Electrolytically generated size-tunable micro-nano bubbles toward high-efficiency antibacterial applications in vitro

Bacterial contamination in water poses severe threats to global water safety, particularly in drinking water. Micro-nano bubbles (MNBs) have attracted significant interest for antibacterial applications due to their high efficiency and environmental friendliness. In this study, size-tunable MNBs were electrochemically fabricated using TiO₂ nanotube arrays (TNTAs) as electrodes. A strong positive correlation (R² = 0.965) was established between the pore diameter of TNTAs and the size of the generated MNBs, enabling precise control over bubble dimensions. Crucially, bactericidal efficiency was found to be negatively correlated with MNB size, with the smallest MNBs achieving exceptional inactivation rates of 98.8 % for Escherichia coli (E. coli) and 98.0 % for Staphylococcus aureus (S. aureus). Mechanistic studies revealed that smaller MNBs generate higher concentrations of hydroxyl radicals (•OH) upon collapse, which are primarily responsible for the enhanced antibacterial activity. This work establishes a clear structure-activity relationship: electrode pore size dictates MNB size, which in turn determines •OH generation and antibacterial performance. These findings provide a scientific basis for developing efficient, environmentally friendly disinfection technologies.