Nanostructured gold colloid electrode based on in situ functionalized self-assembled monolayers on gold electrode

Adsorption behavior of 6-Mercaptonicotinic acid on self-assembled gold nano-substrates explored by SERS combined with theoretical calculations

As a typical Raman reporter molecule, 6-Mercaptonicotinic acid (C6H5NO2S, MNA) has three atoms (i.e., N, O, and S), which could be potential to chemically interact with gold nano-surface. In the present report, the adsorption behavior of MNA on self-assembled gold nano-substrates is explored by means of surface-enhanced Raman scattering and theoretical calculations. The results reveal that all the enhanced bands are assigned to in-plane vibrations. The ring triangle breathing coupling with CS stretching band at 1108cm(-)(1) is enhanced a lot and redshifts to 1088cm(-)(1) in the SERS spectra. Furthermore, most of the bands related to N atom are apparently enhanced and shift in the SERS spectra. Based on the surface selection rule, it infers that MNA is vertically chemisorbed on self-assembled gold substrates through the S and the N atoms. The spectroscopic results are further interpreted by the density functional theory (DFT) calculations.

An approach for fabricating self-assembled monolayer of gold nanoparticles on NH2(+) ion implantation modified indium tin oxide as the SERS-active substrate

In this paper, an approach for fabricating an active surface-enhanced Raman scattering (SERS) substrate was adopted. This approach was based on the assembling of gold nanoparticles (AuNPs) film on NH(2)(+) ion implantation modified indium tin oxide (NH(2)/ITO) substrate. Scanning electron microscopy (SEM) was used to investigate the surface morphology of the active SERS substrate, which showed that large quantities of AuNPs were coated on the substrate. Rhodamine 6G (R6G) was used as probe molecules for SERS experiments, showing that this new active substrate had sensitivity to SERS response. The substrate efficiency was strictly related to the AuNPs morphology, which depended on the pH value of the Au colloid used in the assembly process.

An electrochemical study of 4-aminothiophenol/pt nanoparticle multilayers on gold electrodes

Quartz crystal microbalance (QCM) measurements of the formation of a 4-aminothiophenol (4-ATP) self-assembled monolayer (SAM) at a gold electrode showed that a surface coverage of 118 ng cm(-2) was obtained after a 3 h exposure period, indicating that good surface coverage was achieved. Cyclic voltammetry of the ferricyanide redox couple across this SAM modified surface produced similar results to those of a bare electrode; however, the electroreduction of oxygen was found to be impaired. The 4-ATP SAM layer was not stable to repeated electrochemical oxidation and reduction; it is believed that the 4-ATP SAM layer was first converted to a 4'-mercapto-N-phenylquinone diimine (NPQD) layer followed by subsequent formation of a 4'-mercapto-N-phenylquinone monoimine (NPQM) layer. We also report a quartz crystal microbalance study of the attachment of platinum nanoparticles to such SAM modified electrodes. We show that five times the amount of platinum nanoparticles can be attached to a 4-ATP modified electrode surface (observed frequency change -187 Hz) compared with an NPQD modified electrode surface (observed frequency change -35 Hz). The presence of the platinum particles was confirmed electrochemically by their surface electrochemical properties, which were different from those of the underlying gold electrode. It is believed that this is the first time that such direct evidence of electrochemical communication between platinum nanoparticles and a SAM modified electrode surface has been obtained. It was also shown to be possible to build up multilayer SAM/nanoparticle modified surfaces while maintaining efficient electrochemical communication. Up to three SAM/nanoparticle sandwich layers were constructed.