Layer-by-layer assembly for all-graphene coated conductive fibers toward superior temperature sensitivity and humidity independence

Conductive fibers are key parts in smart textiles. Layer-by-layer (LbL) technique based on the alternating coating of graphene oxide (GO) and the adhesive layer is usually used to increase the conductivity of graphene coated fiber. However, the insulation of the adhesive layer may deteriorate the conductivity of graphene coated fiber. Here with the positively charged GO as the adhesive layer, a novel and efficient method was proposed to prepare all-graphene coated conductive fibers, which means LbL electrostatic assembly of negatively charged GO and positively charged GO on the fiber substrate, followed by the reduction of GO. The charge of GO was reversed to positive with Al3+. This method provided higher coating efficiency of graphene than repeated coating of negatively charged GO usually used in the literature (40 times larger amount of graphene under 5 cycles), resulting in a significant conductivity increase of graphene coated fiber. Moreover, because of the crosslinking interaction between Al3+ and the residual polar groups of reduced GO, the conductive fibers also exhibited better stability against water washing, good temperature sensitivity (−0.4%/°C) and independence on the environmental humidity and mechanical deformation, demonstrating a promising potential application in flexible temperature sensor.