This New Articles Channel contents the latest articles published in Inderscience's distinguished academic, scientific and professional journals.
Data collection in field-based environments with alternative mobile devices using mobile geographic information systems and services for quality flexible platforms
The study of various facets of Geographic Information Systems (GIS) and Global Positioning Systems (GPS) integration has been ongoing since the early 1990s. Mobile GIS followed closely behind this with a lag in technological developments for mobile devices such as size, computing power, cost and accessibility. Once mobile technologies caught up to the integration of GIS and GPS through the advent of smart mobile devices of the 21st century, the capabilities were nearly limitless. The integration of GIS and GPS functionality in smart devices started a new era of mobile GIS. This study analyses GPS horizontal positional accuracy for selected smart mobile devices under ideal GPS data collection conditions in reference to National Geodetic Survey benchmark sites within central Arkansas. For the study, smart devices are denied network connectivity to ascertain the robustness of autonomous GPS compared to these same device's assisted-GPS modes and selected dedicated GPS devices. The study area provides many field-based environments that one might typically encounter when collecting location and attribute information such as no connectivity to cellular service, canopy density, urban canyons, and rural and idyllic conditions. Observed differences between study GPS readings and benchmark data are examined statistically to determine each device's effectiveness.
Does international experience count in the cross-cultural management course effectiveness?
The rapid increase in globalisation processes in many aspects of social and work life has pushed educators to develop students with cross-cultural competence to work in culturally diverse settings. We extend the current understanding of the effectiveness of cross-cultural management courses by emphasising multidimensional learning outcomes. Furthermore, we investigate the influence of international experience on the effectiveness of cross-cultural management education. By studying 179 students at two universities, our results showed that students' international experience through international student status was positively associated with their cognitive cultural intelligence, and students' international experience through military affiliation was positively related to their motivational cultural intelligence and cross-cultural adjustment efficacy. We discuss ways to utilise experience for better learning and implications for management education.
Comparison of WiBro and TD-LTE deployment networks: implications for standards competition
It has been an enigma for the communities of practice and academia in the field of standards as to why, when the capabilities of a technology are not much different or even superior to those of their competitors, only some standards lead to commercial success. Previous literature indicates that a standard needs organisational support and legitimacy amongst audiences, including distributors, influenced by network connectivity and configuration. Using a social network analysis, this paper visualises and compares the networks of wireless broadband and time domain-long-term evolution deployment in the global market. The results show that the presence of a few key sponsors with financial resources and a large installed base is more important than the size of the network. Consequently, we draw some implications for sustainable deployment of future standards.
The impact of hedging on firm value: evidence from US multinational corporations
This paper examines whether hedging can affect multinationals' firm value. Employing pooled cross-sectional time-series analysis of manually collected data of US multinational corporations from 2008 to 2015, this manuscript finds that (i) hedging activities are positively related to the firm value of multinational companies as implied by firm value maximisation theories; (ii) hedging significantly increases firm value by above 10% over the full-sample and the post-crisis sub-sample periods; but (iii) hedging appears insignificant and irrelevant during the global financial crisis period, which may indicate that global economic conditions could dominate any firm-level hedging activity effect. This is a new finding that contributes to the current hedging literature.
Measuring internal service quality in business schools
This paper explores the different constituents determining the internal service quality in business schools and further develops a model representing different factors made up of these constituents. The proposed model went through exploratory and confirmatory factor analysis to test its reliability and validity. This model of internal service quality in business schools consists of seven dimensions, including work resources, rewards, academic freedom, professional development support, vision of top management, communication and teamwork. This study highlights the ways to boost the internal service quality in business schools.
Tunable resistive pulse sensing and nanoindentation of pH-responsive expansile nanoparticles
Experimental studies of pH-responsive expansile nanoparticles (eNPs) have been carried out using tunable resistive pulse sensing (TRPS) and nanoindentation. The eNPs are initially ∼200 nm in diameter, but increase in size owing to a compositional change resulting from cleavage of pH-labile protecting groups on the polymer backbone at low pH. TRPS detected expected changes in the size of eNPs, most clearly through an increase in the size distribution close to ∼1 μm diameter with time after exposure to pH 5.0 electrolyte. Heavily cross-linked nanoparticles and eNPs kept at neutral pH did not produce such pronounced changes. Nanoindentation results demonstrate that for accurate measurement of eNP mechanical properties, particles must be precisely located and securely fixed to the substrate. Moreover, the expanded eNPs may be too weak to respond to conventional nanoindentation. Nanoscale physical characterisation of soft matter is of burgeoning importance in medical and biotechnological research and applications.
Enumeration of colloidal sub-micron particles using tunable resistive pulse sensing
Tunable resistive pulse sensing (TRPS) has been implemented alongside dynamic light scattering (DLS) and scanning electron microscopy (SEM) to characterise a particle size distribution between 400 nm and 1 μm effective diameter. The carboxylate polystyrene particles studied were synthesised by dispersion polymerisation, and overall the data suggest that there are two modal peaks in the distribution. TRPS data indicated that the primary mode was near 630 nm, with a lesser peak near 830 nm. Two pores of different sizes were used for TRPS, and the lower size measurement threshold was apparent for both pores. High throughput particle-by-particle size measurement techniques such as TRPS are of interest for measuring synthetic particles, with potential roles including quality control and compliance, in addition to fundamental studies.
Periodic upright nanopyramid fabricated by ultraviolet curable nanoimprint lithography for thin film solar cells
In this work, a periodic upright nanopyramid structure was developed for light harvesting applications suitable for thin film solar cells. The periodic inverted nanopyramid structure was fabricated on Si substrate by laser interference lithography (LIL) and subsequent pattern transfer by combined reactive ion etching and KOH wet etching. The silicon substrate was used as a master mould in the replication process utilising ultraviolet curable nanoimprint lithography (UV-NIL) process. The inverted nanopyramid patterns were transferred onto OrmoStamp resist layer to form upright pyramids on glass substrates by UV-NIL. The replicated periodic upright nanopyramid structures can be used as light trapping structures in thin film solar cells and as soft mould in the 3D imprint process.
Nanotoxicity of nanodiamond in two and three dimensional liver models
Among classes of nanoparticles developed as drug carriers and theranostics, nanodiamond (ND) has been gaining an increasing attention owing to its biocompatibility, easy functionalisation and chemical stability. Although biocompatibility studies on nanodiamond produced by detonation technique have been explored extensively, NDs produced by laser assisted technique are yet to be investigated. Here, we present comparative study on toxicity of NDs in 2D and 3D liver models. Results suggest toxicity occurs on the 2D model at higher concentrations of NDs after long term exposure. However, cytotoxic effect was not observed in the case of the 3D model. In addition, alterations in nanomechanical properties of the cells after uptake of NDs were detected by a Lorentz contact resonance (LCR) spectroscopic study. Overall, the results indicate differences in the toxicity profile of NDs in 2D and 3D and long term toxicity studies on NDs produced by laser assisted technique must be done prior to any biomedical applications.
Synthesis, characterisation and antimicrobial effect of starch capped silver sulphide nanoparticles against Escherichia coli and Staphylococcus aureus
Silver sulphide nanoparticles were synthesised at room temperature using a green synthetic method. Silver nitrate and thiourea have been used as the sources of silver and sulphide ions, respectively. Starch was used as the capping agent while water was used as the solvent. The effect of precursor and capping agent concentrations was investigated for their influence on the size and shape of the synthesised nanoparticles. The concentrations were varied in the ranges 0.1-;0.6 g and 0.25-1 g for the precursor and capping molecule, respectively. The nanoparticles obtained were spherical and cubic shaped with size distribution of 7-31 nm. Absorption spectra gave blue shifted band edges with Stokes shift of 2 nm. XRD patterns were confirmed to have monoclinic crystallinity with α-phase. FTIR results showed that the nanoparticles were successfully capped with starch capping agent. Increasing both the precursor and capping agent concentrations resulted in a decrease in the nanoparticle sizes. The antibacterial activity of Ag2S nanoparticles against Escherichia coli and Staphylococcus aureus showed susceptibility towards the Gram negative and positive bacteria, respectively. The lower precursor ratio had the lowest minimum inhibitory concentration (MIC) of less than 0.023 mg/ml, while the higher precursor ratios had MIC value of 0.046 mg/ml. The growth curve studies of bacteria treated with nanoparticles showed an increase in growth and then a decrease as the exposure time was increased. This indicated that the growth inhibition is dependent on time exposure of the bacteria to the nanoparticles.
Soil chemistry influences the phytotoxicity of metal oxide nanoparticles
Nanoparticles (NPs) of ZnO and CuO are used in an array of different commercial products. NPs could be introduced into soils by contamination after production from distribution and use, especially from their end-of-life fate. Purposeful introduction to soils may occur in formulations as pesticides, because of their antimicrobial properties, and as fertilisers, to increase the loading of the essential metals Zn and Cu into plant tissues. Use as fertilisers must ensure that application rates do not lead to phytotoxicity. Dose-dependent phytotoxicity is seen in several crops including wheat, Triticum aestivum, when grown hydroponically or in sand. Phytotoxicity is evidenced in wheat by reduced growth and higher tissue loads of Cu or Zn than control plants. Soil properties, however, can mitigate phytotoxicity. Growth reduction in the wheat seedlings was not observed when an alkaline calcareous field soil with initial pH of 8.3 was amended with 300 mg Cu/kg soil from CuO NPs although metal loads increased in the shoots, paralleling observations with ZnO NPs. Phytotoxicity of both NPs was evident in acidic commercial field soils. The level of soluble metal released from the NPs in the aqueous phase varied with soil. Solubility was determined by the soil water pH and in part by the nature of the materials present in the plant root exudates. For example, a typical root exudate, citrate, at pH 5, dissolved more Cu from CuO NPs than did a suspension in water. These findings indicate that phytotoxicity of these metal oxide NPs in soils will vary with the properties of the soils. Consequently soil properties will influence how the NPs could be used as fertilisers.
Effect of medium solvents on crystalline degree and specific surface area of Cu3BiS3 nanoparticles synthesised by biomolecule-assisted hydrothermal and solvothermal methods
Cu3BiS3 nanoparticles were successfully synthesised by hydrothermal and solvothermal methods using L-cysteine biomolecules as a sulphur source and complexing agent. Phase and purity of the samples were characterised by X-ray diffraction (XRD) and selected area electron diffraction (SAED). Scanning and transmission electron microscopy (SEM and TEM) revealed the increasing of particle size from 29.8 ± 6.3 nm to 89.6 ± 17.2 nm by changing the medium solvents from de-ionised (DI) water to ethylenediamine (EN), in accordance with the decrease in the BET surface area from 17.5560 ± 0.1170 m2/g for the DI particles to 4.0297 ± 0.0370 m2/g for the EN particles. The absorption spectrum of highly crystalline Cu3BiS3 nanoparticles synthesised in EN was used to determine the direct energy gap (Eg) which was found to be 1.6 eV. In this research, a formation mechanism is proposed and discussed according to the experimental results.
Development of modifying compounds for multilayer nanostructured coatings for cutting tools
The subject of this study was to research and develop modified multilayer nanostructured wear-resistant coatings (NWC) for cutting tools. NWC are formed through the innovation process of filtered cathodic vacuum-arc deposition (FCVAD). The processes of FCVAD allow forming NWCs by filtering vapour-ion flow of macro/micro particles in the plasma torch of vacuum arc, using the plasma duct of special structure isolated from the station chamber, when the angle of rotation of the plasma stream is 120°. This work presents the configuration of the system, alongside the influence of process parameters on the output. The topology of the coatings is presented together with the hardness and a comparison between standard physical vapour deposition (arcPVD) and FCVAD coating technologies. Machining tests were undertaken in turning of standard HB200 steel and heat resistant nickel alloy. The results are presented in terms of tool flank wear. It is shown that the application of the NWC secured 2-6 fold extended tool life.
The effects of post-growth thermal annealing on the structural and electrical properties of RF-magnetron sputtered ZnO
The effects of two thermal annealing steps on the crystallographic orientation, film stress and crystal domain size in RF-magnetron sputtered ZnO thin films for ultrasonic transducers were investigated. As-grown films contained high levels of compressive stress introduced by the sputtering process, as well as low (002) crystal orientation selectivity. It was shown that residual stress could be eliminated by post-growth annealing at temperatures of 400°C or higher, however, that annealing process also lead to a reduction in the desired (002) crystal orientation selectivity. The use of the relatively low temperature (250°C) in-situ anneal in the sputtering chamber in an oxygen-rich environment was found essential for prompting grain growth and recrystallisation, resulting in (002) textured ZnO films that have high electrical resistivity.
A luminescence study of NaMgF3:Dy3+ and NaMgF3:Nd3+ for applications in radiation dosimetry
Photoluminescence (PL) and radioluminescence (RL) from Dy3+ and Nd3+ were observed in the fluoroperovskite host NaMgF3 at visible and near infrared wavelengths. In the case of NaMgF3:Dy3+, the emission lifetime is long enough to efficiently separate the PL emission from more prompt emissions, such as Čerenkov photons, by temporal means. This property is useful in certain fibre optic dosimeter applications involving pulsed high energy X-rays, such as radiotherapy dosimetry. Such applications are often complicated by a background of Čerenkov photons and an emphasis on emission in the infrared may also prove valuable in mitigating this problem. At doses above approximately 1 kGy, the dependence of RL intensity on absorbed dose was found to be largely free from the influence of radiation induced colour centres for the near infrared emissions exhibited by both the Dy3+ and Nd3+ dopant.
Site-specific thrombolytic and anticoagulant biomaterials
Thrombolytic drugs are used in medicine to dissolve blood clots in a procedure termed thrombolysis. To prevent occlusion, patients are treated with an antiplatelet or antithrombotic drug, or a combination of both. However, the traditional thrombolytic therapies have often been associated with the risk of severe bleeding. We have incorporated low molecular weight heparin (LMWH) and/or streptokinase to biodegradable polyvinyl alcohol (PVA) and gelatine biomaterials in a form of films. These biomaterials will be used to decorate inner surfaces of experimental vascular grafts to evaluate the potential of enhancing their thromboresistance by controlled release of one or both the active compounds. Solvent casting method was used to produce the PVA and crosslinked gelatine films. High initial burst release of LMWH has been observed during our in vitro experiments, followed by a slow stable release during subsequent hours. Biomaterials with LMWH incorporated in the vascular graft luminal surface can be used to prevent thrombus formation shortly after the surgery graft implantation and decrease it in the following hours. Slow stable streptokinase release can be used to attenuate excessive fibrin deposition inside the graft.
The influence of polyethylenimine molecular weight on hydrothermally-synthesised ZnO nanowire morphology
Polyethylenimine (PEI) is a polymer commonly used in the hydrothermal synthesis of ZnO nanowires as an aspect-ratio enhancing agent. To this end, several studies have focused on optimising the PEI concentration to achieve the best results. However, the effect of the polymer's molecular weight on nanowire growth is relatively unstudied. We investigate three different molecular weights of PEI (Mw = 2000, 1300, and 800) at 8 mM, 6 mM, 4 mM and 2 mM concentrations. We find that the Mw = 2000 and Mw = 1300 varieties only yield homogeneous nanowires at 2 mM, while the Mw = 800 variety yields homogeneous nanowires over the entire range of concentrations investigated. The dimensions of the nanowires grown at 2 mM with PEI (Mw = 800, 1300) show minimal variation, with average diameters of 60 nm and average lengths of 2.5 µm, while the nanowires grown at 2 mM PEI (Mw = 2000) have an average diameter of 40 nm and an average length of 4 µm. The nanowires grown with PEI (Mw = 800) at concentrations of 8 mM, 6 mM, and 2 mM show a clear length dependency on concentration, with average lengths of 11 µm, 8 µm and 2.5 µm, respectively. A relationship between concentration and diameter is less clear, with average nanowire diameters of 90 nm, 40 nm and 60 nm, respectively.
Multiferroic nanocrystalline BiFeO3 and BiCrO3 thin films prepared by ion beam sputtering
BiFeO3 and BiCrO3 films were made by room temperature sputtering followed by thermal annealing in a partial oxygen atmosphere. The annealed films were found to be nanocrystalline, with an average particle size of 11 nm for BiFeO3 and 8 nm for BiCrO3. The saturation moment per formula unit is 0.39 μB for BiFeO3 which is significantly greater than that found in bulk BiFeO3 (0.02 μB). A similar enhancement was also found in previous studies of BiFeO3 nanoparticles where the nanoparticle size was small. However, no large enhancement of the saturation moment per formula unit was identified for the annealed BiCrO3 films. The annealed BiFeO3 films displayed superparamagnetic behaviour and the particle size estimated from the blocking temperature is comparable to that estimated from the X-ray diffraction data. Our results show that sputtering and oxygen annealing is a method that can be used to make nanocrystalline BiFeO3 and BiCrO3 films.
Finite element analysis of thermally actuated medical stent and staple implants using shape memory alloy
In this paper, a thermally actuated medical stent and staple using shape memory alloy (SMA) are designed, numerically analysed, and compared to similarly designed stents and staples made of 316L stainless steel and Co-Cr alloy. The numerical analysis was carried out using finite element method. A consistent 3D model is used to investigate the effect of materials on the performance of the stent and staple. This study takes into account the interaction between the stent/staple and the in vivo environment, by modelling the in vivo environment forces. The results are in good agreement with those reported in the literature. According to the results, it can be concluded that when these three commercially available materials undergo an external force, SMA yields much better results in terms of maximum displacement under the same amount of stress. Especially when undergoing large loads, the SMA produces considerably more displacement than 316L stainless steel and Co-Cr, which suggests that using SMA is a promising path to make biomedical stents and staples.
Optimisation of DNA hybridisation and toehold strand displacement from magnetic bead surfaces
Here, we present work on the improved hybridisation and release of specially designed pegylated double stranded DNA strands with a pendant toehold. For this forensically relevant DNA namely amelogenin (AMEL) (a sex determination gene) and the human c-fms (macrophage colony-stimulating factor) proto-oncogene for the CSF-1 receptor (CSF1PO) short tandem repeat (STR) were employed. Magnetic beads functionalised with oligonucleotide capture probes with complementarity to the dsDNA PCR product toehold were fabricated. Characterisation of the beads was achieved through dynamic light (DLS) scattering and attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy showing successful attachment of the oligonucleotides. The time frame of hybridisation between the dsPCR product toehold and the oligonucleotide modified beads was decreased from 6 h to 10 min by pre-incubation of the oligonucleotide functionalised magnetic beads in 2% aqueous sodium dodecyl sulphate (SDS) solution. Fluorescent microscopy was used to determine the time of toehold mediated strand displacement of the captured dsPCR product from the magnetic bead. Initially, displacement was achieved within 6 h. This was subsequently reduced to 3 h by the addition of a rate accelerator, PEG6000 at 10% v/v.
Effect of graphene oxide loading in GO/SiO2/Ag/AgCl photocatalyst
In the presented work, Ag/AgCl decorated silica nanoparticles were introduced over graphene oxide (GO) sheets to prepare GO/SiO2/Ag/AgCl nanocomposite powders for absorption and photocatalytic application. Nanocomposite powders were synthesised by sol-gel method and then characterised by various analytical techniques including X-ray diffraction (XRD), scanning electron microscopy and transmission electron microscopy. The amount of GO in nanocomposites was varied from 1 wt.% to 50 wt.% to investigate the role of graphene oxide on the absorption and photocatalytic properties of the nanocomposites. The photocatalytic activity of the GO/SiO2/Ag/AgCl nanocomposites was examined under UV light taking methylene blue (MB) as a model dye.
Ferromagnetism in a diamond-like carbon film after nickel implantation
Mass selective ion beam deposited diamond-like carbon (DLC) films were implanted with Ni+ ions at 30 keV with a fluence of 3.6 × 1016 atoms cm−2. The peak concentration of nickel in the implanted film was calculated to be 12.5% at an implantation depth of ∼30 nm into the DLC film. Raman measurements showed that the integrated intensity of the D peak at ∼1370 cm−1 divided by the G peak at ∼1560 cm−1 increases after ion implantation, which indicates that the implanted films are more graphitic. The implanted film shows ferromagnetic order at room temperature. However the saturation moment of the implanted film increased significantly when the measurement temperature was lowered. This may suggest that implantation leads to a dilute ferromagnetic semiconductor although more research is required.
Sodium ion conducting NaI-Na3PO4 solid electrolyte with PLLTMEDA as an additive for solid state batteries
In this work poly(L-leucine)1,3-diamino propane (PLLTMEDA) has been chosen as an additive to the binary compound sodium iodide (NaI) and sodium phosphate (Na3PO4). A small amount of PLLTMEDA was added to the optimum composition of the binary compound (0.5 NaI-0.5 Na3PO4). Results from EIS have proven this new compound is superionic with maximum conductivity of 1.12 × 10−3 S cm−1. Fourier transform infrared spectroscopy (FTIR) analysis revealed the band of C=O at 1650 cm−1 experienced a shift, indicating that some interaction had occurred. The ionic transference number was found to be ≈1 for the optimum composition with maximum conductivity which suggests that the sample is ionic in nature. The optimum composition of the sample was used as solid electrolyte in solid state sodium battery. The sodium battery was tested by the discharged characteristic at a current of ≈1.0 µA. The solid state sodium batteries exhibited a discharge capacity of 173 mAh/g.
Surface changes of polymer modified by gold nanoparticles
A limitation of polymers is that the materials lack active sites or substances that can promote cell adhesion, proliferation and tissue recovery. Biopolymers with functional groups or synthesised polymers modified with different methods show many potential applications. The way to create nanostructured surfaces with new functionalities is grafting of the nanoparticles to polymer surfaces. The different uptake behaviours for surface modified nanoparticles can be explained by different charges on the nanoparticles and on the cell membrane. In this work surface changes of the biopolymers substrate modified by gold nanoparticles were studied. Biopolymer foil of polyhydroxybutyrate with 8% polyhydroxyvalerate was treated by plasma and the activated surface was subsequently modified by gold nanoparticles. Modified substrates were analysed by different methods. The elemental composition and the structure of modified polyhydroxybutyrate with 8% polyhydroxyvalerate were studied by X-ray photoelectron spectroscopy (XPS). Surface morphology was determined using atomic force microscopy (AFM). Changes in the surface wettability were determined from the contact angle by goniometry. Cytocompatibility of the pristine and modified samples was assessed in vitro by determining degree of adhesion and proliferation of mouse fibroblasts. It was found that the plasma treatment and subsequent modification with gold nanoparticles leads to dramatic changes in surface morphology, roughness and wettability. Rate of changes of these features strongly depends on the modification parameters. Plasma treatment and subsequent grafting of nanoparticles significantly affects the adhesion and proliferation of cells on the surface of polymer. Biological experiments indicated favourable effect of the presence of the AuNS grafted from the citrate-stabilised AuNS solution on the cells' adhesion, proliferation and viability.
Ablation threshold dependence on incident wavelength during ultrashort pulsed laser ablation
Ultrashort pulse laser micromachining is an advanced materials processing technique that allows "cold cutting" of almost any material. This is especially of interest in the semiconductor industry, where mechanical cutting of wafers generates large amounts of waste - if laser micromachining could be applied here, there is the potential for huge increases in the efficiency and flexibility of semiconductor manufacturing. The biggest barrier to industrial application of this technology is the cutting speed, however by tailoring the pulse properties, we hypothesise that machining speed can be increased greatly. The commonly used metric for evaluation of laser micromachining is the ablation threshold - the energy density required to cause material ablation. In this study the effect of incident laser wavelength on the ablation threshold for materials of interest for microfabrication (e.g., silicon) was investigated. This was achieved using a Ti:Sapphire pumped optical parametric amplifier (TOPAS-C) producing femtosecond pulses (τ = 110 fs, repetition rate = 1 kHz) with wavelengths ranging from 400 nm to 1200 nm using the D-Scan technique. Future work will employ advanced beam shaping technology to tailor pulses in both the spatial and temporal domains to further improve machining efficiency.
Application of advanced nanoclay material as a chemical fertiliser loss control agent for loss control fertiliser development in Thailand
In development of novel chemical fertiliser loss control techniques for promoting agriculture, nanomaterials and nanotechnology have been involved in applications. In this study a type of natural nanoclay material, attapulgite, was applied after electron beam treatment of the as-mined material as a chemical fertiliser loss control agent (LCA). The LCA was mixed with normal chemical fertiliser to form loss control fertiliser (LCF). The LCF was applied to Thai rice growing in a farm field. In the aqueous phase, LCF self-assembled to form 3D micro/nano networks. The fertiliser could form fibrous crystals with the clay rods as the nucleus, obtaining a higher nitrogen spatial scale, so that the nutrient could be retained by the soil filtering layer, and thus nitrogen loss was reduced. Two types of LCFs, machine-made and manmade, were applied. After the LCF was applied, the growth and crop yield of the rice were studied and compared with that obtained with normal fertiliser, and the pH, N and K in soil were measured and analysed. On the control of releasing nitrogen, the two LCFs played some roles compared with the fertiliser control, particularly for some varieties, and the machine-made LCF performed better. On the control of the soil pH to be not too acidic, the manmade LCF performed better but was variety dependent. On the control of releasing K, a comparison showed that the manmade LCF was better than the machine-made LCF. The differences in the LCF behaviour should be correlated with the LCF structure which was due to how they were made.
Template-less and surfactant-free solvent-driven direct synthesis of urchin-like gold nanoparticles in anisole
In this study, we present a simple template-less and surfactant-free method for the synthesis of urchin-shaped gold nanoparticles. Anisole, the reaction solvent also acted as the reducing agent. When compared with other harsher solvent-mediated methods for the synthesis of gold nanoparticles, the method presented here allows the formation of nanoparticles at the relatively low temperature of 60°C. The effect of reaction time was studied, and it was observed that the urchin-shaped particles initially formed transformed into smooth-edged particles when the reaction was continued for more than 30 minutes owing to the thermodynamic instability of gold nanourchins. The effect of added capping agents such as dodecanethiol, hexadecylamine and polyvinylpyrrolidone (PVP) was also studied, and it was found that nanoparticles were not formed in their presence. The gold nanosystems obtained in this study were characterised by transmission electron microscopy and UV-visible absorption spectroscopy.
Synthesis of magnetic nanoparticles by low-energy dual ion implantation of iron and nickel into silicon dioxide followed by electron beam annealing
Magnetic nanoparticles have been made by low-energy dual ion implantation of iron and nickel into SiO2 with a nickel fluence ratio of 82% followed by electron beam annealing for 1800 s at 1000°C. After annealing, there is significant diffusion of iron and nickel into the silicon dioxide layer. Annealing also led to the formation of superparamagnetic nanoparticles with a narrow particle size distribution. The saturation moment at 5 K was 0.7 µB and a similar value was observed at 300 K, which indicates that the Curie temperature is far above room temperature. This moment is lower than that expected for Ni0.82Fe0.18. While the results clearly show the formation of superparamagnetic nanoparticles, it is not possible to determine whether nickel-iron, iron or nickel has formed.
Change of magnetic behaviour of nitrogenated carbon nanotubes on chlorination/oxidation
The magnetic effects of chlorine and oxygen functionalised NCNTs have been studied. The diamagnetic behaviour of non-functionalised NCNTs changes to paramagnetic behaviour on Cl-functionalisation; on O-functionalisation NCNTs become ferromagnetic. A prominent cusp-like behaviour is observed at around ≈45 K in MFC and MZFC measurements, further confirming the ferromagnetic behaviour of O-functionalised NCNTs; but Cl-functionalised NCNTs do not shows any cusp-like behaviour indicating formation of paramagnetic behaviour. The change of magnetic behaviour occurs owing to formation of different bonding with carbon/nitrogen and/or Fe-catalyst atoms that is verified with theoretical calculation. The initial computational results show that the differential bonding patterns of the Cl-functionalised and the O-functionalised NCNTs are the main cause for the different magnetic behaviour in these systems.
In-situ ellipsometric study of calcium phosphate biomineralisation on organic thin films
In this study, in-situ ellipsometry and scanning electron microscopy (SEM) were used to follow the growth kinetics of calcium phosphate (CaP) films on zein and hexadecanoic acid (HDA) layers self-assembled at the air-liquid interface. The duration of the mineral film induction period was heavily dependent on the organic template used, presence or absence of Mg2+, solution pH and concentration. In a standard simulated body fluid (SBF) solution at 20°C and pH 7.4, CaP film growth occurred after an induction period of 40 min for HDA and 100 min for zein. In the absence of Mg2+ the mineralisation induction period was reduced, for only the zein protein, to 50 min. At pH 6, HDA and zein-induced CaP films started forming after 100 min and 180 min, respectively. No induction period was observed when the SBF concentration was doubled, with immediate CaP growth observed for both HDA and zein. This study shows the effect of biomineralisation conditions on the growth of CaP with the organic template playing an important role. Knowledge of the factors that influence mineral growth processes is of importance in areas of biomineralisation and controlled crystal growth.
Periodic nanostructure induced on PEN surface by KrF laser irradiation
There are several kinds of periodic surface structures, ranging from dots to ripples. The most common pattern is a ripple-like structure, where the direction of the ripples is parallel with the main polarisation of the laser beam. The distance between individual ripples (their period) depends on several factors, namely: the chemical structure of the polymer, wavelength of the laser irradiation and the angle of laser beam incidence. Oriented polyethylene naphthalate (PEN) foils with a thickness of 50 μm were used. The samples were irradiated with a KrF laser under laser beam incidence 0-45° to the laser beam. Selected polymer samples were also exposed by irradiation through a contact mask. Surface roughness and the dimensions of the ripple-like structures were measured by atomic force microscopy in tapping mode. The concentration of the elements on the surface was obtained from Angle Resolved X-ray Photoelectron Spectroscopy (ARXPS) spectra measured by X-ray Photoelectron Spectroscopy (XPS) spectrometer. The surface morphology and dimensions of prepared structures were evaluated and compared with those prepared on pristine samples without mask. The transition between the irradiated surface under the slits and the shielded surface in between the slits was evaluated. The optimal input parameters for nanopattern with high periodicity were determined. The shape and the surface roughness of the ripple pattern depend strongly on the angle of incidence of the laser beam. The surface roughness and ripple width increase with the angle of laser beam incidence. Irradiation with laser leads to changes in chemical composition of the PEN surface layer. Even at initial phase of pattern formation a significant increase of carbonyl and carboxyl groups was detected.
Hybrid gas sensor having TiO2 nanotube arrays and SnO2 nanoparticles
To obtain a good performance of gas detection, a newly-designed metal oxide semiconductor gas sensor has been fabricated by micromachining process. The micro platform consisted of Pt heater and electrode and its size was 2.5 mm × 2.5 mm. For hybrid sensing materials, such as SnO2 nanoparticles and TiO2 nanotube arrays were deposited on the micro platform. To obtain a clean and open window of TiO2 nanotube, two-step anodic oxidation was conducted. The diameter of window and length of TiO2 nanotubes were ∼60 nm and ∼5.5 µm, respectively. Detection performances for CO and CH4 gases were investigated with operation circuit at operating temperature of 100°C and 300°C, respectively. The power consumption of fabricated micro platform was 28 mW and 94 mW at 2 V and 4 V of heater voltages, respectively. High sensitivity and short response time were observed. The microstructures of gas sensor were systemically characterised by FESEM and X-ray diffraction patterns.
High resolution imaging and analysis of residual elastic strain in an additively manufactured turbine blade
Using recently developed microchannel plate (MCP) neutron area detectors at a pulsed neutron source provides a method of fast non-destructive imaging and characterisation of advanced materials at unprecedented spatial resolution. The energy resolved neutron transmission spectrum can be found from the neutron time of flight (ToF), this provides valuable information about the crystallographic structure within the sample such as the average residual elastic strain in the incident beam direction. By measuring this spectrum at a number of sample orientations information is built up about the strain distribution throughout the specimen. The energy-resolved neutron transmission spectrum of an additively manufactured turbine blade was measured at the Engin-X instrument, ISIS, UK. A high resolution three-dimensional reconstruction of the neutron attenuation coefficient of the blade was recovered, then analysis of the energy resolved spectrum gave insight into the underlying residual elastic strain profile imparted by the advanced manufacturing process.
Methanol production via CO2 hydrogenation reaction: effect of catalyst support
In this project, Cu-based catalyst was synthesised via impregnation method on various supports such as Al2O3, Al2O3-ZrO2, SBA-15 and Al-modified SBA-15. Samples were characterised by N2 adsorption-desorption, field-emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), temperature-programmed desorption/reduction (TPD/R) and pulse chemisorption. The activity of the supported Cu-based catalyst was evaluated in a fixed-bed micro-reactor at 483 K, 2.25 MPa, and H2/CO2 ratio of 3 : 1. Our results showed that the nature of the oxide support influenced the physicochemical properties of the catalysts as well as the catalytic activity and product selectivity. The size of catalyst nanoparticles ranged from 9 nm to 37 nm, depending on the type of support used. The Cu-based catalyst supported on SBA-15 resulted in 13.96% CO2 conversion and methanol selectivity of 91.32% and these values were higher than those obtained using Cu-based catalyst supported on other oxide carriers.
Porous conducting polymer prepared through liquid crystal template for drug delivery
Unlike conventional controlled drug delivery systems where drug is released at a constant pre-programmed rate, drug release from conducting polymers (CPs) can be controlled through electrical stimuli and adjusted based on the patient's needs. However, owing to their low drug loading capacity and limited electrical responsiveness CP systems cannot currently be applied for systemic drug delivery or to treat chronic disease. To overcome that obstacle one approach is to fabricate porous CP structures. In this work, polypyrrole (PPy) was used owing to its electrical responsiveness and biocompatibility. Liquid crystals were used as a template through which PPy was grown. Dexamethasone phosphate was loaded as a dopant into PPy during polymerisation and its release was quantified by HPLC after the removal of liquid crystal; release could be modified by electrical stimulus. This system has potential applications in conditions where required drug dosing changes with time, such as in age-related macular degeneration.
Sidechain engineering in anthracene derivatives: towards photofunctional liquid crystals
A series of anthracene derivatives were synthesised to explore how their sidechain configurations influenced their phase behaviour and thereby guiding the design of photofunctional liquid crystalline materials. In the case of 9,10-diphenylanthracene derivatives, longer and more alkyl sidechains resulted in lower melting temperatures, yet liquid crystallinity was not observed. A novel room-temperature molecular liquid was synthesised based on 9,10-diphenylanthracene, the optical properties of which may be exploited in photonic applications. Liquid crystallinity was observed in one of the derivatives of 9,10-bis(phenylethynyl)anthracene, forming a nematic phase at around 210°C. These results highlight the potential opportunities for photofunctional materials with enhanced properties if liquid crystalline anthracenes can be found with lower phase transition temperatures.
Synthesis and functionalisation of stable 'naked' gold nanoparticles
Gold nanoparticles (AuNPs) exhibit interesting physico-chemical properties, which is a reason why they have become a highly useful and intensely studied material. The optical properties of AuNPs arise from their localised surface plasmon resonance (LSPR) property where the colour generated depends foremost on size and shape of the AuNPs. The surface chemical properties of AuNPs are generally a function of the ligand molecules that adsorb or bind onto the NP surface. This occurs either during synthesis where the reducing agent and or its product adsorb onto the AuNP surface, or by post-synthesis modifications of the AuNPs via, e.g., ligand-exchange reactions. Engineering or functionalising the surface chemistry of NPs allows for customising the surface chemical properties of such NPs for particular applications, e.g., biosensing. To facilitate this surface engineering or functionalisation, it is desirable that the surface is essentially free of adsorbed entities, i.e., it is 'naked'. However, naked NPs tend to agglomerate/aggregate easily and need arises for stable naked NPs. Here, we demonstrate the synthesis and functionalisation of stable 'naked' AuNPs in aqueous medium using Na2S2O5 to reduce an Au3+ precursor salt at room temperature and within a few minutes. Such AuNPs have optical properties similar to those of commonly used AuNPs produced with trisodium citrate (TSC) and are stable for several months at ambient conditions. The zeta potential of such AuNPs is close to zero mV suggesting that only a surface layer adsorption of SO42- ions occurs to provide this near electrically neutral NP surface. The 'naked' AuNPs were subsequently functionalised with poly(methacrylic acid), polyvinylpyrrolidone, Tween 20 and following this, with 16-mercaptohexadecanoic acid to facilitate binding of the resulting functionalised AuNPs to a particular reactive target. We provide evidence for the successful and reliable functionalisation of AuNPs produced with Na2S2O5, which can open up a range of applications.
Resistance-temperature characteristics of CVD and high strength metallurgical graphene
Gas sorption conditions on the graphene surface, as well as their influence on graphene properties, play a significant role when applications are considered. The influence of temperature and pressure on electric properties of graphene were investigated and discussed within this work, which was conducted in order to determine the border values for the sorption and desorption process of hydrogen on the graphene surface. The temperature was changed within the range of 243-373 K. Two types of graphene were used for comparison: one of graphene synthesised by our own method using chemical vapour deposition (CVD) and one of high strength metallurgical graphene (HSMG) in both conducting (cHSMG) and semiconducting (scHSMG) varieties. The characteristics were determined under hydrogen atmosphere in a fitted apparatus under pressure. The overall target material relies on the hydrogen storage of a designed graphene-based composite.
Resonant absorption in dielectric thin films for humidity sensing
We have designed and fabricated novel humidity sensors based on thin-film systems capable of sustaining optical resonances in subwavelength thick absorbing dielectric coatings on reflecting surfaces, as a result of coupling between molecular absorption and Fabry-Perot resonances. Specifically, our experiments demonstrate that a strong resonance can be observed in the reflection spectrum of a 105 nm thick Rhodamine 6G-doped polyvinyl alcohol (PVA) coating on a silver surface under certain illumination conditions; this resonance shows an excellent spectral and temporal sensitivity to the change of environmental humidity. In addition, we also demonstrate the humidity sensing potential of a 47 nm thick titanium dioxide coating on an aluminium substrate as a more robust system for practical implementation.
Demonstration of the use of a photosynthetic microbial fuel cell as an environmental biosensor
Microbial fuel cells (MFCs) are bioelectrochemical systems (BESs) that exploit biological catalytic processes for the generation of electrical power or the accumulation of useful compounds. Photosynthetic MFCs (pMFCs) are those that utilise photosynthetic microorganisms, such as algae and cyanobacteria, to provide reducing power at the anode. A reproducible light-dependent electrogenic effect occurs as algae or cyanobacteria convert light to electrical energy in the BES. In addition to the generation of electricity, the phenomenon may be useful in niche circumstances such as for bioelectrosynthesis or for use in environmental biosensors. In this study we measure the effect of common toxicants (copper, thallium, zinc and glyphosate) on the electrogenic activity of electrode surface-dwelling algae and cyanobacteria. We observed a decrease in the light-dependent electrical response via these photosynthetic microorganisms in our pMFC that was proportional to the concentration of toxicants. This demonstrates the utility of these BESs as potential environmental biosensors where the metabolism of photosynthetic microorganisms acts to sense signals from the environment.
Protein and polysaccharide conjugates as emerging scaffolds for drug delivery systems
Protein and polysaccharide conjugates are ideal for developing coatings for medical scaffolds and drug delivery systems owing to their high biocompatibility and biodegradability. In this study, we are conjugating a hydrophobic protein zein with a hydrophilic polysaccharide, pectin. A specific covalent linkage is introduced between the reducing end of pectin and the amine groups of zein that are surface accessible. After successful coupling of pectin to zein, the conjugate is water-soluble. A film was prepared with the zein-pectin conjugates on a hydrophilic silica surface. SEM shows that the film is mainly composed of zein nanoparticles coated with pectin, and these nanoparticles arrange themselves into individual arrays that are separated by several wide channels. Films with such nanostructures can be exploited for developing bioactive coatings.
Graphene antidot lattice transport measurements
We investigate graphene devices patterned with a narrow band of holes perpendicular to the current flow, a few-row graphene antidot lattice (FR-GAL). Theoretical reports suggest that a FR-GAL can have a bandgap with a relatively small reduction of the transmission compared to what is typical for antidot arrays devices. Graphene devices were fabricated using 100 keV electron beam lithography (EBL) for nanopatterning as well as for defining electrical contacts. Patterns with hole diameter and neck widths of order 30 nm were produced, which is the highest reported pattern density of antidot lattices in graphene reported defined by EBL. Electrical measurements showed that devices with one and five rows exhibited field effect mobility of ∼100 cm2/Vs, while a larger number of rows, around 40, led to a significant reduction of field effect mobility (<5 cm2/Vs). The carrier mobility was measured as a function of temperature, with the low-temperature behaviour being well described by variable range hopping, indicating the transport to be dominated by disorder.
Modulation of cell adhesion to conductive polymers
Our work on conductive polymer (CP) systems grafted with stimuli-responsive polymer brushes is motivated by the prospect of precisely controlling cellular behaviour by tailored smart interfaces. Here, the effects on cell adhesion by applying a potential to poly(3,4-ethylenedioxythiophene) (PEDOT) during both protein coating and cell culture is investigated. The results highlight the importance of pre-adsorbing fibronectin in this case, especially for the reduced polymer which binds protein strongly. The effects of changing the surface chemistry of the PEDOT electrode by grafting of brushes by atom transfer radical polymerisation (ATRP) is also investigated. Specifically, the composition of the salt-sensitive poly(oligo(ethylene glycol methyl ether methacrylate))-based brushes was tailored to control the level of cell adhesion to the interface. The composition, and also the length of the grafted brushes was seen to be important to the cell adhesion. It is also demonstrated how PEDOT films grafted with a protein and cell rejecting brush can be converted to a cell adhesive state by attaching an integrin ligand to the brush to mediate cell adhesion.
Nanoscale mapping of the three-dimensional deformation field within commercial nanodiamonds
The unique properties of nanodiamonds make them suitable for use in a wide range of applications, including as biomarkers for cellular tracking in vivo at the molecular level. The sustained fluorescence of nanodiamonds containing nitrogen-vacancy (N-V) centres is related to their internal structure and strain state. Theoretical studies predict that the location of the N-V centre and the nanodiamonds' residual elastic strain state have a major influence on their photoluminescence properties. However, to date there have been no direct measurements made of their spatially resolved deformation fields owing to the challenges that such measurements present. Here we apply the recently developed technique of Bragg coherent diffractive imaging (BCDI) to map the three-dimensional deformation field within a single nanodiamond of approximately 0.5 µm diameter. The results indicate that there are high levels of residual elastic strain present in the nanodiamond which could have a critical influence on its optical and electronic properties.
Adsorption effects during the analysis of caffeic acid at PEDOT electrodes
Polyphenol compounds, such as caffeic acid, are important substrates of oxidation in beverages such as wine, and more rapid and sensitive methods of analysis are being sought. The conducting polymer poly-3,4-ethylenedioxythiophene (PEDOT) provides good separation of caffeic acid from antioxidant additives in wines, and produces a clear anodic peak that can be used to quantify caffeic acid and related hydroxycinnamic acids. Various adsorption effects are examined in this report, as shown through electrochemical tests such as sweep rate dependence of the anodic peak current and voltammetric shape. The importance of a controlled holding time prior to measurement is seen, owing to the gradual increase in anodic peak current over a period of 10-20 min, with implications for the design of a measurement system involving PEDOT electrodes.
Facile fabrication of carbon nanotube network thin film transistors for device platforms
Carbon nanotube network thin film transistors with channel lengths of 10-40 μm are fabricated from a nanotube buckypaper with 99% semiconducting carbon nanotubes by surfactant free solution routes. The carbon nanotubes are suspended in 1,2-dichlorobenzene by ultrasonication at concentrations of 7.9 μg/ml, 3.4 μg/ml and 2.6 μg/ml, resulting in carbon nanotube field effect transistors with tube densities ranging from 5 tube/μm2 up to 32 tube/μm2. The device percolation threshold is 11 tube/μm2 with optimum device performances of on/off current ratio 7200, mobility 0.55 cm2/V·s and Vth = +1 V. Devices with tube density above the percolation threshold are typically metallic-like. By encapsulating with poly-4-vinylphenol cross-linked with poly-(melamine-co-formaldehyde), the hysteresis becomes independent of channel length and the device performance approaches the best devices at the percolation threshold.
Base dependent adsorption of single-stranded homo-oligonucleotides to gold nanoparticles
Many bioanalytical devices now feature DNA immobilised on optically or electrically addressed gold surfaces, either via covalent (thiol) tethers, or non-specifically adsorbed via the DNA nucleobases. To guide the development of colorimetric biosensors that depend on the dissociation of adsorbed DNA aptamers, the interaction of homo-30-mers composed of each of the bases with gold nanoparticles was investigated. Through colorimetric measurements of the stability of DNA-coated gold nanoparticle dispersions, stability was found to decrease in the order A > T > C ≥ G, counter to expectations based on intrinsic affinities. These observations were reconciled using electrochemical measurements of DNA surface densities on gold nanoparticle electrodes; while the measured surface densities correlated with the dispersion stabilities, it was apparent that many bases of a long DNA strand were dangling from the surface, rather than directly adsorbed. Thus, even (dT)30, whose bases have the weakest affinity to gold, can cover a gold surface with high total density since many of the bases will simply be tethered, and still contributing to the stability of a nanoparticle dispersion.
The spontaneous motion of a slug of miscible liquids in a capillary tube
This contribution explores a droplet actuation mechanism which involves mixing slugs of two different liquids in a glass capillary. The resulting contrast in surface tension which arises provides the necessary propulsive power for the droplet. The conceptual idea is demonstrated for an ethanol-water system. The droplet is observed to rapidly reach a peak velocity which then gradually decreases with time as the two miscible liquids mix. A model is proposed based on Newton's second law which is able to capture the main observed flow phenomena and explain the driving and dissipative mechanisms simultaneously at play in the droplet. This passive actuation mechanism could prove an attractive alternative in digital microfluidics systems for which bulky pumping systems are often required.
Hydrothermal synthesis of mixed phase blue titanium dioxide from oxalate stabilised sols
Blue coloured titanium dioxide nanoparticles were synthesised by the hydrothermal treatment of oxalic acid stabilised titania sols in the presence of NH4F as a modifying agent. The NH4F concentration determined the phase of titania produced and influenced the shape of the rutile crystallites produced. The blue colour originated from the F-stabilised Ti3+ centres formed under the reaction conditions. Organic residues in the sol decomposed to generate a hydrogen-rich atmosphere. Photocatalytic activity studies revealed the rutile phase titania produced was extremely active for a given surface area when compared to P-25.
Grain size dependence of tin oxide nanopaste on sintering temperature
Grain size and porosity are two of the key parameters which are strongly affecting and dictating the sensitivity of tin oxide and gas sensors in general. Grain size and porosity are dependent on the firing temperature profile and in this study the emphasis is on investigation of grain size dependence on the sintering temperature. It is well known that with decreasing grain size, gas sensitive materials have larger selectivity, higher sensitivity, the sensor response increases steeply and they are more immune to poisoning. The core of the investigation is to observe how grain size of SnO2 changes with an increase of sintering temperature and to determine its influence on material porosity. For the first interaction, custom-designed SnO2 nanopaste has been deposited on sintered alumina (Al2O3) substrates using screen-printing technique. Specimens have been sintered at peak temperatures in the range of 800-1500°C. Afterwards they have been characterised with scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS).