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, sluggish kinetics and imbalanced adsorption/desorption impede their performance. Here, we report oxygen vacancy-rich MoO₃ microbelts for room-temperature (RT) volatile organic compounds (VOC) sensors, effectively overcoming these limitations. Benefiting from the synergistic effect of large specific surface area, surface oxygen vacancies, and optimized electronic structure, the exceptional trimethylamine (TMA) sensing performance of rich oxygen vacancy-MoO₃ (MoO_3-x-R) was achieved, including notably high response, rapid response/recovery, high selectivity, a low limit of detection (400 ppb), and reliable operational stability. Experimental and density functional theory studies revealed that the controlled oxygen vacancies contribute to tuning the surface redox activity of 1D MoO₃, as well as regulating the interfacial electron transfer efficiency. Molecular dynamics simulations find 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 non-destructive fish freshness detection. This research provides novel perspectives for designing high-performance gas sensors by optimizing the interfacial redox kinetics.