Highly Stable and Selective Sensing of Hydrogen Sulfide in Living Mouse Brain with NiN Single-Atom Catalyst-Based Galvanic Redox Potentiometry.

Hydrogen sulfide (HS) is recognized as a gasotransmitter and multifunctional signaling molecule in the central nervous system. Despite its essential neurofunctions, the chemical dynamics of HS during physiological and pathological processes remains poorly understood, emphasizing the significance of HS sensor development. However, the broadly utilized electrochemical HS sensors suffer from low stability and sensitivity loss in vivo due to sulfur poisoning-caused electrode passivation. Herein, we report a high-performance HS sensor that combines single-atom catalyst strategy and galvanic redox potentiometry to overcome the issue. Atomically dispersed NiN active sites on the sensing interface promote electrochemical HS oxidation at an extremely low potential to drive spontaneous bipolarization of a single carbon fiber. Bias-free potentiometric sensing at open-circuit condition minimizes sulfur accumulation on the electrode surface, thus significantly enhancing the stability and sensitivity. The resulting sensor displays high selectivity to HS against physiological interferents and enables real-time accurate quantification of HS-releasing behavior in the living mouse brain.