Inhomogeneous electrochemiluminescence. II Markovian encounter theory of the phenomenon |
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| Affiliation: | 1. College of Bioresources Chemical and Materials Engineering, Shaanxi University of Science & Technology, Xi''an 710021, PR China;2. State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, Guangzhou 510640, PR China;1. State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, Guangzhou 510640, China;2. School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510640, China;3. School of Environmental and Chemical Engineering, Foshan University, Foshan 528000, China |
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| Abstract: | The free energy dependence of the electro-chemiluminescence quantum yield is specified, with the Markovian encounter theory accounting for the reversibility of triplet production competing with the irreversible recombination to the ground state. It is shown that diffusional ion recombination is highly inhomogeneous in space. It proceeds at either large positive ionization free energy (mainly to the triplet product) or at large negative free energy when recombination to the ground state dominates. On the contrary at medium free energies, the quasi-resonant generation of triplets is under kinetic control and therefore much more homogeneous. In this case, both recombination products are generated in comparable amounts.The multiple reversible ionization is shown to act as an independent quenching mechanism previously unknown. The role of the triplet quenching at the electrode is also specified. These effects reduce noticeably the luminescence quantum yield but only at larger triplet life times and in different free energy regions. |
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