Development of graphene oxide based capacitive gas sensor for selective detection of NO2

Abstract

NO2 gas is a harmful vapor that, when present in large quantities, can impose severe threats on health and environment. Gas sensors for NO2 have been in development over the past few decades albeit selectivity towards the gas still remains somewhat unperfected. A method was suggested to improve selectivity towards NO2 by registering a unique and recurring feature of the signal behavior as the selection criterion i.e. gradient of sensor response. A parallel plate capacitive gas sensor was fabricated taking graphene oxide as the dielectric medium and was tested for NO2. Graphene oxide was synthesized adhering to the Improved Hummer’s Method (Tours Method) which produced sufficiently oxidized graphene with a yield of 193% with respect to the starting material. Synthesized graphene oxide was characterized by Fourier Transform Infrared Spectroscopy (FTIR), Thermo Gravimetric Analysis (TGA) and X-ray Diffractometry (XRD) techniques ascertaining that the products were well oxidized with acceptable d-spacing values. Sensor assembly was tested for capacitance variation in the frequency domain, time domain and under the influence of constant temperature ramp. The results showed an average response time of about 1 minute to reach the steady state signal and an equal time to go back to the initial reference signal level once the target gas was evacuated. Keywords— graphene oxide, capacitive sensor, selective sensing, FTIR