Green Light, green Chemistry: TiO2@PPHs nanocomposite for Eco-Friendly photocatalytic oxidation of amines and degradation of Brilliant green dye

For the first time, this work demonstrates an environmentally benign and sustainable catalytic process using a TiO2@PPHs nanocomposite prepared by green synthesis. This was achieved by preparing a nanocomposite by decorating TiO2NPs with polyphenols (PPHs) extracted from black carrots (Daucus carota), which resulted in an active photocatalyst for oxidation reactions and Brilliant Green (BG) dye degradation under visible light (green LED light). The prepared TiO2@PPHs nanocomposite was comprehensively characterized by XRD, SEM, FT-IR, EDX, and BET analysis for pore-size distribution and specific surface area measurement. Zeta potential measurement and UV-visible DRS spectroscopy were also conducted. XRD and SEM with EDX analysis confirmed the crystallinity of the TiO2@PPHs nanocomposite with a particle size of 67.92 nm. Surface interactions and improved optical properties with a reduction in band gap energy from 3.04 for pure TiO2NPs to 2.02 eV for TiO2@PPHs nanocomposite make it a suitable catalyst that can be activated under green light irradiation. The catalytic activity of TiO2@PPHs was studied for the aerobic oxidation of amine to imines and degradation of BG dye in aqueous solution. The nanocomposite showed excellent efficiency in amine oxidation (up to 99 % conversion) and dye degradation (96 %). Mechanistic studies confirmed the significant role of the generated ROS, in particular hydroxyl and superoxide radicals, during these photocatalytic reactions. The TiO2@PPHs catalyst also exhibited recycling sequences with stable efficient synergistic catalytic results, which highlights light on sustainability in industrial applications.