IoT-enabled surface-active Pd-anchored metal oxide chemiresistor for H<inf>2</inf>S gas detection

The Internet of Things (IoT) has a crucial role in advancing various fields such as Industry 4.0, Big Data, and Machine-to-Machine technologies. All systems continuously gather information on various parameters such as temperature, speed, pressure, health data, environmental conditions, and consumption. Considering this, we've developed a novel fabrication method for H2S gas sensor prototypes. These sensors are based on noble metal-functionalized on metal oxide semiconductor (MOS) chemiresistors. The fabrication process involved growing CuCrO2 sensing thin film on SiO2/Si substrates using the RF sputtering method. Subsequently, Pd nanoparticles, known for their excellent gas-sensing catalyst properties, were functionalized onto the CuCrO2 films using DC sputtering with varying sputtering times of 3, 6, 9, and 12 s. Nanorice morphology boosts gas absorption, capturing more target molecules. A 9 s Pd sputtering time greatly improved H2S sensing over other gases. CuCrO2 film with Pd showed the highest 72.3% response to 50 ppm H2S, detecting down to 0.5 ppm. These results were achieved at the optimal working temperature of 150 °C. After optimizing parameters, we transferred the technology to develop a sensor module for the prototype with IoT integration. The prototype sensor connects to NODEMCU-ESP8266 Wi-Fi, which links to a smartphone through a mobile hotspot.