2-hydroxypropyl-β-Cyclodextrin (2-Hp-β-CD) -functionalized CdTe quantum dots (QDs) were used for coumarin-sensing with high sensitivity and selectivity. This fluorescence resonance energy transfer (FRET)-based sensor was established by attaching Rhodamine 6G (Rh6G) to the QDs via 2-Hp-β-CD linker. Rh6G could get into the cavity of 2-Hp-β-CD, and then trigger the FRET between QDs and Rh6G, providing an “off” state of the QDs. However, the effect of FRET was weakened by the coumarin, because of its larger hydrophobic association constant with 2-Hp-β-CD, resulting in the dissociation of Rh6G. The fluorescence intensity of QDs@2-Hp-β-CD@Rh6G would be heightened along with the additive coumarin (an “on” state). The FRET-based off-on nanoprobe shows a good linear relationship in the range of 0-25 μM with a good correlation coefficient (R2=0.9986). We also obtained an excellent result using this spectrophotometric method for coumarin-sensing in cosmetics, which affords potentials in the biomedical area. We expect this sensing platform could be useful for other analogous nanoprobes in relevant fields.

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