Selective detection of hydrogen sulphide from the background of low concentration reducing gases

Highlights: • Au-doped SnO₂ nanofibers were synthesized by electrospinning technique. • The fabricated nanofiber sensors showed excellent response to H₂S. • Response of the Au doped sample was nearly independent of humidity at 370 °C. • Selective detection of H₂S was confirmed in the presence of acetone. One dimensional pristine and Au doped tin oxide (SnO₂) nanofibers were successfully synthesized by versatile electrospinning technique followed by calcination at 600 °C for 2 h. As-synthesized nanofibers were characterized by X-ray diffraction (XRD), scanning electron microscopy (FE-SEM) equipped with energy dispersive X-ray spectroscopy (EDAX), transmission electron microscopy (TEM), and UV visible spectrophotometer. The response of the sensors strongly depends on the operating temperature and the amount of additives. The optimum performance was obtained at 370 °C for 3 wt% Au doped SnO₂ sample. The fabricated devices show response to reducing gases like hydrogen sulphide (H₂S), acetone, ammonia, ethanol, propanol etc. and the lowest detectable concentration was 1 ppm for H₂S and 10 ppm for all other gases. Thus, the device can be used for the selective detection of H₂S avoiding the problem of cross linking response of other reducing gases with concentration below 10 ppm. The theoretically calculated detection limit for H₂S is 550 ppb. The effect of humidity is tested on pristine and 3 wt% Au doped SnO₂ samples at room temperature and 370 °C. At higher operating temperature of 370 °C, the effect of humidity can be neglected for Au doped samples. Also we tested the response towards the mixture of H₂S and acetone and found that at lower concentrations the device show response only to H₂S gas. The device can be used for the breath analysis for disease diagnosis such as halitosis due to the negligible effect of humidity and the selective nature at lower concentrations since the concentration level of H₂S in the exhaled breath of halitosis patient is found to be in the range of 80 ppb-2 ppm.