Exploring ammonia plasma functionalization of graphenic surfaces: experiments, theoretical insights, and biological implications

• Ammonia plasma treatment for controlled functionalization of graphenic surface. • Dramatic change of surface properties, i.e. , electronic and wettability after plasma treatment. • Beneficial biological response for cells and bacteria on graphenic surface. • Molecular interpretation of plasma modification via DFT modelling. Surface properties of graphene-based materials, mainly electronic and wettability , play a crucial role in biomedical applications and need to be modified as carbon surfaces are chemically inert and hydrophobic. We investigate the effect of ammonia plasma modification on the surface properties of graphenic materials: electronic, wettability , and biocompatibility (work function, water contact angle measurements, and biological tests were performed). The microscopic and spectroscopic (AFM, RS, XPS, SIMS) results indicated the generation of surface functional groups such as –NH 2 , –OH, and –NO which substantially modify surface chemistry while preserving the bulk properties of the graphenic material. The water contact angle decreases from 99° to 30°, making the surface hydrophilic and suitable for cells attachment. The electronic properties, parametrized by work function, showed time- (30–300 s) and power-dependent (50–100 W) changes, in particular, a decrease in work function at shorter plasma exposure times, followed by a slight increase with a longer treatment. The experimental results are discussed in terms of charge redistribution, surface dipoles, Fermi, and vacuum level changes obtained from the Density Functional Theory calculations (VASP code, GGA-PBE + D functional). The biological tests revealed that the plasma-modified surfaces enhanced NIH/3T3 fibroblast adhesion and spreading. In contrast, bacterial adhesion of Staphylococcus aureus and Pseudomonas aeruginosa was not promoted, suggesting that the altered electronic properties, particularly the lowered work function, do not promote bacterial attachment. The results demonstrate the superiority of ammonia plasma against the most commonly used oxygen plasma for functionalization of carbon materials in biomedical applications.