A highly responsive methanol sensor based on graphene oxide/polyindole composites

Graphene-based materials, namely commercial graphene (cm-G), commercial graphene oxide (cm-GO), reduced graphene oxide (rGO), and synthesized graphene oxide (OIHM-GO), and their composites with polyindole (PIn) were used as sensing materials for methanol vapor. The synthesized graphene oxide was prepared by the optimized improved Hummers' method. rGO was prepared from cm-GO by two different methods: thermally mild reduction at 120 °C to yield T-rGO and chemical reduction by ascorbic acid to yield C-rGO. Graphene-based material/polyindole composites were prepared by in situ polymerization. In this report, the sensing responses were evaluated from the responsive electrical currents at room temperature. cm-GO showed the highest methanol response because it possessed the highest number of oxygen species, which act as the active sites. The relative electrical conductivity response of the in situ cm-GO/dPIn composite to methanol was the highest amongst the composites. The in situ OIHM-GO/dPIn composite possessed the high relative conductivity response of 81.89 ± 2.12 at 11.36 ppm, a sensitivity of 7.37 ppm−1 with R2 of 0.9967 in the methanol concentration range of 1.14–11.36 ppm, a theoretical LOD of 0.015 ppm, and repeatability of at least 4 cycles with good selectivity. This work represents the first report of the preparation and testing of graphene-based materials/polyindole composites as methanol sensors.