A novel highly selective colorimetric sensor for Ni(II) ion using coumarin derivatives

A new coumarin based colorimetric nickel sensor 1 with high selectivity and sensitivity toward Ni 2+ ion was reported. The absorption maximum of 1 shows a large red shift from 341   nm to 540   nm (Δ   =   200   nm) in the presence of Ni 2+ ion, and the resulted color change from colorless to pink upon addition of Ni 2+ is very easily observed by the naked eye, while other metal ions , such as Zn 2+ , Cd 2+ , Cu 2+ , Fe 3+ , Ag + , Pb 2+ , alkali metal and alkaline earth metal cations do not induce such a change. By the “naked eye”, the detection limit of Ni 2+ is as low as 0.5   μM in solution, which is lower than the current American Environmental Protection Agency (EPA) standard for drinking water . As far as we are aware of, this is the first reported colorimetric chemosensor capable of detecting Ni 2+ ion.