Augmented Visible-Light-Driven Antibacterial Mechanism of CuxS Quantum Dots Engineered by Gallium and Cationic Cellulose as a Dual-Carrier System

Quantum dots (QDs), with adjustable bandgaps, high interfacial reactivity, and efficient charge transfer, are promising in photocatalytic bacteriostasis. However, challenges like fast charge recombination, instability, and aggregation limit their catalytic efficiency and broader applications. A dual-carrier system of regenerated cationic cellulose (RCC) and Ga is first proposed to achieve steady-state Cu x S QDs with quantum confinement, sulfur-rich vacancies, and p-type Schottky structure, maximizing their photocatalytic activity. The Schottky junction interface and internal electric field accelerate carrier separation, while sulfur vacancies act as hot electron traps, further suppressing electron–hole recombination. Therefore, this ternary composite system demonstrates an optimal bandgap (2.25 eV), low electrochemical impedance, extended photoluminescence decay (9.87 ns), and broad-spectrum light absorption, thereby improving carrier conversion into ROS, including 1 O 2 . These reactive species high-efficiently sterilize E. coli , S. aureus , and drag-resistant bacteria, achieving logarithmic removal values of 6–8 at a high bacterial concentration (10 8 CFU mL −1 ) under visible-light illumination. Pathogen demise primarily results from photo-excited ROS, which induce instability and even substantial damage to microbial membranes, leading to excessive oxidative stress and degradation of essential cellular components, including superoxide dismutase, catalase, and DNA. This study introduces an innovative organic/inorganic strategy for designing semiconductor QD-based disinfection photocatalysts.