Plasma-induced chemical and structural activation of 2D nanomaterial coatings for antibacterial surfaces.

The growing prevalence of antibiotic-resistant infections highlights the need for antimicrobial surfaces that do not rely on conventional drug release. Two-dimensional (2D) nanomaterials such as graphene oxide (GO) and MXenes (Ti3C2Tx) are known to exhibit intrinsic antibacterial properties; however, when used as coatings, their efficacy is often limited by low surface reactivity, nanosheet restacking, and a lack of chemically active sites. In this work, we demonstrate that a non-thermal argon atmospheric plasma jet (Ar-APJ) provides an effective route to chemically and structurally activate GO and MXene coatings through a combination of surface oxidation, defect formation, and nanoscale topographical modifications. Optical emission spectroscopy confirmed a reactive plasma environment dominated by atomic Ar emission and excited nitrogen species, with possible contributions from weak oxygen-containing species generated through plasma-air interactions. Surface analysis revealed marked increases in oxygen-containing groups, defect density, and surface roughness after plasma treatment. These chemically activated coatings displayed strong, broad-spectrum antibacterial activity against methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa, with more than 90% bacterial inactivation achieved under optimised conditions. The antibacterial response arises from a combined effect of membrane destabilisation and intracellular oxidative stress, as evidenced by elevated reactive oxygen species levels, severe morphological disruption, and extensive chemical damage to lipids, proteins, and nucleic acids, captured by synchrotron macro attenuated total reflectance Fourier-transform infrared (ATR-FTIR) microspectroscopy and multivariate analysis. The plasma-induced modifications did not compromise mammalian cell compatibility, and fibroblast adhesion, morphology, and viability remained comparable to untreated controls. These results establish non-thermal plasma activation as a practical, solvent-free strategy for engineering chemically active 2D antibacterial surfaces and provide general guidelines for the design of next-generation antimicrobial coatings for implant and healthcare applications.