Engineering the surface structure of brookite-TiO₂ nanocrystals with Au nanoparticles by cold-plasma technique and its photocatalytic and self-cleaning property

Titanium dioxide (TiO2), a non-toxic semiconductor, has garnered extensive interest due to their excellent photocatalytic and self-cleaning properties. Its wide bandgap with rutile phase (3.0 eV), anatase, and brookite phases (3.2 eV) restricts the visible light photocatalytic applications. An effective approach to address this limitation is decorating the brookite-TiO2 surface by metallic gold nanoparticles (Au NPs) leading to the multi-function photocatalyst. Herein, we have successfully prepared TiO2-Au nanocomposites and investigated their photocatalytic activity and self-cleaning behavior. The obtained photocatalysts were prepared by chemical route (sol-gel and hydrothermal methods) and plasma technique. Characterization was analyzed by X-ray diffraction, Raman spectroscopy, scanning, and transmission electron microscopy techniques. TiO2 nanostructures with flower- and rod-like morphology were synthesized by a simple hydrothermal method. The TiO2 rod-like morphology, which contains 24% anatase and 76% brookite phase, favors the TiO2 surface modification and the later reduction of gold precursor to Au NPs under the microplasma-liquid interaction confirming the durability of material. Photocatalytic properties were evaluated through the photodegradation of dyes rhodamine 101 under the simulated visible light irradiation. The TiO2-Au photocatalysts are active under this condition while the pure TiO2 in form of anatase/brookite mixture exhibit high activity under the ultraviolet light. TiO2-Au NPs showed their enhanced the adsorption capacity (42%), followed by the dye decomposition (87%). Self-cleaning behavior was assessed by measuring the contact angle. The results of anti-fogged and self-cleaning properties from the contact angle measurement express highly applicable for the commercial products in sanitation.