Tuning Quantum Dots Coupling Using Organic Linkers with Different Vibrational Modes

Signatures of long-lived quantum coherence in light-harvesting complexes invoked a hypothesis that the protein-scaffold vibrations assist energy transfer by bridging energy gaps. To address this hypothesis experimentally in a model system, we compare the coupling strength of donor-acceptor quantum dots (QDs) linked by different organic linkers. The linkers are of the same length, with the same headgroups, but differ in one atom at the center of the chain (carbon, sulfur, or oxygen), which changes the vibrational modes of the molecule. We have studied the energy transfer using these linkers both in dimers of QDs, suspended in solution, and in solid multilayered films. Strongest coupling is achieved when a linker vibration (asymmetric stretch around the central atom in this case) matches the energy gap. The results provide experimental support for the theoretical idea of vibration-assisted transport and noise-assisted quantum transport (NEQT) and have important implications for the artificial design of many-particle nanodevices in which interparticle coupling tuning is required.