Construction of CDs@β-CD@CCM ratiometric fluorescence probe for FRET-based ClO--sensing.

β-Cyclodextrin (β-CD) -functionalized carbon quantum dots (CDs) loaded with curcumin (CCM) were used for ClO--sensing with high sensitivity and selectivity. This fluorescence resonance energy transfer (FRET)-based sensor was created through attaching CCM to the CDs via β-CD linker. CCM could get into the interior of β-CD triggering the FRET from CDs to CCM, providing an "off" state of the CDs. However, the effect of FRET was weakened by the ClO-, because the o- methoxyphenol structure from CCM was oxidized to be benzoquinone. The fluorescence intensity of CDs@β-CD@CCM at 440 nm can be heightened and 520 nm from CCM can decrease along with the increased ClO-. Therefore, a ratiometric fluorescence probe for ClO--sensing is successfully constructed. It conforms to a polynomial curve equation which is I440/I520 = -0.0268+0.0315 CClO-+0.0055[CClO-]2 (R2= 0.9958) between 0-18.4 μM ClO-. Furthermore, we also obtain excellent results using this spectrophotometric method for ClO-- sensing in pure water and commercial disinfectants, which afford potential in the environment monitoring area. We expect this sensing platform could be helpful in other analogous probes in relevant fields.