Unsaturated carbon linear chains created during bacteria incubation with amorphous carbon thin films produced by a clean technology

Abstract

Graphene production is usually an expensive process, time-consuming, with low yield and often uses environmental hazardous chemicals during the process. For these reasons, many applications consider the use of graphene based materials (GBM), such as carbon thin films, instead of graphene. In this work, the aim was to produce GBM, by sputtering deposition, from a graphite target. The ability to reduce the defects of the carbon thin films was evaluated by using several bacterial strains to pursue a sustainable practice. The highest reduction of the number of defects of the as-deposited coatings was obtained when the surfaces were exposed to Escherichia coli. The analysis by Raman spectroscopy revealed that the ID/IG ratio reduced from 0.75 to 0.56 which indicate a 75% in defects reduction. The use of different bacterial species also allowed to evaluate the antimicrobial ability of different coatings. For Gram positive bacteria a 95% decrease in colony forming units (CFU) was registered, while for Gram negative bacteria a maximum of 80% decrease of CFU was observed. The Raman characterization after the incubation with bacterial strains indicate that, for one Gram negative bacteria, the antimicrobial activity of the carbon thin films may be related with the formation of linear carbon chains with electronic transport properties similar to metals. During the incubation process the microorganisms effectively reduced the defects of the produced carbon coatings. Moreover, this approach allowed the use of green technology to produce metal-free surfaces with the ability to present different levels of antimicrobial activity against the studied bacterial strains.