Reevaluating the effects of reorganization energy on electron transfer rate for quantum dot-molecular acceptor complexes in different solvents

Huifang Zhao; You Li; Lihe Diao; Chaofan Sun; Ying Shi

doi:10.1016/j.saa.2019.04.016

Reevaluating the effects of reorganization energy on electron transfer rate for quantum dot-molecular acceptor complexes in different solvents

Spectrochim Acta A Mol Biomol Spectrosc. 2019 Jul 5:218:237-242. doi: 10.1016/j.saa.2019.04.016. Epub 2019 Apr 11.

Authors

Huifang Zhao¹, You Li¹, Lihe Diao¹, Chaofan Sun¹, Ying Shi²

Affiliations

¹ Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012, China.
² Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012, China. Electronic address: shi_ying@jlu.edu.cn.

PMID: 31003048
DOI: 10.1016/j.saa.2019.04.016

Abstract

The electron transfer (ET) rate in quantum dot (QD)-molecular acceptor systems is dependent upon system reorganization energy (RE, λ), which comprises contributions from solvent (λ₀) and reactants (λ_i). However, to date, the effect of λ_i on ET rate has been largely ignored. Herein, the ET from CdSe/ZnS QDs to 1-chloroanthraquinone (1-CAQ) in different solvents was investigated using ultrafast transient absorption spectroscopy as a means to evaluate the effect of λ_i on ET rate. The results revealed that ET rate is strongly solvent dependent. Amazingly, the ET rate in carbon disulfide is 300-times higher than that in n-dodecane. Theoretical calculations indicated that the λ_i contribution from 1-CAQ alone accounts for a large proportion of system RE and varies greatly in different solvents. Furthermore, the ET rate increases first and, then, decreases with the λ value in different solvents. This trend was interpreted consistently in terms of Marcus theory by adding λ_i to λ for different solvents. Thus, our present work demonstrates that the RE of the acceptor molecule has a non-negligible effect on ET rate, providing new insight into the mechanisms of ET process and for the development of QD-based devices.

Keywords: Electron transfer; Quantum dots; Reorganization energy; Ultrafast transient absorption spectroscopy.