Sulfobutylether β‐Cyclodextrin‐Draped Gold Nanoparticles With Coumarin 30: Enhanced Fluorescence Behavior and Photostability

Supramolecular host‐guest assemblies of fluorophores induces modulation in the photophysical behavior of dyes by influencing photostability, solubility, and aggregation behavior in solution. Coumarins, in general, are less soluble and prone to aggregation limiting their application in aqueous medium. To mitigate this issue, the host–guest interaction between coumarin 30 (C30) and sulfobutylether β ‐cyclodextrin (SBE 7 βCD)‐stabilized gold nanoparticles (AuNP‐SBE 7 βCD) has been explored as an effective strategy to demonstrate utility of self‐assembled coumarin dye conjugate in aqueous medium. Surface‐functionalized gold nanoparticles received massive response from the researchers in the areas such as drug delivery systems, biological detection, sensing technologies, and bioimaging applications, showcasing their potential across various scientific and medical fields. Gold nanoparticles coated with SBE 7 βCD demonstrated improvement in their stability where surface functionalization reduces the coagulating tendency of gold nanoparticles by acting as a stabilizer. The AuNP‐SBE 7 βCD macrocycle interacts with C30 dye with a binding constant of the order of ∼10 9 M −1 leading to significant enhancement in the fluorescence intensity and average fluorescence lifetime of C30 through the confinement inside the hydrophobic cavity of SBE 7 βCD attached to the surface of AuNP. Complex formed with AuNP‐SBE 7 βCD:C30 showed better photostability allowing prolonged bioimaging when captured with gut of Drosophila fly.