IoT-Enabled Pd-Anchored CuO/SnO₂ Hybrid Thin Films via RF Sputtering for H₂S Gas Sensing

The advancement of various fields, including Industry 4.0, Big Data, and Machine-to-Machine technologies, is significantly influenced by the integration of the Internet of Things (IoT) and Machine Learning (ML). These technologies play a crucial role in continuously collecting and analyzing information related to parameters such as temperature, speed, pressure, health data, environmental conditions, and consumption. The development of high-performance toxic gas sensing devices is essential for public safety, environmental control, industrial operations, and other applications, contributing to improved living standards. In this context, a novel fabrication method has been devised for H2S gas sensor prototypes. These sensors utilize noble metal-functionalized metal oxide semiconductor (MOS) chemiresistors. The fabrication process involves the growth of CuO/SnO2 hybrid nanostructures sensing thin film on SiO2/Si substrates using the RF sputtering method. Subsequently, Pd nanoparticles, known for their excellent gas-sensing catalyst properties, are functionalized onto the CuO/SnO2 hybrid films using DC sputtering, with varying sputtering times of 3, 6, 9, and 12 seconds. The resulting nanostone morphology enhances gas absorption, enabling the capture of more target molecules. Notably, a 9-second Pd sputtering time significantly improves H2S sensing compared to other gases. The CuO/SnO2 film with Pd exhibits the highest response, registering a 74.7% response to 50 ppm H2S and detecting concentrations as low as 0.5 ppm. These promising results are achieved at the optimal working temperature of 150 °C. Following the optimization of parameters, the technology is transferred to the development of a sensor module with IoT integration. The prototype sensor seamlessly connects to a NODEMCU-ESP8266 Wi-Fi module, establishing a link with a smartphone through a mobile hotspot. This integration enhances the real-time monitoring and data transmission capabilities of the sensor, contributing to efficient and connected systems for diverse applications.