Thioglycolic acid-capped CdS quantum dots modified with $$\hbox {Co}^{2+}$$ Co 2 + as a fluorescent sensor for dopamine

Abstract

A new selective fluorescent sensor for detection of dopamine (DA) using \(\hbox {Co}^{2+}\) -decorated thioglycolic acid-capped CdS QDs (\(\hbox {Co}^{2+}\)@TGA–CdS QDs) was proposed. Basically, the fluorescent intensity of TGA–CdS QDs can be quenched by \(\hbox {Co}^{2+}\). However, with the addition of dopamine into the solution of \(\hbox {Co}^{2+}\)@TGA–CdS QDs, the fluorescent intensity was efficiently quenched due to the formation of the efficient quencher (\(\hbox {Co}^{2+}\)–dopamine complex). Thus, the concentration of dopamine can be determined by tracking the decrease in the fluorescent intensity of the \(\hbox {Co}^{2+}\)@TGA–CdS QDs. The proposed sensor showed high selectivity towards the detection of dopamine over other catecholamine derivatives and related compounds. Under optimal conditions, the quenching efficiency of dopamine on the \(\hbox {Co}^{2+}\)@TGA–CdS QDs system was linearly proportional to the concentration of dopamine in the range of \(20{-}100\,{\upmu }\hbox {mol }\hbox {l}^{-1}\). The limits of detection and quantification were 1.8 and \(12.7\,{\upmu }\hbox {mol }\hbox {l}^{-1}\), respectively. This sensor system was demonstrated to detect dopamine in real urine samples with satisfactory results.