Quantum Dot Antennas for DTE-BODIPY Dyads: Efficient "on-off" Photoluminescence Switching with a Broad Excitation Spectrum

A dye-photoswitch dyad (consisting of BODIPY and DTE) has been studied spectroscopically. In this system, the fluorescent dye can be quenched via FRET by closing the photoswitch, resulting in a photomodulated fluorescence. CdSe/ZnS quantum dot (QD)/dyad complexes have been prepared to investigate the suitability of QDs as antennas to extend the excitation range of this system. Illumination experiments show that the photoswitch retains its functionality even after the dyad is attached to the QD surface. Furthermore, photoluminescence (PL) measurements show a very efficient FRET from the QD to the dyad. Transient absorption experiments reveal signals indicative of a direct FRET from the QD to the closed switch and two successive FRET processes - from the QD to the dye and subsequently from the dye to the closed switch. With this integrated spectroscopic approach, we demonstrated that QDs are well suited for enhancing photomodulated fluorescence.