Review of recent advancements in fluorescent chemosensor for ion detection via coumarin derivatives

Fluorescent chemosensors are highly valuable in a variety of fields including environmental chemistry, analytical chemistry and biomedical science. They have provided accurate, online and low-cost detection of toxic heavy metal ions, anions and enzymes with high selectivity and sensitivity. Coumarins, with the structure of benzopyrone, have many advantages including high fluorescence quantum yield, large Stokes shift, excellent light stability and less toxicity. By far coumarin has been used as fluorescent probes of pH, for detection of nitric oxide, nitroxide and hydrogen peroxide. Moreover, coumarin derivatives have served as good chemosensors of anions including cyanide, fluoride, pyrophosphate, acetate, benzoate and dihydrogenphosphate as well as various metal ions comprised of Hg(II), Cu(II), Zn(II), Ni(II), Ca(II), Pb(II), Mg(II), Fe(III), Al(III), Cr(III) and Ag(I). Several systems containing coumarin exhibited simultaneous sensitivity toward two or more different metal ions, e.g., Ca(II) and Mg(II), Ni(II) and Co(II), Cu(II) and Hg(II), Na(I) and K(I), Cu(II) and Ni(II), Hg(II) and Ag(I), Cu(II)/Ni(II)/Cd(II), Zn(II)/Cd(II)/Pb(II) or Ni(II)/Pd(II)/Ag(I). The sensing approach toward the ion has been discussed in detail along their detection limit to find the efficacy of the probe easier. Recently, scientists have been working on synthesizing novel fluorescence chemosensors with multiple-ion recognition ability to make the fluorescence sensing more effective and prolific.