Surface Plasmon Enhancement of FRET

Gold nanogratings support surface plasmon waves that can enhance fluorescence. Surface plasmon waves travel along metal surfaces due to the oscillation of conduction electrons in response to light. Förster resonance energy transfer (FRET) is the transfer of energy between a donor and acceptor fluorescent molecules and is strongly dependent on the donor/acceptor spacing. Use of FRET is limited by the Förster radius which is the donor/acceptor spacing where the transfer efficiency is 50%. Gold nanogratings are uniquely suited to enhance the efficiency of FRET because they support a wide range of surface plasmon wavelengths. By enhancing the energy transfer rate and efficiency, surface plasmon enhanced FRET can be utilized more broadly.  

Gratings are fabricated using a soft lithography method then coated with fluorescent molecules. The enhancement of FRET was measured as a function of surface plasmon wavelength by varying the angle of incidence of the excitation laser, and measuring fluorescence emitted as a function of detector angle with respect to the grating surface. We are currently building a setup to measure the lifetime of the fluorescent molecules using a pulsed laser. This measurement will provide a greater understanding of how surface plasmons enhance FRET processes.