Synthesized trimanganese tetraoxide functionalized zinc oxide hierarchical structures with abundant oxygen vacancies for ppb-level volatile organic compounds detection.

Hierarchical heterostructures have been proven to be the great material structures for the fabrication of gas sensors, due to they high surface area, well-aligned porosity and synergy effect. Here, ZnO hierarchical structures with various amount of Mn dopant were synthesized through a simple one-step solution route followed by annealing treatment. The characterization results demonstrated that Mn dopant existed in the forms of Mn 3 O 4 nanoparticles and lattice Mn2+ ions. The as-synthesized Mn 3 O 4 /ZnO hierarchical structures with abundant oxygen vacancies (Mn x ZnO with x values of 0, 0.25, 0.5, 1 and 3) were used as the sensing materials toward volatile organic compounds (VOCs) detection, illustrating that the introduction of Mn dopant can significantly improve the gas sensing performance. Especially, under optimal working temperature, Mn 0.5 ZnO hierarchical structures-based gas sensor exhibits the highest responses, fast response/recovery speed (2/9 s), a low detection limit (150 ppb), good selectivity and long-term stability toward acetone. In addition, the enhanced gas sensing mechanisms were explained by large surface area, oxygen vacancies and p-n heterojunction, boosting the surface reactions, which was further verified through DFT calculations. This work also confirmed that Mn element could be a promising dopant in metal oxides for high-performance VOCs gas sensors. [Display omitted] • Mn x ZnO hierarchical structures were synthesized through a simple solution route. • Mn 0.5 ZnO sensor exhibits high response, fast response/recovery speed, low detection limit toward acetone. • Sensing mechanisms were studied by large surface area, oxygen vacancies and p-n heterojunction. [ABSTRACT FROM AUTHOR]