Unraveling the Effect of Synthesis Temperature and Metal Doping on the Structural, Optical, and Photocatalytic Properties of g-C3N4 for Enhanced E. coli Photodisinfection and Self-Cleaning Surface Applications

The development of efficient photocatalytic materials for waterborne pathogen inactivation and self-cleaning surfaces in biomedical applications remains a critical challenge due to the rising prevalence of antimicrobial-resistant bacteria. This study systematically investigates the structural, optical, and photocatalytic disinfection properties of graphitic carbon nitride (g-C3N4) synthesized at variable temperatures (450–600 °C) and doped with transition metals (Mn, Co, Cu). Through FTIR and UV/Vis spectroscopy, we demonstrate that synthesis temperatures between 450 and 550 °C yield a well-ordered polymeric network with enhanced π-conjugation and charge separation, while 600 °C induces structural degradation. Metal doping with Mn and Co significantly enhances photocatalytic disinfection, achieving complete E. coli inactivation (6-log reduction) within 6 h via optimized reactive oxygen species (ROS) generation. The best material (g-C3N4 synthesized at 500 °C and doped with Mn) was integrated into sodium alginate hydrogel surfaces, demonstrating reusable self-cleaning functionality with sustained bactericidal activity (5.9-log CFU/mL reduction after five cycles). This work provides a roadmap for tailoring metal-doped g-C3N4 composites for practical antimicrobial applications, emphasizing the interplay between synthesis parameters, ROS dynamics, and real-world performance.