Steering selectivity in the detection of exhaled biomarkers over oxide nanofibers dispersed with noble metals

Abstract

The trace detection of biomarker molecules in exhaled breaths enables a facile disease diagnosis in early stages. However, the selective detection of each pathognomonic gas was difficult to achieve due to a poor understanding of the selectivity mechanism, which impeded the development of a rational design for practical diagnostics. Herein, we report a systematic study of the explicit roles of noble metal catalysts in modulating the gas selectivity of metal oxides and provide an in-depth mechanistic understanding of the reaction pathways specific to each element. Using a consistent synthetic platform to prepare highly dispersed catalysts on In₂O₃ nanofibers, we identified that Ru and Pd catalysts showed exceptional selectivity to CH₃SH and H₂S, respectively, while Pt selectively interacted with CH₃COCH₃ molecules. Furthermore, we revealed that the element-specific gas adsorption and the ensuing charge transfer form the basis for regulating selective surface reactions of target gases. Altogether, we propose a set of design principles for sensing layers based on the prominent, element-dependent roles of catalysts toward the development of a rational synthesis of sensing materials with optimal sensing performance. These principles can be summarized as follows: controlled chemisorption of oxygen species, selective gas adsorption, and subsequent activation of adsorbed gases.