The self-quenched fluorescence of Coumarin 6 can be revived by host–guest chemistry and further increased by about 40% on increasing the solvent viscosity and hence restricting the motion of the molecules.

The nearly extinct fluorescence of coumarin 6 in water due to microcrystal formation is revived by micelles. Practically complete transfer of energy from coumarin 6 to rhodamine 123 through resonance energy transfer could be achieved.

Coumarin 6 (C6) briskly aggregates in water, and as a result, rapidly loses fluorescence. However, vicinal hydrophobic cavity can induce disintegration of the aggregates, and thus reviving the fluorescence. It is shown that carrier protein, such as bovine serum albumin (BSA), can disintegrate the microcrystals of C6 to smaller fragments and trap them inside the hydrophobic domain of the folded protein. This results into a 12-fold enhancement in the fluorescence signal of C6. However, on unfolding BSA by micelles, the C6 microcrystals break into single molecules by getting trapped in the micelles, and hence emission enhances by more than 100-folds.

No abstract

We report a unique phenomenon of physical adsorption of coumarin 6-β-cyclodextrin (C6-β-CD) inclusion nanostructures on graphene oxide (GO) nanosheets, thus inducing ground-state electron transfer from the C6-β-CD composite to GO. On excitation, the C6-β-CD composite initially transfers energy to the attached GO surface and subsequently collides with similar C6-β-CD@GO adducts leading to dynamic quenching of energy. The ground-state two-electron transfer process has been confirmed by cyclic voltammetry in aqueous medium, whereas the excited-state processes were inferred from steady-state and time-resolved fluorescence spectroscopy. The concept is developed toward conceiving control over the ground-state electron transfer and excited state energy transfer from the C6-β-CD composite by the adsorbed electron accepting medium (GO in this case). The C6-β-CD composite has been prepared to isolate single C6 molecules that readily undergo microcrystal formation in aqueous medium. The results show its potential toward fabrication of energy-harvesting antenna for further applications.