Charge-Tunable Antimicrobial Activity and Oxidation Inhibition of Ti ₃ C ₂ T x MXene Nanosheets and Films via Layer-by-Layer Polyelectrolyte Deposition

MXenes are a rapidly emerging class of two-dimensional transition metal carbides and nitrides that exhibit high electrical conductivity, hydrophilicity, and tunable surface chemistry, making them promising materials for applications in environmental and biological systems. However, their susceptibility to oxidation and degradation in aqueous environments remains a major limitation for practical applications. In this study, we demonstrate that Ti 3 C 2 T x MXene nanosheets and films can be modified with nanoscale polyelectrolyte coatings using a layer-by-layer (LbL) deposition strategy. The resulting coatings significantly improve the stability of MXenes in aqueous environments while preserving their intrinsic electrical conductivity. Spectroscopic and electrochemical analyses show that the polyelectrolyte multilayers inhibit oxidative degradation of MXene films under strongly oxidizing conditions. In addition, the surface charge of the outermost polyelectrolyte layer enables control over the interaction of MXenes with microorganisms, allowing the antimicrobial activity of MXene materials to be tuned. These findings demonstrate that polyelectrolyte surface modification provides a simple and versatile strategy for improving the chemical stability of MXenes while retaining their high electrical conductivity, and enabling control over their biological interactions, highlighting the potential of these materials for applications in biointerfaces, antimicrobial coatings, and environmentally relevant systems.