Room temperature ammonia gas sensor using Meta Toluic acid functionalized graphene oxide

Abstract

A gas sensor has been fabricated by depositing the thin film of Functionalized Graphene Oxide (GO) using Langmuir Blodget (LB) technique on SiO2/Si wafers. Aluminum (Al) contacts were deposited using thermal evaporation technique for measuring the resistance of fabricated thin film. Three different concentrations (15 mM, 50 mM, 75 mM) of Meta Toluic acid (MTA) have been used for functionalization of GO. X-Ray Diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR) and Raman spectroscopy were used to characterize the Graphene Oxide (GO) after functionalization. Also, Scanning Electron Microscopy (SEM) was carried out for both GO and functionalized GO to study the surface morphology. Gas sensing behavior of functionalized GO has been investigated using two probe resistance measurement method for different concentration of ammonia gas. Sensor response was studied for ammonia concentration varied from 100 to 2000 ppm. Highest response obtained at 100 ppm concentration was found to be ~12.2% for sample TG75. Higher concentration of MTA (up to a critical value) in GO leads to higher response of ammonia gas. This enhanced gas response has been due to the increased ester formation reaction at the surface of sensing film, which eventually leads to more interaction with NH3 gas molecules. In addition, defects and carbon vacancy in functionalized GO also acts as the trapping sites for gas molecules being sensed. The selectivity of the sensor has been investigated in different environment and sensor was found to be very selective towards ammonia gas. For stability investigation of the fabricated sensor, the sensor response has been recorded for 45 days.