Orientational Assembly of Carbon Dots-Enabled Electrochemiluminescence Sensors for Ultrasensitive Detection of Halogenated Phenols

Developing simple, sensitive, and miniaturized sensors is crucial for the prevention and control of halogenated phenolic pollutants exposed to the environment. In this work, oriented carbon dot assemblies are developed for the electrochemiluminescence (ECL) sensing of halogenated phenolic pollutants for the first time. Leveraging liquid-liquid phase separation during ternary solution evaporation, carbon dots (C-dots) self-organize into mesoporous structures (o-Cdots) and granular structures (r-Cdots) on the hydrophobic glass carbon surface, enabling immobilized C-dot ECL sensors. Their superior ECL performances are displayed upon cathodic potential scan in 0.1 mol/L pH 7.4 PBS with the coreactant S₂O₈^2-. Compared to hydrophilic o-Cdots, hydrophobic r-Cdots exhibit robust ECL. Physical adsorption of halogenated phenols onto the hydrophobic r-Cdot surface significantly elevates the resistance of interfacial charge transfer and disrupts the recombination of intermediate C-dot^•- and SO₄^•- within the r-Cdot ECL, endowing a novel and broad-spectrum sensor development. The r-Cdot-based ECL sensor enables the detection of several typical halogenated phenolic compounds in a wide concentration range from 5 × 10^-11 to 5 × 10^-7 mol/L. Remarkably, the detection limit for 2-chlorophenol can even reach 10^-14 mol/L. The developed ECL sensor also demonstrates outstanding stability and resistance to interference from common ions and natural metabolites in the environment. These peculiarities enable its superior performance in detecting halogenated phenols in lake water and tap water with ideal recoveries at different spike levels. This work offers significant insights into the relationship between C-dot assembly structures and their ECL behaviors, paving the way for the rational design of portable C-dot-based sensors for pollutant detections.