Electrodeposition Of Ag Research Articles

Optical properties of Ag–Al 2O 3 nano-array composite structure

Ag/Al 2O 3 nano-array composite structures were obtained by alternating current (AC) electrodeposition of Ag into the pores of anodic alumina membrane (AAM). The ordered wire-grid structure of Ag nanowires formed along a preferential direction, typically 20 nm in diameter, was fabricated. XRD revealed that Ag 2O is also preserved in the pores of AAM. Optical properties of Ag/Al 2O 3 prepared at different annealing temperatures were measured by using spectrometer. Transmission spectra indicate that the transmittance of Ag/Al 2O 3 increases obviously with the increasing of annealing temperature. Polarization spectra indicate that Ag/Al 2O 3 has good polarization in the range of 900–2000 nm, and the extinction ratio increases with the increasing of the annealing temperature or incident angle.

Pulsed Electrodeposition of Two-Dimensional Ag Nanostructures on Au(111)

One-step pulsed potential electrodeposition of Ag on Au(111) in the underpotential deposition (UPD) region has been studied in 0.5 mM Ag2SO4 + 0.1 M H2SO4 aqueous electrolyte at various pulse durations from 0.2 to 500 ms. Evolution of the deposited Ag nanostructures was followed by in situ scanning tunneling microscopy (STM) and by measurement of the respective current transients. At short pulse durations a relatively high number density (4 x 10(11) cm(-2)) of two-dimensional Ag clusters with a narrow size and distance distribution is observed. They exhibit a remarkably high stability characterized by a dissolution potential which lies about 200 mV more anodically than the typical potential of Ag-(1 x 1) monolayer dissolution. To elucidate the underlying nucleation and growth mechanism, two models have been considered: two-dimensional lattice incorporation and a newly developed coupled diffusion-adsorption model. The first one yields a qualitative description of the current transients, whereas the second one is in nearly quantitative agreement with the experimental data. In this model the transformation of a Ag-(3 x 3) into a Ag-(1 x 1) structure indicated in the cyclic voltammogram (peaks at 520 vs 20 mV) is taken into account.

貴金属ナノロッドアレーによるAlアノード酸化皮膜のマルチカラー化

Anodization of aluminum plate followed by the electrodeposition of Ag or Au has yielded the metal nanorod-incorporated porous aluminum oxide film (NR/AO). This 2-step electrochemical method enabled us to arbitrarily control the aspect ratio of the nanorods by changing the electrodeposition time. The Ag- and Au-NR/AO exhibited clear light-incident-angle dependent color variation, the so-called flip-flop phenomenon. This was achieved by the synergy of the interference wave of AO and the surface plasmon absorption of the NRs. Further, the color was finely tunable by variation of their aspect ratio.

Linear and nonlinear optical properties of Ag nanorods/AAM composite films

An optically transparent Ag nanorods/AAM composite film was prepared by AC electrodeposition of Ag within the nanoporous anodic alumina membrane (AAM). Because the incident light excited different surface plasmon resonance modes along different directions, the composite film displayed an optical anisotropy for the rod-shape of Ag particles. Its three-order nonlinear optical properties were measured by z-scan technique, and the values of |Re χ (3)| and |Im χ (3)| were about 2.6028 × 10 −6 and 5.7614 × 10 −7 eus, respectively.

A SERS investigation of the electrodeposition of Ag–Au alloys from free-cyanide solutions – part II

Some aspects of the in situ SERS behaviour of free cyanide containing Ag, Au and Ag–Au solutions during electrodeposition are reported in this paper. The basic spectroelectrochemical phenomenology has been treated in a companion paper [J. Electroanal. Chem. 563 (2004) 133] and discussed in relation to electrochemical (cyclic voltammetry and potentiostatic electrodeposition), structural (X-ray diffraction), morphological (scanning electron microscopy) and compositional (energy dispersive spectroscopy) results. In the present work we evaluated and discussed the Stark-tuning of the surface CN − stretching band. The non-linear Stark-tuning of the cyanide-stretching band was correlated to the covalent vs. ionic character of the cyanide–metal adsorption bond and to the pzc of the specific systems. In addition, we stressed the peculiarities of the highly negative potential range, in which remarkable changes in the spectral patterns occur and fluorescence sets in.

A SERS investigation of the electrodeposition of Ag–Au alloys from free-cyanide solutions

In this paper we investigated the electrodeposition of Ag–Au alloys from cyanide baths by in situ surface-enhanced Raman spectroscopy. The spectroelectrochemical investigation is complemented by electrochemical experiments (cyclic voltammetry and potentiostatic electrodeposition) and structural (X-ray diffraction), morphological (scanning electron microscopy) and compositional (energy dispersive spectroscopy) characterisation of the alloys. Electrochemical and spectroelectrochemical results on single-metal electrodeposition baths of otherwise identical composition are reported for comparison. Single-phase deposits of composition ranging from 13% to 75% Au were obtained potentiostatically. The voltammetric behaviour was correlated to the vibrational characteristics of adsorbed ligands. Quantitative and qualitative differences in interfacial chemistry as a function of applied potential were assessed and explained on the basis of variations in the nature of cyanide-related surface species. The cyanide and metal-adsorbate stretching bands have been analysed.

In situ FTIR monitoring of Ag and Au electrodeposition on glassy carbon and silicon

Formation of Ag, Au and Ag–Au alloys on Si and Glassy Carbon (GC) electrodes from alkaline cyanide electrolytes was investigated using a combination of electrochemical and spectroscopic techniques. Metal deposition and dissolution processes could be studied in situ by monitoring the ν(CN) bands of the metal complexes and the free cyanide ion in the region between 2000 and 2200 cm −1 using FTIR reflectance spectroscopy. Under the experimental conditions, two different silver complexes, namely [Ag(CN) 2] − and [Ag(CN) 3] 2− (whilst only one gold complex, namely [Au(CN) 2] −), were identified. In the case of the Ag–Au alloys, both species co-deposit even in the activation region, where Ag reduction is expected to be the main reaction. Experimental results indicate that in a mixed electrolyte containing equal amounts of Ag and Au, Ag deposition is thermodynamically favoured ( E eq, Ag 0〉E eq, Au 0 ), while Au deposition is kinetically favoured. The Ag–Au alloy deposition follows a progressive nucleation mechanism even at relatively high negative potentials. The morphology and adhesion of all deposits, as well as the alloy composition, were found to be strongly dependent on the deposition conditions. A better adhesion of the films with a higher Au content was observed, due to the formation of a more stable AuSi bond.

Silver nanowire array infrared polarizers

A silver nanowire array micropolarizer within an anodic alumina membrane(AAM) was fabricated by anodization of pure Al foil and electrodeposition of Ag,respectively. X-ray diffraction, scanning electron microscopy, and transmissionelectron microscopy investigations reveal that the nanowires are essentially singlecrystals, and have an average diameter of 90 nm. Spectrophotometermeasurements show that the silver nanowire arrays embedded in the AAM canonly transmit vertically polarized light to the wires. An extinction ratio of 25–26dB and average insertion loss of 0.77 dB in the wavelength range 1–2.2 μmwere obtained, respectively. Therefore the Ag nanowire/AAM can be used as awire-grid type polarizer.

Functionalized self-assembled monolayers and their influence on silver electrodeposition

We have studied the Ag electrodeposition on bare Au and on Au(111) surfaces covered with alkanethiol SAM (self-assembled monolayer) using cyclic voltammetry (CV) and in situ scanning tunneling microscopy (STM). The SAM composition was varied with respect to the alkyl chain length using ethylene or hexylene backbones on the one hand and with respect to the layer termination on the other hand, introducing –CH 3, –OH or –SH groups, respectively. The electrochemical and structural studies in absence of silver ions allowed us to know the density of the different SAMs for the further Ag deposition. Differences among the SAMs as well as between the SAMs and bare gold were noted during the Ag bulk deposition. Such differences are more remarkable when hexanedithiol is used for the SAM. This molecule is adsorbed by only one thiol moiety whereas the other one remains free and exerts silver/thiolate interactions at the SAM/electrolyte interface.

Electrodeposition and characterisation of Ag–ZrO 2 electroplated coatings

Ag–ZrO 2 electroplated coatings were produced using a classical DC technique in a silver cyanide bath with added ZrO 2 particles. Plating parameters, particle concentration and the stirring rate of the bath were systematically investigated in order to calculate the incorporation rate V p of the particles in the deposit. It was found that the relationships between V p , current density and stirring rate were related to the particle concentration in the bath. Moreover, it was established that the mechanical and tribological properties of coating composite, like hardness, friction coefficient and wear resistance increased with the increase in incorporation rate V p .

Functionalized Self-Assembled Alkanethiol Monolayers on Au(111) Electrodes: 2. Silver Electrodeposition

We have studied the early stages of Ag electrodeposition from dilute sulfuric acid solutions on modified Au(111) electrodes with cyclic voltammetry and in situ scanning tunneling microscopy. Several differently functionalized short-, medium-, and long-chain alkanethiols were used for electrode modification. Ag underpotential deposition onto such surfaces is hindered depending on chain length, but the differences between self-assembled monolayers with different endgroups were less significant. Two Ag layers are deposited at the thiol/Au(111) interface in an island growth mechanism at underpotentials. Bulk deposition originates almost exclusively at step edges burying the underlying self-assembled monolayer. Oxidative desorption of the organic film is promoted in contact with a Ag+-containing electrolyte as compared to the metal ion free solution.

Design and Characterization of a Rotating Electrochemical Quartz‐Crystal‐Microbalance Electrode

A novel design for a rotating electrochemical quartz‐crystal microbalance (rEQCM) which includes easily and reproducibly exchangeable quartz‐crystal holders is described. The rEQCM allows for well‐controlled mass‐transport conditions at the working electrode on a 10 MHz quartz crystal. Together with the flexibility of the proposed design, this makes it useful for a wide range of applications in electrochemistry. At a data acquisition rate of 5 Hz, noise level and stability of the resonant frequency were better than 1 Hz at rotation rates of 0–3500 rpm. This corresponds to a mass density on the quartz crystal of . The small recess needed to fix the quartz crystal in the electrode holder was shown not to affect the primary current distribution and the mass‐transport conditions. Electrodeposition of Cu and Ag was used for the in situ characterization of the frequency dependence of the Sauerbrey constant (mass sensitivity) of the quartz as a function of mass load on the crystal. It was found that, in the initial phase of Ag and Cu deposition on Au, the mass sensitivity is affected by internal stresses in the deposit. © 2000 The Electrochemical Society. All rights reserved.

Smoothening Mechanism of Thiourea on Silver Electrodeposition. Real Time Imaging of the Growth Front Evolution

Ag electrodeposits were grown on a polycrystalline Ag cathode at either 0.01 or 1 mA cm-2 from aqueous 5 × 10-3 M Ag2SO4 + 10-2 M H2SO4 + 0.5 M Na2SO4, in the absence and presence of different amounts of thiourea (TU). The cathode/solution interface evolution in a quasi-bidimensional electrochemical cell was followed with a video microscope imaging system. From TU-free solution a nodular morphology at 0.01 mA cm-2 and a branched morphology at 1 mA cm-2 were observed. At 0.01 mA cm-2 the presence of TU drove the interface motion to a stable roughness regime by suppressing the nucleation and growth of instabilities. Accordingly, the characteristics of the growth front were consistent with the predictions of the Edwards−Wilkinson equation for the interface motion. At 1 mA cm-2, those electrodeposits grown in the presence of TU showed a decrease in both the nucleation and growth rates of instabilities, although they were not fully suppressed.

Electrochemical in situ STM study of phase formation during Ag and Al electrodeposition on Au(111) from a room temperature molten salt

The electrodeposition of Ag and Al on flame annealed Au(111) films from an acidic aluminium chloride–1-methyl-3-butylimidazolium chloride room temperature molten salt has been investigated by electrochemical scanning tunneling microscopy, cyclic voltammetry and potential step experiments. The cyclic voltammogram of Ag on Au(111) is characterized by adsorption controlled Ag underpotential deposition (upd) and diffusion controlled Ag overpotential deposition (opd). Starting from the anodic limit, bulk oxidation of Au is observed to start near +1.25V vs. Ag/Ag+ reference electrode (RE). In the upd range, two dimensional Ag islands form which merge in a coherent Ag monolayer near 0.05 V vs. RE. With further reduction of the potential, a second monolayer grows. The corresponding chronoamperometric measurements show exponential behaviour with time constants of the order 10 s-1 consistent with a Langmuir adsorption model. In the opd range, a diffusion controlled layer by layer growth of Ag clusters occurs, the bulk Ag+ diffusion coefficient being (1.4±0.2)×10-6 cm2 s-1. Alloying of Ag with codeposited Al from the electrolyte has to be considered. For the Al electrodeposition on Au(111), strong indications for alloying have been observed starting at a potential of +0.95 V vs. Al/Al3+ RE. Below +0.55V, the formation of two dimensional Al islands is seen followed by a three dimensional growth whereby a strong tendency for alloying has to be considered.

Time-resolved surface differential diffraction study of Ag electrodeposition on Au(111) and the role of surface stress

An insitu X-ray diffraction investigation using surface differential diffraction (SDD) was carried out to study the mechanism and kinetics of Ag electrodeposition on Au(111). The effect of the surface stress on SDD measurements employing a thin film electrode has been investigated, which reveals that stress-induced peak shifts can account for some inconsistency in previous SDD results. Potential dynamic and potential step modes of deposition were used and the adlayer spacing of Ag on Au(111) was determined as a function of potential and time, respectively. A structural change in adlayer spacing during Ag electrodeposition on Au(111) was observed in both modes of deposition, which is consistent with a transition from initial adsorption in a mixture of bridge and atop sites to three-fold hollow sites.

In Situ Study of Silver Electrodeposition at MoSe2 by Electrochemical Scanning Tunneling Microscopy

The electrodeposition of Ag at MoSe2 has been investigated, in situ, by electrochemical scanning tunneling microscopy (EC-STM). The process was investigated by observing MoSe2 at fixed electrode potentials which were referenced to the onset potential in the cyclic voltammograms of Ag electrodeposition at MoSe2. When an electrode potential more negative than the onset potential was applied to MoSe2, continuous Ag bulk deposition occurred. Consistently, the scanning tunneling microscopy (STM) image showed Ag deposits which exhibit a growth mode between island and layer growth. In the STM images taken near the onset potential, a small amount of Ag, presumably with sub-monolayer level coverage, was thought to be deposited. This initial deposition occurred so as to make the MoSe2 surface smooth in the STM images. STM imaging was difficult in the electrode potential region positive of the onset potential because the applied bias voltage became small. However, the STM images acquired during Ag deposition after applying such an electrode potential exhibited a characteristic morphological change, from which we infer that those processes were related to the MoSe2 reaction with Ag.

Three-Dimensional Mesoscale Self-Assembly

Three-Dimensional Mesoscale Self-Assembly

In situ atomic force microscopy combined with a quartz-crystal microbalance study of Ag electrodeposition on Pt thin film

SO4, Na2SO4, and Ag2SO4 has beer observed by this novel instrument. Pt thin film is evaporated on the surface of the quartz-crystal resonator that oscillates at its resonance frequency. The mass change of the Pt film under the electrochemical reaction can be measured by detecting the frequency change of the quartz-crystal resonator. Large crystals were distributed on the Pt surface in clumps. The mass change measured by the microbalance technique agrees not only with that calculated from the integrated charge obtained by cyclic voltammetry but also that estimated from the topographical image. With this novel technique, the deposited substance on the Pt surface could be identified as Ag, not a complex mixture of platinum oxides.

The growth of the second underpotentially deposited silver layer on Pt(100)

The electrodeposition of Ag on Pt(100)-(1 × 1) in perchlorate electrolyte was studied by means of time-resolved in situ scanning tunnelling microscopy (STM) and cyclic voltammetry. One monolayer of Ag is deposited underpotentially (upd) ca. 500 mV positive of the Ag+/Ag equilibrium potential. Several millivolts positive of the equilibrium potential, a second well defined upd layer forms. Its growth was observed to proceed via island formation and coalescence. This process occurs in two separate stages that manifest themselves in voltammetric peaks as well as in the STM images.

Sequential electrodeposition of silver and bismuth on a gold surface

AbstractSequential electrodeposition of Ag and Bi from a single electrolyte on Au (111) was studied by means of voltammetry and ion scattering spectroscopy (ISS). Silver was electrodeposited first under diffusion control. Subsequently, bismuth was deposited under potential sweep conditions. Underpotential deposition of BI on the gold surface modified with five Ag monolayers takes place similar to the deposition on the Ag (111) electrode. The deposited Bi can be electrodissolved completely with Ag remaining on the surface. However, the voltammetric characteristics of this process are different from the one in the case of Bi on the (111) surface of a silver single crystal. The ISS data suggest that this might be due to intermixing at the Ag/Bi interface occurring subsequent to the formation of the initial Bi on Ag structure on Au(111).