Sensing Performance of Visible Light-Activated SnO2Functionalized with CuInS2 @ZnS QDs for Hydrogen Detection

In recent years, the detection of air pollution has gained an increasing interest due to the impact that this has on human health and the environment. In this context, one of the key challenges is the real-time and selective monitoring of the air quality. To this aim, chemiresistive gas sensors represent one of the most widely used technologies, due to their low cost, fast response, and portability. Nowadays, chemiresistive gas sensors based on semiconducting metal oxides (SMOX) are the most widely used thanks to their reliability and high sensitivity. However, despite the important advantages, there are two main drawbacks associated with their use, namely the low selectivity of SMOX-based gas sensors and the high power consumption associated to the need of high temperatures for thermal activation of the sensing film. To address these drawbacks, there is an urgent need for novel approaches. One interesting strategy to decrease energy consumption involves the use of light radiation for sensor activation instead of the traditional heating methods. However, a significant limitation is the low absorption of visible radiation by many sensing materials, notably SMOX. To overcome this issue, an effective strategy involves functionalizing SMOX with antenna molecules capable of absorbing visible light and facilitating electron transfer to the conduction band of the SMOX. Quantum dots (QDs) have emerged as a promising class of molecules for this purpose. In this study, an innovative composite material composed of SnO2nanoparticles functionalized with CuInS2 @ZnS (Z-CIS) QDs acting as an antenna for blue light activation was investigated. The experimental results showed a significant change in sensor resistance under blue light illumination (464 nm), yielding a notable response value of 43.18. Leveraging this illumination, hydrogen (H2) detection at concentrations of 30, 60, 150, and 300 ppm was tested, yielding responses of 1.05%, 1.35%, 2.89%, and 4.07%, respectively. Another significant outcome of the study is the recovery time of the sensor. It was observed a consistent recovery time of approximately 2 hours across all tested H2 concentrations.