Low-trace monitoring of airborne sulphur dioxide employing SnO2-CNT hybrids-based energy-efficient chemiresistor

Room temperature low-trace detection (lower than 2 ppm) of sulphur dioxide (SO2) through compact, economic and sustainable chemiresistor has created a large demand-supply gap in sensor market. For the first time, this communication reports the room-temperature detection of 1 ppm of airborne SO2 utilizing tin-oxide (SnO2)/carbon nanotube (CNT) hybrids based chemiresistors in variable humidity and temperature environment. The precursor's concentrations were optimized in terms of conductivity to attain utmost sensitivity and lowest detection limit. Amongst all engineered hybrids and pristine precursors, the chemiresistor possessing the highest conductivity (S-2: 0.5 wt% of CNT) exhibited utmost sensitivity (2.3%) towards 1 ppm of SO2 at room temperature under 67% RH. The sensing response is rapid (110 s), repeatable, recoverable (110 s), and steady (for 7 weeks), showing high selectivity against prominent interfering analytes. It is attributed to the formation of p-n type interfacial heterojunctions and faster charge transport pathways in hybrid. Besides, the underlying room temperature SO2 sensing phenomenon is explained in terms of space charge modulation in the depletion region of the p-n hybrid using band theory. These unprecedented outcomes highlight the prospects of engineering intelligent, sustainable and point-of-detection SO2 monitoring strategies based on SnO2/CNT hybrids in terms of cost, time, human resources, energy requirements, and stability.