Electrochemistry and electrogenerated chemiluminescence of films of silicon nanoparticlesin aqueous solution

Abstract

Films of octadecyl-capped Si nanoparticles (NPs) (diameter,3.4 ± 0.7 nm) prepared by drop-coating on indium tin oxide (ITO) showed electrogeneratedchemiluminescence (ECL) for both cathodic and anodic potential sweeps in KOH solutionscontaining peroxydisulfate. The redox potentials of the Si NPs can be estimated as approximately−0.9 and+0.95 V(versus Ag|AgCl) based on the anodic potential for the onset of ECL minus the ECLpeak energy. The ECL exhibits a relatively broad spectrum (FWHM = 160 nm) with apeak wavelength of ∼670 nm (1.85 eV), similar to the photoluminescence spectra. In electrochemical studies in KOHsolution in the absence of peroxydisulfate, an anodic current peak appears at about−1 V(versus Ag|AgCl) following a scan to negative potentials. A similar peak has been observed during theetching of a bulk single crystal Si electrode in alkaline aqueous solution. Unpassivatedsurface sites of Si NPs seem to be etched at potentials negative of the anodic oxidationpeak.