Abstract:
The daily population activities linked to the emission of various hazardous gases that can be toxic, explosive, and flammable such as CO, H2S, SO2, NOx, CO2, and volatile organic compounds have a negative impact on human lives and the environment. The development of NO2 and CO gas sensors is vital for prompt detection due to their poisonous behaviour, which may lead to immediate deaths.
Consequently, tin dioxide (SnO2) and vanadium pentoxide (V2O5) nanostructures were prepared following a facile hydrothermal method using different bases for the detection of various gases. The SnO2-NaOH displayed hollow sphere-like structures with etched surfaces, while the SnO2-NH4OH and SnO2-Urea illustrated nanoflakes and hierarchically arranged nanoflakes forming spheres, respectively. The V2O5 nanostructures showed nanorod like structures that varied in thickness and length with base. Structural findings exhibited improved crystalline structure of the SnO2 in the following behaviour: SnO2-NaOH<SnO2-Urea<SnO2-NH4OH. In-situ electron paramagnetic resonance and photoluminescence studies disclosed that the SnO2-NaOH possessed a significantly high concentration of oxygen vacancies (VO). Consequently, the SnO2-NaOH based sensor disclosed an exceptional selectivity to CO gas amid other target gases while operating at low temperature (75 °C). The sensor displayed a higher resistance ratio (≈32) at 60 ppm, a sensitivity of 0.49 ppm-1, and a low theoretical detection limit of 70 ppb. Such unprecedented performance towards CO was owing to a higher number of surface defects induced by the strategy of utilizing NaOH as a base to tailor the surface properties of the SnO2SnO2/CuO-(1.0:1.0 M), SnO2/CuO-(0.5:1.0 M) and SnO2/CuO-(1.0:0.5 M) heterostructures-based sensors were also fabricated for detection of NO2 gas at room temperature. The fabricated materials were characterized using various techniques, to investigate the structure, morphology, internal structure, and optical properties. The elemental mapping was also carried out to investigate the distribution of both Cu and Sn. To test their suitability in gas sensing applications, the nanomaterials were tested towards various gases at different temperatures. Among the tested sensors, the SnO2/CuO-(1.0:1.0 M)-based sensor showed a higher response towards NO2, in the presence of other four gases at room temperature. At 100 C, the sensors showed a poor response, justifying that their optimal temperature is 25 C. These results indicate that these sensors could be considered as low-power consumption sensors for the detection of NO2.
