an elastic medium. The accuracy of the solutions in this study is demonstrated by comparison with published results in the literature. Furthermore, a number of numerical results are presented to investigate the effects of various parameters (boundary conditions, nonlocal parameter, aspect ratio, side length, elastic foundation parameter, and temperature) on the frequency of DLGSs.



Sputtered PdO Decorated TiO2 Sensing Layer for a Hydrogen Gas Sensor

Tue, 10 Apr 2018 00:00:00 +0000

We report a sputtered PdO decorated TiO2 sensing layer by radiofrequency (RF) sputtering methods and demonstrated gas sensing performance for H2 gas. We prepared sputtered anatase TiO2 sensing films with 200 nm thickness and deposited a Pd layer on top of the TiO2 films with a thickness ranging from 3 nm to 13 nm. Using an in situ TiO2/Pd multilayer annealing process at 550°C for 1 hour, we observed that Pd turns into PdO by Auger electron spectroscopy (AES) depth profile and confirmed decorated PdO on TiO2 sensing layer from scanning electron microscope (SEM) and atomic-force microscope (AFM). We also observed a positive sensing signal for 3, 4.5, and 6.5 nm PdO decorated TiO2 sensor while we observed negative output signal for a 13.5 nm PdO decorated one. Using a microheater platform, we acquired fast response time as ~11 sec and sensitivity as 6 μV/ppm for 3 nm PdO under 33 mW power.



Facile Fabrication of Stretchable Electrodes by Sedimentation of Ag Nanoparticles in PDMS Matrix

Sun, 08 Apr 2018 00:00:00 +0000

This study reports a facile fabrication method for highly conductive stretchable electrodes composed of a conductive 0D nanomaterial filler and an elastomer matrix. The local volume fraction of the Ag nanoparticles at the composite surface could be significantly increased by the sedimentation of Ag nanoparticles in uncured polydimethylsiloxane (PDMS) fluid. The stretchable electrodes had a surface resistance of  Ω/sq and were stretchable up to 100% of strain without the reduction of the electrical conductivity, demonstrating their potential as high-performance electrodes for applications in stretchable electronics.



Characterization and Thermal Stability Properties of Bulk Hierarchical Porous Pd Prepared by Kirkendall Effect and Dealloying Method

Thu, 05 Apr 2018 06:52:26 +0000

We present a facile strategy to synthesize bulk hierarchical porous Pd materials (BHPPd) with pores ranging from a few nanometers to tens of micrometers through chemical dealloying of porous PdAl intermetallics. Owing to the small surface diffusivities of Pd atoms, the pore/ligament size of BHPPd did not coarsen remarkably as the concentration of HCl aqueous solution increases. Thermal stability properties of BHPPd materials at different temperature ranging from 673 to 1073 K were evaluated. BHPPd materials show superior thermal stability, whose bicontinuous interpenetrating ligament-channel structure can be maintained even after being annealed at 1073 K for 30 min. Such properties can be attributed to less defects and less-noble metal residues. Moreover, compression properties of BHPPd materials were also investigated.



Evolution Mechanism of Metallic Dioxide MO2 (M = Mn, Ti) from Nanorods to Bulk Crystal: First-Principles Research

Wed, 04 Apr 2018 00:00:00 +0000

Using first-principle calculations, the surface energy, cohesive energy, and electronic properties of α-MnO2 and rutile TiO2 nanorods and microfacets were investigated and clarified to, in the first instance, determine the evolution mechanism. The results show that the surface energies of α-MnO2 nanorods and microfacets conform to function 1.0401 Jm−2 + N × 0.608 Jm−2, while the surface energies of the rutile TiO2 nanorods and microfacets are governed by a 1.0102 × 1.1997 rule. Their electronic properties, such as the Mulliken population and Mulliken charge, can only be normalized by their surface areas to attain a linear function. Meanwhile, the surface energy of α-MnO2 with the nanostructure closely conforms to the function for normalized Mulliken population and Mulliken charge as with an value of 0.995. Thus, our research into the evolution mechanism affecting the surface effect of nanometer materials will be useful for investigating the intrinsic mechanism of the nanometer effect and doping process of metallic dioxide catalysts.



Detection of HER2 through Antibody Immobilization Is Influenced by the Properties of the Magnetite Nanoparticle Coating

Mon, 02 Apr 2018 00:00:00 +0000

Considerable effort has been focused on improving the control of size, shape, and surface modifications to detect proteins. The purpose of this study was to compare the efficiencies of aminosilane-coated magnetite (As-M) nanoparticles (NPs), dextran-coated magnetite nanoparticles (Dx-M), and bare nanoparticles for conjugating single-chain variable fragment antibodies (scFvs) with the aim of detecting the human epidermal growth factor receptor 2 (HER2) protein. Dx-M and As-M NPs were characterized using scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and Raman spectroscopy. Dx-M and As-M were conjugated with a monoclonal scFv for active targeting of the HER2 antigen. Aminosilane surface coating enhanced the scFv conjugation efficiency over twofold compared to that of the dextran-coated magnetite NPs for the detection of HER2 proteins.



Degradation Behavior of Electrospun PLA and PLA/CNT Nanofibres in Aqueous Environment

Sun, 01 Apr 2018 00:00:00 +0000

The aim of the work was to compare the degradation behavior of electrospun nanofibres obtained from pure poly(lactic acid) (PLA) and modified with carbon nanotubes (CNTs) in aqueous environment. The nanofibres in the form of mats were manufactured using the electrospinning technique (ES) with potential biomedical application. To investigate the degradation behavior, one-component and composite (containing CNTs) nanofibres were compared using scanning electron microscopy (SEM), water contact angle measurements, differential scanning calorimetry (DSC), and mechanical testing. The changes in their morphology, structure, and selected physical and mechanical properties during incubation up to 14 days were analysed. Two types of CNTs differing in concentration of surface functional groups were used to modify the PLA nanofibres. PLA and composite nanofibres (PLA + CNT) during incubation underwent swelling and partial degradation due to the penetration of water into polymer matrix. Changes in the mechanical properties of composite mats were higher than those observed for pure PLA mats. After 14-day incubation, samples retained from 47 to 78% of their initial tensile strength, higher for PLA samples. Morphological changes in pure PLA nanofibres were more dynamic than in composite nanofibres. No significant changes in crystallinity, wettability, and porosity of the samples occurred.



Advances in Synthesis and Functional Modification of Nanohydroxyapatite

Sun, 01 Apr 2018 00:00:00 +0000

Nanohydroxyapatite material has been used to substitute for bone repair materials in clinical therapy in recent years. However, its osteogenesis effects are different due to its morphology, size, calcium phosphate ratio, crystallinity, and other differences. Thus, synthesis methods are continuously being improved to obtain synthetic materials similar to the nanohydroxyapatite in natural bone tissues in terms of biocompatibility and biological activity. Many synthesis methods are available for nanohydroxyapatite, and, among them, biological template biomimetic synthesis is the optimal method for obtaining highly bioactive and biocompatible nanohydroxyapatite, achieved by manipulating the morphology and physical and chemical properties, such as size, calcium phosphorus ratio, and degree of crystallinity. This article reviews the synthesis and functional modification of nanohydroxyapatite.



Carbon Nanomaterials for Breast Cancer Treatment

Mon, 26 Mar 2018 08:11:11 +0000

Currently, breast cancer is considered as a health problem worldwide. Furthermore, current treatments neither are capable of stopping its propagation and/or recurrence nor are specific for cancer cells. Therefore, side effects on healthy tissues and cells are common. An increase in the efficiency of treatments, along with a reduction in their toxicity, is desirable to improve the life quality of patients affected by breast cancer. Nanotechnology offers new alternatives for the design and synthesis of nanomaterials that can be used in the identification, diagnosis, and treatment of cancer and has now become a very promising tool for its use against this disease. Among the wide variety of nanomaterials, the scientific community is particularly interested in carbon nanomaterials (fullerenes, nanotubes, and graphene) due to their physical properties, versatile chemical functionalization, and biocompatibility. Recent scientific evidence shows the potential uses of carbon nanomaterials as therapeutic agents, systems for selective and controlled drug release, and contrast agents for diagnosing and locating tumors. This generates new possibilities for the development of innovative systems to treat breast cancer and can be used to detect this disease at much earlier stages. Thus, applications of carbon nanomaterials in breast cancer treatment are discussed in this article.



A Facile Synthesis of La2O3/GO Nanocomposites in N,N-Dimethylformamide with High Dye Degradation Efficiency

Mon, 26 Mar 2018 00:00:00 +0000

La2O3/graphene oxide (GO) nanocomposites were simply synthesized from commercially available LaCl3·7H2O and multilayer GO (5–10 layers) in N,N-dimethylformamide (DMF) under reflux condition without extra stabilizer. The characterization results of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectrum (XPS) spectroscopies showed that the crystalline La2O3 nanoparticles were successfully attached on the surface of GO. Moreover, the as-prepared nanocomposites greatly enhanced the degradation efficiency of organic dyes after 15 min under ultrasound irradiation in pure water. The degradation efficiency of the nanocomposites for methylene blue could be over 99%.



Stretchable and Hydrophobic Electrochromic Devices Using Wrinkled Graphene and PEDOT:PSS

Thu, 22 Mar 2018 00:00:00 +0000

We present an electrochromic device (ECD) fabricated using PEDOT:PSS and graphene as active conductive electrode films and a flexible compliant polyurethane substrate with 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMI-TSFI) additive, as ionic medium. This device with a docile, elastic intermediate substrate along with a transparency controlled PEDOT:PSS film provides a wide color contrast and fast switching rate. We harness wrinkling instability of graphene to achieve a hydrophobic nature without compromising transparency of the ECD. This mechanical self-assembly approach helps in controlling the wavelength of wrinkles generated by inducing measured prestrain conditions and regulating the modulus contrast by selection of underlying materials used, hereby controlling the extent of transparency. The reduction and oxidation switching times for the device were analyzed to be 5.76 s and 5.34 s for a 90% transmittance change at an operating DC voltage of 15 ± 0.1 V. Strain dependent studies show that the performance was robust with the device retaining switching contrasts even at 15% uniaxial strain conditions. Our device also exhibits superior antiwetting properties with an average water contact angle of 110°  ± 2° at an induced radial prestrain of 30% in the graphene film. A wide range color contrast, flexibility, and antiwetting nature of the device envision its uses in smart windows, visors, and other wearable equipment where these functionalities are of outmost importance for developing new generation of smart interactive devices.



Structural Characterization and Magnetic Properties of Undoped and Ti-Doped ZnO Nanoparticles Prepared by Modified Oxalate Route

Thu, 22 Mar 2018 00:00:00 +0000

Ti-doped zinc oxide and pure zinc oxide nanoparticles were synthesized by a modified oxalate route using Averrhoa carambola fruit juice as a natural source of oxalate. The characteristics of the precursors have been investigated by FTIR, TGA, and XRD. The results from the investigation revealed that the precursors are zinc oxalate and Ti-doped zinc oxalate which readily decompose at 450°C. The as-prepared precursors were calcined at 450°C for 4 hours, and the decomposition products have been characterized by XRD, SEM, EDX, and VSM. XRD results revealed crystallinity with hexagonal wurtzite structure, while the average grain size was found to be 26 nm for Ti-doped ZnO and 29 nm for ZnO, using calculations based on Debye-Scherrer equation. Furthermore, the morphological studies by SEM showed particle agglomeration, while the presence of Ti3+ in the zinc oxide lattice is indicated by EDS analysis. Finally the hysteresis loop from VSM results shows that Ti-doped ZnO exhibits ferromagnetism.



Effects of Sintering Temperature on the Morphology and Photoluminescence of Eu3+ Doped Zinc Molybdenum Oxide Hydrate

Wed, 21 Mar 2018 00:00:00 +0000

Synthesis of shape controlled and rare-earth doped ZnMoO4 nanostructures on a large scale with low costs is a present challenge in nanotechnology. The precursor of Eu3+ doped zinc molybdenum oxide hydrate (Zn5Mo2O11·5H2O) was synthesized at room temperature via the coprecipitation method. The influences of the sintering temperature on the microstructures and photoluminescence (PL) of the precursor were investigated by means of X-ray diffraction, scanning electron microscopy, thermal gravimetry, differential scanning calorimetry, energy dispersive X-ray spectroscopy, diffuse reflectance spectroscopy, and PL spectrophotometry. It is found that Eu3+ doped ZnMoO4 nanostructures can be derived by sintering the precursor at a relatively low temperature of about 400°C. Our results have demonstrated that Eu3+ doped ZnMoO4 nanostructures can be cost-effectively derived by sintering the precursor at a relatively low temperature.



Silver Nanoparticles Obtained by Aqueous or Ethanolic Aloe vera Extracts: An Assessment of the Antibacterial Activity and Mercury Removal Capability

Mon, 19 Mar 2018 00:00:00 +0000

Silver nanoparticles (AgNPs) were synthesized by chemical reduction of Ag+ ions (from silver nitrate AgNO3), using aqueous or ethanolic Aloe vera extracts as reducing, stabilizing, and size control agent. The nanoparticles’ sizes were between 2 and 7 nm for ethanolic extract and between 3 and 14 nm for aqueous extract, as measured by High-Resolution Transmission Electron Microscope (HRTEM). The antibacterial activity against a mesophilic microorganism, Kocuria varians, a Gram-positive coccus, was measured by counting bacterial colonies in agar plate for both extracts. We found that 4% effective concentration is the lowest concentration that completely inhibited visible growth. Mercury removal was investigated by Atomic Absorption Spectroscopy (AAS) measurements, where it was shown that it is not necessary to use high concentrations of nanoparticles for effective removal of mercury inasmuch as with a 20% V/V concentration of both extracts; the Hg(II) removal percentage was above 95%. These results show that the mercury remaining unremoved from the different essays is below the level allowed by World Health Organization (WHO) and the Environmental Protection Agency (EPA).



Graphene Synthesis Using a CVD Reactor and a Discontinuous Feed of Gas Precursor at Atmospheric Pressure

Sun, 18 Mar 2018 00:00:00 +0000

The present work shows a new method in order to cost-effectively achieve the synthesis of graphene by Chemical Vapor Deposition (CVD). Unlike most usual processes, where precursors such as argon, H2, CH4, and high purity copper foil are used, the proposed method has replaced the previous ones by N2, N2 (90%) : H2 (10%), C2H2, and electrolytic copper (technical grade) since the use of industrialized precursors helps reduce production costs. On the other hand, the process was modified from a continuous flow system with vacuum to a discontinuous one at atmospheric pressure, eliminating the use of vacuum pump. In addition, this modification optimized the consumption of gases, which reduced the waste and the emission of pollutant gases into the atmosphere. Graphene films were grown under different gas flowrates and temperatures. Then, the obtained material was characterized by TEM, Raman spectroscopy, and AFM, confirming the presence of few graphene layers. In brief, the growth time was reduced to six minutes with acetylene as a carbon precursor at 1000°C and at atmospheric pressure, with a flow rate of 30 sccm. Finally, the reported conditions can be used for the synthesis of good quality graphene films in industrial applications.



Geometry-Controlled Carbon Coils by SF6 Flow Injection Time with Reaction Temperature

Sun, 18 Mar 2018 00:00:00 +0000

Carbon nanocoils and/or microcoils were synthesized using C2H2 as the source gas along with the injection of SF6 as an incorporated additive gas under the thermal chemical vapor deposition (TCVD) system. To control the geometries of the carbon coils, we varied the SF6 flow injection time at different reaction temperature ranges. At the lowest reaction temperature (550°C), carbon microcoils were dominantly formed within a relatively short initial SF6 flow injection time (less than 5 min). By increasing the SF6 flow injection time, carbon nanocoils could be well developed on the entire surface of the sample. At 750°C, the formation of carbon microcoils dominated over the entire sample surface, irrespective of the SF6 flow injection time. Based on these results, the growth mechanism for the dominantly formed carbon coils was suggested and discussed. In addition, the causes for the dominant formation of carbon nanocoils and/or microcoils according to the SF6 flow injection times with the different reaction temperatures were analyzed.



New In Situ Synthesis Method for Fe3O4/Flake Graphite Nanosheet Composite Structure and Its Application in Anode Materials of Lithium-Ion Batteries

Thu, 15 Mar 2018 00:00:00 +0000

High-pressure torsion (HPT), a severe plastic deformation (SPD) method, is rarely used in the manufacturing process of functional materials. In the present work, the authors creatively proposed using HPT as an alternative method an approach for high energy ball-milling in the preparation of an Fe3O4 and lamellar graphite nanosheet (GNS) composite material. The corresponding electrochemical experiments verified that the in situ synthesized Fe3O4/GNS composite material has good lithium-storage performance and that it can retain good capacity (548.2 mA h g−1) even after several hundred cycles with high current density (8 C). Meanwhile, this performance has directly confirmed that SPD technique has great potential for the preparation of anode materials of lithium-ion batteries, especially in manufacturing metallic functional nanomaterials.



Tunable Multilayers of Self-Organized Silica Nanospheres by Spin Coating

Wed, 14 Mar 2018 06:58:23 +0000

The coating of fused silica by an organized layer of silica nanospheres (NS) is an important issue for the design of optical and topographic properties especially for lithography techniques such as nanosphere lithography (NSL) or nanosphere photolithography (NSPL). Here, the spin coating of NS dispersed in N,N-dimethylformamide (DMF) is studied. The role of the NS diameter, the spin-coating acceleration, and the volume fraction are the parameters to take into account for the formation and organization of NS in single or double closely packed layers. We propose an explanation for this behavior based on the transition between sedimentation and a viscous regime on the basis of the silica NS organization.