3-Aminophenylboronic acid-functionalized CuinS2 quantum dots as a near-infrared fluorescence probe for the detection of dicyandiamide

In this paper, a simple and highly selective method for the determination of dicyandiamide (DCD) was developed based on the fluorescence quenching of functionalized CuInS2 quantum dots (ODs). Watersoluble CuInS2 QDs, capped by mercaptopropionic acid, were directly synthesized in aqueous solution and then covatently linked to 3-aminophenylboronic acid molecules to form the 3-aminophenylboronic acid-functionalized CuInS2 ODs (F-CuInS2 ODs) that had a fairly symmetric fluorescence emission centered at 736 nm. Based on the cyclization of the guanidine group of DCD with 2,3-butanedione and 3-aminophenylboronic acid, the fluorescence of the F-CuinS(2) QDs is quenched by DCD in the presence of 2,3-butanedione. This method effectively distinguishes DCD from other amino acids and nitrogen pollutants, such as melamine, in real milk samples. Under optimum conditions, there was a good linear relationship between the fluorescence intensity of F-CuInS2 ODs and the concentration of DCD in the range of 2.0 x 10(-6) to 2.0 x 10(-3) mol L-1, with a detection limit of 0.6 mu mol L-1.