Bifunctional Au–TiO2 thin films with enhanced photocatalytic activity and SERS based multiplexed detection of organic pollutant

Abstract

In the current study, Au–TiO2 thin films were prepared on glass substrates through the combined approach of spin-coating thermal evaporation method. The decoration of Au nanoparticles on to TiO2 surface has been achieved by the thermal annealing process under Ar atmosphere. Au–TiO2 thin films with improved optical absorption and effective bandgap narrowing exhibits outstanding photodegradation activity and ultra-sensitivity towards surface-enhanced Raman spectroscopy (SERS) based detection of the organic molecules. The existence of Au nanoparticles on TiO2 nanostructures efficiently controls the rate of recombination consequently Au–TiO2 thin films show significantly improved sun-light induced photodegradation efficiency for methylene blue (MB) dye. Au–TiO2 thin films decomposed 5 µM MB dye solution in 40 min under sun light exposure (850 W/cm2). Au–TiO2 thin films also exhibit efficient detection capabilities for the two organic molecules rhodamine 6G (R6G) and methylene blue (MB) with the Raman intensity enhancement factors of the order of ~ 107. The observed excellent SERS sensitivity of Au–TiO2 thin films towards the pollutant molecules are ascribed to the contribution of charge transfer mechanism among TiO2 and dye molecules. Furthermore, the fabricated Au–TiO2 thin films were also evaluated for the multiplexed detection by simultaneously detecting the two analytes (MB and R6G) from their mixture with superior sensitivity. Au–TiO2 nanohybrids thin films with these tremendous applications can be further employed for different applications like solar cell, gas sensing, energy production, and water splitting.