10.1021/acs.jpcc.6b05008.s001
Somnath Koley
Somnath
Koley
Manas Ranjan Panda
Manas Ranjan
Panda
Subhadip Ghosh
Subhadip
Ghosh
Study of Diffusion-Assisted Bimolecular Electron Transfer
Reactions: CdSe/ZnS Core–Shell Quantum Dot Acts as an Efficient
Electron Donor and Acceptor
American Chemical Society
2016
SQCK
electron donor molecule N
electron injection rates
Efficient Electron Donor
DNT
SV
NMA
ET kinetics
QD
2016-06-13 00:00:00
Journal contribution
https://acs.figshare.com/articles/journal_contribution/Study_of_Diffusion-Assisted_Bimolecular_Electron_Transfer_Reactions_CdSe_ZnS_Core_Shell_Quantum_Dot_Acts_as_an_Efficient_Electron_Donor_and_Acceptor/3444092
Excited-state lifetimes and steady-state
emission of two different
size CdSe/ZnS core–shell quantum dots (QDs) in toluene were
quenched by an electron donor molecule <i>N</i>-methyl aniline
(NMA) and an electron acceptor molecule 2,4-dinitrotoluene (DNT) in
two separate sets of experiments. Static quenching Collins-Kimball
(SQCK) diffusion model enabled a conclusive fitting only to the electron
transfer (ET) kinetics of QD-NMA pairs. However, for QD-DNT pairs,
a clear break down of SQCK model was observed. Interestingly, when
we considered a QD-to-DNT static complex formation, we observed even
a classic Stern–Volmer (SV) fitting equation can provide an
adequate fitting to the ET kinetics. ET kinetics we studied here are
strongly controlled by the chemical driving forces (Δ<i>G</i>). For example, electron injection rates (by NMA) to the
two QDs with core dimensions ∼3.4 nm (QD560) and ∼2.5
nm (QD480) were found to be similar (∼1.50 × 10<sup>9</sup>–1.60 × 10<sup>9</sup> M<sup>–1</sup> S<sup>–1</sup>), which is nicely correlated with their nearly same values of the
chemical driving force (−Δ<i>G</i> ∼
0.18–0.19 eV) associated with their ET reactions. Conversely,
electron donating rates (to DNT) of the same two QDs are found to
be ∼7.0 × 10<sup>9</sup> M<sup>–1</sup> S<sup>–1</sup> (QD480) and ∼3.7 × 10<sup>9</sup> M<sup>–1</sup> S<sup>–1</sup> (QD560), respectively, for QD480 and QD560,
which is again congruent to their chemical free energy changes (−Δ<i>G</i><sub>QD480‑DNT</sub> ∼ 1.18 eV and −Δ<i>G</i><sub>QD560‑DNT</sub> ∼ 0.44 eV). A nonadiabatic
sink term of ET kinetics from QD-NMA pair shows distinct regimes associated
with the ET reaction (i.e., static, nonstationary, and stationary).