Resonance energy transfer (RET) between a molecular donor and a molecular acceptor is a photophysical process crucial to many applications, such as photosynthesis, solar cells, bio and chemical sensing, structural and dynamical study of biomolecules, etc. Usually RET process would occur between two molecules in a homogeneous host medium, such as aqueous solutions, and the donor-acceptor distance is less than 10 nm, above which the RET rate is too small to be observed. In these cases, there is no preferred direction for RET and the wavelength dependence is entirely determined by the excitation of the molecules. To be able to enhance or modify RET, exotic and complex host environments could be utilized. For example, plasmonic nanoparticles or photonic cavities could change the local photonic states and in turn change the electonic coupling between the donor and the acceptor molecules. The shape and material of these nanostructures induces nontrivial wavelength dependence in RET process. Furthermore, the possible structural asymmetry introduced by the nanoparticles or cavities provides additional control over how resonance energy is being transferred. To study these complex systems, we utilize the plasmon-coupled resonance energy transfer (PC-RET) method to describe the wavelength-dependent donor-acceptor coupling via a classical electrodynamic expression derived from macroscopic quantum electrodynamics (MQED) framework. The finite-difference time-domain (FDTD) method is used to solve the Maxwell's equations associated to the inhomogeneous, complex environments. Using these methods, we focus on studying the property-structure relation between the shape, size, and material of the nanostructures and their ability to enhance or modify the RET process between a donor-acceptor molecule pair in the vicinity.

Extended molecular systems, such as metal-organic framework (MOF) and polymeric materials, are an important component in many organic optoelectronic applications, such as solar cells and organic light-emitting diodes (OLEDs). An essential function of these materials is exciton transport carrying excitonic energy from the point of excitation to any desired location like reaction center or dissociation interface. Several processes are involved in the transport dynamics, including exciton generation (light absorption), diffusion (energy transfer), spontaneous emission, exciton-exciton annihilation, bleaching, etc. These processes could be modified by the environment hosting the molecular systems. We would like to study the exciton dynamics in extended molecular systems when they are coupled to complex environments, such as plasmonic nanorods. Careful incorporation of nanoparticles into extended molecular systems could greatly enhance the exciton transport property, produce directional transfer, limit unwanted diffusion, etc.

The scattering of light from objects is an important factor influencing many physical processes and phenomena, such as enhanced molecular emission, resonance energy transfer, optical response of nanoparticles, scattering of nearby molecules, etc. We would like to develop new theory and computational methods to expand the capability of efficiently computing the scattered electric and magnetic fields from nanoparticles with various structures and materials due to incident light generated by different types of sources. We are particularly interested in cylindrical nanoparticles with micrometer lengths (candidates for ultra-long energy transport) paired with oscillating dipole and quadrupole sources (associated to molecular excitations). The approaches we would like to explore include generalized Mie theory, T-matrix method, finite-difference time-domain method, etc.

Concerted mechanisms are a type of reaction mechanism that occur in chemical reactions. These mechanisms involve the simultaneous breaking of all reactant bonds and the formation of new bonds, resulting in the formation of the desired products. Unlike other reaction mechanisms, concerted mechanisms occur in a single step and involve a single transition state that reflects the simultaneous rearrangement of atoms involved in the reaction. These mechanisms are essential for understanding the underlying principles of chemical reactions and how different factors, such as temperature, pressure, and catalysts, can affect the rates and outcomes of these reactions. By studying these mechanisms, we aim to understand how to design and optimize chemical reactions for various applications, such as pharmaceuticals and materials.