Analyte-Specific "Signal-On" Uranyl Sensitive Sensing Based on Temperature-Programmed Nanozyme Activity of CoOx.

Abstract

As alternatives to bioenzymes, nanozymes find promising applications in biochemical sensing thanks to their recognized superiorities, but their lack of specific interactions with targets of interest seriously hinders the exploration of selective analytical strategies when no external receptors are employed. Additionally, most nanozymes exhibit poor catalytic efficiency, much lower than their natural counterparts, thus restricting the sensitivity of detection. Different from the explored "turn-off" analytical principle relying on the coordination of the target with a nanozyme catalytic product, here we proposed an analyte-unique "signal-on" strategy based on the direct target-nanozyme interaction for the sensitive sensing of uranyl via temperature-programming the peroxidase (POD)-mimetic activity of CoOx. As wet-chemical temperature increased, the oxygen vacancy (OV) content on CoOx surfaces exhibited a volcano-type trend, and its catalytic efficiency correlated with the former positively. UO22+ was found to stimulate the POD-like activity of CoOx via increasing OV, exhibiting excellent specificity against other common species. Leveraging the unique CoOx-UO22+ interaction and the temperature-programmed activity of CoOx, we validated a "light-up" colorimetric approach for UO22+ selective determination, achieving a wide detection range (0.01-2 μM) and a low limit (5 nM). A deployable device based on intelligent reading was further fabricated to enable on-site monitoring of the analyte. Our work provides a "signal-on" nanozyme sensing strategy for the quantification of UO22+, featuring specific response, catalytic signal amplification, and free from bioreceptors. Also, it proves a facile route to achieve dual modulation of enzyme-mimetic activity and analyte response for broader applications.