Approaches for selectivity improvement of conductometric gas sensors: an overview

Conductometric gas sensors (CGS) have been extensively explored in recent decades owing to easy fabrication and miniaturization, low cost and distributable detectability. Among numerous performance parameters, selectivity is a critical one to evaluate the operation quality of CGS in diverse application scenarios such as environment monitoring, food quality assessment, individual healthcare, etc. Nevertheless, in most preceding work either the underlying mechanism for the shown selectivity is not explained clearly or the strategies to improve the selectivity are not detailed, which necessitates an urgent need to address these. Also, there is still a lack of comprehensive summaries reported in this aspect thus far. A favorable selectivity always means a stronger sensitivity toward a specific gas than that toward other interference gases. Thus, it is very essential to conduct a comprehensive overview to understand the sensitivity, selectivity and their relationships from both quantitative and qualitative perspectives. In this review, the sensing mechanism of CGS is first studied according to the selectivity coefficient simultaneously concluding the factors that influence the detection selectivity. Subsequently, chemical and physical modification strategies to improve the selectivity are discussed. Finally, challenges and perspectives of the selectivity optimization methods are proposed for future research. Conductometric gas sensors (CGS) have been extensively explored in recent decades owing to easy fabrication and miniaturization, low cost and distributable detectability.