Carbon Quantum Dots for Rapid and Ratiometric Fluorescence Determination of Hypochlorite

Herein, we present a method for rapid ratiometric fluorescence detection of hypochlorite (ClO – ) by carbon quantum dots (CDs). Glutathione (GSH) was utilized as the starting material for the synthesis of CDs through a hydrothermal process. A maximum fluorescence intensity at an emission wavelength of 435 nm was observed under an excitation wavelength of 335 nm. The inner filter effect (IFE) of curcumin (CCM) on CDs could be utilized to reduce the fluorescence intensity of CDs at 435 nm, while an emission peak emerged at 540 nm. ClO – could rapidly oxidize CCM due to its oxidizing properties, which weakened the IFE, leading to a decrease in the fluorescence intensity of CCM at 540 nm, while the fluorescence intensity of CDs at 435 nm is restored. In addition, CDs exhibited excellent selectivity and sensitivity in the fluorescence detection of ClO –, and a substantial sensitivity in the detection of ClO – was established within a concentration range of 1–1500 μM with a limit of detection of 36.54 nM. The spiked recovery tests of tap water, swimming pool water, and milk samples showed the feasibility of using CDs for the ratiometric fluorescence detection of ClO – in real samples.