Fluorescence detection of mercury ions and cysteine based on magnesium and nitrogen co-doped carbon quantum dots and IMPLICATION logic gate operation

Abstract

Novel magnesium and nitrogen co-doped carbon quantum dots (Mg-N-CQDs) were developed as a fluorescent switch for sensitive and selective sensing of Hg(II) and cysteine (Cys). The Mg-N-CQDs synthesized by hydrothermal method possess high fluorescence intensity. However, after the addition of Hg(II), the fluorescence of Mg-N-CQDs aqueous solution was dramatically quenched, which may be attributed to the formation of non-fluorescent complex between Mg-N-CQDs and Hg(II). Interestingly, the fluorescence of the Mg-N-CQDs aqueous solution containing Hg(II) could be recovered gradually in the presence of Cys, due to the stronger binding affinity of Hg(II) toward Cys than toward Mg-N-CQDs. Based on these phenomena, a fluorescent probe for detection of Hg(II) and Cys was explored, and further applied to detect Hg(II) in real water samples with satisfactory results. Moreover, an IMPLICATION logic gate was constructed using Hg(II)/Cys as inputs and the fluorescence signal of Mg-N-CQDs as an output.