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.