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

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.