Highly sensitive determination of Co(II) ions in solutions by using modified silver nanoparticles.

In this manuscript, we report the development of a rapid and facile optic sensor for highly sensitive and selective detection of cobalt ions (Co(II)). The detection strategy was based on the specific silver nanoparticle-glutathione interaction and later on secondary interaction of this structure with cysteine and Co(II) ion. The interaction of these structures creates a new absorption band in the UV region. The intensity change of this band can be correlated by Co(II) ion concentration. The addition of cysteine decreases the Surface Plasmon Resonance (SPR) of silver nanoparticles but does not provide quantitative information. The proposed method offers the advantage of improved sensitivity for detection of Co(II) ions in a very short time period. Co(II) ions create a unique absorption peak during the complex formation and this peak provides sensitive determination of this metal ion in existence of other metal ions. The peak is visible only after taking the first derivative of absorption spectra. Under the optimized conditions, the detection limit of the method is around 0.68 μM. In addition, the synthesized silver nanoparticles (AgNPs) were characterized by atomic force microscopy (AFM). The proposed metal ion sensor provides a very facile and convenient way to determine the concentration of Co(II) ions in aqueous system.