Temperature-Responsive Covalent Organic Framework-Encapsulated Carbon Dot-Based Sensing Platform for Pyrethroid Detection via Fluorescence Response and Smartphone Readout

In this paper, carbon dot (CD)-encapsulated 1,3,5-tris(4-formylphenyl)benzene (TFB)/2,5-dihydroxyterephthalohy-drazide (DHTH) covalent organic frameworks (TDCOFs) grafted with thermoresponsive poly(N-isopropylacrylamide) (PNIPAM)(CDs@TDCOFs@PNIPAM) were fabricated for the detection of pyrethroids. CDs@TDCOFs@PNIPAM achieved a temperature-responsiveon/offdetection of pyrethroids based on the target-triggered electron-transfer mechanism. The detection limit ofpyrethroids was as low as 0.69 mu g/L in the wide linear range of 5-400 mu g/L (R2> 0.9523). Simultaneously, CDs@TDCOFs@PNIPAM with red, green, and blue (RGB)fluorescence emissions were integrated with a smartphone-assisted device, enabling thevisual smart quantitative detection of pyrethroids with a detection limit of 4.875 mu g/L. Ultimately, agricultural products were chosenas actual samples to verify the applicability of both recognition modes, and the calculated recovery rate was 105.48-113.40%.Accordingly, CDs@TDCOFs@PNIPAM featuring temperature-responsive switching behavior and RGBfluorescence emissionprovided a promising analytical strategy for ensuring agricultural and food safety

Automated summary

This paper presents a carbon dot-encapsulated covalent organic framework that can detect pyrethroids. The material achieved temperature-responsive detection of pyrethroids through a target-triggered electron-transfer mechanism. The detection limit was low and the method was further integrated with a smartphone-assisted device for visual smart quantitative detection. Real agricultural samples were used to validate the applicability and the recovery rate was satisfactory.