Ratiometric fluorescence determination of carbon disulfide in water using surface functionalized carbon dots

Trace level of CS2 in water causes a serious threat to the environment and living organisms. Thus, the development of reliable methods for its sensitive detection is quite necessary. Herein, we design a dual-emission platform composed of blue and yellow emissive carbon dots (B-CDs and Y-CDs) for ratiometric fluorescence determination of CS2. B-CDs, serving as the indicator, are functionalized by hydrophilic polyethylenimine groups on the surface, which can react with CS2 to produce hydrophobic dithiocarbamate moieties, resulting in the aggregation of nanoparticles and quenching of blue fluorescence. In contrast, Y-CDs without polyethylenimine groups exhibit no reactivity toward CS2 and act as the internal reference. With the increase of CS2 concentration, the blue fluorescence of the sensing platform at 461 nm continually drops, but the yellow fluorescence at 560 nm keeps nearly constant. Correspondingly, the vivid color change from blue-white to yellow can be observed by the naked eyes, realizing the visual detection. There is a linear relationship between the fluorescence intensity ratio (I461/I560) and CS2 concentration in the range of 7.7–1400 μM. The detection limit is as low as 2.3 μM. Furthermore, the sensing platform is successfully applied to monitor CS2 in real water, validating its good practicability.