Guishan Liu

Preparation and photoelectric properties of Ho3+-doped titanium dioxide nanowire downconversion photoanode

Abstract Ho3+-doped titanium dioxide (TiO2:Ho3+) downconversion (DC) nanowires were synthesized through a simple hydrothermal method followed by a subsequent calcination process after being immersed in Ho(NO3)3 aqueous solution. Moreover, TiO2:Ho3+ nanowires (HTNWs) were used as the photoanode in dye-sensitized solar cells (DSSCs) to investigate their photoelectric properties. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to characterize the morphology and structure of the material, respectively. The photofluorescence and ultraviolet–visible absorption spectra of HTNWs reveal a DC from the near and middle ultraviolet light to visible light which matches the strong absorbed region of the N719 dye. Compared with the pure TNW photoanode, HTNWs DC photoanodes show greater photovoltaic efficiency. The photovoltaic conversion efficiency (η) of the DSSCs with HTNWs photoanode doped with 4% Ho2O3 (mass fraction) is two times that with pure TNW photoanode. This enhancement could be attributed to HTNWs which could extend the spectral response range of DSSCs to the near and middle ultraviolet region and increase the short-circuit current density (Jsc) of DSSCs, thus leading to the enhancement of photovoltaic conversion efficiency.

Multistep Controllability Synthesis and Growth Mechanism of ZnO Nanopagoda for Schottky Diode Device

Ordered ZnO arrays with a peculiar nanostructure were synthesized by a multistep synthesis process. The first step was the preparation of ZnO seed to induce the formation of ZnO array via potentiostatic electrodeposition method using a typical three electrode set-up. The second step was fabricating ZnO array along seed by Chemical Bath Deposition. Structural analysis of ZnO was carried out with X-ray diffraction (XRD), which showed a hexagonal wurtzite structure, and the selected area electron diffraction (SAED) patterns indicated that nanocrystalline is a part of monocrystal. The scanning electron microscope (SEM) and transmission electron microscope (TEM) were used to study the microstructure, and showed a pagoda-like microstructure with a tiny top and large bottom, which had an average top diameter of exceeding 800nm at seed-depositing time of 60s, and then growth mechanisms are subsequently given a further explanation, viewed from kinetics and thermodynamics. In addition, the current–voltage curves of...

A Phase Separation Route to Synthesize α-Fe 2 O 3 Porous Nanofibers via Electrospinning for Ultrafast Ethanol Sensing

A facile and economic procedure was provided to synthesize α-Fe2O3 nanofibers. In this procedure, porous α-Fe2O3 nanofibers were obtained by a single-polymer/binary-solvent system, while solid α-Fe2O3 nanofibers were prepared by a single-polymer/single-solvent system. The crystal structure and morphology of both samples were characterized by x-ray diffraction, scanning electron microscopy, transmission electron microscopy and nitrogen adsorption/desorption isotherms. The formation mechanism of porous structure was based on solvent evaporation-induced phase separation by the use of mixed solvents with different volatility. Furthermore, ethanol-sensing performance of the porous α-Fe2O3 nanofibers was evaluated and compared with solid α-Fe2O3 nanofibers. Results from gas-sensing measurements reveal that porous α-Fe2O3 nanofibers exhibit higher sensitivity and slightly longer recovery time than solid α-Fe2O3 nanofibers. Over all, the gas sensor based on porous α-Fe2O3 nanofibers shows excellent ethanol-sensing capability with high sensitivity and ultrafast response/recovery behaviors, indicating its potential application as a real-time monitoring gas sensor.

Synthesis and performance of Ca-α/β-SiAlON composites from tailings

Ca-α/β-SiAlON composites were prepared using Ca-α/β-SiAlON powder synthesized from gold ore tailings, which contained abundant Si and Al elements as the major raw materials together with minor additives, through a pressure-less sintering method. The influences of sintering temperature on the phase composition and microstructure of the composites were analyzed. The scanning electron microscopy images of the composites show the interlacing of grains with elongated columnar, short columnar and plate-like morphologies. The composites sintered at 1520°C for 6 h have a flexural strength of 352 MPa, Vickers hardness of 11.2 GPa, and fracture toughness of 4.8 MPa·m1/2. The relative content of each phase in the products is I(Ca-α-SiAlON):I(β-SiAlON):I(Fe3Si) = 23:74:3, where Ii stands for the diffraction peak intensity of phase i.

An effective method for simulation and estimation of dye-sensitized solar cells parameters

A computer simulation and calculation method has been proposed in this paper to provide an effective and simple way to estimate the five parameters of dye-sensitized solar cells including photocurrent, reverse saturation current, diode ideality factor, series resistance and parallel resistance of the output characteristic equation. The computer program which was used to calculate these parameters automatically was written in the VB compiler environment. With the program we can get five parameters within several seconds and the maximum error is only about 5.6% which is much smaller than those gotten by computer simulation methods until now. Combining with practical experiment, this method was proved to be an effective and quick way to get the five parameters of DSSC and can aid to analyze their influence to the output V-I characteristics.