Graphene Functionalization by O, H, and Ar Plasma Treatments for Improved NH Gas Sensing.

Graphene-based materials have gained attention for their promise in various applications owing to their two-dimensional structure. Functionalizing the graphene surface can help realize materials with noble properties. In this study, graphene was functionalized by plasma treatment in O, H, and Ar environments, and the effects on the NH gas-sensing performance were evaluated. The O plasma treatment induced oxidation of the graphene (i.e., graphoxide), while the H plasma treatment induced hydrogenation (i.e., graphane). Raman scattering spectroscopy suggested that graphoxide had vacancy-type defects and graphane had sp-type defects, while Ar-treated graphene had both types of defects. Graphane had the highest sheet resistance followed by graphoxide, Ar-treated graphene, and pristine graphene, which can be attributed to the large bandgap of 3.0 eV for graphane. In contrast, graphoxide had the best NH gas-sensing performance, which indicates that NH gas interacts more strongly with vacancy-type defects than with sp-type defects. The results showed that functionalizing the graphene structure generated noble materials with a superior NH gas-sensing performance compared with pristine graphene.