Silver Coatings Research Articles

Electrochemical Formation of Functional Silver Coatings: Nanostructural Peculiarities

The microstructure of silver coatings electrodeposited from different types of baths without brightening agents had been studied. The principal formulations of baths were following: cyanide: 0.75M KAg(CN)2+1.5M KCN+0.2M KOH; dicyanoargentate-thiocyanate (DCAT): 0.75M KAg(CN)2+6M KCNS + 1M K2CO3; dicyanoargentate-borate-phosphate-carbonate (BPC): 0.75M KAg(CN)2+0.82M KH2PO4+ 0.41M H3BO3+0.15M K2CO3+0.69M KOH; thiocyanate: 0.75M AgNO3 + 6M KCNS. The values of grain size was evaluated based on the XRD examination and are in the range 60 nm (for coatings electrodeposited from cyanide baths at current densities (15-40 mA cm-2) to 100 nm (for thiocyanate and BPC baths). The values of lattice parameter and interplanar distance obtained for Ag coatings are higher than that obtained for metallurgically prepared silver. Regardless on the type of bath, the obtained coatings were polycrystalline and nanocrystalline. The coatings electrodeposited at low current densities (< 10 mA cm-2) are rather crystalline that evidently was confirmed by SEM examination of surface morphology.

Facile Preparation of Silver Nanoparticles and Application to Silver Coating Using Latent Reductant from a Silver Carbamate Complex

Facile Preparation of Silver Nanoparticles and Application to Silver Coating Using Latent Reductant from a Silver Carbamate Complex

Elliptical Hollow Fiber With Inner Silver Coating for Linearly Polarized Terahertz Transmission

Silver-coated elliptical hollow polycarbonate fibers for transmission of linearly polarized terahertz (THz) radiation are fabricated and characterized. A polarization ratio of 90% and a transmission loss of 0.79 dB/m at 0.65 THz are obtained for a 290-mm long fiber with major and minor inner radii of 2.42 and 1.18 mm. Modal birefringence in the order of 10-3-10-2 is predicted in the frequency region of 0.3-1.5 THz. We also investigate the transmission characteristics of deformed fibers and found that the fiber with a semicircle cross section could rotate the direction of a linear polarization.

Surface plasmon resonance based fiber optic pH sensor utilizing Ag/ITO/Al/hydrogel layers

The fabrication and characterization of a surface plasmon resonance based pH sensor using coatings of silver, ITO (In2O3:SnO2), aluminium and smart hydrogel layers over an unclad core of an optical fiber have been reported. The silver, aluminium and ITO layers were coated using a thermal evaporation technique, while the hydrogel layer was prepared using a dip-coating method. The sensor works on the principle of detecting changes in the refractive index of the hydrogel layer due to its swelling and shrinkage caused by changes in the pH of the fluid surrounding the hydrogel layer. The sensor utilizes a wavelength interrogation technique and operates in a particular window of low and high pH values. Increasing the pH value of the fluid causes swelling of the hydrogel layer, which decreases its refractive index and results in a shift of the resonance wavelength towards blue in the transmitted spectra. The thicknesses of the ITO and aluminium layers have been optimized to achieve the best performance of the sensor. The ITO layer increases the sensitivity while the aluminium layer increases the detection accuracy of the sensor. The proposed sensor possesses maximum sensitivity in comparison to the sensors reported in the literature. A negligible effect of ambient temperature in the range 25 °C to 45 °C on the performance of the sensor has been observed. The additional advantages of the sensor are short response time, low cost, probe miniaturization, probe re-usability and the capability of remote sensing.

Electrodeposition of Silver-Carbon Coatings with Low Contact Resistance and Wear Rate

Composite coatings of silver with self lubricating carbon nano particles were made by electrocodeposition. Ultrasonic disintegration during deposition was used to prevent coagulation of particles in the electrolyte in order to obtain a high and uniform particle incorporation. The effect of current density, particle concentration and rotation speed on particle incorporation was studied. Depending on the deposition parameters, a particle incorporation of 14 vol% could be obtained. The contact resistance of the coatings was measured during reciprocating fretting in order to study their behavior for electrical connector applications. It was found that there was a threshold value of 9 vol% carbon black particles in the coating above which the friction coefficient, the wear rate and the electrical properties drastically change. When there is less than 9 vol% of carbon black, the friction coefficient equals the friction coefficient of pure silver, the wear rate is large and the contact resistance shows spikes above 100 Ω during fretting. With more than 9 vol% of carbon black, a friction coefficient of 0.2 is obtained which is 4 times smaller than below the threshold value, the wear rate is lowered by a factor 14 and the contact resistance during fretting is below 1 mΩ without spikes.

Investigation on Post Treatment of Nano-Size Silver Conductive Film

This paper provides a novel post treatment method to achieve high conductivity of nano-size silver coatings. Based on the preparation of nano-size conductive ink and conductive circuit, the printed sample and the coated conductive film were treated by series concentrations of silver nitrate solution and hydrazine hydrate solution in this order. The samples were dipped in 1%~20% solutions of silver nitrate and hydrazine hydrate successively, to form the new conductive layer of Ag particles only. It was investigated that the relationship between the thickness of printed and coated layers on photo paper and final conductivity after dipped in two kinds of solutions in turn, which were printed from one to three times and coated by screw (6#). Atomic force microscopy (AFM) was used to characterize the morphologies of as printed and coated samples. The surface sheet resistance of sample was tested by four-probe tester. It was found that when the coated silver conductive ink samples were dipped in 2% silver nitrate solutions and 2% hydrazine hydrate solution at room temperature, the conductivity reaches 0.82Ω/□. The samples with thicker conductive film before dipping need solutions at lower concentration to get high conductivity. The roughness of samples after treatment falls down, as the concentrate of dipping solutions rising. It is therefore considered that the “dip in” method provides an efficient alternative to improve the conductivity of samples.

Biofilm formation on coated silicone tympanostomy tubes

ObjectivesTympanostomy tube (TT) surface modifications have been promoted as a means of reducing biofilm formation, otorrhea, and occlusion. The goal of this study was to determine if biofilm formation on silicone TTs could be prevented by commercially available surface coatings. MethodsSilicone TTs with and without polyvinylpyrrolidone (PVP) or/and silver oxide were exposed to human plasma and cultured with Pseudomonas aeruginosa or Staphylococcus aureus (22 TTs per group). After 4 days, antibiotics were added to kill planktonic bacteria. Biofilm formation was assessed by quantitative bacterial counts and scanning electron microscopy. ResultsPVP, silver, and PVP–silver coatings reduced P. aeruginosa biofilm formation relative to silicone by over 1 log (p<0.0001). PVP was superior to silver (p=0.04) and PVP–silver (p<0.0001). PVP and PVP–silver coatings increased S. aureus biofilm formation nominally (p=0.01 & 0.003). ConclusionPVP and silver coatings reduce P. aeruginosa biofilm formation on silicone TTs. Combining PVP and silver coatings does not further improve biofilm resistance. TT surface coatings warrant further study through clinical trials.

Investigation of Residual Stresses and some Elastic Properties of Brush-Plated Gold and Silver Galvanic Coatings

Nickel-hardened gold and silver coatings were brush-plated from a commercial SIFCO Dalic Solution (Gold Hard Alloy), Code SPS 5370, and Silver Hard Heavy Build, Code SPS 3080, on unclosed thin-walled copper ring substrates. To determine residual stresses, the conventional curvature method (common among the electrodeposition methods) was applied, where the substrate was coated with certain thickness and then the slit increment (bending deflection) of the substrate was measured as an experimental parameter. Residual stresses on gold coatings were also determined by X-ray diffraction (XRD) based on the sin2 method. The values of residual stresses determined by the curvature method and by the XRD technique were comparable. Relaxation of residual stresses was observed. An equation for approximation of the change of residual stresses was applied assuming that the dependence of residual stresses on relaxation time is linear-fractional. The surface morphology and microstructure of the coatings was studied by means of scanning electron microscopy (SEM). The magnitudes of the modulus of elasticity and of the nanohardness of the coatings were obtained by instrumented indentation.

Ultrasensitive strain sensors made from metal-coated carbon nanofiller/epoxy composites

A set of resistance-type strain sensors has been fabricated from metal-coated carbon nanofiller (CNF)/epoxy composites. Two nanofillers, i.e., multi-walled carbon nanotubes and vapor growth carbon fibers (VGCFs) with nickel, copper and silver coatings were used. The ultrahigh strain sensitivity was observed in these novel sensors as compared to the sensors made from the CNFs without metal-coating, and conventional strain gauges. In terms of gauge factor, the sensor made of VGCFs with silver coating is estimated to be 155, which is around 80 times higher than that in a metal-foil strain gauge. The possible mechanism responsible for the high sensitivity and its dependence with the networks of the CNFs with and without metal-coating and the geometries of the CNFs were thoroughly investigated.

Corrosion Properties of Electrodeposited Thin Coatings of Polycrystalline Silver

For polycrystalline silver coatings electrodeposited from electrolytes based on different Ag(I) coordination compounds such as [Ag(CN)2]−, [Ag(CN)3]2−, [Ag(SCN)4]3−, [Ag(CN)2(SCN)2]3−, and [Ag(SO3)2]3− at current densities of 2.5 to 75 mA⋅cm−2, we have established a relationship between the corrosion parameters of these deposits determined by the methods of electrochemical impedance spectroscopy and voltammetry and their crystalline roughness (uniformity at the nanolevel). We have also established that, with decrease in the surface roughness of an electrolytic silver deposit (R a ∼ 40–80 nm), the corrosion resistance increases. In this case, as the surface roughness increases by 20 nm, the corrosion resistance is halved, and the resistance to a corrosive medium decreases noticeably, though the deposit is uniformly distributed over the thickness on the microprofile. For silver coatings with the same true surface area, the larger the mean roughness R a , the larger the corrosion rate, independently of the texture of the deposit and deposition conditions.

Electrochemical Formation of Functional Silver Coatings: Nanostructural Peculiarities

not Available.

Oxygen Reduction Activity of Carbon-Conductive Polymer-Silver Composite Electrodes

Preparation, characterization, and electrochemical activity of a novel three-component composite electrode consisting of a carbon substrate with conductive polymer and silver coatings are described here. The composite electrode concept is described and the composite electrode is evaluated as a cathode for non-aqueous oxygen reduction. Improvement of cathode oxygen reduction activity will increase current capability and power output of metal air batteries, facilitating future development of small, lightweight, long-life power sources.

Surface Plasmon Mapping of Dumbbell-Shaped Gold Nanorods: The Effect of Silver Coating

We report on the identification of surface plasmons in individual gold dumbbell-shaped nanoparticles (AuDBs), as well as AuDBs coated with silver. We use spatially resolved electron energy-loss spectroscopy in a scanning electron microscope, which allows us to map plasmon-energy and intensity spatial distributions. Two dominant plasmon resonances are experimentally resolved in both AuDBs and silver-coated AuDBs. The intensity of these features is peaked either at the tips or at the sides of the nanoparticles. We present boundary element method simulations in good agreement with the experiment, allowing us to elucidate the nature of such modes. While the lower-energy, tip-focused plasmon is of longitudinal character for all dumbbells under consideration, the second side-bound plasmon has a more involved symmetry, starting as a longitudinal quadrupole in homogeneous AuDBs and picking up transversal components when silver coating is added. The longitudinal dipolar mode energy is found to blue-shift upon coating with silver. We find that the substrate produces sizable shifts in the plasmons of silver-coated AuDBs. Our analysis portraits a complex plasmonic scenario in metal nanoparticles coated with silver, including a transition from the original homogeneous gold dumbbell plasmons to the modes of homogeneous silver rods. We believe that these findings can have potential application to plasmon engineering.

Optimized Electroless Silver Coating for Optical and Plasmonic Applications

Electroless metal deposition is a simple and convenient technique to fabricate metallic films and to provide isotropic metal functionalization of 3D structures with complex geometries. In this work, we describe the synthesis of silver coatings by means of a modified Tollens reaction and their use as optical coating. The chemical composition of the metallization bath is here addressed to optimize the metal coating deposition. The synthesis parameters have been tailored in order to deposit very smooth films which were characterized by scanning electron microscopy, atomic force microscopy, and optical spectroscopy. 2D diffraction gratings and sinusoidal plasmonic gratings were produced with the proposed method. Optical characterization confirmed the plasmonic activities of the resultant structures, proving the efficiency of the described method for optical applications. Thermal annealing was found to improve the surface roughness of the coating and therefore the optical properties of the plasmonic gratings.

Antimicrobial particulate silver coatings on stainless steel implants for fracture management

We have used particulate silver coating on stainless steel to prevent in vivo bacterial infection. Stainless steel is commonly used as an implant material for fracture management. The antimicrobial use of silver has been well documented and studied, therefore the novelty of this research is the use of a particulate coating as well as facing the real world challenges of a fracture repair implant. The variable parameters for applying the coating were time of deposition, silver solution concentration, voltage applied, heat treatment temperature between 400 and 500°C and time. The resultant coating is shown to be non-toxic to human osteoblasts using an MTT assay for proliferation and SEM images for morphology. In vitro silver release studies of various treatments were done using simulated body fluid. The bactericidal effects were tested by challenging the coatings with Pseudomonas aeruginosa in a bioreactor and compared against uncoated stainless steel. A 13-fold reduction in bacteria was observed at 24h and proved to be statistically significant.

Ultrathin, Flexible, and Transparent Polymer Multilayer Composites for the Protection of Silver Surfaces

Silver coatings at the nanoscale became of high interest for the integration of electronic functionalities on all kinds of objects for daily use. In these thin coatings, corrosion is a big problem as it destroys these thin layers and leads to a loss of conductivity due to missing bulk material. For protection of thin silver coatings against H(2)S induced corrosion, we developed nanocoatings based on the covalent layer-by-layer technique. We prepared composites by subsequent deposition of polyamines like polyethylenimine (PEI) or polyallylamine (PAAm) and polyanhydrides like poly(maleic anhydride-alt-methyl vinyl ether) (Gantrez) or poly(styrene-co-maleic anhydride) (PSMA). For the tuning of the hydrophobicity, the layers were terminated by reaction with palmitoylic acid derivatives. Reflectivity measurements, contact angle measurements, and AFM measurements were made to investigate how the coatings affect the surface properties. All coatings show a lower reflectivity below 450 nm compared to pure silver, depending on the number of layers deposited. The addition of a palmitoylic derivative to the surface increases the hydrophobicity, but only in case of the Gantrez-PVAm-composite, this approach leads to real hydrophobicity, reaching contact angles above 90°. AFM measurements show a decrease of the roughness of the polymer coated surfaces compared to the pure metal surfaces. Corrosion tests in a H(2)S atmosphere show a good protective effect of the palmitoyl-terminated composites. Martindale abrasion tests on coated textiles reveal a good stability of the prepared polymer composites.

Protection and functionalisation of silver as an optical sensing platform for highly sensitive SPR based analysis

Silver thin films are well known as the most sensitive material for surface plasmon resonance (SPR) based analysis. However, the use of silver for this purpose is limited by three main issues, namely poor adhesion to plastic substrates, chemical instability in both air and aqueous environments and hence the difficulty in functionalizing the silver coated substrate for immobilizing biomolecular ligands by conventional liquid phase methods. In this work, we have successfully addressed these problems using gas-phase coating processes. We demonstrate highly adherent sputter-deposited silver coatings on low cost polymer substrates using a sputter-deposited thin gold adhesion layer. The problems of chemical instability and functionalisation have been addressed by using the gas phase process of plasma enhanced chemical vapour deposition (PECVD) to deposit thin films with a base SiO(x)C(y)H(z) layer (using tetraethyl orthosilicate precursor) functionalised with carboxylic acid (from sequential deposition with acrylic acid precursor). The resultant coating serves as a protective layer against degradation of the optical properties of silver under long term storage and use in ambient conditions. The reactive carboxyl functionality is used for the covalent immobilization of biomolecules. The successful stabilisation and functionalization of silver films on plastic sensor chips is demonstrated by mouse IgG immunoassays. The expected superior performance of the silver thin films over gold thin films for SPR analysis is demonstrated.

Planar SERS nanostructures with stochastic silver ring morphology for biosensor chips

Surface-enhanced Raman spectroscopy (SERS) of living cells has rapidly become a powerful trend in biomedical diagnostics. It is a common belief that highly ordered, artificially engineered substrates are the best future decision in this field. This paper, however, describes an alternative successful solution, a new effortless chemical approach to the design of nanostructured silver and heterometallic continuous coatings with a stochastic “coffee ring” morphology. The coatings are formed from an ultrasonic mist of aqueous diamminesilver hydroxide, free of reducing agents and nonvolatile pollutants, under mild conditions, at about 200–270 °C in air. They consist of 30–100 micrometer wide and 100–400 nm high silver rings composed, in turn, of a porous silver matrix with 10–50 nm silver grains decorating the sponge. This hierarchic structure originates from ultrasonic droplet evaporation, contact-line motion, silver(I) oxide decomposition and evolution of a growing ensemble of silver rings. The fabricated substrates are a remarkable example of a new scalable and low cost material suitable for SERS analyses of living cells. They evoke no hemolysis and reduce erythrocyte lateral mobility due to suitable “coffee ring” sizes and a tight contact with the silver nanostructure. A high SERS enhancement, characteristic of pure silver rings, made it possible to record Raman scattering spectra from submembrane hemoglobin in its natural cellular environment inside single living erythrocytes, thus making the substrates promising for various biosensor chips.

High current density electrodeposition from silver complex ionic liquids

Liquid metal salts are electrolytes with the highest possible metal concentration for electrodeposition, because the metal ion is an integral part of the solvent. This paper introduces the new ionic silver complexes [Ag(MeCN)(4)](2)[Ag(Tf(2)N)(3)], [Ag(MeCN)][Tf(2)N] and [Ag(EtIm)(2)][Tf(2)N], where MeCN stands for acetonitrile, EtIm for 1-ethylimidazole and Tf(2)N is bis(trifluoromethylsulfonyl)imide. These complexes have been characterized by differential scanning calorimetry, single crystal X-ray crystallography, thermogravimetrical analysis, Raman spectroscopy and cyclic voltammetry. [Ag(MeCN)(4)](2)[Ag(Tf(2)N)(3)] is a room temperature ionic liquid. Smooth silver layers of good quality could be deposited from it, at current densities of up to 25 A dm(-2) in unstirred solutions. [Ag(EtIm)(2)][Tf(2)N] melts at 65 °C and can be used as an electrolyte for silver deposition above this temperature. [Ag(MeCN)][Tf(2)N] has a melting point that is too high to be useful in electrodeposition. Addition of thiourea or 1H-benzotriazole to the electrolyte decreased the surface roughness of the silver coatings. The morphology of the metal layers was investigated by atomic force microscopy (AFM). Adsorption of 1H-benzotriazole on the silver metal surface has been proven by Raman spectroscopy. This work shows the usefulness of additives in improving the quality of metal films electrodeposited from ionic liquids.

Typical defects on automobile windscreens at the interfaces of silver coatings, copper filaments and glasses

Typical defects on automobile windscreens at the interfaces of silver coatings, copper filaments and glasses