Gold nanoparticle formation was found from tetrachloroaurate(III) in the presence of Good’s Buffers, such as 2-morpholinoethanesulfonic acid (MES) and 2-[4-(2-hydroxyethyl)-1-piperazinyl]ethanesulfonic acid (HEPES), which are used widely in laboratories for studies of analytical, inorganic, physical, and bio-chemistry as well as biology. The obtained gold nanoparticles were examined by Ultraviolet–Visible Spectroscopy (UV–vis), Dynamic Light Scattering (DLS) and Electrophoretic Light Scattering (ELS) in an aqueous system and by transmission electron microscopy (TEM) for particle morphologies. UV–vis spectra showed absorption maxima at ∼530 and ∼750 nm, depending on the buffer reagents and their concentration, pH, and ionic strength. The size and the surface zeta potential of the formed nanoparticles were 23 to 73 nm and −30 to −12 mV, respectively. The TEM pictures clearly indicated the formation of finely dispersed, chained, or aggregated gold nanoparticles, depending on the experimental conditions. The mechanism of gold nanoparticle formation was studied by the measurements of cyclic voltammetry (CV) and electron spin resonance (ESR). MES and HEPES showed a positive anodic peak at approximately +800 mV vs Ag/AgCl electrode, which indicated that these buffering agents have mild reducing ability. ESR results indicated the generation of nitrogen-centered cationic free radicals from these Good’s Buffers in the presence of Au(III), resulting in the formation of gold nanoparticles. A reaction mechanism is proposed.

Surface-enhanced Raman scattering (SERS) of the 4-mercaptopyridine (4-MPy) molecules adsorbed on the electrochemically roughened silver electrodes were investigated under practical electrochemical conditions. The adsorbed 4-MPy molecules are converted from a perpendicular orientation to a parallel orientation as the electrode potential is successively changed from 0 to -1.0 V. The coordination of the nitrogen atom of the pyridine ring to the silver metal weakens the ability of the 4-MPy molecules with a parallel orientation to capture the proton, because of the distribution of the electron density of the nitrogen to the silver metal. The applied potential has a large effect on the protonation/deprotonation process of the adsorbed 4-MPy molecules. More adsorbed 4-MPy molecules are protonated as the electrode potential becomes more negative. This is ascribed to the increase in the charge density on both the electrode surface and the nitrogen atom of the pyridine ring at the negative potentials.

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Micrometer polystyrene particles were uniformly assembled into a two-dimensional structure on an indiumdoped tin oxide (ITO) electrode. An array of zinc oxide (ZnO) microcavities was fabricated with the template of the assembled polystyrene particles by electrodeposition. Due to the resistance gradient of the ZnO cavity structure, the ZnO cavity exhibits a confinement effect on the electrochemical reactions, making the electrode function as an array of "soft" microelectrodes. The electrochemical reduction of silver cations leads to the formation of the silver nanoparticles localized at the bottom of the ZnO cavities.

Surface-enhanced Raman scattering under near-IR excitation is investigated for p-aminothiophenol (PATP) molecules that are either adsorbed on an electrochemically roughened silver electrode or embedded in an Au/PATP/Ag molecular junction assembled on an indium-doped tin oxide electrode. The contribution from chemical enhancement can be amplified relative to the contribution from electromagnetic enhancement, because the energy of the near-IR excitation is far from the surface plasmon resonance of the nanosized metal particles. The energy required for the charge-transfer process for the Au/PATP/Ag molecular junction is much lower than that of the PATP molecules adsorbed on the electrochemically roughened silver electrode. Coadsorption of chloride ions on the metal nanoparticles may result in an alteration of the local Fermi level of the metal nanoparticles, thus leading to better energy matching between the energy level of the interconnecting PATP molecules and the Fermi level of the metal nanoparticles.