Dual-Emission Carbon Dots for Fluorescent Sensing of Permanganate

Dual-emission carbon dots (D-CDs) were facilely synthesized from fluorexon in ethanol via a solvothermal method. The prepared D-CDs with abundant O-/N-containing groups show two significant emissions with a wavelength in the visible region. A fluorescence (FL) platform with high sensitivity and selectivity was developed for detecting MnO4– in actual matrices using the D-CDs. The intensity ratio at 520 to 436 nm exhibited good linearity across the MnO4– concentration. Structural and optical characterizations reveal the oxidation of groups on the D-CD surface, which is crucial for amplifying the 520 nm emission while quenching the 436 nm. The oxidation restricted the electron transfer between the receptor and fluorophores associated with 520 nm; however, it also induced dynamic quenching which acted together with static quenching and the inner filter effect (IFE) to decrease the FL intensity of 436 nm. This study presents a general strategy to enable the efficient sensing of contaminants in environmental waters and facilitates the rational design of optical platforms.