Yuncai Li

Template synthesis and characterization of WO3/TiO2 composite nanotubes

Highly ordered WO3/TiO2 composite nanotubes have been successfully prepared by the combination of the sol?gel chemical method and the anodic aluminium oxide (AAO) templating method. The diameter of the WO3/TiO2 composite nanotubes is about 100?nm, which is in good agreement with the pore diameter of the AAO template. The composite nanotubes are composed of mixed oxides of W6+ and Ti4+.

The effect of electronegative difference on the electronic structure and visible light photocatalytic activity of N-doped anatase TiO2 by first-principles calculations

The effect of electronegative difference between nitrogen and oxygen on electronic properties of N-doped anatase TiO2 has been studied using first-principles calculations. The results indicate that the valence band maximum (VBM) shifts to high energy by 0.27 eV and the band gap states composed of N 2p, O 2p, and Ti 3d states are formed through the three states entering into the gap after N doping. The interactions of three states widen and delocalize the band gap states. The raised VBM and the wide band gap states can improve the visible light photocatalytic activity.

Oscillation of absorption bands of Zn1-xmnxs clusters : an experimental and theoretical study

Electroporation of synthetic vesicles is utilized for the preparation of molecular size uncapped Zn(1-x)Mn(x)S clusters. The absence of caps permits (i) continued growth of the Zn(1-x)Mn(x)S clusters formed, (ii) the assessment of their true absorption spectra unaltered by stabilizing ligands, and (iii) the previously inaccessible live observation of the growth of the clusters in the molecular size regime. Upon cluster growth, the UV spectra exhibit novel, time-dependent, oscillation of red and blue shifts of the characteristic absorption band. The structure and electronic properties of Zn(N-1)MnS(N) clusters with N = 1-9 are calculated using the first-principles DMol(3) package. On the basis of similarities between the oscillating trend of the experimentally observed absorption spectra and that of the calculated highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gap of Zn(N-1)MnS(N) clusters with N = 1-9, the wavelengths of the sequential spectral peaks can be assigned to Zn(2)MnS(3), Zn(3)MnS(4), Zn(4)MnS(5), Zn(6)MnS(7), and Zn(8)MnS(9), respectively. Our results demonstrate that both the cluster size and the composition can be used to tune the optical properties.

Study of the size-dependent properties of ScnAl (n = 1–14) clusters by density-functional theory

The geometries, stabilities, and electronic and magnetic properties of Sc(n)Al (n = 1-14) clusters with different spin configurations have been investigated systematically within the framework of the gradient-corrected density-functional theory. Our resulting geometries show that the aluminum atom remains on the surface of clusters with n<9, while it takes up the center of Sc-cage clusters with n≥9. Besides, the doping of Al improves the stability of the host clusters. Maximum peaks are observed for Sc(n)Al clusters at n = 3, 6, 10 and 12 with the size dependent on the second-order energy differences and fragmentation energies, implying that these clusters are relatively more stable. For all the Sc(n)Al clusters studied, we find the charge transfer from Sc to Al sites and the coexistence of ionic and covalent bonding characteristics. The doping of the Al atom induces the magnetic moments of the host clusters decrease except for n = 8 and 14 and the total magnetic moments are quenched at n = 5, 7, 9 and 11.

SYNTHESIS AND CHARACTERIZATION OF DIFFERENT MORPHOLOGICAL LITHIUM TITANATE

Lithium titanate powders of different morphologies were synthesized by improved hydrothermal technique, which was performed at 90°C and atmospheric pressure for 20 h. By changing the solution in the reaction, nanoparticles, flowers petal-like structures, and nanorods of lithium titanate have been obtained, especially nanoparticles with well-crystalline structures were obtained. The morphology and micro-structure of the as-synthesized products were characterized using powder X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM) and selected-area electron diffraction (SAED).

TEMPLATE SYNTHESIS OF ALIGNED SiO2 SUBMICRO-WIRES

Aligned silicon dioxide (SiO2) submicro-wires have been synthesized from tetraethyl orthosilicate (TEOS) by anodic aluminum oxide (AAO) template method. The products were characterized by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS) and X-ray diffraction (XRD).