A novel dual-function chemosensor for visual detection of Cu2+ in aqueous solution based on carbazole and its application

A novel carbazole derivative, named as 3-(9-butyl-9H-carbazol-3-yl)-2-{4-[(4-di-ethylamino-2-hydroxy-benzy-lidene)-amino]-phenyl}-acrylonitrile (CPA), was obtained for the detection of Cu2+. CPA exhibited dual-function responses to Cu(2+ )over other competitive metal ions in CH3CN-Tris (20 mM, v/v = 1:1, pH = 7.2) solution. CPA could detect Cu2+ by UV-vis method, and the color changed from yellow-green to colorless, which could be readily distinguished by the naked eye. With the addition of various metal ions into the CPA solution, only Cu2+ caused the fluorescence of the CPA quenching. Other cations such as Na+, K+, Ca2+, Mg2+, Ni2+, Fe3+ , Co2+, Cu2+, Zn2+, Hg2+, Ag+, Cd2+, Pb(2+ )and Al3+ could not induce similar response. The binding process was reasonably speculated by UV-Vis absorption and fluorescence measurements, H-1 NMR titration, mass spectroscopy (MS) and density functional theory (DFT) calculation. In addition, the coordination reaction was reversible and rapid. Strip papers were also devised and used to detect Cu2+ in aqueous solution, whose color change showed their potential application for on-site detection of Cu2+ in pollution water. And CPA could be visual in Hela cells with excellent cell permeability, viz, monitoring exogenous Cu2+ ions as well as realizing an "on-off" process.