Gram-scale synthesis of UV–vis light active plasmonic photocatalytic nanocomposite based on TiO2/Au nanorods for degradation of pollutants in water

Semiconductor/metal nanocomposites based on anatase TiO2 nanoparticles and Au nanorods (TiO2/AuNRs) were prepared by means of a co-precipitation method and subsequently calcinated at increasing temperature (from 250° to 650 °C) obtaining up to 20 g of catalysts. The structure and the morphology of the obtained nanocomposite material were comprehensively characterized by means of electron microscopy (SEM and TEM) and X-ray diffraction techniques. The photocatalytic performance of the TiO2/AuNRs nanocomposites was investigated as a function of the calcination temperature in experiment of degradation of water pollutants under both UV and UV–vis irradiation, Photocatalytic experiments under UV irradiation were performed by monitoring spectrophotometrically the decolouration of a target compound (methylene blue, MB) in aqueous solution. UV–vis light irradiation was, instead, used for testing the photocatalytic removal of an antibiotic molecule, Nalidixic acid, by monitoring the degradation process by HPLC-MS analysis. Interestingly, TiO2/AuNRs calcined at 450 °C was up to 2.5 and 3.2 times faster than TiO2P25 Evonik, that is a commercially available reference material, in the photocatalytic degradation of the Methylene Blue and the Nalidixic Acid, under UV and visible light, respectively. The same nanocomposite material showed a photocatalytic degradation rate for the two target compounds up to 13 times faster than the bare TiO2-based catalysts. The obtained results are explained on the basis of the structure and morphology of the nanocomposites, that could be tuned according to the preparative conditions. The role played by the plasmonic domain in the heterostructured materials, either under UV and UV–vis illumination, is also highlighted and discussed. The overall results indicate that the high photoactivity of TiO2/AuNRs in the visible range can be profitably exploited in photocatalytic applications, thanks also to the scalability of the proposed synthetic route, thus ultimately envisaging potential innovative solution for environmental remediation.