Q. Su

Synthesis of one-dimensional TiO2/V2O5 branched heterostructures and their visible light photocatalytic activity towards Rhodamine B

We present the synthesis and visible-light-induced catalytic activity of one-dimensional (1D) TiO(2)/V(2)O(5) branched heterostructures. The 1D TiO(2)/V(2)O(5) heterostructures were prepared by RF reactive magnetron sputtering of V(2)O(5) onto electrospun TiO(2) nanofibers. Then, the samples were annealed at 300u2009°C for 2 h in air ambient to form the 1D TiO(2)/V(2)O(5) branched heterostructures. The photodecomposition rate of Rhodamine B (RhB) by the 1D TiO(2)/V(2)O(5) branched heterostructures under visible light was much faster than that of pure TiO(2) nanofibers, revealing that the visible-light-induced catalytic activity of the 1D TiO(2)/V(2)O(5) branched heterostructures was greatly improved. The enhancement of the photocatalytic activity of the 1D TiO(2)/V(2)O(5) branched heterostructures can be ascribed to the coupling with a small bandgap semiconductor material V(2)O(5), where the absorption range is extended, the photogenerated electrons and holes are highly separated and the surface charge carrier transfer rate is promoted.

Low temperature growth of vanadium pentoxide nanomaterials by chemical vapour deposition using VO(acac)2 as precursor

Vanadium pentoxide (V2O5) nanomaterials with various morphologies were prepared by chemical vapour deposition at a relatively low temperature (evaporation temperature of 250u2009°C and growth temperature of 500u2009°C) using vanadyl acetylacetonate (VO(acac)2) powder as the vanadium precursor. The obtained samples were characterized by scanning electron microscopy, x-ray diffraction, Raman scattering and photoluminescence spectra. The results revealed that the samples including a V2O5 nanocluster film, V2O5 nanowires and V2O5 nanospheres were synthesized at different distances from the source material. For our chemical vapour transport system, we suggested that VOx vapour and VO(acac)2 vapour existed simultaneously during the growth process, which resulted in different morphologies of V2O5 nanomaterials. The quite different supersaturation distributions of VOx vapour and VO(acac)2 vapour led to three main growth areas. The V2O5 film was grown in the region where the supersaturation of the VOx vapour was high, V2O5 nanowires were obtained where the supersaturation of the VOx vapour was relatively low and V2O5 nanospheres were synthesized in the region where the supersaturation of the VO(acac)2 vapour was high. The growth pressure that influenced the vapour concentration controlled the morphologies of the nanowires. It was found that a specific level of low concentration was necessary to ensure the growth of V2O5 nanowires.

The simulated vibrational spectra of HfO2 polymorphs

The Raman and infrared (IR) spectra of HfO2 polymorphs are simulated within the framework of density functional perturbation theory. The joint lattice-dynamical model treatment of the monoclinic, orthorhombic-I, orthorhombic-II and tetragonal-polymorphs of HfO2 is conducted with an emphasis on the evolution of their vibrational spectra. Our method is based upon the local density approximation with Hartwigsen–Goedecker–Hutter-type pseudopotentials and it gives a precise description of the phonon energies in these polymorphs with small deviations relative to the available experimental data. The simulated Raman spectra of the orthorhombic-I and II HfO2 are consistent with the data from high-pressure experiments, which indicates that these samples are well crystallized and randomly oriented. Rigid assignments of all the Raman peaks of these four polymorphs are obtained. Further, the simulated IR spectra of these four polymorphs are firstly presented, and the characteristics of these spectra are obtained, which provide potential ways to identify these phases in production environments.