A new ratiometric electrochemical sensor using electroactive GO/MB/Ag nanocomposites for H₂S detection in biological samples

In this study, we report a new ratiometric electrochemical sensor to accurately and selectively detect hydrogen sulfide (H₂S) in biological samples. In this system, it contains electroactive Ag dendritic nanocomposites (NCs) as a special recognition element of H₂S and methylene blue (MB) as an inner reference molecular for a built-in correction to improve the accuracy. The Ag NCs are prepared and synthesized by a electrodeposition method, and the branches consist of rounded and smooth segments with a diameter of about 300 nm. In the presence of H₂S, combining with the good adsorption ability of GO and more active sites of dendritic Ag nanostructure, the Ag NCs of GO/MB/Ag can be oxidized to Ag₂S in the oxygen environment, resulting in the decrease of electrochemical oxidation peaks of Ag (0.42 V) and constant of current responses of MB. On the basis of the ratio of I_Ag/I_MB at two distinct potentials, the developed ratiometric electrochemical sensor displays a wide linear range from 30 to 500 μM with high accuracy, selectivity, and stability. This strategy provides a reliable and feasible method for the detections of H₂S in real samples, including biological samples related to physiological and pathological events of hydrogen sulfide production.