Ratiometric Fluorescent Sensor Based on Hydrogen-Bond Triggering the Internal Filter Effect for Enzyme-Free and Visual Monitoring Pesticide Residues

Real-time/field sensing techniques to keep track of methyl parathion (MP) are crucial to human health. In this work, a ratiometric fluorescence probe was constructed by integrating green carbon dots and CdTe quantum dots (CdTe QDs) for highly selective quantitative detection of MP. Under alkaline conditions, MP can be rapidly hydrolyzed to produce p-nitrophenol (p-NP); the instantaneous reaction that strengthens the hydrogen bond results in the internal filter effect between the carbon dots and p-NP, which quenches green fluorescence, thus leading to an obvious and immediate change from green to red. The probe displayed a sensitive limit of detection of 8.9 nM and exhibited a significant linear response to MP residue concentrations in the range of 0–100 M. In addition, we have created a brand-new smartphone-based intelligent detection tool by measuring the RGB value of the fluorescent probe solution and the matching paper-based sensor, and we are able to visually and quantitatively identify the levels of MP residues present in water, apples, and vegetables. This ratiometric fluorescence sensing method can realize rapid visual and quantitative detection of MP residues, which provides a more reliable guarantee promising strategy for constructing a risk detection technique for traces without enzymes.