Antimicrobial Activity of Thin-Film Composite Membranes Functionalized with Cellulose Nanocrystals and Silver Nanoparticles Via One-Pot Deposition and Layer-by-layer Assembly

In this study, we propose the production of a thin-film composite (TFC) membrane with efficient antimicrobial properties by modifying it with cellulose nanocrystals (CNC) and silver nanoparticles (AgNP). Two approaches (i.e., "one-pot" and "layer-by-layer") were employed to incorporate CNC and AgNP onto the membrane surface and their impact on the membrane antimicrobial properties was examined. Firstly, the "one-pot" method involved reacting CNC with AgNO3 and NaBH4 to form a CNC/Ag hybrid material. This CNC/Ag hybrid was then applied to the TFC drawmembranes using polydopamine (PDA) chemistry, allowing the deposition of both CNC and AgNP in a single step. Secondly, the "layer-by-layer" method involved attaching CNC to the membrane surface using PDA chemistry, which was then followed by an in situ reaction of AgNO3 and NaBH4 to deposit the AgNP directly on top of the CNC layer. Membranes modified with a CNC/Ag hybrid using the one-pot method were able to deactivate 75.7 +/- 15.6% of attached E. coli cells without detrimental impact to membrane separation performance. The membranes modified using the layer-by-layer assembly demonstrated improved antimicrobial activity when compared to those modified with the one-pot CNC/Ag hybrid, being capable of inactivating 90% of the attached E. coli cells. On the other hand, the layer-by-layer modification method led to a significant loss in the membrane's salt rejection capacity. These water-based, straightforward, and simple functionalization strategies can tailor the antimicrobial and anti-biofouling performance of membranes for water treatment applications.