表面修饰的二氧化钛纳米材料的结构相变和光吸收性质

采用胶体化学法制备表面修饰的二氧化钛纳米材料，并使用XRD，TEM，UV-vis光谱等手段研究表面修饰的二氧化钛纳米微粒的结构相变和光吸收性质.结果表明，表面修饰可以改变二氧化钛的晶化行为、加快锐钛矿→金红石的相变进程、引起二氧化钛纳米粒子的光吸收带边大幅度红移.光吸收系数与光子能量之间关系的计算分析显示，在吸收带边附近，二氧化钛纳米微粒溶胶及二氧化钛纳米薄膜的(αhν)^1/2vs hν(间接)和(αhν)² vs hν(直接)均呈线性关系，其间接和直接光学带隙能可以分别通过外推这种线性关系来测量. 关键词： 二氧化钛纳米材料 结构相变 表面改性 光吸收

Structural phase transformation and optical absorption of capped TiO2 nanoparticles

TiO₂ nanoparticles capped with a layer surfactant were prepared by colloid-chemical method, and their structural phase transformation and optical absorption properties were investigated. XRD and TEM results showed that the surfactant capping effectively inhibits the grain growth during heat-treatment, and results in a different crystallization behavior in which titania nanoparticles with amorphous structure can simultaneously transform into anatase and rutile when heat-treated below 400℃. It was found from optical absorption measurement that the capped TiO₂ colloidal particles in toluene sol have a large red shift of absorption band edge in contrast with that without capping, which is mainly attributed to the effects of the interface dipole and dielectric confinement. In the investigation of the relation between the absorption coefficient and photon energy, it was found that there exist two linear correspondences of (αhν)^1/2 vs hν(indirect transition) and (αhν)² vs hν (direct transition) for the titania films and colloidal-particle organic sol. The respective band gap values were obtained by extrapolation of the above linear relation.