Copper-embedded reduced graphene oxide fibers for multi-sensors

Highly flexible and stretchable graphene-based fibers are one of the most synthetically challenging materials that are suitable for next-generation wearable electronics. Graphene-based fibers used in reliable wearable devices should be multifunctional and stable. Here, we report an easy-handling fabrication method for reduced graphene oxide fibers containing semiconducting CuI and metallic Cu particles (CRGO fiber). The fibers were prepared by wet spinning and hydriodic acid treatment from a CuCl₂-ethylene glycol coagulating solution without pre-synthesized CuI and Cu particles. The fabricated CRGO fibers exhibited chemical sensitive/temperature insensitive or chemical insensitive/temperature sensitive characteristics, depending on the Cu concentration in the CRGO. This is the first demonstration of a highly selective chemical and temperature sensor with sensitivity-switching properties fabricated from twisted CRGO fibers comprising two fiber bundles with low and high Cu concentrations.