Abstract
The pristine and functionalized single walled carbon nanotubes are studied as environmental gas sensors. The results for pristine Single walled carbon nanotubes (SWNT) and SnO2 functionalized SWNT hybrid nanostructures have been compared for their response towards the gases, i.e. NO2 and NH3 (for concentrations ranging from 2 to 20 ppm). To study the underlying phenomenon, the adsorption kinetics of pristine and SnO2 functionalized (SWNT) have been next investigated for their sensitivity towards both the prevalent gases. The electrical model of Carbon nanotubes (CNT) networks and its dependence on gas concentration has been investigated. Considering the physisorption of NH3 and NO2, Langmuir adsorption model has been applied to study the change in conductivity with varying gas concentration by fitting experimental data with Langmuir isotherm. Langmuir constants are indicative of adsorption capacity of SWNT surface as well as concentration of gas molecules adsorbed on CNT networks. An increment has been observed in the Langmuir constants from pristine to functionalized SWNT. The observed enhancement may be attributed to the improvement of surface adsorption kinetics when SWNT surface is modified with a functional group.
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