New boronic acid/fluorescein based fluorescent and colormimetric sensors for copper and cyanide ions

Abstract

A major aim of this research is to synthesize new sensors containing fluorescein and boronic acid moieties, F-oBOH F-mBOH, and F-pBOH, for detection of copper and cyanide ions. Initially, the complexation studies of sensors with various cations in acetonitrile, evaluated by UV-vis spectrophotometry and naked-eyes detection, were found that F-oBOH, F-mBOH, and F-pBOH showed a high selectivity toward copper(II) ion. Then, the complexation abilities of three sensors with copper(II) ion were measured by using UV-vis and fluorescence titration techniques. The log values evaluated by UV-vis titration of F-oBOH, F-mBOH, and F-pBOH were 6.67, 8.87, and 9.88, respectively; while, the log values evaluated by fluorescence titration of F-oBOH, F-mBOH, and F-pBOH were 8.02, 8.48, and 11.53, respectively. In addition, we studied all of three sensors in aqueous media and discovered that sensors were hydrolyzed by water. Therefore, we designed the new strategy to prevent the hydrolysis approach by adapting coordination nanoparticles network (F-oBOH-AMP/Gd3+ CNPs). It displayed the enhancement of fluorescent signal after adding copper ion following by cyanide ion. The log K value of F-oBOH-AMP/Gd3+ CNPs copper (II) with cyanide ion is 3.97. Additionally, the detection limit of F-oBOH-AMP/Gd3+CNPs copper(II) with cyanide anion detected by naked-eyes and fluorescence technique was 20 M and 4.03 M, respectively. Furthermore, they possess a high selectivity for cyanide ion compared to other competitive anions.