Singlet oxygen driven enhanced photocatalytic degradation of 1,3,7-trimethylpurine-2,6-dione using surfactant mediated PVA-CuO nanocomposites: Combining physical adsorption and photocatalysis

Despite significant progress in the synthesis of metal nanoparticles, repeatability is a major bottleneck. The difficulty can be attributed to the synthetic methods, precursor materials, and surfactants used for surface modification. To provide a better understanding of the role of surfactants in materials synthesis, properties, and applications, this work reports the effect of surface modifiers using three different surfactants: cationic (cetyl trimethyl ammonium bromide, CTAB), anionic (sodium lauryl sulfate, SLS), and non-ionic (Tween 80, T80). The effect of these surfactants on the catalytic properties and the degradation efficiency of the polymeric matrix (CuO/PVA) has been investigated using 1,3,7-Trimethylpurine-2,6-dione (caffeine) as a major pollutant. From the kinetics studies, R2 = 0.9939 for Freundlich isotherm and 0.9839 for pseudo-first-order kinetics indicate that the reaction in the dark follows the Freundlich isotherm, whereas the adsorption of the pollutant on the catalyst surface follows pseudo-first-order kinetics. In addition, the surface modification has a greater impact on the degradation of caffeine as evident from the 29% higher degradation ability of the CTAB-assisted polymeric CuO compared to its unmodified counterpart. Surface characterization of the obtained polymeric matrix revealed that the degradation is also affected by the smaller particle size, band gap, and morphology of the catalyst. The scavenging experiments suggest significant involvement of the singlet oxygen in the degradation of caffeine by reducing the degradation to 49.8% from 96.5% after the addition of the scavenger. Herein, a simplified view of the variable catalytic affinity brought about by the surface modifications of the photocatalyst with respect to the surfactant employed during the synthesis has been presented.