High Performance Broadband Ultraviolet A/Ultraviolet C Detector Based on Ga2O3/p-GaN Nanocomposite Film Fabricated by Magnetron Sputtering.

Ultraviolet (UV) detector based on ß-Ga2O3/p-GaN was fabricated in this paper. The growth process involved deposition of amorphous Ga2O3 layer by means of magnetron sputtering and conversion of ß-Ga2O3. The obtained detector displays excellent UV sensing properties which covers Ultraviolet A(UVA)/Ultraviolet C(UVC) region with fast response. It will provide a new route to fabricate ß-Ga2O3/p-GaN heterostructure for applications in broadband ultraviolet sensing.

High Performance p-GaN/Oxide Layer/n-GaN Ultraviolet Detector Fabricated by Directly Contacting Method.

High performance p-GaN/oxide layer/n-GaN ultraviolet (UV) photodetector was fabricated in this paper. The UV detector composed of n-GaN and p-GaN film with oxide layer which was constructed by directly contacting way. The detector based on GaN p-GaN/oxide layer/n-GaN structure showed high UV response with fast speed. The results indicated that the fabrication of large-scale GaNbased materials was greatly facilitated with relatively low cost contacting method. Furthermore, it offered a new method to obtain UV detector for GaN-based materials with high performance.

Fabrication of Branched Flower-Like ZnO/Si Hierarchical Heterostructure UV Detector by Aqueous Method.

High performance ZnO/Si hierarchical heterostructure UV detector was fabricated using an aqueous method. The structural, morphological and optical properties of the hierarchical heterostructure were characterized. The heterostructural UV detector was composed of ZnO nanorods grown on Si nanowires to form a flower-like structure. The device results demonstrated that the as-grown ZnO/Si hierarchical heterostructure showed high UV response. The method provides a simple way to fabricate high-response UV photodetectors based on ZnO/Si heterostructure.

Oxygen-Plasma-Assisted Enhanced Acetone-Sensing Properties of ZnO Nanofibers by Electrospinning.

In this Article, ZnO nanofibers were prepared by electrospinning. The as-prepared ZnO electrospun fibers were treated with plasma. The morphology, structure, and element content of the ZnO nanofibers greatly changed after treatment with different plasmas. The test results indicated that the acetone-sensing performance was remarkably improved for oxygen-plasma-assisted ZnO nanofibers. Furthermore, the density function theory (DFT) calculation results revealed that the acetone adsorption energy of ZnO nanofibers treated with oxygen plasma was 2 times greater than that of untreated ZnO nanofibers, and the electrons transferred between ZnO nanofibers and acetone molecules produced a more remarkable change in electronic structure for the oxygen-plasma-treated ZnO nanofibers. Our work demonstrates that the oxygen plasma treatment method can help improve the acetone-sensing performance of ZnO nanofibers.

Ultraviolet Photoconductive Detector Based on MgO/a-GaN Heterostructure Grown by Aqueous Method.

Thin MgO nanostructure layer was grown on a-plane GaN film in this study using low temperature aqueous method. The thin MgO layer showed uniform sheet-like morphology. Meanwhile, ultraviolet (UV) photoconductive detector based on MgO/a-GaN heterostructure was fabricated by simple way. The obtained detector displayed excellent UV sensing properties. Results showed that the thin MgO nanostructure layer can effectively decrease the dark current and passivate the surface defects. The facile method will provide a new route to adopt nanostructures for applications in enhancing the performance of GaN-based UV detector.

Synthesis and high pressure studies of white luminescence host-guest complex nanocrystals based on C60 and p-But-calix[8]arene.

Host-guest structured nanocrystals consisting of p-But-calix[8]arene and fullerene C60 were fabricated with the facial solution deposition method. The as-prepared host-guest complex nanocrystals are well crystallized in a tetragonal structure, in which the guest C60 and host p-But-calix[8]arene molecules interact with each other via the van der Waals force. The host-guest crystal has a wider band gap compared to that of C60 crystals. The luminescence range of the host-guest structured nanocrystals was widely extended, and its photoluminescence (PL) intensity was highly enhanced by one order of magnitude. High pressure studies on such host-guest nanocrystals were carried out using the diamond anvil cell technique with the associated spectroscopic measurements. Raman and PL spectra show a phase transition occurred on the samples owing to the deformation of fullerene molecules. A PL behavior change was also observed synchronously with the phase transition. The host-guest structure strongly influences the structure and optical behaviors of C60 under pressure.

Micellization of Pluronic P123 in Water/Ethanol/Turpentine Oil Mixed Solvents: Hybrid Particle-Field Molecular Dynamic Simulation.

The hybrid particle-field molecular dynamics simulation method (MD-SCF) was applied to study the self-assembly of Pluronic PEO20-PPO70-PEO20 (P123) in water/ethanol/turpentine oil- mixed solvents. In particular, the micellization process of P123 at low concentration (less than 20%) in water/ethanol/turpentine oil-mixed solvents was investigated. The aggregation number, radius of gyration, and radial density profiles were calculated and compared with experimental data to characterize the structures of the micelles self-assembled from P123 in the mixed solvent. This study confirms that the larger-sized micelles are formed in the presence of ethanol, in addition to the turpentine oil-swollen micelles. Furthermore, the spherical micelles and vesicles were both observed in the self-assembly of P123 in the water/ethanol/turpentine oil-mixed solvent. The results of this work aid the understanding of the influence of ethanol and oil on P123 micellization, which will help with the design of effective copolymer-based formulations.

ZnO/GaN Heterostructure as Ultraviolet Photodetector Fabricated by One-Step Aqueous Method.

ZnO thin films were fabricated on p-GaN substrate with zinc acetate as precursors by one-step aqueousmethod in this paper. The morphological and structural properties of ZnO/GaN heterostructure were studied. Meanwhile, the ultraviolet photodetector (UV) device based on ZnO/GaN heterostructure was fabricated and showed excellent UV response. The results demonstrate that the fabrication of large-scale ZnO/GaN heterostructure was greatly facilitated with relatively low cost by one-step growth method.

Ultraviolet Photodetector Based on ITO/MgO/ZnO Structure Grown by Hydrothermal Process.

A simple two-step aqueous method was employed to grow MgO nanostructures on ZnO/sapphire at low temperature. The obtained thin MgO nanostructures were uniformly distributed on the surface of ZnO layer and showed the sheet-like structures. Meanwhile, an ultraviolet (UV) photodetector based on ITO/MgO/ZnO structures was fabricated by simple way. The obtained UV detector showed excellent UV sensing properties. This novel method will greatly facilitate fabrication of large-scale metal-insulator-semiconductor with relatively low cost at remarkably low temperature.

Investigate on Structure and Optical Properties of ZnO Nanostructures Grown on a-GaN/r-Sapphire.

ZnO nanostructures were directly grown on a-GaN/r-sapphire with different growth time via aqueous method. Structural and optical properties of the nanostructures were investigated by using a variety of techniques including X-ray diffraction (XRD), scan electron microscope (SEM), room-temperature photoluminescence (PL), and Raman scattering. The results showed the growth mechanism of ZnO nanostructures grown on a-GaN is Volmer-Weber (VW) mode, which is due to the high interfacial free-energy between a-plane ZnO and GaN. Meanwhile, compressive strains were revealed to exist by the optical characterizations. And the strengths were found to reduce with increasing growth time.

One-Step Hydrothemal Synthesis of Nitrogen Doped ß-Ga2O3 Nanostructure and Its Optical Properties.

Nitrogen doped ß-Ga2O3 nanostructures were synthesized using a simple one-step aqueous approach. The structure and morphology of the nanostructures were characterized. Both the GaOOH precursor and ß-Ga2O3 nanostructures showed the rod-like morphology. Meanwhile, the ß-Ga2O3 nanostructures were doped with nitrogen, which was proved by X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) and cathodoluminescence (CL). The results showed nitrogen-doped one-dimensional ß-Ga2O3 nanostructures were achieved by in situ doping while maintaining the morphology. Meanwhile, as a straightforward method, the excellent luminescence properties are suitable for application in white-LED phosphors and novel optoelectronic devices.

Simple Fabrication of Homogeneous ZnO Core/Shell Nanorod Arrays for Ultraviolet Photodetectors.

A simple technique of two-step growth was employed to fabricate homogeneous ZnO core/shell nanorod arrays which were composed of ZnO nanodisk shell layer on the surface of ZnO nanorod arrays. The ultraviolet (UV) response characteristics of the device were measured. The homogeneous ZnO core/shell photodetector had remarkably enhanced response and recovery speed compared with pure ZnO nanorod arrays. It indicated that surface homogeneous coating can be an alternative method to enhance the response and recovery properties of the ZnO nanorod array photodetectors.

Electrospinning Hetero-Nanofibers In2O3/SnO2 of Homotype Heterojunction with High Gas Sensing Activity.

In2O3/SnO2 composite hetero-nanofibers were synthesized by an electrospinning technique for detecting indoor volatile organic gases. The physical and chemical properties of In2O3/SnO2 hetero-nanofibers were characterized and analyzed by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), Energy Dispersive X-Ray Spectroscopy (EDX), specific surface Brunauer-Emmett-Teller (BET) and X-ray photoelectron spectroscopy (XPS). Gas sensing properties of In2O3/SnO2 composite hetero-nanofibers were measured with six kinds of indoor volatile organic gases in concentration range of 0.5~50 ppm at the operating temperature of 275 °C. The In2O3/SnO2 composite hetero-nanofibers sensor exhibited good formaldehyde sensing properties, which would be attributed to the formation of n-n homotype heterojunction in the In2O3/SnO2 composite hetero-nanofibers. Finally, the sensing mechanism of the In2O3/SnO2 composite hetero-nanofibers was analyzed based on the energy-band principle.

Growth of Indium Hydroxide Nanocubes Film by Hydrothermal Method.

A new strategy has been successfully designed for the first time to synthesize indium hydroxide (In(OH)3) nanocube film by employing a novel hydroxyl (OH−) solution corrosion-base approach. The structure and optical properties of the In(OH)3 structures were investigated. It showed that In(OH)3 cube film structure was formed. Meanwhile, the In(OH)3 obtained exhibits a strong blue PL emission which allows it to be considered as a promising material for electronic and optical properties. The results show that this preparation strategy of In(OH)3 nanocube film is proved to be a simple and effective synthesis method.

Self-assembly of carbon nanotubes in polymer melts: simulation of structural and electrical behaviour by hybrid particle-field molecular dynamics.

Self-assembly processes of carbon nanotubes (CNTs) dispersed in different polymer phases have been investigated using a hybrid particle-field molecular dynamics technique (MD-SCF). This efficient computational method allowed simulations of large-scale systems (up to ∼1 500 000 particles) of flexible rod-like particles in different matrices made of bead spring chains on the millisecond time scale. The equilibrium morphologies obtained for longer CNTs are in good agreement with those proposed by several experimental studies that hypothesized a two level "multiscale" organization of CNT assemblies. In addition, the electrical properties of the assembled structures have been calculated using a resistor network approach. The calculated behaviour of the conductivities for longer CNTs is consistent with the power laws obtained by numerous experiments. In particular, according to the interpretation established by the systematic studies of Bauhofer and Kovacs, systems close to "statistical percolation" show exponents t ∼ 2 for the power law dependence of the electrical conductivity on the CNT fraction, and systems in which the CNTs reach equilibrium aggregation show exponents t close to 1.7 ("kinetic percolation"). The confinement effects on the assembled structures and their corresponding conductivity behaviour in a non-homogeneous matrix, such as the phase separating block copolymer melt, have also been simulated using different starting configurations. The simulations reported herein contribute to a microscopic interpretation of the literature results, and the proposed modelling procedure may contribute meaningfully to the rational design of strategies aimed at optimizing nanomaterials for improved electrical properties.

Hydrothermal Synthesis of ZnO Structures Formed by High-Aspect-Ratio Nanowires for Acetone Detection.

Snowflake-like ZnO structures originating from self-assembled nanowires were prepared by a low-temperature aqueous solution method. The as-grown hierarchical ZnO structures were investigated by X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM). The results showed that the snowflake-like ZnO structures were composed of high-aspect-ratio nanowires. Furthermore, gas-sensing properties to various testing gases of 10 and 50 ppm were measured, which confirms that the ZnO structures were of good selectivity and response to acetone and could serve for acetone sensor to detect low-concentration acetone.

Rigorous determination of the ground-state phases and thermodynamics in an Ising-type multiferroic chain.

To understand the ferroelectricity driven by collinear magnetism in a multiferroic spin-chain system, we have adopted an elastic diatomic Ising spin-chain model with axial next-nearest-neighbor interaction to describe its magnetoelectric properties. By employing magneto-phonon decoupling and the transfer-matrix method, the possible ground-state configurations and thermodynamic behaviors of the system have been determined exactly. The parameter relation for the appearance of electric polarization has been discussed from the perspective of the ground-state configuration. In the case of nearest-neighbor antiferromagnetic coupling, a novel series of zero-temperature transitions induced by magnetic field have been observed, from the ↑↑↓↓ spin configuration associated with ferroelectric order to the ↑↓↑ state with a peculiar 1/3 magnetization plateau, then to the ↑↑↑↓ state, and finally saturation in the ↑↑↑↑ state.

Enhanced upconversion emission in ZrO2-Al2O3 composite oxide.

Aqueous solutions of zirconium oxychloride and aluminum nitrate were coprecipitated and crystallized to form a ZrO2-Al2O3 solid solution. The upconversion (UC) emission from different Er(3+)-doped samples was studied. An enhancement of the green UC emission by as much as 22 times was achieved by co-doping with Yb(3+) and Mo(6+) ions due to an energy transfer at a higher excited-state energy, which partly avoided the non-radiative decay processes at the lower energy levels of Er(3+). The UC emission of the ZrO2-Al2O3 composite system series doped with different agents was enhanced. Excess oxygen vacancies are generated by forming ZrO2-Al2O3 solid solutions, which have an energy level close to the (4)F7/2 level of the Er(3+) ions. The defect state promoted the energy transfer process resulting in an eight-fold increased green UC emission in ZrO2-Al2O3 solid solutions. The solid solutions have a superior color chromaticity of x = 0.25 and y = 0.71 due to the evident enhancement in the green to red emission ratio in the 8ZrO2-2Al2O3 sample.

Hydrothermal synthesis and tunable luminescence of persimmon-like sodium lanthanum tungstate:Tb3+, Eu3+ hierarchical microarchitectures.

Persimmon-like NaLa(WO(4))(2) microarchitectures were prepared via hydrothermal process with using trisodium citrate (Na(3)Cit) as chelated reagent and characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), photoluminescence (PL), and fluorescent dynamics. The influences of Na(3)Cit concentration, organic additivities, and reaction time on the morphologies of NaLa(WO(4))(2) phosphor were studied. The results revealed that Na(3)Cit species had double functions of strong ligand and structure-directing reagent that could efficiently control the formation of persimmon-like NaLa(WO(4))(2) microarchitectures. The possible mechanism for the growth of persimmon-like NaLa(WO(4))(2) microarchitectures was attributed to the Ostwald ripening mechanism. The energy transfer from Tb(3+) to Eu(3+) in the persimmon-like NaLa(WO(4))(2) phosphors was observed. The energy transfer efficiencies and emission colors can be tuned by changing the concentration of Eu(3+). Finally, it was deduced that the electric dipole-dipole interaction (D-D) is the main mechanism for energy transfer between Tb(3+) and Eu(3+) in the persimmon-like NaLa(WO(4))(2) phosphor.

Economical and effective sulfide catalysts for dye-sensitized solar cells as counter electrodes.

Molybdenum sulfide (MoS(2)) and tungsten sulfide (WS(2)) are proposed as counter electrode (CE) catalysts in a I(3)(-)/I(-) and T(2)/T(-) based dye-sensitized solar cells (DSCs) system. The I(3)(-)/I(-) based DSCs using MoS(2) and WS(2) CEs achieved power conversion efficiencies of 7.59% and 7.73%, respectively.