Long-lasting chemiluminescence of luminol on electrochemically pre-oxidized platinum electrodes in NaOH solution

A long-lasting bright chemiluminescence (CL) of luminol was generated at po lycrystalline platinum electrodes with open circuit. The CL can last for se veral hours with the presence of O-2 in the solution when the electrode was preoxidized at potentials more positive than 1.10 V vs. SCE. The effects o f the varieties of solution conditions and surface states of the electrode on the CL intensity and the interfacial potential of the electrode were inv estigated. It was proposed that PtO was generated at the pre-oxidized poten tials and played a role of catalyst of luminol oxidation for generating the CL. The redox couple of PtO/Pt-active at the electrode surface was maintai ned in the presence of O-2 and luminol, and generated the interfacial poten tial more positive than 140 mV. Mathematical treatment of the reaction mech anism was conducted, which led to an approximated expression of a steady CL intensity (I-CL) as a function of the pre-polarization potential (E-h) and time (tau (h)) Of the electrode. An empirical equation, (I-CL)(4/3) 3480(- 1 + 0.82E(h) + 0.037 In tau (h)), was estimated from the experimental data. Copyright (C) 2000 John Wiley & Sons, Ltd.