Room temperature detection of NO2 gas using optical sensor based on surface plasmon resonance technique

Abstract

A gas sensing measurement set up has been indigenously developed using a low cost table top surface plasmon resonance (SPR) system. RF magnetron sputtered WO3 thin film has been incorporated with gold coated prism (BK-7 glass) to excite the surface plasmon modes in Kretschmann configuration (WO3/Au/prim). The structural and morphological properties of WO3 thin film influence the SPR mode significantly. WO3 thin film deposited at a sputtering pressure of 50mT exhibits a very sharp SPR curve with low value of reflectance (0.21) at the resonance angle of 46.6°. The optimized system (WO3 (50mT)/Au/prim) has been utilized for detection of NO2 gas of varying concentration (0.5 to 50ppm) at room temperature. SPR curves obtained on interaction with low concentration (1ppm) of NO2 gas under static configuration show a significant shift in resonance angle from 46.6 to 50.6° with very fast response time (0.8s). The WO3/Au/prism SPR system has been found suitable for efficient and selective detection of low concentration of NO2 gas (minimum concentration=0.5ppm) with high sensitivity at room temperature, thus paving a way for the development of commercial optical sensors for NO2 gas detection.