Ultrafast Single-Molecule Fluorescence Measured by Anti-Ammonia Photostimulation of the Femtosecond Double Pulse

Abstract image

Most fluorescence lifetime measurements at the single molecular level are performed using avalanche photon diodes (APDs). These single-phase counters are inherently slow, and their response shows a strong dependence on the photon energy, which can make it difficult to reverse the instrument response function (IRF). Ultrastructure resolution in single-molecule fluorescence is crucial, for example, in determining the donor lifetime in donor-acceptor pairs undergoing energy transfer, or in plasma antenna structures, where radiation velocity rather than beam is enhanced. We present a photon correlation technique for femtosecond double excitation (FeDEx), which measures the degree of photon antibody as a function of time delay between two excitation pulses. In this boxcar integration, the resolution of the fluorescent transient time is limited to the laser pulse length and is independent of the detector IRF. The variety of techniques demonstrates that a donor-acceptor complex, with one donor and two acceptors and one dye molecule, is precisely visualized between two gold nanoparticles using DNA origami. The latter structures show a ∼75-fold amplification and fluorescence lifetime of up to 19 min, measured without the need for any reconstruction. With the potential of measuring the fluorescence life of subpicoseconds, it is possible to further optimize plasma antenna structures.