Controllable Synthesis, Surface Modification And Optoelectronic Characteristic Of1D TiO₂Nanomaterials

Nanostructured titanium dioxide has received much attention due to itspromising applications such as photocatalysts, photovoltaic cells, gas sensors and soon because of its exceptional optical and electronic properties, nontoxicity, chemicalstability, et al. Compared with porous TiO₂and nanoparticles, photo-induced carriersin1D titania structures posses better mobility, and it has been proven that1D titaniastructures show outstanding performance in optoelectronic devices. However, becauseof the physical properties of TiO₂itself there were few experiments reported on thesynthesis of high-quality1D TiO₂nanostructures at a relative low temperature（<850℃）. In the paper, we have explored an effective, simple and inexpensive routefor the synthesis of different1D titanium oxide nanostructures with high quality andyield. Then we carried out preliminary exploratory research on the microstructure andphotoelectric properties of different morphologies. The main results are as follows:（1） High-quality TiO₂nanowires grown on Ti foil by directly heating Ti foil at alow temperature（680℃）. The length of TiO₂nanowires with sooth surface fell in therange of50-100um and the dimensions is60-90nm. XRD, Raman of a singlenanowire and TEM showed the as-prepared nanowires with high crystallinity weremainly composed of single crystalline rutile. The Pd catalysts were found to play animportant role in reducing sintering temperature for the synthesis of TiO₂nanowiresand vapor liquid solid （VLS） may be the most suitable mechanism for the high-qualityTiO₂nanowires growth.（2） Different morphologies of TiO₂nanostructures were successfully synthesised.By changing the Pd catalyst concentration and reaction temperature, controllablesynthesis of different morphologies of TiO₂nanostructures （nanowires-belt-tower-particles） was first realized. Combined with the technology of near-field optical-microscope the Raman Mapping of a single nanobelts was measured, thestoichiometric ratio Ti/O was speculated to influences the shape and position ofRaman peaks, and the realization of Raman Mapping of a single nanobelt alsoprovides a way to the research of interactions between photons and atoms and phononmovements in the one dimensional structure.（3） CdS was deposited on the surface of TiO₂nanowires by Chemical bathdeposition （CBD） to form the1D TiO₂@CdS core/shell nanostructures and the thickness of CdS shell was controlled by varying the concentration of the citric acid.It was found that the charge transfer （CT） at the TiO₂/CdS interface can enhancesignificantly the raman resulted from both the CdS shell and TiO₂core. The study ofthe surface photovoltage spectroscopy（SPS）indcates the thickness of the CdS shellhas a remarkable effect on the CT between CdS and TiO₂.The systematic study aboutthe dependence of the Raman scattering and SPV on the CdS shell thicknessdemonstrated that the diffusion length of electron in CdS shell is between30and60nm.