Optical and photocatalytic properties of sol-gel AuNPs@TiO2 ultrathin film

Abstract

The optical and photocatalytic properties of ultrathin TiO2 layers were investigated in order to stress out the effect of nanoscale thickness on the film properties. The method relies on monitoring localized surface plasmon resonance (LSPR) through UV–visible spectroscopy and enhanced Raman spectroscopy (SERS). To achieve this, TiO2 thin films were prepared using the sol–gel method on high density gold nanoparticles arrays (AuNPs). TiO2 anatase phase was obtained by thermal annealing and confirmed by XRD, HRTEM, and SERS. Our results reveal that the thinnest TiO2 layers consist of compact TiO2NPs of small dimensions and lower porosity compared to the thicker TiO2NPs layers. Subsequently, these thin TiO2 layers functionalizing AuNPs were applied in plasmonic photocatalysis, specifically for the N-demethylation of methylene blue in the visible range. When comparing layers with the same thickness (a single deposition layer with layers prepared by stacking various thin layers), the stacked layers demonstrated enhanced photocatalytic activity. This novel, stable form of TiO2 has the potential to open numerous opportunities in the fields of photocatalysis and detection.