Oxygen vacancy-rich engineering-optimized molybdenum trioxide microbelts for room-temperature ppb-level trimethylamine detection

Oxygen vacancies in metal oxides play a pivotal role in determining their electronic structure and interfacial redox dynamics. However, their sluggish kinetics and imbalanced adsorption/desorption hinder their performance. Here, we report oxygen vacancy (O_V)-rich molybdenum trioxide (MoO₃) microbelts for room-temperature (RT) volatile organic compound (VOC) sensors, effectively overcoming these limitations. Owing to the synergistic effects of a large specific surface area, surface oxygen vacancies, and an optimized electronic structure, exceptional trimethylamine (TMA) sensing performance richs oxygen vacancy-MoO₃ (MoO_3−x-R), including notably high response, rapid response/recovery, high selectivity, a low limit of detection (400 ppb), and reliable operational stability, was achieved. Experimental and density functional theory studies revealed that controlled oxygen vacancies contribute to tuning the surface redox activity of one-dimensional (1D) MoO₃ and regulating the interfacial electron transfer efficiency. Molecular dynamics (MD) simulations revealed that abundant oxygen vacancies in MoO_3−x-R enhance its affinity for TMA while weakening its interaction with nitrogen, carbon dioxide, or water vapor. Furthermore, a portable device was developed for quantitative TMA monitoring, enabling rapid and nondestructive detection of fish freshness. This research provides novel perspectives for designing high-performance gas sensors by optimizing the interfacial redox kinetics.