Elucidating the photocatalytic mechanism of biomass-derived carbon dots nanocomposite for efficient degradation of MB and CR dyes: Insights into protein binding applications

This study introduces an environmentally sustainable method for synthesizing a nanocomposite using carbon quantum dots derived from green tea waste and zinc oxide. The single-step hydrothermal process not only addresses waste management but also yields a versatile nanocomposite with diverse applications. Rigorous characterization reveals its morphology, crystallinity, phase identification, structural behavior, optical properties, and chemical composition. Incorporating carbon quantum dots into the zinc oxide matrix reduces the band gap to 1.87 eV, enhancing charge separation and light-harvesting. This modification significantly boosts photocatalytic activity, achieving degradation efficiencies of 95.16 % for methylene blue (MB) and 93.21 % for congo red (CR) under visible light. The effects of pH, contact time, and photocatalyst concentration on dye degradation were explored. The nanocomposite, exhibiting both adsorption and photocatalytic performance, is poised for broad applications. Fluorescence quenching studies with lysozyme protein provide insights into potential applications across diverse fields, highlighting its environmentally friendly and multifunctional attributes. [Display omitted] •Hydrothermal synthesis of CDs and its composite from waste green tea bags•The CD nanocomposite reveals efficient dye degradation: key role in MB and CR removal.•A detailed mechanistic overview of photocatalytic dye degradation•Protein binding potential of biomass-derived dots•Degradation kinetics was analyzed.