coumarin-based colorimetricchemosensor 1 was designed and synthesized. It exhibits good sensitivity and selectivity for the copper cation over other cations such as Zn(2+), Cd(2+), Pb(2+), Co(2+), Fe(2+), Ni(2+), Ag(+), and alkali and alkaline earth metal cations both in aqueoussolution and on paper-made testkits. The change in color is very easily observed by the naked eye in the presence of Cu(2+) cation