Temperature-Insensitive Electron Transfer in Quantum Dot-Molecule Hybrids Driven by Nuclear Quantum Tunneling.

Area of Science:

• Physical Chemistry
• Quantum Mechanics
• Materials Science

Background:

• Electron transfer (ET) is fundamental to chemical reactions, biological processes, and optoelectronic devices.
• Observed temperature insensitivity of ET rates challenges existing theoretical frameworks like Marcus theory.
• This suggests a significant, yet not fully understood, role for nuclear quantum tunneling.

Purpose of the Study:

• To develop a theoretical model for electron transfer rates based purely on quantum tunneling.
• To explain the observed weak temperature dependence of ET rates in specific nanoscale systems.
• To investigate the contribution of nuclear tunneling to charge migration.

Main Methods:

• Formulation of a quantum tunneling expression for ET rate.
• Modeling the rate based on reactant-product vibrational wave function overlap in a single quantum mode.
• Experimental measurements of ET rates from quantum dots to naphthalene diimides acceptors across a wide temperature range (4–300 K).

Main Results:

• The developed quantum tunneling model successfully describes the weak temperature dependence of ET rates.
• The model's accuracy was validated in both normal and inverted energy regions.
• Experimental data aligns with the predictions of the pure quantum tunneling model.

Conclusions:

• Nuclear quantum tunneling plays a critical role in electron transfer processes, particularly at the nanoscale.
• The proposed quantum tunneling model provides a robust framework for understanding temperature-independent ET rates.
• This work emphasizes the importance of quantum effects in charge migration phenomena.