Trace level sensitivity and selectivity of room temperature NH 3 gas sensors based on RGO/ZnO@SiNWs heterostructure

Ammonia (NH 3 ) is one of the most common gaseous pollutants in various environmental and industrial processes which is accountable for various health issues, even for life-threatening situations. Due to this, high-precision detection of NH 3 has become a top priority for various sectors so that healthy and safe environment could be ensured. Therefore, this work aims to develop a simple, reliable, and effective sensor with spatially distributed monitoring of NH 3 gas wherein reduced graphene oxide (RGO) and Zinc oxide (ZnO) nanocomposite structure prepared using refluxing method were chosen to interact with NH 3 gas. The vertically aligned silicon nanowires (SiNWs) were developed by using metal-assisted chemical etching (MACE) method. The RGO/ZnO nanostructure was then deposited on SiNWs to develop a selective and stable sensor for the trace level detection of NH 3 gas with varying concentration from 0.01 ppm to 5 ppm at Room temperature (∼30 °C). The prepared materials were characterized using scanning electron microscope (SEM), transmission electron microscope (TEM), energy dispersive spectroscopy (EDS), X-ray diffractometer (XRD), Raman spectrometer, X-Ray Photoelectron Spectrometer (XPS) and Ultraviolet–visible spectrophotometer which provide a thorough explanation about the developed nanostructures. The sensitivity of the sensor was observed to lie between 21 % at 0.01 ppm and 176 % at 5 ppm concentration of NH 3 wherein the response/recovery time was measured to be 3 s/6 s and 5 s/12 s respectively. The fast response of the sensor for NH 3 gas at low limit of detection (LOD) could be attributed due to the precise interaction of the analyte at the interface of RGO/ZnO@SiNWs Schottky heterostructure. Hence, the reported sensor can continuously be utilized to monitor the target analyte that is NH 3 gas at low concentrations and reduces the chance of an unfortunate incident.