Enhanced dual fluorescence quenching of red and blue emission carbon dots by copper dimethyldithiocarbamate for selective ratiometric detection of ziram in foodstuff and water samples

Abstract

The monitoring of ziram levels is of vital importance due to its widespread application in agriculture and the possible risks it poses to human health and the ecosystem. This work proposes an innovative approach for the highly sensitive and selective sensing of ziram, a widely used dithiocarbamate fungicide, through the formation of copper dimethyldithiocarbamate Cu)DDC)2 assisted dual quenching of red and blue emission carbon dots (R/NCDs and B/NSCDs). When ziram is added to a system containing copper-bound B/NSCDs and R/NCDs, the displacement of ziram zinc ions by copper ions leads to the formation of a yellow-colored Cu)DDC)2 complex. This complex induces significant quenching of the fluorescence emissions from both types of carbon dots, consequently enhancing the sensitivity of the detection method. Comprehensive characterization of the R/NCDs and B/NSCDs was conducted using various spectroscopic and morphological techniques to elucidate their structural and optical properties. The quenching mechanism was confirmed through different spectroscopic techniques, including fluorescence lifetime measurements, UV–vis spectroscopy, and Stern-Volmer analysis. The proposed method demonstrated high sensitivity across a wide concentration ranging from 20 to 1000 ng mL−1, making it suitable for trace-level detection of ziram. Moreover, the method exhibited excellent selectivity and recovery when applied to real samples, such as apples, grains, and water matrices. The combination of high sensitivity, selectivity, and applicability to diverse sample matrices makes this carbon dot-based dual quenching method a promising approach for fast and accurate detection of ziram in various environmental and agricultural applications.