Antimicrobial coatings based on amine-terminated graphene oxide and Nafion with remarkable thermal resistance

We present a novel type of layer-by-layer (LbL) waterborne coating based on Nafion and amine-terminated graphene oxide (GO-NH₂) that inhibits the growth of Escherichia coli and Staphylococcus aureus by more than 99% and this performance is not compromised upon extensive thermal annealing at 200 °C. Quartz crystal microbalance (QCM) sensorgrams allow the real time monitoring of the build-up of the LbL assemblies, a process that relies on the strong electrostatic interactions between Nafion (pH = 2.7, ζ = -54.8 mV) and GO-NH₂ (pH = 2, ζ = 26.7 mV). Atomic force microscopy (AFM), contact angle and zeta potential measurements were used to characterise the multilayer assemblies. We demonstrate here that Nafion/GO-NH₂ advanced coatings can offer drug-free and long-lasting solutions to microbial colonization and can withstand dry heat sterilization, without any decline in their performance.