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Department of Chemistry

Research Highlight

Cavity-Free Quantum-Electrodynamic Electron Transfer Reactions

  • The full article entitled “Cavity-Free Quantum-Electrodynamic Electron Transfer Reactions” can be found at The Journal of Physical Chemistry Letters website at https://doi.org/10.1021/acs.jpclett.2c02379
  • Authors: Yu-Chen Wei and Liang-Yan Hsu*

Control of chemical reactions is one of the most significant issues in chemistry. Over the past one hundred years, with the development of quantum mechanics, scientists have established the fundamental principles of modern chemistry, understood the underlying mechanisms of chemical reactions, and exploited quantum mechanical effects to master chemical reactions. In general, quantum electrodynamic (QED) effects are considered small enough to be neglected in chemical reactions, although Richard Feynman once stated “the theory behind chemistry is quantum electrodynamics”. Recently, several experiments demonstrated that QED effects can significantly affect chemical reactions under vibrational strong coupling, which goes beyond the scope of traditional chemistry, providing new insights into fundamental science and promoting the development of cavity chemistry (polariton chemistry). However, the requirement of vibrational strong coupling makes it difficult to reproduce cavity-modified chemical reactions and limits their applications.

Prof. Liang-Yan Hsu and his PhD student Yu-Chen Wei proposed the concept “cavity-free QED electron transfer reactions” and demonstrated that QED effects can significantly enhance electron transfer (ET) reaction rates by several orders of magnitude in the absence of cavities. The proposed concept is implicitly supported by several previous experimental studies. In addition, we would like to emphasize that the concept of cavity-free QED electron-transfer reactions is fundamentally different from that of polariton chemistry. To elaborate how cavity-free QED effects are involved in ET reactions, we derive an explicit expression for the rate of radiative electron transfer, develop the concept of “electron transfer overlap”, and show experimental evidences. Moreover, QED effects may lead to a barrier-free ET reaction in which the rate is dependent on the energy-gap power law. Our results provide a simple but useful guide to master ET reactions by exploiting QED effects, and the proposed mechanism does not require the condition of strong light-matter interaction, polariton formation or confined cavities, providing promising prospect for future applications. This study has been published in The Journal of Physical Chemistry Letter.

Comparison of QED-ET theory and experimental results.

Fig. 1. Comparison of QED-ET theory and experimental results.

 

Arrhenius plot and activation energy plotted against the energy gap in the QED region.

Fig. 2. Arrhenius plot and activation energy plotted against the energy gap in the QED region.