PtCu Nanoparticles Sensitizing Mesoporous In₂O₃ Hexagonal Hollow Nanotubes for ppb-Level Formaldehyde Evaluation in Aquatic Products

The presence of formaldehyde (HCHO) in foods can pose specific health risks, including irritation, allergic reactions, and potential long-term health issues due to its toxic properties. The application of metal oxide semiconductor gas sensors to detect trace levels of HCHO in aquatic products has garnered growing interest. Consequently, a reliable and optimized metal organic framework derivation method combined with a postmodification process is utilized to synthesize different aspect ratio In₂O₃ hexagonal hollow nanotubes (HHNT) assembled by In₂O₃ nanocrystals. After that, PtCu nanoparticles (NPs) are loaded on these materials for further sensitization. The sensors constructed by 1.5 wt % PtCu/In₂O₃ HHNT exhibit significant HCHO sensing properties, including high response, rapid response/recovery time (6 s/9 s), good selectivity, and low limit of detection (50 ppb HCHO) at a low temperature. Moreover, XPS, UV-vis, the time-dependent in situ DRIFTS, and activation energy calculation are applied to analyze the gas-sensing mechanism. The excellent gas-sensing performances of as-prepared materials are attributed to the small aspect ratio, unique hollow morphology, and uniform load of PtCu NPs, which provide a large specific surface area, mesopores that facilitate gas penetration, abundant active sites, oxygen spillover effect, and bimetallic synergistic effect. The outstanding HCHO assessment of seafood (<i>Larimichthys polyactis</i> and scallops) proves that the as-constructed sensors pave the way for in situ and rapid HCHO evaluation in aquatic products and have the potential to be extended to the HCHO detection in the environment and public health.