Silver nanoparticles capped with chalcon carboxylic acid as a probe for colorimetric determination of cadmium(II)

The authors describe a selective and sensitive method for the colorimetric determination of Cd(II) by using silver nanoparticles capped with chalcone carboxylic acid (CCA) as an optical indicator probe. The addition of Cd(II) ions causes particle aggregation and this is accompanied by a color change from yellow to orange, with absorption peaks shifting from 396 to 522 nm. This assay enables selective detection of Cd(II), while other metal ions such as Al(III), Ca(II), Co(II), bichromate, Cu(II), Fe(III), Mn(II), Ni(II), Cr(III), Zn(II), Mg(II), Pb(II) and Hg(II) do not significantly interfere at moderate levels. The visually detectable limit of detection is 0.23 mu M, and the instrumental detection limit is 0.13 mu M. A linear relationship, between the absorbances ratio at 522 and 396 nm and Cd(II) concentration, was obtained in the 0.227 to 3.18 mu MCd(II) concentration range. The colorimetric method was successfully applied to the determination of Cd(II) in spiked drinking water and lake water. The results were in good agreement with results by inductively coupled plasma-optical emission spectrometry.