Inversion of temperature-resistance relationship by enlarged structural defects in graphene oxide

Here we report a novel means to transform a positive temperature coefficient behavior (i.e., electrical resistance increase with temperature) of water-soluble, reduced edge-oxidized graphene oxide (rEOGO) into a negative temperature coefficient (NTC) material (i.e., resistance decrease with temperature). The temperature-versus-resistance relationship of this material could be reversed by introducing enlarged structural defects in the basal plane of rEOGO using nitric acid as an etchant. We found that the degree of the NTC behavior of rEOGO could be correlated to the number of structural defects. Similar effects of structural defects were also observed in influencing the NTC behavior of reduced graphene oxide (rGO) produced by the Hummer's method and thermal treatment. These results suggest that structural defects function as thermally activated electron traps, and can be used to precisely tune the temperature-versus-resistance relationship of GO materials desired for a variety of applications.