Zn(II)-concentration dependent Raman spectra in the dithizone complex on gold nanoparticle surfaces in environmental water samples.

After the formation of dithizone with metal ion complexes, a selective Raman detection method for the Zn 2+ ions in aqueous solutions was developed by observing the intensity change of the ring mode peaks at ∼1585 cm −1 on gold nanoparticles (AuNPs). At high concentrations of Zn 2+ ions, the conformation of the dithizone complex may have different orientations on AuNPs to yield the spectral changes at ca. ∼510 and ∼1585 cm −1 . The concentration dependent spectra changes indicated that a detection limit would be in the submicromolar region of Zn 2+ ions. The other ions of Mg 2+ , K + , Fe 3+ , Hg 2+ , Co 2+ , Fe 2+ , Pb 2+ , Cu 2+ , Ni 2+ , Cr 3+ , NH 4 + , Cd 2+ , Na + , Ca 2+ , and Mn 2+ at micromolar concentrations of 1 μM did not produce such spectral changes. The detection limit based on the Raman band intensities was estimated to be as low as 500 nM of Zn 2+ ion in aqueous solutions. The three real samples of tap, river, and seawater were tested under the interference of the commonly existing interfering ions. Despite the presence of highly concentrated Na, Ca, Mg, and K, our interfacial spectroscopic methodology of Zn 2+ determination could be applied in the environmental water samples. [ABSTRACT FROM AUTHOR]