Microscale structure designing of nanoparticle-based photocatalyst films for enhanced functionalities and efficient energy utilization

Photocatalysts have increasingly become important materials to utilize renewable solar energy for decomposing pollutants, producing clean water, achieving self-cleaning surface, and so on. Therefore, it is desirable to expand the applications of photocatalysts by enhancing the functionalities and allowing ample design flexibility. Here the potential of nanoparticle-based photocatalyst films with microscale surface structures was investigated in order to enhance their useful functionalities. Photocatalyst films with microscale surface structures were prepared using the suspension of titanium dioxide (TiO2) nanoparticles. The micro-scale structural features of prepared films were evaluated using a scanning electron microscope. Also, an atomic force microscope (AFM) was used. The AFM analysis of a film consisting of nanoparticle spherical aggregates revealed a surface profile of subwavelength surface structure. Then the optical and wetting characteristics were investigated. It was found that the visible-light transmittance increased due to subwavelength surface structures and that the microstructured TiO2 films exhibited the contact angles below 10 degrees, i.e., superhydrophilic behavior, without ultraviolet-light illumination. On the basis of the presented results, it was suggested that the microscale surface structures of photocatalyst film can be designed to achieve enhanced functionalities. It is expected to effectively utilize the energy of sunlight in many applications using functional photocatalyst films with optimized design.