Kelly K Lance, Yamashita Koichi
Department of Chemical System Engineering, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo Bunkyo-ku, Tokyo 113-8656, Japan.
J Phys Chem B. 2006 Apr 20;110(15):7743-9. doi: 10.1021/jp0550917.
The optical activity of composite films created by the photocatalytic reduction of silver or gold ions in TiO(2) upon irradiation by UV light has up to now been discussed in terms of the formation and light-induced destruction of distinct nanoparticles molded inside the porous nanocrystalline film. We present results from classical light scattering calculations and a logical analysis of experimental observations to add detail to the mechanism. As opposed to large, solid metal nanoparticles, coatings and small particles in heterogeneous external dielectric environments account for observations such as the broad optical spectrum and multiwavelength photochromic responses. For some steps of the photochromic process, we propose that visible light permits an equilibrium promoting the growth of small metal features or suspended particles. We use a new expression for the restricted path length in our size-dependent broadening corrections of metal shells and discuss this briefly. We conclude by discussing the consequence of plasmon absorption in the proximity of the electronically active TiO(2) surrounding matrix, leading to mass transfer and shape change of the metal and photochromic properties of the film.
通过紫外光照射在TiO₂中光催化还原银离子或金离子所制备的复合薄膜的光学活性，至今一直是根据在多孔纳米晶薄膜内部形成并经光诱导破坏的不同纳米颗粒来讨论的。我们给出了经典光散射计算结果以及对实验观察的逻辑分析，以详细说明该机理。与大型固态金属纳米颗粒不同，异质外部介电环境中的涂层和小颗粒可以解释诸如宽光谱和多波长光致变色响应等观察结果。对于光致变色过程的某些步骤，我们提出可见光允许一种促进小金属特征或悬浮颗粒生长的平衡。我们在对金属壳层进行尺寸相关展宽校正时使用了一种新的受限路径长度表达式，并对此进行了简要讨论。我们通过讨论在电子活性TiO₂周围基质附近等离子体吸收的后果来得出结论，这会导致金属的质量转移和形状变化以及薄膜的光致变色特性。
