Electrons inside metal such as gold or silver can oscillate coherently when irradiated with visible light, a phenomenon called plasmonic excitation. Besides the ability to couple to the far-field and undergo nonradiative decay, plasmons can modify the rate of the resonance energy transfer (RET) by providing additional photonic mode density. Several experiments have demonstrated that the RET rate can be a few times greater with plasmons compared to an isolated donor–acceptor (D–A) pair. However, a detailed investigation of the dependence of the RET rate on the system geometry has been hampered by the difficulty in controlling and determining the position and orientation of the donor and the acceptor on a single-molecular level. Here, we use a Mie-theory-based method to calculate the RET rate in a system consisting of a D–A pair and a spherical gold or silver nanoparticle (NP) to identify the key geometrical factors that lead to the enhancement RET rate. Also, we incorporate the plasmon contribution to the donor absorption to determine the overall enhancement of the acceptor formation (AF) rate. It is found that RET can be often suppressed on a single molecular level with the participation of plasmons, although the plasmon-enhanced donor absorption can lead to a net increase of the AF rate. By analyzing a RET experiment, it is demonstrated that the relationship between the RET rate and the system geometry can provide important structural information of a nanophotonic system. Finally, we propose several NP array structures that can enhance the RET rate.

Theoretical investigation of the dependence of the rate of the plasmon-coupled resonance energy transfer on the geometry of the donor, acceptor, and metal nanoparticles

ACS Fall 2021

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