Hang Lv

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.

The structure and interaction mechanisms of C10H16@(13, 0)SWCNT under high pressure

The high-pressure deformation and polymerization of peapod structure (C10H16 filled into (13, 0) single-walled carbon nanotube) is studied by using density function theory. The guest–host interaction mechanism under pressure is analyzed by combining the van der Waals (vdW) potential with the electron localization function (ELF). Our studies show that the cross-section of the filled single-walled carbon nanotube changes from a circle into an ellipse shape, and then into a walnut shape with the transition pressures of 3 GPa and 10 GPa, respectively. The intertubular bonding of adjacent tubes occurs at 17 GPa, 30 GPa, 32 GPa, 82 GPa and 152 GPa. The attractive and repulsive guest–host interactions are exhibited for the pressures lower and higher than 10 GPa, respectively. Except for the ambient pressure structure, six stable high pressure structures, which can hold their structures when the pressure is released, are identified by combining the systematic binding energy with geometry optimization.

Package of double helical bromine chains inside single-walled carbon nanotubes

The helicity of stable double helical bromine chains inside single-walled carbon nanotubes (SWCNTs) was studied through the calculation of systematic interaction energy, using the van der Waals interaction potential. The results presented clear images of stable double helical structures inside SWCNTs. The optimal helical radius and helical angle of chain structure increase and decrease, respectively, with the increase of tube radius. The detailed analysis indicated that some metastable structures in SWCNTs may also co-exist with the optimal structures, but not within the same tubes. In addition, a detailed simulation of X-ray diffraction patterns was performed for the obtained optimal helical structures.

Preferable Orientations of Interacting C-60 Molecules inside Single Wall Boron Nitride Nanotubes

This work focuses on the preferable orientation analysis of the hybrid system where the C60 molecules are encapsulated inside the boron nitride nanotubes by using the two-molecule model. The low-energy state can be acquired in the contour map, which provides the visual information of the systematical van der Waals interaction potential for the C60 molecules adopting different orientations. Our results show that the C60 molecules exhibit the preferred pentagon and hexagon orientations with the tubes diameter smaller and larger than 13.55 A, respectively. The preferred two-bond orientation obtained in the single-molecule model is absent in this study, indicating that the intermolecular interaction of adjacent C60 molecules plays an important role in the orientational behaviors of this peapod structure.

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.