Effect of Reduced Graphene Oxide Film Thickness on a Chemiresistor's Response to Volatile Organic Compounds and Warfare Agents.

We explore the performance of a chemiresistor sensor array based on thin layers of reduced graphene oxide (rGO). The rGO is deposited with a spray coating technique to fabricate three samples of different layer thicknesses, which are characterized by atomic force microscopy (AFM) and Raman spectroscopy. We expose the chemiresistors to water vapor, three volatile organic compounds (VOC), ethanol, acetone, and formaldehyde, and two simulants of chemical warfare agents (CWA), dimethyl-methyl phosphonate (DMMP) and dipropylene glycol monomethyl ether (DPGME). The rGO-based sensors show noticeable changes in resistance upon parts per million variations of the analyte concentrations. The largest detection sensitivity 0.02%/ppm is observed with DPGME. Furthermore, we investigate a thickness-dependent signal that depends on the nature of the analyte. We show that comparing the signal measured with only a few rGO layers of different thicknesses can be used to distinguish formaldehyde from other VOC and DMMP from DPGME. Our findings represent a step toward the development of practical sensor arrays based on low cost, scalable graphene-based materials, enabling both sensitive and selective detection of analytes.