Eco-friendly poly(aniline boronic acid)/gum tragacanth stabilized silver nanoparticles nanocomposite for selective sensing of Hg2+

Abstract

The stable and dispersed aqueous nanocomposite of poly(aniline boronic acid)/gum tragacanth stabilized silver nanoparticles (PABA/GT@AgNPs) was synthesized and applied as a colorimetric nanoprobe for Hg2+. Aniline boronic acid was used as the only reducing agent of silver nitrate and equally oxidized to PABA based on in situ chemical oxidative polymerization. In the presence of gum tragacanth (GT), hydroxyl groups of GT will bind to PABA at boronic groups to generate the PABA/GT matrix, on which AgNPs are anchored. At the optimal synthesis, absorption spectra at 285 and 421 nm correspond to π -π* transitions of PABA and plasmon resonance band of small sized AgNPs (10–15 nm). Based on the FTIR spectrum, GT is the major constituent of nanocomposite. Under optimal conditions (40 mM phosphate buffer pH 6.0, 150 mM sodium chloride, reaction time of 8 min at room temperature), the PABA/GT@AgNPs was used as a sensing of Hg2+ based on Hg2+ induced transmetalation on arylboronic acid group and redox reaction with Ag0. In the presence of Hg2+, the aggregation of PABA/GT@AgNPs can be seen by a color change from pale yellow to colorless and a blue shift from 407 nm to 370 nm. Good linear ranges in the concentrations of 0.005–1.0 μM and 1.0–40.0 μM were achieved, with a detection limit of 0.85 nM. The practicality of the detection was demonstrated on tap and lake water samples, with no effects of other interfering ions, and satisfactory recoveries of 97–101 % and precisions of 2.9–5.6 %.