Measurements on single molecules and single particles, especially on the dynamical behavior of their interactions, require nanoscale measurement techniques and novel photonic elements to accurately assess the transiently interacting complexes. This project focuses on enhancing the sensitivity and the temporal, spatial, and spectral resolution of the molecular imaging techniques, as well as on the application of these techniques towards a complete understanding of the fundamental mechanism of energy transfer/conversion between single nanoscale materials such as single molecules and single nanoparticles. For instance, in a system of two organic fluorophores in the distance of 10 nm or less, the excited donor can transfer energy to the acceptor by fluorescent resonance energy transfer (FRET) process. In a cluster of single fluorescent nanocrystals such as quantum dots, the transport of the exciton from one fluorescent quantum dot to another or between parts of the quantum dot involves exciton-mediated energy transfer (EMET). The plasmonic resonance energy transfer (PRET) occurs between the resonating dipoles in the nanoparticle and the fluorophore through similar mechanism to that of FRET. Thermal energy transfer (TET) from photonic to thermal energy is also possible in some nanoparticles.
The main goal of this project is to expand the fundamental knowledge of nanoscale energy transfer and conversion mechanisms in the system of single molecules and single particles interacting at the nanoscale. Systems of current interest include fluorescently labeled aptamers and proteins for FRET studies, heterodimers of semiconductor quantum dots for EMET measurements, plasmonic metal particle and quantum dot (or organic fluorophore) pairs for TET characterization, and dimers of a single metal particle and a single organic fluorophore for PRET studies.
Biophysics; Microscopy; Imaging; Nanooptics; Single molecule; Single particle; Nanocrystal; Quantum dot; Energy transfer; Energy conversion, Plasmonic; Fluorescence; Photothermal;