Chemiresistive Gas Sensing by Few-Layered Graphene

A chemiresistive gas sensor based on few-layered graphene (FLG) has been fabricated and evaluated for carbon dioxide (CO2) and liquid petroleum gas (LPG) sensing. The electrochemical exfoliation method was used to synthesize FLG. The resulting sample of FLG was characterized by x-ray diffraction, Raman spectroscopy, atomic force microscopy, and transmission electron microscopy with selected-area diffraction. Ultraviolet-visible and fluorescence spectroscopy were employed to study the optical properties. Thermal behavior was analyzed through thermogravimetric-differential thermal analysis. The sensing response of the chemiresistor is defined as the ratio of resistance in gas to air at the stabilized resistance in air. The FLG chemiresistor exhibited good sensing response (3.83 for CO2, 0.92 for LPG), response time (11 s for CO2, 5 s for LPG), recovery time (14 s for CO2, 18 s for LPG), and resolution limit (3 ppm for CO2, 4 ppm for LPG), and excellent stability at room temperature. The gas sensing mechanism is discussed on the basis of marginal difference in Raman intensity and also by using defect chemistry through fluorescence measurements.