A research team led by Prof. JIANG Changlong from the Hefei Institutes of Physical Science (HFIPS) of the Chinese Academy of Sciences (CAS) has proposed a new sensing system for the detection of carbendazim residues using ultrathin graphitic carbon nitride (g-C₃N₄) nanosheets and rhodamine B (RB).

Results were published in Analytical Chemistry.

Carbendazim, a common pesticide belonging to the benzimidazole family, is widely used in agricultural production. As it degrades slowly in nature, the carbendazim residues could be easily absorbed into the body through respiration, skin or ingestion. At present, the common analytical methods for detecting carbendazim residues are still limited to laboratory instruments and immunoassay, etc., which usually suffer from high cost, complex operation and long time. It is of great importance to develop a new method for carbendazim detection with high sensitivity and selectivity.

The novel photoinduced electron transfer-triggered g-C₃N₄\Rhodamine B sensing system developed in this study was designed for selective and visual quantitative detection of carbendazim residues.

The researchers found that the carbendazim molecules could be enriched onto the g-C₃N₄ nanosheet by π-π stacking, then the blue-emitting fluorescence of the g-C₃N₄ nanosheet could be quenched by photoinduced electron transfer, while the orange fluorescence of RB remained unchanged.

"Our sensor realized a fast visual response to trace carbendazim residues through sensitive fluorescence changes from blue to purple," said ZHANG Qianru, first author of the study. The limit of detection is as low as 5.89 nM, far below the maximum residue standard.

On this basis, with the aid of 3D printing technology and color recognition, the portable intelligent sensing platform designed by the research team can be applied to the detection of carbendazim in actual samples, and shows good anti-interference ability.

This study not only provides an advanced sensing strategy for sensitivity and rapid carbendazim detection in the field, but also offers new insights into other trace analytes quantitative analysis.

This research work was supported by the Research of National Key and Development Program of China, the National Natural Science Foundation of China, and the Key Research and Development Program of Anhui Province.

Illustration of the design of the ratiometric fluorescence sensor for carbendazim detection. (Image by ZHANG Qianru) 

A. Main structure and basic operation flow of the smartphone platform; B. The fluorescence color variation with the Car concentration (0-180 nM); C. Schematic drawing for Car detection by using smartphone color recognizer; D. Linear plot of probe solution (R/B) vs Car concentration. (Image by ZHANG Qianru)