Nanocrystalline PbS as Ammonia Gas Sensor: Synthesis and Characterization

This article reports on the synthesis of lead sulfide (PbS) by precipitation at a reaction temperature of 90°C. For its plausible use as ammonia (NH₃) gas sensor, the sample was characterized. The X-ray diffraction results showed that the produced PbS was nanocrystalline with a crystallite size of 33.31nm. The surface morphology of the sample was studied by scanning electron microscopy. The electrical response of the sample in the form of a thick film was studied in the presence of NH₃ and vapors of volatile organic compounds (VOCs) like methanol, ethanol, and isopropyl alcohol within the detection limit of 0-150ppm at room temperature. The sensing behavior showed that the material synthesized was only influenced by NH₃ amongst other gases (VOCs). In addition, the sample exhibited reversible and consistent responses satisfactorily with a relatively short response time (10s) compared to others. Therefore, it could be used as NH₃ gas sensor without the help of any micro-heater that is traditionally required for existing commercial gas sensors. The gas sensing mechanism is proposed to follow the well-known Freundlich adsorption isotherm. This isotherm is multi-molecular, physical, and reversible in nature. Finally, it is suggested that the present findings could be exploited for manufacturing a PbS sensor in a small scale industrial unit.