Co3[Co(CN)6]2-Mediated Olfactory and Visual Dual-Modality Ammonia Sensing

In the emerging ammonia (NH3) economy, both olfactory and visual sensing are desired for leakage detection, in which olfactory sensing enables a fast response and wide detection range, while visual sensing ensures high selectivity. However, little is reported on the sensing material as a mediator to synergistically combine the dual-modality NH3 sensing. Here, Co3[Co(CN)6]2 microcubes (Co–CN MCBs) mediators have been developed for olfactory and visual dual-modality NH3 sensing. In olfactory sensing, porous chitosan-decorated Co3O4/Co3[Co(CN)6]2 microcages (CS@Co–O/Co–CN MCGs) have been obtained via [Co(CN)6]3–-governed self-assembly, glycerol-assisted reduction, and Kirkendall effect-driven hollowing. Beneficially, MCGs exhibit a 1 s fast response (500 ppm) and a 0.5–10,000 ppm wide detection range at room temperature. In visual sensing, colorimetric sensing paper (CSP) incorporated with anthocyanin, Co–CN, and poly(vinyl alcohol) has been achieved, which presents 10–320 ppm visual NH3 detection through a pink-to-brown transition. Further, highly selective NH3 sensing has been acquired through machine learning-powered classification of MCGs’ response and CSP’s specific NH3 chromogenic behavior. Notably, combining dual-modality sensing has achieved desired NH3 detection due to the boosted NH3 adsorption on Co–CN MCBs’ active sites and the synergistic effect of their-mediated heterostructures. Practically, our dual-modality sensing device has been integrated to detect NH3 with reliable responses.