naked eye detection of cr3+ and co2+ ions by gold nanoparticle modified with azomethine

This paper reports the synthesis of azomethine-modified gold nanoparticles with azomethine (azomethine-aunps) in aqueous media, which were characterized by ft-ir spectroscopy, ultraviolet–visible spectroscopy (uv-vis), dynamic light scattering (dls), thermogravimetric analysis (tga), and transmission electron microscopy (tem). the azomethine-aunps were employed as colorimetric for cr3+ and co2+ ions at ph 6.2–7.5 and 8.1–9.1, at room temperature in aqueous solution. in the presence of cr3+ and co2+, the azomethine-aunps induce aggregation of the nanoparticles. upon aggregation, the surface plasmon absorption band red-shifts so that the nanoparticle solution appears a blue color. the sensitivity of azomethine-aunps towards other metal ions, mg2+, mn2+, cr6+, na+, ni2+, ag+, al3+, ca2+, cd2+, cu2+, fe2+, fe3+, hg2+, cd2+, k+, co3+, ni2+, pb2+, and zn2+ are negligible. this highly selective sensor allows a direct quantitative assay of co2+ and cr3+ with colorimetric detection limits of 83.22 and 108 nm, respectively.