Xueli Yang

Hydrogen sulfide (H2S) is a highly toxic, corrosive, and flammable gas generated from industrial production, petroleum refining, wastewater treatment, municipal waste, and anaerobic decomposition of organic matter. Reliable H2S monitoring is therefore essential for environmental safety, industrial process control, and human health protection. Conventional chemiresistive H2S sensors based on metal oxide semiconductors often require elevated operating temperatures, which increase power consumption and restrict device miniaturization, flexible integration, and long-term deployment. Room-temperature H2S sensors have consequently attracted increasing attention as low-power sensing platforms. This review summarizes recent progress in room-temperature H2S sensing across single-component semiconductors, composite heterojunctions, two-dimensional materials and their heterostructures, metal-organic-framework-based materials, noble-metal-sensitized systems, and photoactivated sensors. Representative preparation methods, structure-performance relationships, and key sensing parameters are compared. Particular emphasis is placed on sensing mechanisms and supporting evidence, including oxygen-adsorption-mediated conductivity modulation, H2S-induced sulfidation, interfacial barrier modulation, defect-related activation, noble-metal-mediated catalytic and electronic sensitization, photoinduced carrier and photothermal effects, and framework-mediated transduction. Humidity interference and mitigation are further discussed, together with advances in micro electromechanical system (MEMS) devices, flexible and self-powered platforms, wireless sensing, sensor arrays, electronic noses, and AI-assisted identification. Finally, challenges and future directions are highlighted, including ppb-level detection, reversibility, humidity tolerance, complex-gas selectivity, long-term stability, standardized evaluation, real-sample validation, and intelligent-system integration. This review provides a systematic framework for developing reliable, low-power, and application-oriented room-temperature H2S sensors.

Layered double hydroxides (LDHs) have attracted considerable attention in gas sensing applications due to their highly tunable chemical composition and unique two-dimensional layered architecture. In this study, a series of ZnAl-LDHs with varying Zn/Al molar ratios were synthesized via a facile hydrothermal method, and their ethanol sensing performance at room temperature was systematically evaluated. The influence of composition on the structural, morphological, and electronic properties of the materials was thoroughly investigated using a suite of characterization techniques, including XRD, FTIR, SEM, TEM, BET, XPS, PL, and EPR. Among the synthesized samples, the Zn/Al = 2 : 1 composition (denoted as ZA2.1) exhibited the highest sensing performance, achieving a 60% response ((R_g − R_a)/R_g × 100%) to 100 ppm ethanol at room temperature, with a rapid response time of 33 s and a recovery time of 4 s. This sample also demonstrated excellent selectivity and long-term stability. The enhanced sensing behavior is attributed to the synergistic effect between the optimized oxygen vacancy concentration (controlled by the Zn/Al molar ratio) and the efficient gas diffusion promoted by the orthorhombic hexagonal nanosheet morphology. The defect and nanostructure of ZnAl-LDHs can be regulated through composition engineering, providing a promising strategy for the development of high-performance room-temperature gas sensors.