Interaction of coumarin 6 with carbon nanotubes: Disintegration of the microcrystalline state by surfactant aggregation on the nanotube surface

Dual Stimuli-Responsive BSA-Protected Silver Nanocluster-Driven “FRET On–Off” within the Niosomal Membrane: An Amalgamation of Restoration of Aggregation-Induced Quenched Fluorescence and Energy Transfer

“…Self-aggregation of coumarin dyes is readily observed in several occasions due to the structural features of the molecule. − Typically, the planar coumarin skeletons are susceptible to aggregation via strong π–π stacking interactions leading to aggregation-caused quenching (ACQ) of photoluminescence (PL) and weakening the activity of optoelectronic devices and many other exciton-controlled performances. ,,, The coumarin member used in the present study is C6 (Figure A) that aggregates readily in water even at 1 μM concentration and hence substantially loses its PL . However, this lost PL can be revived by several host–guest chemistry-based techniques following hydrophobic interactions. − Hence, we have applied the multilamellar niosome vesicles that followed the same mechanism to disintegrate the aggregated C6 molecules, which encapsulate inside the membrane (Figure A), and hence the lost PL is revived (Figure B). The double-humped absorption spectrum of C6 in neat water gradually reduces to a single peak (Figure C), indicating the disruption of the aggregates that absorb at 500 nm. ,− There is a remarkable variation in the fluorescence spectrum of C6, with a considerable change in the structure accompanied by a significant blue shift of 50 nm (Figure D,E).…”

“…During disintegration hydrophobic force overcomes the π interaction. − We observed a considerable decrease in the ICT contribution in C6 aggregates (Table ) with its concomitant increase in the monomers, which decay comparatively slower. The C6 monomers in the ICT state decay very fast in water; however, the ultrafast components in the fluorophores are known to get slowed down on being trapped inside the bilayer membranes. , The appearance and development of a growth or rise component on reaching 25 μM TX-100 concentration, and on further addition, indicate that ICT in the individual C6 molecules slows down considerably and hence can be traced within the temporal resolution of the detection unit.…”

“…However, this lost PL can be revived by several host–guest chemistry-based techniques following hydrophobic interactions. − Hence, we have applied the multilamellar niosome vesicles that followed the same mechanism to disintegrate the aggregated C6 molecules, which encapsulate inside the membrane (Figure A), and hence the lost PL is revived (Figure B). The double-humped absorption spectrum of C6 in neat water gradually reduces to a single peak (Figure C), indicating the disruption of the aggregates that absorb at 500 nm. ,− There is a remarkable variation in the fluorescence spectrum of C6, with a considerable change in the structure accompanied by a significant blue shift of 50 nm (Figure D,E). There was a 90-fold increase in the PL intensity (Figure F) due to the revival of the intramolecular charge transfer (ICT) in C6 monomers.…”

Microviscosity-Assisted Disaggregation of a Model Ophthalmic Drug and FRET-Controlled Singlet Oxygen Generation in Lyotropic Liquid Crystals

“…The structural characteristics of C6 makes it easily susceptible to self-aggregation due to strong π–π stacking interactions in water even at a very low concentration of ca. 1 μM. − As a result, C6 loses a significant amount of PL through ACQ . It has been shown before by our group that the lost PL can be recovered by disintegrating the aggregates using various host–guest chemistry-based methodologies. − In the present case, we applied different LLCs with the same target.…”

β-Cyclodextrin Encapsulated Coumarin 6 on Graphene Oxide Nanosheets: Impact on Ground-State Electron Transfer and Excited-State Energy Transfer

“…This process considerably lowers the fluorescence yield of C6 with time . In a series of studies, we have shown several ways to revive the lost fluorescence of C6 in water by using various hosts that have relatively hydrophobic cavities. ,− Using biocompatible hosts, such as, β-cyclodextrin (β-CD), micelles, proteins, and single-walled carbon nanotubes, the microcrystalline states of C6 could be broken and the fluorescence emission could be revived. This technique could be successfully applied in energy transfer reactions in the excited state …”