All-carbon fiber-based chemical sensor: Improved reversible NO2 reaction kinetics

All-carbon fiber-based chemiresistor is fabricated by assembling reduced graphene oxide (RGO) fiber and carbon nanotube (CNT) fiber as reversible NO2 sensing layer and flexible heater, respectively. Both graphene oxide (GO) and CNT fibers were synthesized by wet-spinning technique facilitating lyotropic nematic liquid crystal (LC) property. Randomly entangled CNT fiber-based heater, which is embedded in one surface of colorless polyimide (cPI) film with thickness of (similar to)200 mu m, exhibits high bending stability and heating property up to 100 degrees C. Single reduced graphene oxide (RGO) fiber obtained after heat treatment at 900 degrees C in H-2/N-2 ambient was integrated on the CNT fiber-embedded cPI heater, thereby establishing a new type of all-carbon fiber sensing platform. As a result, accelerated NO2 adsorption and desorption kinetics were achieved with RGO fiber at an elevated temperature. In particular, a 9.22-fold enhancement in desorption kinetic (k(des) = 8.85 x 10(-3) s(-1)) was observed at 100 degrees C compared with the desorption kinetic (k(des)= 0.96 x 10(-3) s(-1)) at 50 degrees C, which was attributed to the effective heating by CNT fiber networks. This work pioneered a research on the use of emerging carbonaceous fibers for potential application in wearable chemical detectors.