Atomically Dispersed Co To An End-Adsorbing Molecule For Excellent Biomimetically And Prime Sensitively Detecting O-2(Center Dot-) Released From Living Cells

Single-atom catalysis efficiently exposes the catalytic sites to reactant molecules while rendering opportunity to investigate the catalysis mechanisms at atomic levels for scientific insights. Here, for the first time, atomically dispersed Co atoms are synthesized as biomimetic "enzymes" to monitor superoxide anions (O-2(center dot-)), delivering ultraordinary high sensitivity (710.03 mu A.mu M-1.cm(-2)), low detection limit (1.5 nM), and rapid response time (1.2 s), ranking the best among all the reported either bioenzymatic or biomimetic O-2(center dot-) biosensors. The sensor is further successfully employed to real-time monitor O-2(center dot-) released from living cells. Moreover, theoretical calculation and analysis associated with experimental results discover that a mode of end adsorption of the negatively charged O-2(center dot-) on the Co3+ atom rather than a bridge or/and side adsorption of the two atoms of O-2(center dot-) on two Co3+ atoms, respectively, plays an important role in the single-atomic catalysis toward O-2(center dot-) oxidation, which not only facilitates faster electron transfer but also offers better selectivity. This work holds great promise for an inexpensive and sensitive atomic biomimetic O-2(center dot-) sensor for bioresearch and clinic diagnosis, while revealing that the adsorption mode plays a critical role in single-atom catalysis for a fundamental insight.