Electrogenerated Chemiluminescence of ZnS Nanoparticles in Alkaline Aqueous Solution

A band gap-electrogenerated chemiluminescence (ECL) of ZnS nanoparticles (NPs) in alkaline aqueous solution was first observed at a platinum electrode during the potential applied between −2.0 V (versus Ag/AgCl, saturated KCl) and +0.86 V. The ECL peak of ZnS NPs in 0.10 M sodium hydroxide solution appeared at +0.86 V, and the ECL peak wavelength of the ZnS NPs was ∼460 nm. A core/shell structure of ZnS/Zn(OH)2 was demonstrated by a UV absorption and photoluminescence (PL) spectra, high-resolution transmission electron microscopy, and energy dispersive X-ray spectroscopy. The ECL scheme of the ZnS NPs in alkaline aqueous solution was proposed, indicating that the surface passivation effect and the core/shell structure of ZnS/Zn(OH)2 played a significant role in the ECL process and that the similarity of the ECL and PL spectra of semiconductor NPs was dependent on the extent of the surface passivation. The ECL intensity of ZnS NPs in alkaline aqueous solution was greatly enhanced by an addition of K2S2O8.