Nanostructured Photocatalytic Systems to Enable Portable Kidney Dialysis and Precision Synthesis

Abstract

Two distinct types of photocatalytic material systems have been studied for wearable dialysis devices and precise pharmaceutical synthesis: TiO2 nanowire anodes and gold nanoporous membranes. The study on TiO2 involves the development of a novel urea photodecomposition system (POUR) that efficiently and selectively converts urea into N2 and CO2, enabling spent dialysate regeneration for portable kidney dialysis. The long-term stability and regeneration treatments of TiO2 photocatalyst has been investigated. The oxidative environment generated localized around the TiO2 surface is considered as an efficient way to remove the Ti-C and maintain the photocatalytic performance of TiO2. External voltage applied to the TiO2 single crystal nanowires dramatically enhances the collection of photogenerated electrons to the cathode and pushing holes to reaction surface thereby minimizing the recombination process and significantly increasing the photocurrent (~14x) and the urea photodecomposition rate. Further mechanistic investigations revealed the requirement of chloride (Cl-) for the complete oxidation of urea to physiologically safe N2 and CO2. Quenching studies proved a mechanism based on TiO2 surface bound radical intermediates (Ti-Cl·). High photocurrent to reaction efficiency for this 6 e-/h+ process and selectivity of urea suggests urea nitrogens are bound to TiO2 surface (Ti-N bonds) during the complete oxidation process. On the other hand, gold nanoparticles in a plasmonic flow reactor demonstrated an over 200% quantum efficiency for peroxide activation, offering controlled single oxidation reactions for pharmaceutical synthesis. The reactor design, optimized pore diameter, and LED illumination wavelength were crucial factors influencing peroxide activation efficiency. Overall, these findings shed light on the potential applications of TiO2 and gold nanoparticles in advanced photocatalytic systems for the wearable dialysis device and precise pharmaceutical synthesis.