Synergistic inactivation of Aspergillus niger spores by low-dose ClO₂ and photocatalysis via interfacial electron transfer

Fungal spores protected by pigment-rich cell walls are highly resistant to traditional chlorine-based disinfectants, often necessitating high doses that generate toxic by-products and residues hazardous to public health. Here, we present an integrated disinfection strategy that combines low-dose ClO₂ (8.0 mg L⁻¹) with photocatalysis using silver single-atom-loaded graphitic carbon nitride (Ag₁/CN). This synergistic system achieved near-complete inactivation of Aspergillus niger spores at an initial concentration of 10⁶ cells mL⁻¹ in water, while reducing ClO₂ usage by 60% compared to chlorination and effectively eliminating detrimental chlorite formation. Furthermore, the system enabled over 95% disinfection efficiency in natural surface water within 60 min. Mechanistic analysis reveals that photogenerated electrons, rather than reactive oxygen species or ClO₂ itself, are primarily responsible for spore inactivation. ClO₂ pretreatment disrupted the melanin layer, allowing direct contact between Ag₁/CN and the cell membrane. Subsequently, photogenerated electrons from Ag₁/CN were injected into the cell membrane, disrupting the proton motive force and impairing ATP synthesis, ultimately resulting in energy depletion and cell death. This work presents a clean and efficient disinfection strategy that overcomes key limitations of conventional chlorination and offers a promising solution for controlling resistant fungal contaminants in water treatment applications.