Controlled stabilization and flocculation of gold nanoparticles by means of 2-pyrazin-2-yiethanethiol and pentacyanidoferrate(II) complexes

2-Pyrazin-2-ylethanethiol (PZT) interacts with gold nanoparticles (AuNps) and pentacyanidoferrates, providing a suitable bridging ligand for the exploitation of the coordination chemistry involved in the stabilization of the colloidal solutions and in the controlled formation of aggregates in the presence of dimethyl sulfoxide. The electronic and vibrational spectra of the molecules have been investigated and discussed based on DFT and ZINDO/S theoretical calculations. The PZT-modified AuNps exhibit strong SERS, coherent with the electromagnetic enhancement mechanism. In contrast, the charge-transfer mechanism seems to predominate in the Raman spectra of the [Fe(CN)(5)PZT](3-)-modified gold nanoparticles. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007).