Jingshu Wang

Synthesis of porous ZnS, ZnO and ZnS/ZnO nanosheets and their photocatalytic properties

Porous ZnS, ZnO and ZnS–ZnO nanosheets (NSs) are obtained by annealing ZnS(en)0.5 (en = ethylenediamine) NSs under suitable conditions in air. The annealing temperature plays an important role. Porous hexagonal wurtzite ZnS, ZnS–ZnO and ZnO NSs are obtained at 400, 500 and 600 °C, respectively. ZnS–ZnO NSs exhibit the highest photocatalytic activity and good photocatalytic stability in the decomposition of organic dye molecule rhodamine B (RhB) under ultraviolet (UV) light illumination.

The electrical transportation and carrier behavior of ZnSe under high pressure

With in situ electrical resistivity and Hall effect measurement, electrical transportation property and charge carrier behavior of ZnSe were investigated under high pressure using a diamond anvil cell (DAC). The electrical resistivity changed discontinuously at 7.7 and 11.9 GPa, corresponding to the phase transitions of ZnSe. In the pressure interval of 7.7–11.9 GPa, the electrical resistivity changed continuously, indicating the existence of the intermediate phase between the zinc blende and rock salt phases. The difference of carrier characteristic between the intermediate and rock salt phases can also suggest the existence of the intermediate phase. For the intermediate phase, the increase in electrical resistivity is from the decrease in mobility. While for the rock salt phase, the increase in charge carrier concentration leads to the decrease in electrical resistivity.

Mixed conduction in BaF2 nanocrystals under high pressure

The charge transport behavior of barium fluoride nanocrystals has been investigated by in situ impedance measurement up to 23 GPa. It was found that the parameters changed discontinuously at each phase transition. The charge carriers in BaF2 nanocrystals include both F− ions and electrons. Pressure makes both the F− ions diffusion and electronic transport more difficult. The defects at grains dominate the electronic transport process. Pressure could make the charge–discharge processes in the Fm3m and Pnma phases more difficult. The electron conduction plays a dominant role in the transport process. In the Fm3m and Pnma phases, the electron transference number increases with increasing pressure.

High pressure impedance spectroscopy of SrF2 nanocrystals

ABSTRACT The charge transport behavior of strontium fluoride nanocrystals has been investigated by in situ impedance measurement up to 41 GPa. It was found that the parameters changed discontinuously at each phase transition. The charge carriers in SrF2 nanocrystals include both F− ions and electrons. Pressure makes the electronic transport more difficult. The defects at grains dominate the electronic transport process. Pressure could make the charge–discharge processes in the Fm3m and Pnma phases more difficult.

Cracking Performance of Supercritical n-Decane with Mo-promoted Pt/CeO2-Al2O3 Catalysts

The catalytic performances of Pt/MoO3/CeO2-Al2O3 (PCA-M), Pt/V2O5/CeO2-Al2O3 (PCA-V), and Pt/MoO3/CeO2-ZrO2-Al2O3 (PCZA-M) are investigated using n-decane cracking in a plug flow reactor. The catalytic cracking activities of the catalysts are found to increase with the order of the strong acid amount: PCA-M > PCZA-M > PCA-V. Hence, it is concluded that the larger the strong acid amount the better the cracking activities. The gas yield of PCA-M increase by 5.8% at 700°C compared to that of PCA-V, and its heat sink increases by 0.17 MJ/kg correspondingly. PCA-M has the greatest effects on the gas yields and heat sinks.

Effects of pressure on the carrier behavior of HgSe

In situ Hall effect measurement of HgSe was conducted up to 31 GPa. It was found that the carrier parameters changed discontinuously at each phase transition. The resistivity variation under compression was described by the carrier parameters. The decrease in cinnabar mobility indicates that the interaction between the helical chains becomes stronger under pressure. Combining the results of experiment and theory calculation, it can be concluded that in the phase transition process from zinc blende through cinnabar to rock salt, if Hg atom is mainly displaced , hole will be generated and its concentration will increase; on the contrary, if Se atom is mainly displaced, electrons will be generated and their concentration will increase.

Effect of Tb-doped Concentration Variation on the Electrical and Dielectric Properties of CaF2 Nanoparticles

Calcium fluoride (CaF2) nanoparticles with various terbium (Tb) doping concentrations were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), and alternating current (AC) impedance measurement. The original shape and structure of CaF2 nanoparticles were retained after doping. In all the samples, the dominant charge carriers were electrons, and the F− ion transference number increased with increasing Tb concentration. The defects in the grain region considerably contributed to the electron transportation process. When the Tb concentration was less than 3%, the effect of the ionic radius variation dominated and led to the diffusion of the F− ions and facilitated electron transportation. When the Tb concentration was greater than 3%, the increasing deformation potential scattering dominated, impeding F− ion diffusion and electron transportation. The substitution of Ca2+ by Tb3+ enables the electron and ion hopping in CaF2 nanocrystals, resulting in increased permittivity.

Defects driven photoluminescence property of Sm-doped ZnO porous nanosheets via a hydrothermal approach

Samarium doped ZnO porous nanosheets were prepared via a hydrothermal approach and well characterized by X-ray diffraction (XRD), Raman spectroscopy, transition electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), photoluminescence spectroscopy (PL) and UV–vis absorption spectroscopy. With increasing the Sm3+ doping concentrations, the crystallization of the thin nanosheets with irregular porosities became worse and the size of the porosities in the nanosheets gradually diminished due to the obstructions of Zn–O–Sm and the generated volatile gas. It was also found that the Sm3+ ions not only acted as the donors sinks to modulate the defects in host, but also expanded the visible light response of the ZnO. The slight redshift of UV NBE (near-band edge) emission as compared to undoped one indicated the band gap of the doped nanosheets became narrower due to the combination of the formed impurity band and the strong exchange interactions between electrons. The kinds of the defects as the deep-level-defect luminescent centers in DLE (deep-level emission) varied with the Sm3+ doping concentrations, and the detail change of the defects was also discussed in detail. These findings would be useful for the material design and defect modification for optical applications.