Single-molecule Observation Of Photocatalytic Reaction In Tio_2 Nanotube: Importance Of Molecular Transport Through Porous Structures

摘要

Nano- and mesoporous materials have attracted considerable attention because they can be used to produce adsorbents, delivery carriers, photonic devices, and (photo)catalysts. Recently, mesoporous TiO_2 materials such as hollow spheres, opals, and nanotubes have been synthesized with the objective of designing an efficient photocatalyst having a high specific surface area and high molecular selectivity; these materials can also find potential applications as the diffusion-controllable membranes and in dye-sensitized solar cells (DSSCs), and water-splitting systems. In these applications, the performance of reagent molecules should be directly determined by their accessibility to the active sites for adsorption onto and reaction with the surfaces of materials. However, the structural disorders and agglomerates present in bulk samples often hinder efficient molecular transport. Furthermore, because conventional measurement methods cannot be used to observe and distinguish between (photo)catalytic reactions occurring on active sites distributed over the catalyst, the inherent properties can only be obtained as the ensemble mean of heterogeneities. Therefore, an improved technique for examining a single fragment of a porous material is strongly required.