The Cross-Sensitivity of Chemiresistive Gas Sensors: Nature, Methods, and Peculiarities: A Systematic Review.

The evaluation of selectivity/cross-sensitivity is one of the most important tests for gas sensor development, particularly that based on chemiresistive technology. It is known that chemiresistive gas sensors suffer from low selectivity when they provide sensitivity to several analytes. Typically, selectivity testing involves independently assessing a sensor's response to a specific gas. However, there is a growing need to evaluate performance with interfering gases or gas mixtures since gas sensors are always exposed to gas mixtures in practice. Despite the great importance of selectivity characterization, currently, there are no standard methods of selectivity tests at conditions when target gas coexists with interfering gas compounds, which mimics real conditions. We outlined the four main methods researchers use to evaluate the cross-sensitivity of gas sensors. It highlights key aspects of selectivity test performance, assessment methodologies, and procedure features, attempting to classify them by their distinct characteristics. This review covers the essentials of gas properties, adsorption and desorption processes, and gas molecule interactions. Finally, we tried to address the lack of standardized protocols for evaluating chemiresistive gas sensors' cross-sensitivity to interfering gases and guide researchers.