Organo-di-benzoic-acidified ZnO Nanohybrids for Highly Selective Detection of CO at Low Temperature

A chemiresistive carbon monoxide (CO) gas sensor comprising of an organo-di-benzoic acidified zinc oxide (ODBA-ZnO) nanohybrid material is reported. The ODBA-ZnO hybrid material is prepared via a single-pot hydrothermal method. The electrical resistance of the drop-casted ODBA-ZnO film on interdigitated electrodes increases noticeably upon exposure to CO (5-500 ppm). The resistance increase is attributed to the formation of complex ions at the organic (ODBA)-inorganic (ZnO) interface in the presence of CO. The detailed CO sensing properties of the ODBA-ZnO nanohybrids reveal a remarkable selectivity to CO gas in comparison to other gases like CO₂, H₂S, and NH₃ at 125 °C. The maximum response to 100 ppm of CO is observed to be 35% with the achieved selectivity to CO being 88%, which is the best reported CO selectivity result available in the literature to date. The ODBA-ZnO nanohybrid sensor takes nearly 91 s to reach the saturated response to 100 ppm of CO and nearly 175 s to recover from it in a synthetic air environment. A systematic study using field emission scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, nitrogen adsorption-desorption tests, and thermogravimetric analysis reveals that introduction of an organic moiety (ODBA) to ZnO played a key role in achieving improved selectivity and sensitivity toward CO. The present work provides a simple route for fabricating the ODBA-ZnO sensor to achieve better selectivity and sensitivity to CO gas at a relatively low temperature (125 °C).