IoT-enabled surface-active Pd-anchored metal oxide chemiresistor for H₂S 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.