Co 3 [Co(CN) 6 ] 2 -Mediated Olfactory and Visual Dual-Modality Ammonia Sensing

In the emerging ammonia (NH 3 ) 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 NH 3 sensing. Here, Co 3 [Co(CN) 6 ] 2 microcubes (Co–CN MCBs) mediators have been developed for olfactory and visual dual-modality NH 3 sensing. In olfactory sensing, porous chitosan-decorated Co 3 O 4 /Co 3 [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 NH 3 detection through a pink-to-brown transition. Further, highly selective NH 3 sensing has been acquired through machine learning-powered classification of MCGs’ response and CSP’s specific NH 3 chromogenic behavior. Notably, combining dual-modality sensing has achieved desired NH 3 detection due to the boosted NH 3 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 NH 3 with reliable responses.