Synthesis and Characterization of a pH Fluorescence Sensor with Tunable Response Range

Abstract

N,N′-bi(L-glutamic amine)-perylene-3,4;9,10-dicarboxylic diimide(PTCDG)was synthesized and characterized.The compound abovementioned was water-soluble and had high fluorescent quantum yield.A set of novel fluorescent pH sensors with tunable response range were designed based on the PTCDG,which could react with paramagnetic Fe3+ to form a 1:1 complex.The association constant was 6.5×105.The effects of foreign ions were examined and it was shown that PTCDG has a good selectivity to Fe3+.The PTCDG could coordinate the paramagnetic Fe3+ ions to switch off itself by PET quenching and could release Fe3+ to turn on the fluorescence again by forming Fe(OH)3 as the pH increase.Moreover,under the conditions of different good ligands for Fe3+,the formation of Fe(OH)3 moves to the alkaline pH range direction.The tunable response pH range covers 4.0-10.0(4.0-6.0 for PTCDG,5.0-10.0 for PTCDG/Fe3+,5.0-7.0 for PTCDG/Fe3+/triethylamine,6.0-8.0 for PTCDG/Fe3+/pyridine,7.0-9.0 for PTCDG/Fe3+/phenanthroline).The effects of the internal interference were investigated and the pH sensing mechanism was also discussed.The pH sensor had many excellent properties,such as tunable response range including the nearly neutral environment,obvious change of fluorescence and color,fast response and high sensi-tivity.