A molecularly imprinted ratiometric fluorescence sensor based on blue/red carbon quantum dots for the visual determination of thiamethoxam

Neonicotinoids such as thiamethoxam (TMX) were widely used in agricultural production and tended to accu-mulate in the environment, potentially harming human and ecosystem health. To enable widespread monitoring of TMX residues, it was essential to design a reliable and sensitive detection method. Here, we developed a novel smartphone-enablled molecularly imprinted ratiometric fluorescence sensing system for selective on-site detection of TMX. It was based on blue-emission carbon dots (CDs) wrapped with a molecularly imprinted layer (B-CDs@MIPs), which provided the response signal, while red-emission CDs (R-CDs) served as an internal reference. The fluorescence signal ratio of the sensor increased with the TMX concentration, resulting in an obvious fluorescence color change from red to blue. The sensor exhibited a satisfactory limit of detection (LOD) of 13.5 nM in fluorescence analysis while LOD of 70.1 nM in visual determination. In addition, the sensing system was validated using food and environment samples, exhibiting recoveries from 91.40% to 105.7%, indicating excellent reliability for TMX detection in actual samples. Thus, the sensing system developed in this study offered promising prospects for visual detection of pesticide residues in complex environmental samples.

Automated summary

In order to monitor the residual of neonicotinoids, a novel smartphone-enabled molecularly imprinted ratiometric fluorescence sensing system was developed for on-site detection of thiamethoxam (TMX). The system utilized blue-emission carbon dots (B-CDs) wrapped with a molecularly imprinted layer (MIPs) as response signal, and red-emission carbon dots (R-CDs) as internal reference. The fluorescence signal ratio increased with TMX concentration, resulting in a color change from red to blue. The system showed a satisfactory limit of detection (LOD) of 13.5 nM (fluorescence analysis) and 70.1 nM (visual determination), and demonstrated excellent reliability for TMX detection in actual samples with recovery rates ranging from 91.40% to 105.7%. Therefore, this sensing system offers promising prospects for visual detection of pesticide residues in complex environmental samples.