One-pot synthesis of a natural phenol derived fluorescence sensor for Cu(II) and Hg(II) detection

Development of a high performance molecular fluorescence sensor from natural products for metal ions selective detection is also a great challenge. Herein, catechine-dopamine (C-DA) as a fluorescence sensor, was designed for Cu(II) and Hg(II) selective detection in 100% aqueous solution. C-DA with high fluorescence quantum yield of 10.93% was rapidly synthesized from the reaction between two natural phenols, catechine and dopamine, by a simple one-pot organic solvent free approach. Based on fluorescence “on-off”, C-DA could linearly detect the Cu(II) and Hg(II) concentrations in a range of 75 nM - 10 μM and 0.25 μM - 8 μM, respectively, and realized the Cu(II) and Hg(II) determination in tap water samples. Moreover, C-DA exhibited strong affinity to Cu(II) and Hg(II) among 15 kinds of metal ions and 9 kinds of anions. The association constants of C-DA-Cu(II) and C-DA-Hg(II) were respectively calculated as 3.21×104 M-1 and 3.05×104 M-1. Interestingly, although both Cu(II) and Hg(II) formed 1:1 complex to C-DA, they bond to C-DA in a different manner. Cu(II) firstly oxidized the catechol hydroxyl to quinone and was reduced to Cu(I), and then Cu(I) chelated with quinone. Nevertheless, Hg(II) straightly bonded to catechol hydroxyl.