From material design to smart sensing: recent advances in colorimetric sensors for gas monitoring

With the continuous advancement of intelligent manufacturing and the growing demands in health monitoring, the need for gas sensors with enhanced portability, wearable integration, and signal visualization has become increasingly prominent. To address the challenges posed by diverse application scenarios, breakthroughs in sensor sensitivity, response speed, cost-effectiveness, and integration are urgently required. In this context, colorimetric gas sensing technology has emerged as a research hotspot in the field due to its unique advantages. The core of this technology lies in the specific interactions between gas molecules and functional sensitive materials, such as coordination, hydrogen bonding, and charge transfer mechanisms, which induce systematic changes in the optical properties of the materials, thereby converting chemical signals of gases into visually discernible responses. This direct and intuitive sensing mechanism enables on-site rapid detection without the need for complex instruments, offering a promising pathway for developing practical gas sensing systems. This review systematically summarizes recent key advancements in colorimetric gas sensors, focusing on the construction of core material systems, including design strategies for various colorimetric indicators and the synergistic mechanisms of performance-enhancing materials. It details the technical characteristics of major substrate materials and, in addition, provides a comprehensive analysis of sensor array design and the integration of intelligent recognition algorithms. Typical applications include industrial leak monitoring, environmental pollution detection, biomarker analysis, and food freshness assessment. This work analyzes the key current challenges of colorimetric gas sensors to support their advancement into high-performance, practical devices by establishing a theoretical foundation and offering technical guidance.