Nanometer-thick [(FPEA)2PbX4; X = I and Br] 2D halide perovskite based thin films for pollutant detection and nonconventional photocatalytic degradation

Application of three-dimensional (3D)-halide perovskites (HaPs) in photocatalysis encourages the new exercise with two-dimensional (2D) HaP based thin-films for photocatalytic degradation of dyes. The reduced dimensionality to 2D-HaPs, with a structural formula of R2PbX4; R= organic spacer containing long chain amine and X = halide, offers better stability compared to 3D-HaPs. In this study, the potential of 2D-HaP thin-films towards the visible light-driven photocatalytic degradation of 2-mercaptobenzothiazole (MBT) was examined in hexane medium. The photo-physical properties of the 2D-HaPs were investigated as a function of 'X' site and their stability under ambient conditions was monitored. Thermal stability of the synthesized 2D-HaP thin-films was also examined by thermogravimetric analysis (TGA), which was found to be stable up to 250 degrees C. During the photocatalysis experiment, the rate constants of the thin-films were calculated to be 3-6 x 10(-2) min(-1), under visible light illumination. Furthermore, cycling experiments were performed with the thin-films to understand their behaviour under repeated runs. Faster rate kinetics was observed when the 2D-HaP layer was coated over the titanium dioxide (TiO2), indicating hole injection from the 2D-HaP thin-film surface to MBT. The adsorption of MBT over the 2D-HaP was also 'detected' using photoluminescence (PL) analysis. Thus, it revealed a promising photocatalytic behaviour of these 2D-HaP thin-films bringing a possibility of simultaneous 'detection and degradation' of toxic pollutants.