Pattern recognition in oxides thin-film electrodeposition: Printed circuits

A novel method for a low-voltage electrodeposition of insulating oxide sol–gel thin films on complex conducting patterns is described. By this method gold meshes and printed chips were selectively coated with titania and zirconia thin films. This method solves a classical problem in the thin-films world: dip-coating, spin-coating, spraying without masks—all cannot be used for selective coating of a complex conductive pattern, because these methods do not differentiate between conducting vs non-conducting areas. The newly developed method provides an electrochemical pattern recognition, which solves this problem.     

Electrochemical Deposition onto Self‐Assembled Monolayers: New Insights into Micro‐ and Nanofabrication

Pattern transfer with high resolution is a frontier topic in the emerging field of nanotechnologies. Electrochemical molding is a possible route for nanopatterning metal, alloys and oxide surfaces with high resolution in a simple and inexpensive way. This method involves electrodeposition onto a conducting master covered by a self‐assembled alkanethiolate monolayer (SAMs). This molecular film enables direct surface–relief pattern transfer from the conducting master to the inner face of the electrodeposit, and also allows an easy release of the electrodeposited film due their excellent anti‐adherent properties. Replicas of the original conductive master can be also obtained by a simple two‐step procedure. SAM quality and stability under electrodeposition conditions combined with the formation of smooth electrodeposits are crucial to obtain high‐quality pattern transfer with sub‐50 nm resolution.     

Density Functional Theory Study of Pd Aggregation on a Pyridine-Terminated Self-Assembled Monolayer

By using density functional theory calculations, the initial steps towards Pd metal cluster formation on a pyridine-terminated self-assembled monolayer (SAM) consisting of 3-(4-(pyridine-4-yl)phenyl)propane-1-thiol on an Au(1 1 1) surface are investigated. Theoretical modelling allows the investigation of structural details of the SAM surface and the metal/SAM interface at the atomic level, which is essential for elucidating the nature of Pd–SAM and Pd–Pd interactions at the liquid/solid interface and gaining insight into the mechanism of metal nucleation in the initial stage of electrodeposition. The structural flexibility of SAM molecules was studied first and the most stable conformation was identified, planar molecules in a herringbone packing, as the model for Pd adsorption. Two binding sites are found for Pd atoms on the pyridine end group of the SAM. The strong interaction between Pd atoms and pyridines illustrates the importance of SAM functionalisation in the metal nucleation process. Consistent with an energetic driving force of approximately −0.3 eV per Pd atom towards Pd aggregation suggested by static calculations, a spontaneous Pd dimerisation is observed in ab initio molecular dynamic studies of the system. Nudged elastic band calculations suggest a potential route with a low energy barrier of 0.10 eV for the Pd atom diffusion and then dimerisation on top of the SAM layer.     

Kinetics of electrodeposition of Ni–ZrO<Subscript>2</Subscript> nanocomposite coatings from methanesulfonate electrolytes

Regularities of incorporation of zirconia nanoparticles into a nickel matrix in the course of electrodeposition of Ni–ZrO₂ coatings from methanesulfonate electrolyte are established. The content of the dispersed phase in coatings grows at an increase in its concentration in electrolyte. Moreover, nanocomposites containing a greater amount of zirconia are deposited from the methanesulfonate electrolyte as compared to sulfate electrolyte. This is explained by the greater partial concentration of ZrO₂ in the solution due to enhanced aggregative stability of the dispersed phase in methanesulfonate electrolyte. The mechanism of formation of the composite coating is considered that is based on the concept of particle incorporation into the metal matrix due to the different rates of metal electrodeposition on the electrode surface free of nonmetallic particles and on the electrode surface conditionally occupied by them. A physically substantiated mathematical model is suggested that describes the kinetics of formation of the composite coating that agrees well with the experimental data.     

Understanding the copper underpotential deposition process at strained gold surface

Copper underpotential deposition (UPD) on a gold surface is investigated by cyclic voltammetry coupled with in situ cyclic strain to understand the strain-modulated electrodeposition. Our work emphasizes quantification of an electrocapillary coupling coefficient ς, which relates the response of Cu electrodeposition potential, E, to applied strain, ε. The different responses to the strain are observed at two Cu UPD stages. The data indicate that tensile strain could enhance the formation of a Cu monolayer on the Au surface. The typical electrodeposition process could be modulated by an external mechanical strain.     

Initial stages of Ni–P electrodeposition: growth morphology and composition of deposits

The evolution of growth morphology and composition of deposits during the initial stages of Ni–P electrodeposition is studied using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). Combined electrochemical and surface analytical measurements show that the deposition process starts at relatively low cathodic potentials by instantaneous formation and growth of hemispherical centres. The phosphorus content of deposits in the initial deposition stages is found to increase gradually with the deposition time. Additional electrochemical and XPS measurements, carried out on Ni substrates under same polarisation conditions in a Ni²⁺ ion free electrolyte solution, show the occurrence of a time dependent Ni–P surface alloy formation indicating a strong Ni–P interaction. It is suggested that the very early stages of Ni–P electrodeposition involve a primary instantaneous nucleation of Ni followed by a Ni–P alloy formation induced by the strong Ni–P interaction. AFM images show that in advanced deposition stages the coalescence of growing Ni–P centres leads to formation of larger growth mounds. The evolution of the resulting surface roughness is analysed on the basis of the so-called dynamic scaling concept. The estimated values for the roughness exponent and the growth exponent (α=1.07±0.05 and β=0.28±0.05) correspond to a model involving a smoothing of the growing surface driven by surface diffusion.     

Scanning electrochemical microscopy and video microscopy investigations of Tiron-mediated polypyrrole nucleation on AA2024-T3

Scanning electrochemical microscopy (SECM) and video microscopy have been used to examine the mediated electrodeposition of polypyrrole on AA2024-T3. Of particular interest is the role of surface heterogeneity (namely, copper-rich secondary phase particles) on electrodeposition mediated by 4,5-dihydroxy-1,3-benzenedisulfonic acid (Tiron). SECM shows that polymer nucleation occurs exclusively on the aluminum matrix of the alloy. Video microscopy shows this to be true on a model alloy (a pure Al substrate with an embedded Cu wire) as well, and also suggests that polymer growth is directional toward the copper-rich sites in the absence of sulfate in the deposition solution. A model is presented in which polymer deposition on the copper-rich sites is inhibited either by CuSO₄-induced passivation or by the loss of mediator due to Cu–Tiron complex formation.     

Pattern formation during electrodeposition of alloys

The increase in the content of the alloying element in electrodeposited alloys reflects in the changes of their phase composition, when the saturation limit of the lattice of the basic metal is reached. At higher percentages, the excess amount of the alloying element forms one or more new, richer in this element phases. The coatings become multi-phase, heterogeneous and their physical–mechanical properties change. Sometimes an ordered distribution of the different phases of the heterogeneous alloy coating could be observed. Examples of self-organization phenomena during electrodeposition of different alloy systems, such as Ag-Sb, Ag-Bi, Ag-In, Ag-Sn, Ag-Cd, Cu-Sb and In-Co, resulting in pattern formation and formation of spatio-temporal structures on the surface of the obtained coatings are presented and compared. Instabilities resulting in potential or current oscillations are registered in most of the investigated systems. The phase composition of the alloy coatings and especially of the observed pattern is determined and some similarities in the structure of the phases forming the pattern are registered. The pattern formation is registered on the cathode not only in cyanide silver alloys electrolytes, but also during deposition of other alloy systems in acidic electrolytes like Cu-Sb and In-Co. The effect of the natural convection in non-agitated electrolytes on the pattern formation is discussed. The possibility of formation of periodic structured coatings without applying external electrical pulses which could result in appropriate modification of some properties of the electrodeposited alloys is demonstrated. The hypothesis that similar pattern formation could be observed in agitated electrolytes at different hydrodynamic and electrolysis conditions, when the same percentage or the same phase composition of the alloy is reached was examined for Ag-Cd, In-Co and Ag-Sb alloys in jet-plating experiments.     

First evidence of stable P–N bonds after anodic treatment of InP in liquid ammonia: A new III–V material passivation route

This work reports – for the first time – the electrochemical anodic passivation of InP in a relevant nonaqueous solvent: liquid ammonia. A new route of InP passivation was clearly established by the coupling approach electrochemistry-XPS analyses. A specific P–N surface bond chemistry was evidenced and associated to a phosphinimidic amide-like electrodeposition. The efficiency of this new passivation route was supported by the high stability of the complete covering thin film since no air ageing effect is detected on InP surface for both types. The phosphazene surface termination offers new possibilities for further high-speed optoelectronic applications and functional molecular grafting.     

The Mechanical Properties and Rate of Electrodeposition of Co−W Alloys from a Boron−Gluconate Bath: Impact of Anodic Processes

The effects the anode material has on the rate of electrodeposition (current efficiency) and microhardness of Co–W alloys deposited from a boron–gluconate bath are studied in a broad range of bath ages Q (A h/L). We use nonconsumable (platinum and graphite) and consumable (tungsten, cobalt–tungsten) anodes. With the cobalt–tungsten double anode, the total concentration of W and Co species in the bath is maintained constant during electrodeposition. We find that, as Q increases, the anodic processes have a significant impact on both the rate of deposition and microhardness of the prepared coatings. Departing from the mechanism of induced codeposition in which the first stage is the formation of an intermediate species of the metal component that induces codeposition (Co), here we propose a model that takes into account the effects associated with the anodic processes. In this model, along with reduction at the cathode to give an alloy, this metal component can undergo oxidation at the anode.

     

Grayscale surface patterning using electrophoretic motion through a heterogeneous hydrogel material

Chemical surface patterning can be an incredibly powerful tool in a variety of applications, as it enables precise spatial control over surface properties. But the equipment required to create functional surface patterns—especially “grayscale” patterns where independent control over species placement and density are needed—is often expensive and inaccessible. In this work, we leveraged equipment and methods readily available to many research labs, namely 3D printing and electroblotting, to generate controlled grayscale surface patterns. Three-dimensional-printed molds were used to cast polyacrylamide hydrogels with regions of variable polymer density; regions of low polymer density within the hydrogels served as reservoirs for proteins that were later driven onto a target surface using electrophoresis. This mechanism was used to deposit grayscale patterns of fluorescently labeled proteins, and the fluorescent intensity of these patterns was measured and compared to a theoretical analysis of the deposition mechanism.     

Direct electrodeposition of aluminium nano-rods

Electrodeposition of aluminium within an alumina nano-structured template, for use as high surface area current collectors in Li-ion microbatteries, was investigated. The aluminium electrodeposition was carried out in the ionic liquid 1-ethyl-3-methylimidazolium chloride:aluminium chloride (1:2 ratio). First the aluminium electrodeposition process was confirmed by combined cyclic voltammetry and electrochemical quartz crystal microbalance measurements. Then, aluminium was electrodeposited under pulsed-potential conditions within ordered alumina membranes. A careful removal of the alumina template unveiled free standing arrays of aluminium nano-rods. The nano-columns shape and dimensions are directly related to the template dimensions. To our knowledge, this is the first time that direct electrodeposition of aluminium nano-pillars onto an aluminium substrate is reported.     

Uranium electrodeposition for alpha spectrometric source preparation

In this paper a simple method was used to design and set up an electrodeposition device for uranium source preparation for alpha spectrometry measurements. The aim of this work is to find the optimal parameters to be used to achieve uranium alpha sources with good spectral properties and maximum yield of the electrodeposition process. Samples with specific uranium activity were prepared from aqueous solution of uranyl nitrate hexahydrate (UO₂ (NO₃)₂·6H₂O). A series of preliminary experiments was conducted to establish the main parameters that have a significant influence on the deposition efficiency. Among these, the electrodeposition time was studied and the optimum time was found to be 1 h, in the case of our home-made deposition cell. It was also shown that a current of 1,500 mA, plating time of 60 min and pH range of 2–2.2 are the best conditions for deposition of uranium. The alpha spectrometry results show a good spectral resolution for the uranium sources obtained by the electrodeposition using the optimal parameters.     

Directed electrodeposition of polymer films using spatially controllable electric field gradients

We report a method for the directed electrodeposition of polymer films in various patterns using spatially controllable electric field gradients. One- and two- dimensional surface electric field gradients were produced by applying different potential values at spatially distinct locations on an electrode surface. Variations in the resulting local electrochemical potentials were used to spatially manipulate the rate of electrodeposition of several polymers. By controlling the electric field gradient in the presence of sequentially varying deposition solutions, complex polymer patterns could be produced. One-dimensional structures consisting of alternating bands of polyaniline and either poly(phenylene) oxide or poly(aminophenylene) oxide were produced, as well as more complex two-dimensional structures. Film characterization was achieved through optical imaging, UV-vis spectroscopy, and ellipsometry. Results indicate that this directed deposition technique is a simple strategy to create complex, millimeter-sized surface patterns of electrodeposited materials.     

Silver electrodeposition from water–acetonitrile mixed solvents. Part III—an in situ investigation by optical second harmonic generation spectroscopy

In this work, we report an investigation based on silver electrodeposition from water–acetonitrile mixed solvents onto a polycrystalline Au electrode, based on in situ optical second harmonic generation (SHG) spectroscopy. This paper is the last one of a series attacking the same topic by cyclic voltammetry and potentiostatic current transients (Mele et al., J Solid State Electrochem in press, 1) and in situ surface-enhanced Raman scattering (Mele et al., J Solid State Electrochem in press, 2). SHG intensity transients following the application of potentiostatic cathodic steps have been measured in order to obtain detailed information on the formation of Ag clusters and nuclei during the electrodeposition process. Our SHG data have been rationalised in terms of a simple optical model accounting for SHG enhancement brought about by Ag cluster formation.     

Morphological behavior of spherically granulated hydrated zirconium dioxide during its chemical and hydrothermal treatments

Hydrated zirconium dioxide samples were synthesized via original sol–gel route by two-step neutralization of zirconium oxychloride. Spherical granules of zirconia materials were prepared using a well-known “oil-drop” method. By the use of low temperature nitrogen adsorption, it is shown that surface fractal dimension of synthesized xerogels strongly depends on synthesis conditions, chemical and hydrothermal treatments. It is established that the change of synthesis conditions allows to obtain zirconium containing materials with developed porous structure: BET surface area—250–450 m²/g, pore diameter—2.0–4.2 nm, surface fractal dimension—2.28–2.63. It is shown that surface fractal dimension is an important parameter allowing to control the final properties of synthesized material and to determine the reasons of non-reproducibility of adsorptive, catalytic and other physical and chemical properties of zirconium containing oxides from synthesis to synthesis.     

Electrochemical enantiorecognition of tryptophan enantiomers based on graphene quantum dots–chitosan composite film

A graphene quantum dots (GQDs)–chitosan (CS) composite film was prepared via successive electrodeposition of GQDs and CS on the surface of a glassy carbon electrode (GCE). The strong interactions between GQDs and CS resulted in the formation of a regular and uniform film, which can be applied in the electrochemical chiral recognition of tryptophan (Trp) enantiomers. CS in the composite film provides a chiral microenvironment, meanwhile, GQDs can amplify the electrochemical signals and improve the recognition efficiency. Due to the synergetic effect of GQDs and CS, chiral recognition of Trp enantiomers is achieved successfully. Compared with previous reports utilizing GQDs in photoluminescent research, this work opens a new avenue for broadening the applications of GQDs in the electrochemically chiral sensors.     

Copper underpotential deposition at gold surfaces in contact with a deep eutectic solvent: New insights

The electrodeposition of copper on a polycrystalline gold electrode and on Au(hkl) single crystals was investigated in a deep eutectic solvent (DES). The DES employed consisted of a mixture of choline chloride and urea (1:2). The Au(hkl)/DES interface was studied using cyclic voltammetry in the capacitive region. The blank voltammograms showed characteristic features, not previously reported, that demonstrate the surface sensitivity of this solvent. Copper electrodeposition was then studied and it was found that this takes place through the formation of an underpotential deposition (UPD) adlayer, demonstrating the surface sensitivity of this process. Voltammetric profiles showed similarities with those obtained in aqueous solutions containing chloride, suggesting that the copper UPD in this DES is strongly influenced by the presence of chloride.     

CaP/壳聚糖复合膜层的电化学共沉积研究

用电化学共沉积方法在医用钛合金表面成功制备了CaP/壳聚糖复合膜层,并用XRD,SEM,FTIR漫反射光谱和XPS等对复合膜层化学组成及结构进行表征.结果表明,加入壳聚糖可使钙磷沉积层结构发生显著变化,将壳聚糖掺入钙磷沉积层,形成CaP/壳聚糖复合物和杂化物.力学实验表明,在钛基底表面未进行表面预处理条件下,CaP/壳聚糖复合膜层与钛基底的结合力高达2.6MPa,比单一CaP电化学沉积层与基底的结合力提高约4倍.文中还对壳聚糖参与表面电沉积反应机理进行了讨论.