Studies On Preparation And Photoelectric Characters Of Nano-TiO₂

Nanocrystalline TiO₂ was synthesized by sol-gel method. Two different surfactants (dodecylamine and octodecylamine) were adopted as restraining reagent to reduce the agglomeration of TiO₂ particles and to improve the surface area. The microstructures of the nanocrystalline TiO₂ were characterized with different techniques. The electronic state properties of the surface of TiO₂ and photogenic free charge carriers transport characters were probed by employing the photoacoustic and surface photovoltaic techniques.XRD analysis shows that the fraction of the anntase phase decreases with the increase of calcination temperature and that increases with the increase of hydrolyzation temperature. However, the transformation of the nanocrystalline TiO₂ from anntase to rutile is accelerated with the increase of the calcination time. TEM and HRTEM analysis show that comparing the two kinds of surfactant octodecylamine plays a better role on decreasing the agglomeration of TiO₂ granules and increasing their surface area. From the analyses of TG-DSC and FT-IR curves, we found that the sufactant has been wiped off basically.The PAS, SPS, and EFISPS measurements of TiO₂ nanocrystallines were carried out. The analytic results show that the SPV responses appearing at 380 nm of the TiO₂ nanocrystallines is closely dependent on the surface electronic structure of anatase-type TiO₂ nanoparticles, which belongs to a band-band transition; By analyzing the photoacoustic and surface photovoltaic effects of the samples, it is experimentally proved that though the intensity of the photoacoustic signals generated by the nonradiative transitions increases with decreasing the average particle size of the sample, the proper decrease of the anatase fraction in the TiO₂ nanocrystallines can dramatically reduce the fraction of the nonradiative transitions and improve the quantum-optical efficiency.