Colorimetric detection of hg(Ii) ion using silver nanoparticles capped with 3-hydroxybenzoic acid

Abstract

In this paper, we report for the first time the simple method for detection of Hg(II) ion in an aqueous medium using silver nanoparticles capped with 3-hydroxybenzoic acid. Silver nanoparticles capped with 3-hydroxybenzoic acid were prepared by reduction of the silver ion with 3-hydroxybenzoic acid and without surface functionalization. The formation of silver nanoparticles was characterized by a UV-Visible spectrophotometer. The yellow colloid of prepared silver nanoparticles capped with 3-hydroxybenzoic acid showed a surface plasmon resonance peak at 420 nm. The ability of silver nanoparticles capped with 3-hydroxybenzoic acid in detection was tested by doing a reaction with several metal ions individually (Na(I), K(I), Cu(II), Zn(II), Ca(II), Mg(II), Hg(II), Mn(II), Ni(II), Pb(II), and Co(II)). It was found that silver nanoparticles capped with 3-hydroxybenzoic acid highly selective to Hg(II) and then the prepared silver nanoparticles were developed for detection of Hg(II) ion. Addition of 1 mL Hg(II) ion into 4 mL the as-prepared silver nanoparticles reduced the peak of surface plasmon resonance spectra, and the reduction of peak intensity was proportional to the concentration of Hg(II) ion. A good linear relationship (R2 = 0.998) between absorbance at 420 nm and concentration of Hg(II) over the range 1.0x10-3 to 5.5x10-3 M was obtained. Silver nanoparticles capped with 3-hydroxybenzoic acid were highly sensitive to Hg (II) ion with the detection limit down to 4.7x10-5 M. Application the method to the real water sample showed the excellent result with recovery ranged from 98 to 101%. The proposed method was found to be useful for the colorimetric detection of Hg(II) ion in an aqueous medium.