Synthesis of Hyperbranched Polyglycerol-Photosensitizer/TiO 2 Nanocomposite for the Photocatalytic Degradation of Methylene Blue

The escalating environmental challenges posed by organic dye pollution necessitate the development of efficient and sustainable remediation technologies. This study presents a novel strategy to enhance the visible-light photocatalytic performance of TiO₂ through the synthesis of hyperbranched polyglycerol (HPG)-modified nanocomposites functionalized with photosensitizers (hemin and Eosin Y, EY). A sol-gel method was employed to graft HPGs with tailored polymerization degrees and branching architectures onto TiO₂ surfaces, enabling systematic investigation of the effects of modifier content, polymer structure, and light source on photocatalytic activity.The grafted polymers significantly narrowed TiO₂’s bandgap energy (from 2.82 eV for pure TiO₂ to as low as 0.50 eV for HPG2-hemin/TiO₂), extending its light absorption to the visible spectrum. Under optimized conditions, 1% HPG5-EY/TiO₂ achieved a methylene blue (MB) degradation rate of 73.22% within 120 minutes of visible-light irradiation—a 2.11-fold enhancement compared to pristine TiO₂. The composite also demonstrated exceptional recyclability, retaining over 95% of its initial activity after four reuse cycles. Mechanistic studies revealed that the abundant hydroxyl groups in HPG facilitated the generation of reactive oxygen species (•OH and •O₂⁻), which synergistically accelerated MB degradation.This work establishes a robust framework for designing high-performance TiO₂-based photocatalysts by leveraging polymer structural engineering and photosensitizer integration. The approach not only addresses the inherent limitations of TiO₂’s UV-dependent activity but also provides a scalable strategy for sustainable wastewater treatment under solar illumination.