Trace level sensitivity and selectivity of room temperature NH3 gas sensors based on RGO/ZnO@SiNWs heterostructure

Ammonia (NH3) 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 NH3 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 NH3 gas wherein reduced graphene oxide (RGO) and Zinc oxide (ZnO) nanocomposite structure prepared using refluxing method were chosen to interact with NH3 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 NH3 gas with varying concentration from 0.01 ppm to 5 ppm at Room temperature (similar to 30 degrees 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 NH3 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 NH3 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 NH3 gas at low concentrations and reduces the chance of an unfortunate incident.