Xibao Yang

A high pressure Raman study on confined individual iodine molecules as molecular probes of structural collapse in the AlPO4-5 framework

The mechanical stability of porous zeolitic materials has long been an important issue due to their advanced applications in many fields. Here, we choose to study the pressure induced structural modifications on the AlPO4-5 (AFI) framework. We find that the Raman characteristics of the confined iodine molecules in the AFI channels, with a low filling density, show discontinuities at around 3 and 10 GPa, which can be attributed to the implications of framework changes. Subsequent theoretical simulations on the AFI framework demonstrate that both a tilting mechanism along the c axis and a rotating mechanism in the ab plane of the tetrahedrons contribute to the structural deformation, and the AFI framework is collapsible at 4 and 10 GPa, which confirms those values found in the Raman studies. In this nanoconfinement system of I@AFI, the host and guest depend on and interact with each other mutually. No supporting effect on the AFI framework is found for the confined individual iodine molecules with such a low filling density, but they can be regarded as molecular probes to reflect the structural collapse of AFI. Thus, we provide a novel way to detect the structural deformation of porous materials under high pressure.

Preparation of SiO 2 nanowires by using carbon as reducing agent

SiO2 nanowires structures have been grown by a simple thermal evaporation method using C and SiO2 as the source materials at a relatively low. The as-synthesized products were characterized by scanning electron microscopy, electron energy-dispersive X-ray (EDX), X-ray powder diffraction (XRD), Raman spectroscopy (RS) and photoluminescence (PL). The products characterization indicated that the SiO2 nanowires with diameters ranging from 60nm to 120nm with a hexagonal strcture, with the length up to a few centimeters. The photoluminescence spectra of the grown products indicate excellent optical properties for the as-grown SiO2 nanowires.

Amorphous SiO 2 nanoparticles grown on the surface of the nanowires

SiO2 amorphous nanoparticles have been successfully synthesized on the surface of the SiO2 amorphous nanowires via a thermal evaporation method using SiO powders as the source agents. The as-synthesized products have been systematically studied by X-ray powder diffraction (XRD), Raman spectroscopy (RS), scanning electron microscope (SEM), electron energy-dispersive X-ray (EDX) and photoluminescence (PL). The results indicate that SiO2 amorphous nanoparticles grown on the amorphous nanowires at the temperatures of 1135 °C. Furthermore, The RT PL spectral results reveal the obtained composite structures have a stable and strong yellow-green emission range. The products are available for the applications in optoelectronic semiconductor devices with improving performances.

S-doped SiO 2 microsphere structure prepared by thermal evaporation

S-doped SiO2 microspheres have been successfully synthesized via the thermal evaporation method using S powders as the reducing agents. The as-synthesized products have been systematically studied by X-ray powder diffraction (XRD), Raman spectroscopy (RS), scanning electron microscope (SEM), electron energy-dispersive X-ray (EDX) and photoluminescence (PL). The results indicate that pure S-doped SiO2 microspheres were collected at the growth temperatures of 730 °C. Furthermore, The RT PL spectral results reveal the S-doped SiO2 microspheres have a stable and strong green emission band. The products are available for the applications in optoelectronic semiconductor devices with improving performances.

Thermal evaporation synthesis and properties of ZnO nano/microstructures using Sn reducing agents

ZnO nano/microstructures have been successfully synthesized via the thermal evaporation mothed using Sn powders as the reducing agents. The as-synthesized products have been systematically studied by X-ray powder diffraction (XRD), Raman spectroscopy (RS), scanning electron microscope (SEM), electron energy-dispersive X-ray (EDX) and ultraviolet-visible spectrum (UV-vis). The results indicate that pure ZnO and Zn2SnO4-doped ZnO were collected at the growth temperatures of 600 °C and 750 °C, respectively. Furthermore, the band gap energy of the as-synthesized product is estimated to be smaller than the reported value for ZnO. The Zn2SnO4 phase in the ZnO nano/microstructures plays an important role in the optical property.

Preparation and characterization of Cu 2 ZnSnS 4 thin films by solvothermal method

The Cu2ZnSnS4 thin films have been deposited onto FTO glass substrates by a simple solvothermal method. The films were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analyzer, and optical absorption spectroscopy technique, respectively. The influence of the annealing temperature on the structure, morphology, and composition of the films has been studied. The polycrystalline Cu2ZnSnS4 thin films crystallized in the tetragonal structure with nearly stoichiometric after annealing at 550 °C in Ar atmosphere for 1h. The analysis of the optical absorption data gave the bandgap energy to be 1.5 eV. The photoelectrochemical characterization showed that the annealed CZTS thin films behaved as p-type semiconductor photoelectrodes.

Preparation and characterization of CdIn 2 S 4 wedgelike thin films

Cadmim Indium sulfide (CdIn₂S₄) thin films composed of wedgelike crystals were prepared on fluorine-doped tin oxide substrate by a tartaric acid assisted hydrothermal method. The tartaric acid was found to play an important role in the formation of the final product. The formation mechanism of the CdIn₂S₄ film was also discussed. The optical properties and microstructure of the CdIn₂S₄ films were characterized by X-ray diffraction, field-emission scanning electron microscopy, and UV-vis absorption spectroscopy. The results revealed that the wedgelike CdIn₂S₄ thin films were crystallized in the cubic spinel structure. The analysis of optical absorption data shows bandgap energy to be 2.46 eV which is optimal for photovoltaic applications.