Donor-acceptor energy transfer in the presence of photonic and plasmonic structures

Northwestern University, Evanston IL

Investigators

Abstract

George Schatz, of Northwestern University, is supported by the Chemical Theory, Models and Computational Methods program in the Division of Chemistry. They are developing a theory and computational methods to enable calculating the rate of energy transfer processes. Energy transfer processes play a very significant role in telecommunications, in solar energy utilization, in photosynthesis, and in electronic devices where energy is transmitted from one molecule to another through the emission and then absorption of light. The theory that Schatz and coworkers are developing is important for engineering applications in the design of new devices. It provides a framework for organizing components so that energy transfer between emitters and absorbers is selectively optimized. In addition, the project enables an understanding of energy transfer involving quantum light (i.e., light with intrinsically quantum properties). The research activities are used in the training of graduates, undergraduates and postdocs. They are also used in the development of software tools that are made publicly available. In addition, there are several outreach activities that use material related to the research. This program of research describes the development of new theories and computational methods for determining the rates of donor-acceptor energy transfer and related radiative processes associated with emitters and absorbers that are in the presence of complex dispersive optical structures, including semiconductor, dielectric and metallic nanoparticles, surfaces, and other photonic or plasmonic structures. There are a growing number of experiments where the complex optical environment plays an important role in energy transfer, sometimes enhancing energy transfer rates by many orders of magnitude and extending the range of energy transfer beyond the point where electrostatic interactions are adequate. In this situation, traditional F?rster theory and standard improvements thereto are inadequate. Recently the Schatz group has developed a new approach to these problems, one that is fully quantum electrodynamic in nature but which only involves classical electrodynamics calculations for the optical response, making it possible to use existing computational electrodynamics methods with relatively simple modifications to calculate energy transfer rates. In addition, the method can be evaluated in the time domain, which is important in the treatment of complex structures, and allowing for the study of nonstationary donor and acceptor states where coherences and entangled states are excited. The proposal describes the development of theory that builds on this recent work, including (1) the proper incorporation of competing radiative and nonradiative processes in energy transfer, (2) the inclusion of donors and acceptors that are too large for point dipole approximations, (3) the treatment of dielectric response in the optical medium that goes beyond the standard Drude/Lorentz dielectric models, and (4) the description of energy transfer processes associated with coherent superpositions of quantum states, including entangled states. The proposal describes a number of applications of the theory to recent and planned experiments, by collaborators and others, involving donor/acceptor energy transfer in the presence of particles and interfaces, including applications that test all the proposed new elements of the theory. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.