Electrochemical deposition of gold at liquid–liquid interfaces studied by thin organic film-modified electrodes (original) (raw)
Related papers
Journal of the Iranian Chemical Society, 2012
There has been substantial recent interest in studying monolayer-protected gold clusters (MPCs) owing to their diverse applications. The present work is an electrochemical study of novel gold nanoparticles covered with a monolayer of mercapto-dodecanol ended chloro-dicyanoquinone (HS-C12O-CDQ), which was adsorbed on the electrode (CDQ-MPCs film). Our findings reveal a redox behavior for CDQ-MPCs film similar to the solution electrochemistry of dichloro-dicyano-quinone. Furthermore, a diffusion-like mechanism was found for electron transfer, which may have occurred due to proton diffusion towards or outwards the electrode through the film casted. Chronoamperometry confirmed diffusion behavior of the ET process. Finally, EIS was used to find the rate constant of ET process for the redox reaction that occurred and the contribution of MPCs in total interfacial capacitance.
Preparation and Characterization of a Redox Multilayer Film Containing Au Nanoparticles
The Journal of Physical Chemistry C, 2009
Gold nanoparticles encapsulated by negatively charged molecules have been stably anchored at a Au substrate through layer-by-layer deposition technique, employing a redox polyviologen derivative as the cationic counterpart. UV-vis spectroscopy, quartz crystal microbalance, transmission electron microscopy, scanning electron microscopy, atomic force microscopy, and voltammetric measurements have been performed in order to characterize the systems and to give a rationale to the effect of the deposition conditions on the properties of the resulting multilayers. The behavior of two benchmark electroactive species ([Fe(CN) 6 ] 4and [Ru(NH 3) 6 ] 3+) has been studied on nanoparticle-terminated multilayers. The nanoparticles provide charge percolation through the multilayer and charge transfer with redox species in solution. The results imply that the electrochemical behavior of nanoparticle-containing films is partly dependent on the charge compensation mode within polyelectrolyte multilayers.
Electrochemistry Communications, 2006
Hydrophilic gold nanoclusters were tethered onto gold electrodes modified with mixed 1-octane thiol/1,9-nonane dithiol monolayers. The heterogeneous electron transfer (ET) kinetics of soluble redox species in the supporting electrolyte were investigated at these electrodes by cyclic voltammetry (CV) in the presence and absence of the ion-pairing anions PF À 6 and NO À 3 . The redox species investigated, [Fe(CN) 6 ] 3À/4À and [Co(C 12 H 8 N 2 ) 3 ] 3+/2+ where oppositely charged. The results presented here reveal that the rate of ET for the negatively charged redox species decreases with decreasing ionic charging time constant of the electrolyte. The opposite trend is observed for the positively charged redox species. Published by Elsevier B.V.
The Journal of Physical Chemistry B, 2006
In this work, we exploit the molecular engineering capability of the layer-by-layer (LbL) method to immobilize layers of gold nanoparticles on indium tin oxide (ITO) substrates, which exhibit enhanced charge transfer and may incorporate mediating redox substances. Polyamidoamine (PAMAM generation 4) dendrimers were used as template/stabilizers for Au nanoparticle growth, with PAMAM-Au nanoparticles serving as cationic polyelectrolytes to produce LbL films with poly(vinylsulfonic acid) (PVS). The cyclic voltammetry (CV) of ITO-PVS/PAMAM-Au electrodes in sulfuric acid presented a redox pair attributed to Au surface oxide formation. The maximum kinetics adsorption is first-order, 95% of the current being achieved after only 5 min of adsorption. Electron hopping can be considered as the charge transport mechanism between the PVS/ PAMAM-Au layers within the LbL films. This charge transport was faster than that for nonmodified electrodes, shown by employing hexacyanoferrate(III) as the surface reaction marker. Because the enhanced charge transport may be exploited in biosensors requiring redox mediators, we demonstrate the formation of Prussian blue (PB) around the Au nanoparticles as a proof of principle. PAMAM-Au@PB could be easily prepared by electrodeposition, following the ITO-PVS/ PAMAM-Au LbL film preparation procedure. Furthermore, the coverage of Au nanoparticles by PB may be controlled by monitoring the oxidation current.
First-principles investigation of electrochemical properties of gold nanoparticles
Nanotechnology, 2010
A first-principles formalism is employed to investigate the effects of size and structure on the electronic and electrochemical properties of Au nanoparticles with diameters between 0.8 and 2.0 nm. We find that the behavior of the ionization potentials (IP's) and the electron affinities (EA's) as a function of cluster size can be separated into many-body and single-electron contributions. The many-body part is only (and continuously) dependent on particle size, and can be very well described in terms of the capacitance of classical spherical conductors for clusters with more the 55 atoms. For smaller clusters, molecule-like features lead the capacitance and fundamental gap to differ systematically from those of a classical conductor with decreasing size. The single-electron part fluctuates with particle structure. Upon calculating the neutral chemical potential µ 0 =(IP+EA)/2, the many-body contributions cancel out, resulting in fluctuations of µ 0 around the bulk Au work function, consistent with experimental results. The values of IP and EA changes upon functionalization with thiolated molecules, and the magnitude of the observed changes does not depend on the length of the alkane chain. The functionalization can also lead to a transition from metallic to non-metallic behavior in small nanoparticles, which is consistent with experimental observations.
Ferrocenated Au Nanoparticle Monolayer Adsorption on Self-Assembled Monolayer-Coated Electrodes
Analytical Chemistry, 2009
The robust, irreversible adsorption of ω-ferrocene hexanethiolate-protected gold nanoparticles (composition ca. {Au 225 (SC6Fc) 43 }) on electrodes provides an opportunity to investigate their submonolayer and monolayer films in nanoparticle-free solutions. Observations of nanoparticle adsorption on unmodified electrodes are extended here to Au electrodes having more explicitly controlled surfaces, namely self-assembled monolayers (SAMs) of alkanethiolates with ω-sulfonate, carboxylate, and methyl termini, and in different Bu 4 N + Xelectrolyte (X -) C 7 H 7 SO 3 -, ClO 4 -, CF 3 SO 3 -, PF 6 -, NO 3 -) solutions in CH 2 Cl 2 . The nanoparticle surface coverage (Γ NP ) and the stability of the adsorbed nanoparticle film to repeated ferrocene/ferrocenium redox cycling decrease in the order of sulfonate > carboxylate > methyl terminated SAM, with increasing hydrophobicity of Xand with increasing alkyl chain length. The results are consistent with the proposal that the strong surface adsorption is jointly associated with the polyfunctional character of the nanoparticles, analogous to entropically driven adsorptions of polymeric ions on charged surfaces, and with lateral, ion-bridged nanoparticle-nanoparticle interactions.
The paper deals with some preliminary experimental results regarding the investigation of electrocatalytic characteristics of AuNPs prepared by a microemulsion assisted photoreduction procedure towards hydrogen evolution reaction. Cyclic voltammetry and chronoamperometry were carried out to evaluate the influence of Au NPs on hydrogen evolution reaction in acidic media (1M HCl solution) using both glassy carbon working electrode and screen-printed modified carbon electrodes. A very good linearity of the cathodic current at a certain applied cathodic potential (of -1V vs. Ag ref.) against gold nanoparticles concentration has been determined for thiol functionalized AuNPs using sodium 3-mercaptopropane sulfonate. In the last years the use of gold nanoparticles (AuNPs) has been reported in various applications due to their ability to provide a stable immobilization of biomolecules retaining their bioactivity, which is a major advantage for the preparation of biosensors [1-3]. They allo...
Size-Selective Electrophoretic Deposition of Gold Nanoparticles Mediated by Hydroquinone Oxidation
Langmuir, 2019
Here we describe the size-selective, hydroquinone (HQ)-mediated electrophoretic deposition (EPD) of 4 nm and 15 nm diameter citrate-stabilized Au nanoparticles (NPs) onto a glass/ITO electrode. Protons liberated from HQ during electrochemical oxidation at the Au NP surface during collisions with the glass/ITO electrode leads to Au NP deposition through neutralization of the citrate stabilizer surrounding the Au NPs, protonation of the glass/ITO electrode, or some combination of the two. Interestingly, the 4 nm Au NPs deposit at about a 300-400 mV more negative potential than 15 nm diameter Au NPs because of faster HQ oxidation kinetics at the 4 nm NPs, leading to lower overpotentials. This allows for selective deposition of the 4 nm Au NPs over 15 nm Au NPs in a solution containing a mixture of the two by controlling the electrode potential. Controlled pH experiments indicate that significant NP deposition occurs on glass/ITO at a pH of ~3, giving insight into the local pH needed from HQ oxidation in order to deposit the Au NPs. Experiments performed at different ionic strength confirms that migration is a major mode of mass transport of the NPs to the glass/ITO. Long deposition times lead to films of
Journal of Materials Science: Materials in Electronics, 2015
Gold nanoparticles (Au NPs) were synthesized using Au containing CTAB gel as a precursor. The effect of concentration of NaBH 4 on the structural, optical, catalytic and electrochemical properties of the Au NPs was also investigated. With the increase of NaBH 4 concentration from 0.1 to 0.15 M, an increase in the particle size and change in the morphology from spherical to elliptical was observed. Absorption and emission properties of the Au NPs were also probed using UV-Vis and photoluminescence spectroscopy respectively. Synthesized Au NPs samples were explored as catalyst for the reduction of 4-nitrophenol to 4-aminophenol. Catalytic activity of Au NPs samples prepared using 0.1 and 0.15 M concentration of NaBH 4 were also compared. It was found that Au NPs prepared using lower concentration of NaBH 4 (Au-0.1) exhibits better catalytic activity compared to the other Au NPs sample (Au-0.15). Synthesized Au NPs were also utilized as electrode material for the detection of Pb 2? ions, results show that Au NPs modified glassy carbon electrode can detect very low concentration of Pb 2? ions (2 lM). Au-0.1 sample exhibited better electrochemical performance compared to the Au-0.15 sample.