Observation of FRET in collision of droplets

摘要

Forster Resonance Energy Transfer (FRET) is a radiationless distance-dependent transfer of energy from anexcited donor uorophore to an acceptor uorophore. This radiationless interaction of a donor-acceptor pairthrough resonance is observed by an increase/decrease in the acceptor/donor uorescence intensity, respectively.Here we present preliminary results on the uorescence spectra of optically levitated micro-droplets doped withtwo dierent dyes that works as FRET pair. The laser light used for levitation (λ=660 nm) passes through atelecentric system of lenses to form a controllable double optical trap system. Micrometer sized droplets areproduced using two on-demand piezo-driven dispensers. This allows independent trapping of dierently dyeddroplets in two traps where a collision between the droplets can be induced by moving the trap positions. Thedye molecules mix when two droplets collide and coalesce. The emission spectrum obtained when the dropletsare illuminated with laser having a wavelength of 532 nm is observed with a spectrometer which can recordup to 26,000 spectra per second. We compare the results with the spectra taken from the same solutions in acuvette. The results indicate that we are able to observe the FRET eect in single droplets with an exposuretime as short as 100 s. This spectroscopic investigation is an ongoing research project with the long-term goalto investigate environmental eects of aerosols in the atmosphere.