A New Electrochemiluminescence Emission of Mn2+-Doped ZnS Nanocrystals in Aqueous Solution

ZnS nanocrystals are less toxic than cadmium chalcogerride materials, which might have more applications in biological detection. Yet more excitation energy during its electrochemiluminescence (ECL) process should be applied because of the wide energy gap (similar to 3.7 eV) of ZnS. Here, ECL of ZnS doped with Mn2+ nanocrystals (ZnS:Mn2+ NCs) modified on glassy carbon electrode was investigated in aqueous solution with the coreactant hydrogen peroxide (H2O2) for the first time. Besides the ECL process of pure ZnS NCs at a negative potential of more than -2.0 V vs SCE, a new ECL emission peak was observed at ca. -1.50 V vs SCE on the ZnS: Mn2+ NCs-modified glassy carbon electrode in pH 9.0 phosphate buffer solution. This new ECL emission was attributed to the excited state of Mn2+ lying in the Zn2+ sites. The concentration of Mn2+ doped in ZnS NCs played a key role in this new ECL process. Furthermore, this specific ECL emission was dependent on the concentration of H2O2. The largely decreased excitation energy of this new ECL emission would promote the application of doped ZnS NCs in the fields of biological and environmental analysis without the interference of hydrogen bubble in the ECL process.