Microfluidic Reactors for Plasmonic Photocatalysis Using Gold Nanoparticles

This work reports a microfluidic reactor that utilizes gold nanoparticles (AuNPs) for the highly efficient photocatalytic degradation of organic pollutants under visible light. The bottom of microchamber has a TiO₂ film covering a layer of AuNPs (namely, TiO₂/AuNP film) deposited on the F-doped SnO₂ (FTO) substrate. The rough surface of FTO helps to increase the surface area and the AuNPs enables the strong absorption of visible light to excite electron/hole pairs, which are then transferred to the TiO₂ film for photodegradation. The TiO₂ film also isolates the AuNPs from the solution to avoid detachment and photocorrosion. Experiments show that the TiO₂/AuNP film has a strong absorption over 400-800 nm and enhances the reaction rate constant by 13 times with respect to the bare TiO₂ film for the photodegradation of methylene blue. In addition, the TiO₂/AuNP microreactor exhibits a negligible reduction of photoactivity after five cycles of repeated tests, which verifies the protective function of the TiO₂ layer. This plasmonic photocatalytic microreactor draws the strengths of microfluidics and plasmonics, and may find potential applications in continuous photocatalytic water treatment and photosynthesis. The fabrication of the microreactor uses manual operation and requires no photolithography, making it simple, easy, and of low cost for real laboratory and field tests.