Blue emitting gold cluster formation from gold nanorods: Selective and sensitive detection of iron(III) ions in aqueous medium

Fluorescent few-atom gold quantum clusters from gold nanorods have been synthesized through core-etching method in an aqueous medium in the presence of a bioactive peptide, glutathione (reduced), as the stabilizing agent. These gold clusters emit blue light under irradiation with a 365 nm wavelength UV-torch and exhibit emission maxima at 425 nm in water. Interestingly, this blue emitting gold cluster has been successfully used for the sensitive and selective fluorometric detection of Fe(III) in the presence of other interfering ions including Pb(II), Zn(II), Ca(II), Hg(II), Cr(III), Co(II), As(III), Ni(II), Mn(II), Mg(II), and Al(III) in an aqueous medium. Moreover, the blue emitting gold quantum cluster is selective to Fe(III) but not to Fe(II) ions in water. The ratio of Fe(II)/ Fe(III) ions in aqueous medium has also been determined, suggesting the probable use of this method in real iron-rich systems. Furthermore, the sensor can also be reused several times by removing Fe(III) with sulfide ions.