Generation of Free Radicals and Electrochemiluminescence at Pulse-polarized Oxide-covered Silicon Electrodes in Aqueous Solutions.

Cathodic pulse-polarization of thin-oxide-film-covered highly doped silicon electrodes induces tunnel emission of hot electrons into aqueous electrolyte solutions probably resulting in an electrochemical generation of hydrated electrons. Generation of hydrated electrons allows simultaneous production of sulfate radicals from peroxydisulfate ions, and hence, highly reactive radicals are generated in the vicinity of the electrode surface. Generated primary radical species can induce strong redox luminescence from various organic chemiluminophores and luminescent metal chelates, e.g., some lanthanide and transition metal chelates can be detected below nanomolar levels with a linear range of calibration curves of over six orders of magnitude.