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We report on the fabrication of a novel design of GaAs/(In,Ga)As/GaAs radial nanowire heterostructures on a Si 111 substrate, where, for the first time, the growth of inhomogeneous shells on a lattice mismatched core results in straight nanowires instead of bent. Nanowire bending caused by axial tensile strain induced by the (In,Ga)As shell on the GaAs core is reversed by axial compressive strain caused by the GaAs outer shell on the (In,Ga)As shell. Progressive nanowire bending and reverse bending in addition to the axial strain evolution during the two processes are accessed by in situ by x-ray diffraction. The diameter of the core, thicknesses of the shells, as well as the indium concentration and distribution within the (In,Ga)As quantum well are revealed by 2D energy dispersive x-ray spectroscopy using a transmission electron microscope. Shell(s) growth on one side of the core without substrate rotation results in planar-like radial heterostructures in the form of free standing straight nanowires. [ABSTRACT FROM AUTHOR]

The recombination of photoexcited electron–hole pairs greatly limits the degradation performance of photocatalysts. Ultrasonic cavitation and internal electric field induced by the piezoelectric effect are helpful for the separation of electron–hole pairs and degradation efficiency. The activated foam carbon (AFC) owing to its high surface area is often used as the substrate to grow catalysts to provide more reactive active sites. In this work, CuO@BaTiO3 (CuO@BTO) heterostructure is prepared by hydrothermal method on the surface of AFC to investigate the ultrasonic piezoelectric catalysis effect. X-ray diffraction (XRD), Raman spectroscopy, energy dispersive x-ray spectroscopy (EDS) and scanning electron microscopy (SEM) were used to analyze the structure and morphology of CuO-BTO/AFC composite. It is found that the CuO-BTO/AFC composite exhibits excellent piezo-catalytic performance for the degradation of organics promoted by ultrasonic vibration. The CuO-BTO/AFC composite can decompose methyl orange and methylene blue with degradation efficiency as high as 93.9% and 97.6% within 25 min, respectively. The mechanism of piezoelectricity enhanced ultrasound supported catalysis effect of system CuO-BTO/AFC is discussed. The formed heterojunction structure between BTO and CuO promotes the separation of positive and negative charges caused by the piezoelectric effect. [ABSTRACT FROM AUTHOR]

Mg-doped GaN films/nanorods were grown epitaxially on c -sapphire by reactive co-sputtering of GaAs and Mg at different N2 percentages in Ar–N2 sputtering atmosphere. Energy dispersive x-ray spectroscopy revealed that the Mg incorporation increases with increase of Mg area coverage of GaAs target, but does not depend on N2 percentage. In comparison to undoped GaN films, Mg-doped GaN displayed substantial decrease of lateral conductivity and electron concentration with the initial incorporation of Mg, indicating p -type doping, but revealed insulating behaviour at larger Mg content. Morphological investigations by scanning electron microscopy have shown that the films grown with 2%–4% Mg area coverages displayed substantially improved columnar structure, compared to undoped GaN films, along with rough and voided surface features at lower N2 percentages. With increase of Mg area coverage to 6%, the growth of vertically aligned and well-separated nanorods, terminating with smooth hexagonal faces was observed in the range of 50%–75% N2 in sputtering atmosphere. High-resolution x-ray diffraction studies confirmed the epitaxial character of Mg-doped GaN films and nanorods, which displayed complete c -axis orientation of crystallites and a mosaic structure, aligned laterally with the c -sapphire lattice. The catalyst-free growth of self-assembled Mg-doped GaN nanorods is attributed to increase of surface energy anisotropy due to the incorporation of Mg. However, with further increase of Mg area coverage to 8%, the nanorods revealed lateral merger, suggesting enhanced radial growth at larger Mg content. [ABSTRACT FROM AUTHOR]

This study evaluated the efficacy of phytogenic silver and zinc nanoparticles in improving heat resilience in various wheat varieties. The silver and zinc nanoparticles were synthesized using plant leaf extract and characterized using various techniques. Four wheat varieties (DBW187, Black Wheat, DBW 50, and PBW 621) were subjected to field trials. The random block design was used, and nanoparticles in different concentrations were applied at various growth stages and morphologically, and yield parameters were recorded. UV–vis spectroscopy spectral analysis showed peaks for Ag nanoparticles at 420 nm wavelength and Zn nanoparticles at 240 and 350 nm wavelength, depicting the preliminary confirmation of nanoparticle synthesis. Electron microscopic analysis (TEM and SEM) provided morphological insights and confirmed synthesis of fine-sized particle mostly in a range between 10 and 60 nm. Energy dispersive x-ray analysis confirmed the elemental composition of the synthesized nanoparticles, with Ag and Zn elements detected in their respective samples. It also confirmed the oxide nature of synthesized ZnNPs. Dynamic light scattering analysis provided size distribution profiles, indicating average sizes of approximately 61.8 nm for Ag nanoparticles and 46.5 nm for Zn nanoparticles. The concentrations of Ag and Zn nanoparticles in the samples were found to be 196.3 ppm and 115.14 ppm, respectively, through atomic absorption spectroscopic analysis. Fourier transform infrared spectroscopy analysis revealed characteristic functional groups present in the nanoparticles. The results of field experiments established that Ag nanoparticles at 75 ppm concentration exhibited the most significant enhancements in plant growth. Conversely, Zn nanoparticles at a 100 ppm concentration demonstrated the most substantial improvements in the growth and yield of heat-stressed wheat varieties. The study concludes that optimized concentrations of silver and zinc nanoparticles can effectively improve heat stress resilience in wheat. These findings are promising to enhance abiotic stress resilience in crops. [ABSTRACT FROM AUTHOR]

We demonstrate the selective area growth of InGaAs nanowires (NWs) on GaAs (111)B substrates using hydride vapor phase epitaxy (HVPE). A high growth rate of more than 50 μ m h−1 and high aspect ratio NWs were obtained. Composition along the NWs was investigated by energy dispersive x-ray spectroscopy giving an average indium composition of 84%. This is consistent with the composition of 78% estimated from the photoluminescence spectrum of the NWs. Crystal structure analysis of the NWs by transmission electron microscopy indicated random stacking faults related to zinc-blende/wurtzite polytypism. This work demonstrates the ability of HVPE for growing high aspect ratio InGaAs NW arrays. [ABSTRACT FROM AUTHOR]

Triboelectric nanogenerators (TENGs) are crucial for applications such as smart sensors and bio-electronics. In the current work, we aimed for improved performance of TENGs with incorporation of BaTiO3 powder, which is known for its strong ferroelectric properties, combining it with epoxy resin to improve the flexibility of our devices. We observed that our TENGs can operate for over 24 000 cycles with no degradation of function. Additionally, we improved the electrical performance of the TENGs by incorporating various aluminum concentrations that change the electronic properties in the form of mixed epoxy resin, BaTiO3, and Al nanopowders. To identify the optimum conditions for the best performance, we analyzed the electrical characteristics and material properties by employing scanning electron microscopy, energy dispersive x-ray spectroscopy, and x-ray diffractometry characterization techniques. Our findings suggest that this innovative combination of materials and optimization techniques can significantly improve the performance of TENGs, making them ideal for practical applications in various fields, such as low-power electronics, environmental monitoring and healthcare. Moreover, these enhanced TENGs can serve as sustainable and dependable energy sources for various applications. [ABSTRACT FROM AUTHOR]

In the current work, we report on the synthesizing of a series of novel nanocomposite materials obtained by functionalizing the SBA-15 silica matrix with anchored iron phosphonate molecules and the following thermal treatment. The obtained results reveal the formation of a unique amorphic layer of Fe-based compounds on the surface of silica walls of SBA-15 channels as a result of the organic groups' decomposition after moderate thermal treatment. Due to their unique structure, represented in an active Fe-containing amorphous coating spread over a large surface area, these materials are of great interest for their potential applications in fields such as catalysis, adsorption, and non-linear optics. The obtained materials remain amorphous, preserving the SBA-15 mesoporous structure up to temperatures of approximately 800 °C, after which the partial melting of the silica backbone is observed with the simultaneous formation of nanocrystals inside the newly-formed glassy mass. All obtained materials were characterized using such techniques as thermogravimetry, transmission and scanning electron microscopy combined with energy dispersive x-ray spectroscopy mapping, Raman spectroscopy, N2 sorption analysis, x-ray diffraction, x-ray photoelectron spectroscopy, Mössbauer spectroscopy, and SQUID measurements. [ABSTRACT FROM AUTHOR]

Si/SiGe stacked multilayers are key elements in fabrication of gate-all-around (GAA) structures and improvement of electrical properties, with the evolution of the Si/SiGe interfaces playing a crucial role. In this work, a model is developed based on the simplified bond hyperpolarizability model (SBHM) to analysis the anisotropic reflective second harmonic generation (Ani-RSHG) on a three-period stacked Si/Si1− x Ge x multilayer, which builds on Si(100) diamond structures. The C 4v symmetry of the Si(100) structure enables the second harmonic generation (SHG) contribution from the bonds to be simplified and the effective hyperpolarizabilities of the interfacial and bulk sources to be obtained. The effective interface dipolar and bulk quadrupolar SHG hyperpolarizabilities in the Si1− x Ge x sample with various Ge concentration profiles are modeled by interpreting the concentration of a component element as the probability of the element occupying an atomic site. On the basis of the developed model, the Ani-RSHG spectra of the as-grown samples with various Ge ratios for each layer and the samples annealed at 850 °C and 950 °C are analyzed to inspect the change in Ge distribution and its gradient in depth. The ani-RSHG analysis on as-grown samples showed difference in Ge distribution in samples with the multi Si/SiGe structure, which is not well observed in synchrotron x-ray diffraction (XRD) spectra. For the annealed samples, the response to changes in Ge concentration and its gradient in depth reveal the Si/Si1− x Ge x interface intermixing. Results of high-angle annular dark-field scanning transmission electron microscopy and energy dispersive x-ray spectroscopy agree well with the Ani-RSHG with SBHM findings. Compared with the Raman and synchrotron XRD spectra, the Ani-RSHG with SBHM simulation result demonstrates much better response to changes in compositions of the Si/Si1− x Ge x stacked multilayered structures, verifying the potential for characterizing the concentration distribution in stacked multilayered thin films for GAA structures. [ABSTRACT FROM AUTHOR]

Optical metamaterials are widely used in electromagnetic wave modulation due to their sub-wavelength feature sizes. In this paper, a method to plate an achiral nanopillar array with chiral coating by the secondary effect in focused ion beam induced deposition is proposed. Guided by the pattern defined in a bitmap with variable residence time, the beam scan strategy suppresses the interaction between adjacent nanostructures. A uniform chiral coating is formed on the target nanostructure without affecting the adjacent nanostructure, under carefully selected beam parameters and the rotation angle of the sample stage. Energy dispersive x-ray spectroscopy results show that the chiral film has high purity metal, which enables the generation of localized surface plasmon resonances and causes the circular dichroism (CD) under circularly polarized light illumination. Finally, the tailorable CD spectrum of the coated array is verified by the finite difference time domain method. [ABSTRACT FROM AUTHOR]

Phenolic compounds (like 4-nitrophenol) and dyes (like methyl orange) are common by-products discharged by many industries as wastes; they are toxic and may induce discomfort and irritation in humans when ingested. Most of these compounds can be made less toxic through catalytic degradation. Metal oxide nanoparticles are found to have high catalytic activity and can degrade toxic phenolic compounds and dyes. In the current study, pomegranate rind extract was used for the green synthesis of iron oxide nanoparticles that exhibited an octahedron morphology revealed by scanning electron microscopy analysis. Energy dispersive x-ray analysis showed 47.96% content of Fe (by weight); high resolution-transmission electron microscopy analysis confirmed that the nanoparticles had a particle size of 22.54 ± 4.13 nm. The particles were further characterized by x-ray diffraction, fourier transform-infrared spectroscopy, vibrating sample magnetometer, and thermogravimetric analysis. The nanoparticle proved to be efficient in reducing 4-nitrophenol and methyl orange. It was also found to be non-toxic towards murine macrophages, RAW 264.7 with good ROS-scavenging potential compared to control. [ABSTRACT FROM AUTHOR]

We demonstrate the conversion to quasi two-dimensional (2D) β -Ga2O3 by thermally oxidizing layered GaSe of different thicknesses (from bilayer to 100 nm). GaSe flakes were prepared by mechanical exfoliation onto Si with a 300 nm SiO2 layer, highly oriented pyrolytic graphite, and mica substrates. The flakes were then annealed in ambient atmosphere at different temperatures ranging from 600 °C to 1000 °C for 30 min. Raman spectroscopy confirmed the formation of β -Ga2O3 in the annealed samples by comparison with the Raman spectrum of a β -Ga2O3 reference crystal. Atomic force microscopy was employed to study the morphology and the thickness of the β -Ga2O3 flakes. In addition, we used energy dispersive x-ray spectroscopy together with scanning electron microscopy to investigate the evolution of the composition, especially Se residuals, and the sample topography with annealing temperature. β -Ga2O3 appears at temperatures above 600 °C and Se is completely evaporated at temperatures higher than 700 °C. The thicknesses of the resulting β -Ga2O3 flakes are half of that of the initial GaSe flake. Here we therefore present a straightforward way to prepare 2D β -Ga2O3 by annealing 2D GaSe. [ABSTRACT FROM AUTHOR]

Designing heterojunction photocatalysts with matched band structure and good interface contact is an effective method to improve the photoelectrochemical activity. Herein, novel CaIn2S4/TiO2 nanotube arrays (NTAs) heterojunction photoanodes were successfully prepared by electrochemical anodization and hydrothermal method. The microstructures, compositions, crystal structures, chemical valence states and light absorption performances of the composites were evaluated by field emission scanning electron microscopy, energy dispersive x-ray spectroscopy transmission electron microscope, high-resolution transmission electron microscope, x-ray diffractometer, x-ray photoelectron spectroscopy and ultraviolet–visible diffuse reflectance spectroscopy (UV–vis DRS), respectively. The photocathodic protection performances of CaIn2S4/TiO2 composites for 316 stainless steel (SS) and the influences of the CaIn2S4 content on the performances were studied. The microstructural examination revealed the uniform doping of CaIn2S4 nanofragments on the TiO2 NTAs, and the composite was made up cubic CaIn2S4 and anatase TiO2. The photogenerated electrons were transferred from the TiO2 to CaIn2S4 at the interface of the composite. Compared with pure TiO2 NTAs, CaIn2S4/TiO2 NTAs exhibited better photocathodic protection performance for 316 SS under visible light. Potential drop reached 0.78 V versus saturated calomel electrode for the 316 SS coupled with CaIn2S4/TiO2 NTAs. The photocurrent density of the 316 SS coupled with the composite photoanode (235.4 μA cm–2) was 17.4 times that of TiO2. The improved photocathodic protection property of CaIn2S4/TiO2 NTAs was ascribed to the enhanced separation efficiency of the photogenerated carriers and the strong visible light absorption of the material. The CaIn2S4/TiO2 NTAs exhibited continuous protection of the 316 SS for more than 12 h even in the dark. Therefore, the CaIn2S4/TiO2 NTAs heterojunction composite is an outstanding and efficient photoanode for the photocathodic protection of metals. [ABSTRACT FROM AUTHOR]

Gd2O3:1% Er3+, 18% Yb3+, x% Mg2+ (x = 0; 2.5; 4; 5; 6; 8;10; 20; 25; 50) and Gd2O3:1% Er3+, 18% Yb3+, 2,5% Mg2+, y% Li+ (y = 0.5–2.5) nanoparticles were synthesized by homogenous precipitation method and calcined at 900 °C for 3 h in air atmosphere. Powder x-ray diffraction, scanning electron microscopy, cathodoluminescence, transmission electron microscopy, energy dispersive x-ray spectroscopy and photoluminescence techniques were employed to characterize the obtained nanoparticles. We observed a 8-fold increase in red luminescence for samples suspended in DMSO solution for 2.5% of Mg2+ doping. The x-ray analysis shows that for the concentration of 2.5% Mg, the size of the crystallites in the NPs is the largest, which is mainly responsible for the increase in the intensity of the upconversion luminescence. But the addition of Li+ ions did not improve the luminescence of the upconversion due to decreasing of crystallites size of the NPs. Synthesized nanomaterials with very effective upconverting luminescence, can act as luminescent markers in in vivo imaging. The cytotoxicity of the nanoparticles was evaluated on the 4T1 cell line for the first time. [ABSTRACT FROM AUTHOR]

Nanostructured Sb2O3 thin films have been deposited onto glass substrates by using the chemical spray pyrolysis technique, and the effect of precursor solution volume on the physical properties was investigated for the first time. The prepared films were characterized in detail by using x-ray diffraction, field-emission scanning electron microscopy with energy dispersive x-ray analysis (FESEM-EDAX), UV-vis absorption and transmission spectroscopy, Raman spectroscopy analysis and electrical resistivity measurement. X-ray diffraction analysis shows that the senarmontite cubic phase is completely transferred to the valentinite orthorhombic phase as the precursor solution volume is increased. This phase transformation as a function of precursor volume is discussed in detail. The FESEM-EDAX analysis reconfirms the phase change showing well-defined nano-dimensional cubic hexagonal and orthorhombic octahedral morphologies with excellent stoichiometry. The optical property studies show that the bandgap energy of Sb2O3 varies from 3.43–3.98 eV as a function of precursor quantity. The as-grown Sb2O3 thin films are semiconducting in nature. The measured values of electrical resistivity and activation energy are found to be dependent on the spray solution volume. The electrical resistivity of deposited Sb2O3 thin films shows variation from 26.15 × 102–34.27 × 102 Ω cm and the activation energy of the films is in the order of 0.763–0.773 eV. [ABSTRACT FROM AUTHOR]

Cu nanoparticles were prepared in an aqueous phase by means of a simple reduction-route using sodium borohydride as the reducing agent in the presence of ascorbic acid and polyvinylpyrrolidone (PVP). The hydrosol of the Cu nanoparticles deteriorated within a day. It compelled to initiate a scheme to stabilize the nanoparticles for a long period of time. Phase transfer to organic solvents using Benzyldimethylstearylammonium chloride (BDSAC) as a phase transfer agent was found to be an effective path in this respect. BDSAC performed the dual role of dragging the Cu nanoparticles from water to organic solvent and also acted as a capping agent along with PVP for better stabilization of Cu nanoparticles. The organosol of the Cu nanoparticles exhibited excellent stability and promising catalytic activity towards N-formylation reactions on a number of amine substrates in presence of visible green LED light. The yield and reusability of the catalyst were promising. All the samples were thoroughly characterized by UV-visible spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, energy dispersive analysis of x-rays, x-ray photoelectron spectroscopy and thermo gravimetric analysis. [ABSTRACT FROM AUTHOR]

Energy dispersive x-ray spectroscopy in a transmission electron microscope is often the first method employed to characterize the composition of nanowires. Ideally, it should be accurate and sensitive down to fractions of an atomic percent, and quantification results are often reported as such. However, one can often get substantial errors in accuracy even though the precision is high: for nanowires it is common for the quantified V/III atomic ratios to differ noticeably from 1. Here we analyse the origin of this systematic error in accuracy for quantification of the composition of III–V nanowires. By varying the electron illumination direction, we find electron channelling to be the primary cause, being responsible for errors in quantified V/III atomic ratio of 50%. Knowing the source of the systematic errors is required for applying appropriate corrections. Lastly, we show how channelling effects can provide information on the crystallographic position of dopants. [ABSTRACT FROM AUTHOR]

Co(OH)2 nanosheets/Cu(OH)2 nanorods composite electrodes for non-enzymatic glucose detection were fabricated by electrodepositing Co(OH)2 nanosheets on Cu(OH)2 nanorods substrate grown directly on the copper sheet via a simple one-step reaction. The Co(OH)2 nanosheets/Cu(OH)2 nanorods composite electrode was characterized by scanning electron microscopy, energy dispersive x-ray spectroscopy, x-ray diffraction and x-ray photoelectron spectroscopy. The glucose sensing performance of the composite electrode was investigated by cyclic voltammetry and chronoamperometry. The composite electrode shows high sensitivity of 2366 µA mM−1 cm−2 up to 2 mM with a lower detection limit of 0.17 mM (S/N = 3). The composite electrode is highly selective to glucose in the presence of various substances that always co-exist with glucose in real blood samples. The response of the composite towards human blood serum was in good agreement with that of commercially available glucose sensors, suggesting that a promising electrode material for highly sensitive and selective non enzymatic detection of glucose can be envisioned. [ABSTRACT FROM AUTHOR]

Black phosphorus has many potential applications in optoelectronic devices because of its unique properties. Adjusting its performance by doping is an important issue of research. In this paper, we synthesized high-quality Te-doped crystals by the chemical vapor transport method. Tellurium doping with an atomic ratio of 0.1% was confirmed by X-ray photoelectron spectroscopy, X-ray diffraction, and energy dispersive X-ray analysis. The performance of field effect transistors devices shows that the hole mobility of Te-doped black phosphorous (BP) is significantly improved compared with that of undoped-BP. The highest hole mobility at room temperature is 719 cm2 V−1 s−1, and the electron mobility is 63 cm2 V−1 s−1. Te-doped BP field effect transistors show an obvious bipolar behavior. [ABSTRACT FROM AUTHOR]

The strongly correlated rare earth nitrides display unusual coupled magnetic, electronic and superconducting properties, with predicted topological states. However, their air-sensitiveness has prevented in-depth investigations of their properties. In this paper, we show that a 100 nm thick epitaxial samarium layer provides adequate passivation of 100 nm thick thin films of gadolinium nitride (GdN), the prototypical rare earth nitride, enabling ex-situ magnetic and structural characterizations. Using reflection high-energy electron diffraction, atomic force microscopy and energy dispersive x-ray spectroscopy, we investigate the thermal desorption of the samarium layer under vacuum. We finally demonstrate successful removal of the samarium capping layer in a separate vacuum chamber after exposure to air using a combination of argon ion sputtering and thermal desorption at 400 °C, recovering the GdN surface. [ABSTRACT FROM AUTHOR]

Electrochemical etching of silicon carbide (SiC) material has received increasing attention in recent years, due to its simple procedure, low cost and significance in the exploration of novel optoelectronic devices. In this paper, 4H-SiC substrates were electrochemically etched at a constant current density of 392.98 mA cm−2 in an electrolyte made up of hydrofluoric acid and deionized water. The layering of a SiC porous layer and periodic fluctuation of the voltage were witnessed for the first time, with the layering phenomenon corresponding well to the voltage period. However, no such phenomenon was observed when the SiC substrates were anodic etched under the same conditions with magnet stirring. As a result, the periodic variation of voltage was hypothesized to be the cause of regular layering during constant current electrochemical etching. Electrochemical etching in potentiostatic mode was thus performed at different voltages. We found that the diameter of the SiC nanopores increased while the thickness of the sidewall decreased with the increasing voltage. Based on the experimental findings, a model of mass transport was proposed. The mass transport process leads to periodic changes in resistance, hence the periodic change in voltage. This successfully explained the reason for the layering. Furthermore, SiC substrates were also electrochemically etched at high and low current densities, finding the existence of a threshold current density for the occurrence of the layering. Energy dispersive x-ray spectroscopy analysis showed that the composition of the SiC porous layer remained unchanged compared to the pure SiC wafer, implying that the peeling-off of the SiC porous layer obtained by electrochemical etching can be directly adopted for use on devices requiring a SiC porous structure. [ABSTRACT FROM AUTHOR]

We report on a simple strategy for the direct synthesis of a thin film comprising interconnected NiO nanoparticles deposited on both sides of a graphene sheet via cathodic deposition. For the co-electrodeposition, graphene oxide (GO) is treated with water-soluble cationic poly(ethyleneimine) (PEI) which acts as a stabilizer and trapping agent to form complexes of GO and Ni2+. The positively charged complexes migrate toward the stainless steel substrate, resulting in the electrochemical deposition of PEI-modified GO/Ni(OH)2 at the electrode surface under an applied electric field. The as-synthesized film is then converted to graphene/NiO after annealing at 350 ° C. The interconnected NiO nanoparticles are uniformly deposited on both sides of the graphene surface, as evidenced by field emission scanning electron microscopy, transmission electron microscopy and energy dispersive spectrometry. This graphene/NiO structure shows enhanced electrochemical performance with a large reversible capacity, good cyclic performance and improved electronic conductivity as an anode material for lithium ion batteries. A reversible capacity is retained above 586 mA h g−1 after 50 cycles. The findings reported herein suggest that this strategy can be effectively used to overcome a bottleneck problem associated with the electrochemical production of graphene/metal oxide films for lithium ion battery anodes. [ABSTRACT FROM AUTHOR]

Coating of gold-decorated silica nanoparticles with polyethylene glycol (PEG) was carried out in the aerosol phase. The process involves first functionalizing the nanoparticles at ∼225 °C with a bifunctional reactant, 2-mercaptoethanol (ME), for which one end is a thiol that attaches to the gold surface and the other end is a terminal hydroxyl group, and then introducing ethylene oxide (EO), which reacts at ∼440 °C with the hydroxyl group via a ring-opening polymerization to grow PEG. The morphology, elemental composition and surface chemistry of the PEGylated nanoparticles were characterized by means of transmission electron microscopy, energy dispersive x-ray spectroscopy in scanning transmission electron microscopy, x-ray photoelectron microscopy and Fourier transform infrared spectroscopy. The increase in mobility diameter of the nanoparticles due to PEG growth was measured on-line by tandem differential mobility analysis. The PEG coating thickness was found to increase with increases in gold decoration density, flow rate of ME, and flow rate of EO. Coating thicknesses up to ∼4.5 nm were measured on nanoparticles whose initial mobility diameter equaled 39 nm. [ABSTRACT FROM AUTHOR]

A single-step solid-state synthetic approach was developed for the synthesis of silicon-coated carbon nanotube (CNT) core/shell structures. This was achieved through laser-induced melting and evaporation of CNT-deposited Si substrates using a continuous wavelength CO2 laser. The synthesis location of the CNT/Si structures was defined by the laser-irradiated spots. The thickness of the coating was controlled by tuning the laser power and synthesis time during the coating process. This laser-based synthetic technique provides a convenient approach for solid-state, controllable, gas-free, simple and cost-effective fabrication of CNT/Si core/shell structures. [ABSTRACT FROM AUTHOR]

We report on the self-catalysed growth of vertical InAs1-xPx nanowires on Si(111) substrates by solid-source molecular-beam epitaxy. High-resolution transmission electron microscopy revealed the mixed wurtzite and zincblende structure of the nanowires. Energy dispersive x-ray spectroscopy and x-ray diffraction measurements were used to study the phosphorus content x in the InAs1-xPx nanowires, which was shown to be in the range 0-10 %. The dependence of phosphorus incorporation in the nanowires on the phosphorus flux in the growth chamber was investigated. The incorporation rate coefficients of As and P in InAs1xPx nanowires were found to be in the ratio 10 ± 5 to 1. [ABSTRACT FROM AUTHOR]

Orthorhombic molybdenum oxide (α-MoO3) nanostructures were deposited on the surface of carbon cloth (CC) as a flexible and high conductive scaffold by reactive RF magnetron sputtering technique. Structure and morphology of the as prepared molybdenum coated carbon cloth (MoO3CC) were thoroughly characterized with field emission scanning electron microscopy, x-ray diffraction, energy dispersive x-ray and Raman spectroscopy. Benefiting from high surface area and superior conductivity of CC as well as electrocatalytic activity of α-MoO3 nanostructures, an electrochemical sensor was fabricated. The electrochemical behavior of this new sensor toward determination of dopamine was studied in detail by cyclic voltammetry, amperometry (AM) and square wave voltammetry (SWV). Results reported here reveal that using SWV not only enhances the sensitivity of sensors to dopamine by more than 14 times compared to AM, but also offers higher linear dynamic range (1–700 μM compared to 5–550 μM). Limit of detection, for signal to noise ratio 3, was calculated to be 0.48 μM. Applicability of the proposed sensor for measurement of dopamine in real samples, like urine and pharmaceutical formulation, was also evaluated that concluded to satisfactory results. [ABSTRACT FROM AUTHOR]

We report on structural, compositional, and thermal characterization of self-assembled in-plane epitaxial Si1−xGex alloy nanowires grown by molecular beam epitaxy on Si (001) substrates. The thermal properties were studied by means of scanning thermal microscopy (SThM), while the microstructural characteristics, the spatial distribution of the elemental composition of the alloy nanowires and the sample surface were investigated by transmission electron microscopy and energy dispersive x-ray microanalysis. We provide new insights regarding the morphology of the in-plane nanostructures, their size-dependent gradient chemical composition, and the formation of a 5 nm thick wetting layer on the Si substrate surface. In addition, we directly probe heat transfer between a heated scanning probe sensor and Si1−xGex alloy nanowires of different morphological characteristics and we quantify their thermal resistance variations. We correlate the variations of the thermal signal to the dependence of the heat spreading with the cross-sectional geometry of the nanowires using finite element method simulations. With this method we determine the thermal conductivity of the nanowires with values in the range of 2–3 W m−1 K−1. These results provide valuable information in growth processes and show the great capability of the SThM technique in ambient environment for nanoscale thermal studies, otherwise not possible using conventional techniques. [ABSTRACT FROM AUTHOR]

It is demonstrated that growing InGaN nanowires in metal-rich conditions on top of GaN nanowires results in a widening of the InGaN section. It is shown that the widening is eased by stacking faults (SFs) formation, revealing facets favorable to In incorporation. It is furthermore put in evidence that partial dislocations terminating SFs efficiently contribute to elastic strain relaxation. Indium accumulation on top of the InGaN section is found to result in an axial growth rate decrease, which has been assigned to increased N–N recombination and subsequent effective nitrogen flux decrease, eventually leading to the formation of InGaN nano-umbrellas/nanoplatelets. [ABSTRACT FROM AUTHOR]

Highly pure metallic structures can be deposited by electron beam induced deposition and they have many important applications in different fields. The organo-metallic precursor is decomposed and deposited under the electron beam, and typically it is purified with post-irradiation in presence of O2. However, this approach limits the purification to the surface of the deposit. Therefore, ‘in situ’ purification during deposition using simultaneous flows of both O2 and precursor in parallel with two gas injector needles has been tested and verified. To simplify the practical arrangements, a special concentric nozzle has been designed allowing deposition and purification performed together in a single step. With this new device metallic structures with high purity can be obtained more easily, while there is no limit on the height of the structures within a practical time frame. In this work, we summarize the first results obtained for ‘in situ’ Au purification using this concentric nozzle, which is described in more detail, including flow simulations. The operational parameter space is explored in order to optimize the shape as well as the purity of the deposits, which are evaluated through scanning electron microscope and energy dispersive x-ray spectroscopy measurements, respectively. The observed variations are interpreted in relation to other variables, such as the deposition yield. The resistivity of purified lines is also measured, and the influence of additional post treatments as a last purification step is studied. [ABSTRACT FROM AUTHOR]

High resolution nanoscale imaging in liquid environments is crucial for studying molecular interactions in biological and chemical systems. In particular, electron microscopy is the gold-standard tool for nanoscale imaging, but its high-vacuum requirements make application to in-liquid samples extremely challenging. Here we present a new graphene based wet cell device where high resolution scanning electron microscope (SEM) and energy dispersive x-rays (EDX) analysis can be performed directly inside a liquid environment. Graphene is an ideal membrane material as its high transparancy, conductivity and mechanical strength can support the high vacuum and grounding requirements of a SEM while enabling maximal resolution and signal. In particular, we obtain high resolution ( nm) SEM video images of nanoparticles undergoing Brownian motion inside the graphene wet cell and EDX analysis of nanoparticle composition in the liquid enviornment. Our obtained resolution surpasses current conventional silicon nitride devices imaged in both a SEM and transmission electron microscope under much higher electron doses. [ABSTRACT FROM AUTHOR]

Using elastic scattering theory we show that a small set of energy dispersive x-ray spectroscopy (EDX) measurements is sufficient to experimentally evaluate the scattering function of electrons in high-angle annular dark field scanning transmission microscopy (HAADF-STEM). We then demonstrate how to use this function to transform qualitative HAADF-STEM images of InGaN layers into precise, quantitative chemical maps of the indium composition. The maps obtained in this way combine the resolution of HAADF-STEM and the chemical precision of EDX. We illustrate the potential of such chemical maps by using them to investigate nanometer-scale fluctuations in the indium composition and their impact on the growth of epitaxial InGaN layers. [ABSTRACT FROM AUTHOR]