A composite photocatalyst of cdS nanoparticles deposited on TiO2 nanosheets

A nanocomposite photocatalyst consisting of deposited CdS nanoparticles on TiO2 nanosheets was fabricated by a simple one-pot method. The contact between two phases was maximized by making a composite structure of TiO2 nanosheet decorated with CdS nanoparticles. The composite photocatalyst showed higher photoactivity for hydrogen production from aqueous Na2S/Na2SO3 solution and decomposition of methylene blue under visible light irradiation (lamda > or =420 nm) compared with single component CdS nanoparticles or a physical mixture of CdS nanoparticles and TiO2 nanorods. The intentional formation of nanoscale heterojunctions between two phases appears beneficial for inducing an efficient electron-hole separation.     

CdS@SiO2 Core–Shell Electroluminescent Nanorod Arrays Based on a Metal–Insulator–Semiconductor Structure

Enormous advancement has been achieved in the field of one‐dimensional (1D) semiconductor light‐emitting devices (LEDs), however, LEDs based on 1D CdS nanostructures have been rarely reported. The fabrication of CdS@SiO₂ core–shell nanorod array LEDs based on a Au–SiO₂–CdS metal–insulator–semiconductor (MIS) structure is presented. The MIS LEDs exhibit strong yellow emission with a low threshold voltage of 2.7 V. Electroluminescence with a broad emission ranging from 450 nm to 800 nm and a shoulder peak at 700 nm is observed, which is related to the defects and surface states of the CdS nanorods. The influence of the SiO₂ shell thickness on the electroluminescence intensity is systematically investigated. The devices have a high light‐emitting spatial resolution of 1.5 μm and maintain an excellent emission property even after shelving at room temperature for at least three months. Moreover, the fabrication process is simple and cost effective and the MIS device could be fabricated on a flexible substrate, which holds great potential for application as a flexible light source. This prototype is expected to open up a new route towards the development of large‐scale light‐emitting devices with excellent attributes, such as high resolution, low cost, and good stability.     

Wire-shaped quantum dots-sensitized solar cells based on nanosheets and nanowires

Wire-shaped quantum dots-sensitized solar cells (WS-QDSCs) based on nanosheets and nanowires were fabricated and investigated for this paper. The nanosheets grown on stainless steel (SS) wire by electrodeposition were mainly composed of Zn?(OH)?Cl?·H?O and most of the Zn?(OH)?Cl?·H?O was converted to ZnO by post-treatment, and ZnO nanowires were directly grown on SS wire by the hydrothermal method. CdS QDs were deposited on nanosheets and nanowires by successive ionic layer adsorption and reaction method. The results of photoelectrochemical performance indicated that WS-QDSCs showed a similar conversion efficiency in polysulfide and Na?SO? electrolytes, while the WS-QDSCs based on the Cu2S counter electrode achieved much higher performance than those based on SS and Cu counter electrodes. By optimizing electrodeposition duration, the WS-QDSCs based on nanosheets presented the highest conversion efficiency of 0.60% for the duration of 20 min. Performance comparison indicated that the WS-QDSC based on nanosheets showed very superior performance to that based on the nanowires with similar film thickness.     

Self-assembly deposition and luminescence properties of TiNbO5(-) and TiTaO5(-) nanosheets

Through a novel mechanical cleavage technology, TiNbO5(-) and TiTaO5(-) nanosheets were obtained by the exfoliation of the layered KTiTaO5 and KTiNbO5. Lamellar aggregates of the pre-prepared nanosheets accommodating Eu3+ ions have been fabricated by flocculation of colloidal nanosheet. A series of methods including X-ray diffraction (XRD), transmission electron microscopy (TEM) were used to analyze the structure of the as-obtained composites. The results indicated that the restacking nanosheets could form a uniform layered structure. Meanwhile, the Eu3+ ions could enter into the interlayer of the flocculated nanosheets. The Photoluminescence (PL) spectra were also employed to investigate the optical property of the hybrids. The characteristic emission from the composites either by exciting the nanosheet host with UV light or by directly exciting RE at a longer wavelength were studied in details.     

Electrochemical performance of a graphene-polypyrrole nanocomposite as a supercapacitor electrode

A unique nanoarchitecture has been established involving polypyrrole (PPy) and graphene nanosheets by in situ polymerization. The structural aspect of the nanocomposite has been determined by Raman spectroscopy. Atomic force microscopy reveals that the thickness of the synthesized graphene is ～ 2 nm. The dispersion of the nanometer-sized PPy has been demonstrated through transmission electron microscopy and the electrochemical performance of the nanocomposite has been illustrated by cyclic voltammetry measurements. Graphene nanosheet serves as a support material for the electrochemical utilization of PPy and also provides the path for electron transfer. The specific capacitance value of the nanocomposite has been determined to be 267 F g(-1) at a scan rate of 100 mV s(-1) compared to 137 mV s(-1) for PPy, suggesting the possible use of the nanocomposite as a supercapacitor electrode. After 500 cycles, only 10% decrease in specific capacitance as compared to initial value justifies the improved electrochemical cyclic stability of the nanocomposite.     

MOVPE 生长 InGaN/GaN 单量子阱绿光LED

采用金属有机物气相外延（MOVPE）方法,生长出InGaN/GaN单量子阱结构的绿光发光二极管（LED）。测量了其电致发光光谱及发光强度与注入电流的关系。室温正向偏置下,在20mA的注入电流时,发光波长峰值为530nm,半高宽为30nm。当注入电流小于40mA时,发光强度随注入电流的增大递增。这是中国国内首次研制出的InGaN单量子阱结构的绿光LED。     

High-performance single CdS nanowire (nanobelt) Schottky junction solar cells with Au/graphene Schottky electrodes

High-performance single CdS nanowire (NW) as well as nanobelt (NB) Schottky junction solar cells were fabricated. Au (5 nm)/graphene combined layers were used as the Schottky contact electrodes to the NWs (NBs). Typical as-fabricated NW solar cell shows excellent photovoltaic behavior with an open circuit voltage of ～0.15 V, a short circuit current of ～275.0 pA, and an energy conversion efficiency of up to ～1.65%. The physical mechanism of the combined Schottky electrode was discussed. We attribute the prominent capability of the devices to the high-performance Schottky combined electrode, which has the merits of low series resistance, high transparency, and good Schottky contact to the CdS NW (NB). Besides, a promising site-controllable patterned graphene transfer method, which has the advantages of economizing graphene material and free from additional etching process, was demonstrated in this work. Our results suggest that semiconductor NWs (NBs) are promising materials for novel solar cells, which have potential application in integrated nano-optoelectronic systems.     

Synthesis and dye-sensitized solar cell performance of nanorods/nanoparticles TiO2 from high surface area nanosheet TiO2

High surface area nanosheet TiO2 with mesoporous structure were synthesized by hydrothermal method at 130 degrees C for 12 h. The samples characterized by XRD, SEM, TEM, SAED, and BET surface area. The nanosheet structure was slightly curved and approximately 50-100 nm in width and several nanometers in thickness. The as-synthesized nanosheet TiO2 had average pore diameter about 3-4 nm. The BET surface area and pore volume of the sample were about 642 m(2)/g and 0.774 cm(3)/g, respectively. The nanosheet structure after calcinations were changed into nanorods/nanoparticles composite with anatase TiO2 structure at 300-500 degrees C (10-15 nm in rods diameter and about 5-10 nm in particles diameter). The solar energy conversion efficiency (eta) of the cell using nanorods/nanoparticles TiO2 (from the nanosheet calcined at 450 degrees C for 2 h) with mesoporous structure was about 7.08% with Jsc of 16.35 mA/cm(2), Voc of 0.703 V and ff of 0.627; while eta of the cell using P-25 reached 5.82% with Jsc of 12.74 mA/cm(2), Voc of 0.704 V, and ff of 0.649.     

Synthesis of CdS hierarchical microspheres and their application in electrochemiluminescence sensing

CdS microspheres with hierarchical structures were prepared with sodium dodecylbenzenesulfonate (SDBS) as structure directing reagent. SEM analysis indicated that the CdS microspheres were constructed with CdS nanosheets, which were further built up with assembled CdS nanoparticles. Optical investigation showed that the obtained CdS microspheres have an UV-vis absorption at 445 nm and photoluminescence (PL) emissions at 498 and 573 nm. The CdS hierarchical microspheres were immobilized on a glassy carbon electrode and the electrochemiluminescence (ECL) properties were investigated. The first application to sensing H₂O₂ was studied based on ECL from CdS hierarchical microspheres. A linear relation between the ECL intensity and H₂O₂ concentration, I = 2.4212 + 2.1713 c, was obtained with a detection limit of 1 × 10⁻⁸ mol·L^− 1.     

Epoxy Resin/Graphite Electrically Conductive Nanosheet Nanocomposite

In this study, graphite nanosheets were prepared by powdering expanded graphite with sonication in aqueous alcoholic solution. Epoxy resin/graphite nanosheet nanocomposites were fabricated and their electrical and mechanical properties were investigated. The results revealed that graphite sheets 30-80 nm in thickness could be effectively dispersed within the epoxy resin. The percolation threshold of epoxy resin/graphite nanoparticles was about 0.015, much lower than that of composites with conventional graphite. However, tensile strength, impact strength, and elongation at break of the composites, with increase in graphite nanosheets content, were all sacrificed.     

Nanocomposite organic films on silicon

Metal-insulator-semiconductor structures were fabricated using 40-layers-thick Langmuir-Blodgett (LB) films of stearic acid (SA) on hydrophobic n-type silicon (n-Si) substrates. Cadmium sulphide (CdS) nanoparticles were introduced by exposure to H/sub 2/S gas for a period of 12 h. Samples containing CdS nanoparticles exhibit lower dc leakage current but higher effective dielectric constant. The effective dielectric constant of the CdS embedded SA matrix is found to be 5.1. The Poole-Frenkel effect is prevalent for charge transport in the LB films containing CdS nanoparticles at the field higher than 10/sup 7//spl middot/ Vm/sup -1/. The effect becomes saturated at higher fields.     

Violet-blue LEDs based on p-GaN/n-ZnO nanorods and their stability

In this paper, we report a fabrication, characterization and stability study of p-GaN/n-ZnO nanorod heterojunction light-emitting devices (LEDs). The LEDs were assembled from arrays of n-ZnO vertical nanorods epitaxially grown on p-GaN. LEDs showed bright electroluminescence in blue (440 nm), although weaker violet (372 nm) and green-yellow (550 nm) spectral components were also observed. The device characteristics are generally stable and reproducible. The LEDs have a low turn-on voltage (～5 V). The electroluminescence (EL) is intense enough to be noticed by the naked eye, at an injection current as low as ～ 40 μA (2.1 × 10(-2) A cm(-2) at 7 V bias). Analysis of the materials, electrical and EL investigations point to the role of a high quality of p-n nano-heterojunction which facilitates a large rectification ratio (320) and a stable reverse current of 2.8 μA (1.4 × 10(-3) A cm(-2) at 5 V). Stability of EL characteristics was investigated in detail. EL intensity showed systematic degradation over a short duration when the LED was bias-stressed at 30 V. At smaller bias (<20 V) LEDs tend to show a stable and repeatable EL characteristic. Thus a simple low temperature solution growth method was successfully exploited to realize nanorod/film heterojunction LED devices with predictable characteristics.     

Magnetic, optical and structural property studies of Mn-doped ZnO nanosheets

We report the synthesis of pure and Mn doped ZnO in the form of nanosheets using a simple and single step procedure involving a microwave assisted chemical method. As prepared Mn-doped ZnO nanosheets were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), ultra violet-visible (UV-Vis), Raman spectroscopy and magnetization measurements. The structural studies using XRD and TEM revealed the absence of Mn-related secondary phases and showed that Mn-doped ZnO comprise a single phase nature with wurtzite structure. FESEM and TEM micrographs show that the average diameter of Mn-ZnO assembled nanosheets is about approximately 50 nm, and the length of a Mn-doped ZnO nanosheet building block which is made up of thin mutilayered sheets is around approximately 300 nm. Concerning the Raman scattering spectra, the shift in peak position of E2 (high) mode toward low frequencies due to the Mn doping could be explained well by means of the spatial correlation model. Magnetic measurements showed that Mn-doped ZnO nanosheets exhibit ferromagnetic ordering at or above room temperature.     

Room-temperature preparation of ZnO nanosheets grown on Si substrates by a seed-layer assisted solution route

A facile route to prepare two-dimensional ZnO nanosheet structures on Si substrates was developed through the adoption of a ZnO seed-layer and suitable growth medium in this work. The characterization results showed that ZnO nanosheets could be grown on Si substrates with a pre-formed ZnO seed-layer at room temperature. The ZnO nanosheets, with thickness of 20-25?nm, were interwoven into networks to form a continuous nanosheet film. Room-temperature measurements of the photoluminescence (PL) spectra and water wettability for the resulting ZnO nanosheet structures showed high intensity ratio of the UV emission to the defect emissions and good hydrophilic property without UV illumination. The present work demonstrates that the adoption of a ZnO seed-layer is an effective approach for room-temperature growth of ZnO nanosheets grown on substrates.     

Solution-processed graphene/MnO2 nanostructured textiles for high-performance electrochemical capacitors

Large scale energy storage system with low cost, high power, and long cycle life is crucial for addressing the energy problem when connected with renewable energy production. To realize grid-scale applications of the energy storage devices, there remain several key issues including the development of low-cost, high-performance materials that are environmentally friendly and compatible with low-temperature and large-scale processing. In this report, we demonstrate that solution-exfoliated graphene nanosheets (～5 nm thickness) can be conformably coated from solution on three-dimensional, porous textiles support structures for high loading of active electrode materials and to facilitate the access of electrolytes to those materials. With further controlled electrodeposition of pseudocapacitive MnO(2) nanomaterials, the hybrid graphene/MnO(2)-based textile yields high-capacitance performance with specific capacitance up to 315 F/g achieved. Moreover, we have successfully fabricated asymmetric electrochemical capacitors with graphene/MnO(2)-textile as the positive electrode and single-walled carbon nanotubes (SWNTs)-textile as the negative electrode in an aqueous Na(2)SO(4) electrolyte solution. These devices exhibit promising characteristics with a maximum power density of 110 kW/kg, an energy density of 12.5 Wh/kg, and excellent cycling performance of ～95% capacitance retention over 5000 cycles. Such low-cost, high-performance energy textiles based on solution-processed graphene/MnO(2) hierarchical nanostructures offer great promise in large-scale energy storage device applications.     

InGaN-based nano-pillar light emitting diodes fabricated by self-assembled ITO nano-dots

InGaN/GaN based nano-pillar light emitting diodes (LEDs) with a diameter of 200-300 nm and a height of 500 nm are fabricated by inductively coupled plasma etching using self-assembled ITO nano-dots as etching mask, which were produced by wet etching of the as-deposited ITO films. The peak PL intensity of the nano-pillar LEDs was significantly higher than that of the as-grown planar LEDs, which can be attributed to the improvement of external quantum efficiency of the nano-pillar LEDs due to the large sidewall of the nano-pillars. We have also demonstrated electrical pumping of the InGaN/GaN based nano-pillar LEDs with a self-aligned TiO2 layer as a passivation of sidewall of the nano-pillars.     

Development of nanostructured CdS sensor for H2S recognition: structural and physical characterization

In the present work, we report on the performance of a nanostructured CdS gas sensor. The sensor was fabricated using spin coating technique on glass substrate. The CdS sensor was characterized for their, structural microstructural as well as optoelectronic and H₂S response was studied. The XRD analysis showed formation of nanocrystalline CdS. Morphological analysis using SEM revealed nanostructured morphology with average grain size in the range of 40–50nm. Optical investigations showed a high absorption coefficient (10⁴ cm⁻¹) with a direct band gap of 2.54 eV. Electrical transport studies revealed films shows n-type conduction mechanism with room temperature dc electrical conductivity 10⁻⁶ (Ω cm)⁻¹. The CdS sensors showed the maximum response of 13.2% upon exposure to 100 ppm H₂S at operating temperature 100 °C.     

Electrical,electrochemical and photo-electrochemical studies on the electrodeposited n-type semiconductor hexagonal crystalline CdS thin film on nickel substrate

Electrodeposited cadmium sulfide (CdS) on nickel substrate of new properties from aqueous solutions of Cd²⁺ and S₂O₃ ^2? at 313 K has been obtained using cyclic voltammetric and potentiostatic techniques. The mechanism of the electrode reactions for the electrodeposition of CdS has been evaluated and proposed. Energy dispersive X-ray florescence elemental analysis and X-ray diffraction investigations demonstrate that, the electrodeposited CdS is pure and hexagonal polycrystalline in nature, at our optimal conditions. Furthermore, the electrodeposited CdS is of n-type semiconductor was investigated and confirmed by Mott–Schotky test. Donor concentration (N_D) was determined to be 1.0 × 10¹⁷ cm^?3. In this research we discovered that, the electrodeposited semiconductor CdS on Ni substrate has low resistivity and magnetic properties (became as a strong magnet) at the mentioned conditions. The photoelectrochemical measurements of the electrodeposited CdS on nickel electrode had been investigated at room temperature and under illumination giving good results.     

Gold nanowires fabricated by immersion plating

The growth mechanism of oriented Au nanowires fabricated by immersion plating was investigated. Both n-type crystal Si (c-Si) and amorphous Si (a-Si) with an electron-beam (E-beam) patterned resist nanotrench were immersed into the plating bath HAuCl(4)/HF. For the Au nanowires fabricated on c-Si, voids, nanograins, and clusters were observed at various plating conditions, time and temperature. The voids were often found in the center of the Au nanowires due to there being fewer nucleation sites on the c-Si surface. However, Au can easily nucleate on the surface of a-Si and form continuous Au nanowires with grain sizes about 10-50?nm. The resistivities of Au nanowires with width 105?nm fabricated on a-Si are about 4.4-6.5?μΩ?cm. After annealing at 200?°C for 30?min in N(2) ambient, the resistivities are lowered to about 3.0-3.9?μΩ?cm, measured in an atomic force microscope (AFM) in contact mode. The grain size of Au is in the range of ～50-100?nm. A scanning electron microscope (SEM) examination and grazing incident x-ray diffraction (GIXRD) analysis were also carried out to study the morphology and crystalline structure of the Au nanowires.     

Ultraviolet lasing action in ZnO nanosheets

We report room-temperature ultraviolet lasing action in large quantities of uniform multilayer ZnO nanosheets grown by a vapor-transport method via thermal evaporation of Zn powder. An excellent multimode lasing emission at a center wavelength of 390 nm with a mode linewidth less than 0.33 nm occurs above an excitation threshold of 8 mJ pulse(-1) cm(-2). The observed multimode lasing action may be attributed to microcavity effect and low concentration of defects in the nanosheets. We believe that the single-mode lasing emission can be obtained by growing completely uniform nanosheets. ZnO nanosheet is an attractive candidate as gain medium to realize ultraviolet semiconductor diode lasers.