Reversible simultaneous switching between bacteria-killing/superhydrophobicity and bacteria-releasing/superhydrophilicity cotton fabric for potential oil/water separation application

Bacterial contamination of oil/water separation materials can reduce their efficiency during use and storage. Therefore, it is critical to develop materials with antibacterial properties for this purpose. This study presents a smart multifunctional antibacterial cotton fabric designed for oil/water separation using traditional finishing methods. Functionalized nano-silica and thermal-responsive Poly (N–isopropyl-acrylamide) (PNIPAM) were applied to the cotton fabrics. Notably, this cotton fabric demonstrates a reversible and simultaneous transformation between bacteria-killing/superhydrophobic and bacteria-releasing/superhydrophilic states. This change is driven by the alteration of the N–H and N–Cl bonds in the PNIPAM chains through a chlorinatioN–reduction process. Consequently, the fabric efficiently separates both heavy and light oil/water mixtures, leveraging the reversibility of its superhydrophobic and superhydrophilic properties. It also exhibits remarkable antibacterial activity, eliminating approximately 99.98% of E. coli and 99.99% of S. aureus within 30 min in its N–halamine form. Moreover, it can release most previously attached bacteria after reduction. Overall, this multifunctional cotton fabric, which is capable of switchable simultaneous transformation between bacteria-releasing/superhydrophilicity and bacteria-killing/superhydrophobicity, shows considerable potential for oil/water separation applications.