Structured Graphene Oxide/Reduced Graphene Oxide Interfaces for Improved NO₂ Sensing

Abstract

Here, we demonstrate an improvement in sensitivity toward the NO2 analyte by varying the width ratio of adjacent graphene oxide (GO) and reduced graphene oxide (rGO) layers using the GO laser reduction technique. We evaluated changes brought by laser reduction in material morphology, structure, electrical characteristics, and sensing performance depending on the GO/rGO ratio, which we supported by density functional theory calculations. Our results indicate that the reduction of GO yields the appearance of a chemiresistive response to NO2. An optimum GO/rGO width ratio ensures high conductivity paired with good sorption capacity, allowing to achieve chemiresistive response of 18.1% toward 100 ppm of NO2 at 25 ± 1 °C and a limit of detection of 230 ppb. The improved chemiresistive response of GO/rGO sensors upon NO2 physisorption is due to an increase in sorption energy and improved charge transfer in the presence of NO2 at the sites corresponding to the individual epoxy and hydroxyl groups at the GO/rGO interface area when compared to fully reduced GO.