Water-Soluble, Cyclodextrin-Modified CdSe−CdS Core−Shell Structured Quantum Dots

β-Cyclodextrin (β-CD)-modified CdSe (β-CD/CdSe) and CdSe−CdS core−shell structured (β-CD/CdSe−CdS) quantum dots (QDs) were synthesized by a single-phase approach in aqueous solutions. These receptor-modified QDs are very soluble and stable in water over a wide range of pH values and ionic strengths. Coating a CdS shell on the CdSe core greatly increased the quantum yield (QY) of original CdSe QDs. Photoactivation of these particles by the room light results in 46% QY for β-CD/CdSe−CdS in water. The surface-anchored β-CD still retains its host capability for the complexation of different organic species in aqueous solutions. More interestingly, the fluorescence sensitivity of these QDs to the same substrate is ten times higher than that of their counterparts reported in our previous work. Furthermore, the fluorescence of these receptor-modified QDs could be reversibly tuned in two directions, enhancement or quenching, by selectively introducing different redox-active substrates in aqueous media.