Film sensor of a ligand-functionalized cellulose nanofiber for the selective detection of copper and cesium ions

A fluorescence sensor film for metal ion detection was prepared from a 2,2,6,6-tetramethyl-1-piperidinyloxy radical-oxidized cellulose nanofiber (TOCNF), which was chemically immobilized the metal ion selective ligand, namely, 3,5-bis(((2-hydroxynaphthalen-1-yl)methylene)amino)benzoic acid. The ligand in the TOCNF/ligand films exhibited fluorescence at a 310 nm excitation wavelength and at an similar to 410 nm emission wavelength. Then, the sensing efficiency and limits were evaluated from the fluorescence of the metal ion-bound ligand. The Stern-Volmer plot of the fluorescence emission intensity of the films increased with increasing of Cu2+ or Cs(+)concentration. Accordingly, the sensing of metal ions was more effective on TOCNF with a greater amount of ligand, the sensing of Cu2+ was superior to that of Cs+, and the detection range of the TOCNF/ligand film was wider for Cu2+ than for Cs+. Thus, although the sensitivity of this sensor is lower than the electrochemical detection previously reported, the noticeable potential of the current sensing system is that it is a film type to be easily removable from the sensing water and there is no remaining sensing residue in the water.