Self-powered gas sensor based on SiNWs/ITO photodiode

Low-Power Consumption IGZO Memristor-Based Gas Sensor Embedded in an Internet of Things Monitoring System for Isopropanol Alcohol Gas

Low-power-consumption gas sensors are crucial for diverse applications, including environmental monitoring and portable Internet of Things (IoT) systems. However, the desorption and adsorption characteristics of conventional metal oxide-based gas sensors require supplementary equipment, such as heaters, which is not optimal for low-power IoT monitoring systems. Memristor-based sensors (gasistors) have been investigated as innovative gas sensors owing to their advantages, including high response, low power consumption, and room-temperature (RT) operation. Based on IGZO, the proposed isopropanol alcohol (IPA) gas sensor demonstrates a detection speed of 105 s and a high response of 55.15 for 50 ppm of IPA gas at RT. Moreover, rapid recovery to the initial state was achievable in 50 μs using pulsed voltage and without gas purging. Finally, a low-power circuit module was integrated for wireless signal transmission and processing to ensure IoT compatibility. The stability of sensing results from gasistors based on IGZO has been demonstrated, even when integrated into IoT systems. This enables energy-efficient gas analysis and real-time monitoring at ~0.34 mW, supporting recovery via pulse bias. This research offers practical insights into IoT gas detection, presenting a wireless sensing system for sensitive, low-powered sensors.

A Self-Powered Portable Nanowire Array Gas Sensor for Dynamic NO2 Monitoring at Room Temperature

The fast development of the Internet of Things (IoT) has driven an increasing consumer demand for self-powered gas sensors for real-time data collection and autonomous responses in industries such as environmental monitoring, workplace safety, smart cities, and personal healthcare. Despite intensive research and rapid progress in the field, most reported self-powered devices, specifically NO₂ sensors for air pollution monitoring, have limited sensitivity, selectivity, and scalability. Here, a novel photovoltaic self-powered NO₂ sensor is demonstrated based on axial p-i-n homojunction InP nanowire (NW) arrays, that overcome these limitations. The optimized innovative InP NW array device is designed by numerical simulation for insights into sensing mechanisms and performance enhancement. Without a power source, this InP NW sensor achieves an 84% sensing response to 1 ppm NO₂ and records a limit of detection down to the sub-ppb level, with little dependence on the incident light intensity, even under <5% of 1 sun illumination. Based on this great environmental fidelity, the sensor is integrated into a commercial microchip interface to evaluate its performance in the context of dynamic environmental monitoring of motor vehicle exhaust. The results show that compound semiconductor nanowires can form promising self-powered sensing platforms suitable for future mega-scale IoT systems.

Highly Selective Self-Powered Organic-Inorganic Hybrid Heterojunction of a Halide Perovskite and InGaZnO NO2 Sensor

Self-powered sensors can lead to disruptive advances in self-sustainable sensing systems that are imperative for evolving human lifestyles. For the first time, we demonstrate the fabrication of a heterojunction sensor using p-type hybrid-halide perovskites (CH₃NH₃PbBr₃) and an n-type semiconducting metal oxide thin film [InGaZnO (IGZO)] for the detection of NO₂ gas and power generation. Combining the excellent photoelectric properties of perovskites and the remarkable gas-sensing properties of IGZO at room temperature, the devised sensors generate open-circuit voltage and modulate according to the ambient NO₂ concentration. The major challenge in devising self-powered gas sensors is to attain harvesting capability and selectivity simultaneously, owing to perovskites reactivity in the presence of oxygen and humidity. In this work, we developed a novel approach and fabricated a heterojunction sensor using parylene-c as an additional layer to curb the cross-sensitivity and to enhance the selectivity of the sensor. Even under the low concentrations of NO₂, the developed sensor exhibits remarkable sensitivity, selectivity, and repeatability. The devices are sensitive and robust even under extreme humidity conditions (80% R_H) and synthetic air. The devised sensor configuration is one way to eliminate the cross-sensitivity issue of the perovskite-based devices and serves as a reference for the development of self-powered sensors.

A Photovoltaic Self-Powered Gas Sensor Based on All-Dry Transferred MoS2 /GaSe Heterojunction for ppb-Level NO2 Sensing at Room Temperature

Traditional gas sensors are facing the challenge of low power consumption for future application in smart phones and wireless sensor platforms. To solve this problem, self-powered gas sensors are rapidly developed in recent years. However, all reported self-powered gas sensors are suffering from high limit of detection (LOD) toward NO2 gas. In this work, a photovoltaic self-powered NO2 gas sensor based on n-MoS2 /p-GaSe heterojunction is successfully prepared by mechanical exfoliation and all-dry transfer method. Under 405 nm visible light illumination, the fabricated photovoltaic self-powered gas sensors show a significant response toward ppb-level NO2 with short response and recovery time and high selectivity at room temperature (25 °C). It is worth mentioning that the LOD toward NO2 of this device is 20 ppb, which is the lowest of the reported self-powered room-temperature gas sensors so far. The discussed devices can be used as building blocks to fabricate more functional Internet of things devices.