Electroless Deposition Of Silver Research Articles

Site-Selective Catalytic Surface Activation via Aerosol Nanoparticles for Use in Metal Micropatterning

There is great interest in the fabrication of micro- and nanopatterned metallic structures on substrates for a wide range of electronic, photonic, and magnetic devices. One of the most widely used techniques is the electroless deposition (ELD) of metal, which requires the surface activation of the substrates with a metal catalyst. This paper introduces a method of catalytic surface activation by producing platinum aerosol nanoparticles via spark generation and then thermophoretically depositing the particles onto a flexible polyimide (PI) substrate through the pattern hole of a mask. After annealing, the catalytically activated substrate is placed into a solution for electroless silver deposition. The silver is then formed only on the activated regions of the substrate. Silver line patterns having a width of 18 microm and a height of 1 microm are created with the ability to be effectively reproduced. The average value of the resistivities is approximately 6.8 mu Omega.cm, which is almost comparable to the theoretical resistivity of bulk silver (1.6 mu Omega.cm). Other silver micropatterns containing square dot array, line, line array, Y-branched line, and tapered line using different pattern masks are also demonstrated.

Catalytic Activation of Activated Carbon Fibers via Palladium Aerosol Nanoparticles for Use in Electroless Silver Deposition

A method of catalytic activation with palladium aerosol nanoparticles produced by spark generation was introduced. These catalytic particles were deposited onto the surfaces of activated carbon fibers (ACFs). After thermal curing, the catalytically activated ACFs were placed into a solution for electroless deposition (ELD) of silver. Homogeneous silver coatings on ACFs were achieved under various activation intensities and ELD times, and the results were compared to those obtained with a conventional “two-step” activation. Morphological, chemical, and textural properties of both catalytically activated ACFs and electroless silver deposited ACFs were characterized. When the activation intensity increased from 0.23 to 4.25 mg/g (palladium/ACFs) for an ELD time of 10 min, our aerosol activation increased the silver deposition from 7.1 to 13.2 mg/g (silver/ACFs) and the average size of the silver particles from 4.9 to 38.8 nm. However, the surface area and pore volume of the ACFs decreased from 1382 to 1286 m...

Antimicrobial Effect of Silver Particles on Bacterial Contamination of Activated Carbon Fibers

Even though activated carbon fiber (ACF) filters have been widely used in air cleaning for the removal of hazardous gaseous pollutants, because of their extended surface area and high adsorption capacity, bacteria may breed on the ACF filters as a result of their good biocompatibility; ACF filters can themselves become a source of bioaerosols. In this study, silver particles were coated onto an ACF filter, using an electroless deposition method and their efficacy for bioaerosol removal was tested. First, various surface analyses, including scanning electron microscopy, inductively coupled plasma and X-ray diffraction were carried out to characterize the prepared ACF filters. Filtration and antimicrobial tests were then performed on the filters. The results showed that the silver-deposited ACF filters were effective for the removal of bioaerosols by inhibition of the survival of microorganisms, whereas pristine ACF filters were not. Two bacteria, Bacillus subtilis and Escherichia coli, were completely inhibited within 10 and 60 min, respectively. Electroless silver deposition did not influence the physical characteristics of ACF filters such as pressure drop and filtration efficiency. The gas adsorptive ability of the silver-deposited ACF filter, as represented by the micropore specific surface area, decreased by about 20% compared to the pristine filter because of the blockage of the ACF micropores by silver particles. Therefore, the amount of silver particles on the ACF filters needs to be optimized to avoid excessive reduction of their adsorptive characteristics and to show effective antimicrobial activity.

Assessment of roughness and chemical modification in determining the hydrophobic properties of metals

“Etch and coat” methods, potentially useful for large scale production of superhydrophobic surfaces on metals, have been extended by introduction of a thin 20 nm Au interlayer which allowed thiol surface modifiers to be investigated. Fe, Ti and Zn surfaces modified in this way with a polyfluorothiol generally had lower contact angles, θ, than their silane modified equivalents but were more uniform and reproducible. The higher θ values for silanes appear to be associated with an increased effective roughness that is not seen in the thiol coatings, which follow the underlying surface. For Fe, Ti and Zn, θ increased to a maximum with etching time but then decreased significantly. Electron microscopy of samples etched for long times showed fewer grain boundaries, suggesting that the loss of hydrophobicity was related to reduced roughness. This was confirmed through quantitative measurements of roughness parameters which were directly correlated with the observed contact angles through the Wenzel equation. The observation of this behaviour for 3 different metals suggests it is a general effect and the assumption that increased etch times will give increased roughness is incorrect. Although etching, Au coating and thiol modification did not provide sufficient roughness for superhydrophobicity, electrodeposition of a Cu layer onto the metal substrates followed by electroless deposition of silver gave uniform surfaces with very high contact angles (up to θ = 168.9°) and low roll-off angles (α < 1°). This method is sufficiently simple and inexpensive to be suitable for application on industrial scales, for example in marine or aeronautical engineering.

Reflective and conductive surface‐silvered polyimide films prepared by surface graft copolymerization and electroless plating

AbstractArgon plasma‐pretreated polyimide (PI) films were subjected to UV‐induced surface graft copolymerization with 4‐vinylpyridine(4VP) under atmospheric conditions. Electroless plating of silver was carried out effectively on the 4VP graft copolymerized PI (PI‐g‐P4VP) surface after PdCl2 activation and in the absence of SnCl2 sensitization (the Sn‐free process). The surface compositions of the modified PI films were studied by X‐ray photoelectron spectroscopy (XPS). XPS results showed that the PI‐g‐P4VP surface is ready for electroless deposition of silver via the Sn‐free process. The grafted 4VP layer with well‐preserved pyridine groups was used not only as the chemisorption sites for the palladium complexes (without the need for prior sensitization by SnCl2) during the electroless plating of silver, but also as an adhesion promotion layer for the electrolessly deposited silver. The silver metallized PI films show high reflectivity and conductivity with a surface resistance of 1.5 Ω and a reflectivity of 91.3%, respectively. Copyright © 2007 John Wiley &amp; Sons, Ltd.

Homogeneous Detection of Nucleic Acids Based upon the Light Scattering Properties of Silver-Coated Nanoparticle Probes

Herein we report the development of a simple, rapid, homogeneous, and sensitive detection system for DNA based on the scattering properties of silver-amplified gold nanoparticle probes. The assay uses DNA-functionalized magnetic particle probes that act as scavengers for target DNA, which can be collected via a magnetic field. Once the DNA targets are isolated from the initial sample, they are sandwiched via hybridization by a second set of probes. The latter probes are 13-nm gold nanoparticles modified with a different target complementary DNA. Excess probes are removed through repetitive washing steps. The gold particles are dispersed in solution by dehybridization, corresponding to an assumed 1:1 ratio with the target DNA. Electroless deposition of silver on the surface of the gold probes results in particle growth, which increases their scattering efficiency with time. The scattering efficiency and the extinction signatures of the particle sizes are monitored as a function of time and correlated with target concentration. The limit of detection for this novel assay was determined to be 10 fM.

Ellipsometric study of percolation in electroless deposited silver films

Using spectroscopic ellipsometry in the visible and near-infrared spectral range we investigate the optical properties of a growing silver film starting from predeposited gold nanoparticles. The effective pseudodielectric functions, obtained by direct inversion of the ellipsometry spectra, reveal a surface plasmon resonance for the nanoparticulate films. Upon prolonged electroless silver deposition, the resonance shifts to lower energies. The redshift is due the longer electron mean free path in larger silver structures and is analyzed by describing the optical response of the developing silver film in terms of a Lorentz line shape. The position of the oscillator, i.e., its resonance energy, is discussed in relation to the transition from isolated nanoparticles to an interconnected, eventually continuous metal film. This transition is also observed in the optical conductivity which exhibits an abrupt, stepwise increase at the same energy where the aforementioned resonance energy becomes zero. For longer deposition times, the optical spectra can be described in terms of a Drude-like free-electron metal. The development of the Drude–Lorentz parameters, i.e., the relaxation time and electron density, are compared to values for bulk silver; the latter were obtained from an optical measurement on a thick bulk silver sample. The saturation values for the relaxation time and thus the conductivity amount to approximately 40% of the bulk value, in agreement with direct current conductivity measurements on these films.

&lt;I&gt;In Situ&lt;/I&gt; Microscopic Observations of Magnetic Field Effects on the Growth of Silver Dendrites

The effect of magnetic fields on electroless silver deposition was investigated through in situ microscopic observation using a periscope system developed on the basis of a confocal scanning laser microscope. At the growth front of a silver dendrite, under a 12 T magnetic field applied perpendicularly to the sample plane, a straight silver branch was grown for a while; then, a given length of the branch at the neighbor of the tip started moving rapidly and was bent in an integrated manner. As a result of the process, a dense silver dendrite in the shape of a vortex was formed. When the sample space was narrowed, the branch did not bend due to the increase in the static friction between the branch and the glass plates. Judging from these observations, the mechanism underlying the formation of a dense vortex dendrite was thought to be the effect of the Lorentz force acting on the branch due to the electric current flowing through the branch itself accompanied by the silver deposition and the copper dissolution reactions. Furthermore, the reason that the silver dendrite grown under high magnetic fields looked denser by macroscopic observation was investigated by evaluating the reaction amount and the microstructure of the silver branch. No significant difference was observed in the reaction amount between the experiments with and without magnetic fields. On the other hand, the microstructures of the silver branch were significantly different from each other. The silver branch grown under high magnetic fields had a low-density structure, which seems to account for its denser appearance in the macroscopic observation. This low-density structure may be formed because of the interference of the static crystal growth due to the rapid bend of the silver branches. [doi:10.2320/matertrans.MI200721]

Application of nanoparticles for the enhancement of latent fingerprints

Two different types of nanoparticles dissolved in organic solution, gold stabilized by n-alkanethiols and CdSe/ZnS stabilized by n-alkane-amine, adhere preferentially to the ridges of latent fingerprints; the gold deposits catalyze silver electroless deposition from "Silver Physical Developer" (Ag-PD), an aqueous solution containing silver colloids stabilized by cationic surfactants, to form dark impressions of the ridge details; the hydrophobic capped gold nanoparticles significantly improve the intensity and clarity of the developed prints compared with Ag-PD alone; finger marks treated with CdSe/ZnS nanoparticles can be viewed directly, due to their fluorescence under UV illumination.

Electroless silver deposition on polypyrrole and poly(3,4-ethylenedioxythiophene): The reaction/diffusion balance

Processes of spontaneous metallic silver deposition from AgNO 3 solutions on electrodes coated by semi-oxidised conducting polymers: polypyrrole and poly(3,4-ethylenedioxythiophene) were studied. Kinetic information was obtained from open circuit potential transients, showing that for slightly oxidised polymers in quiescent solution the rate of Ag(I) reduction is dependent on Ag(I) ion diffusion in solution. In stirred solutions or for more oxidised polymers the initial step of the process is controlled by new phase (Ag on conducting polymer) formation, as shown using rotating disk electrode voltammetry. The influence of Ag(I) concentration, conditioning time, kind of polymer and its thickness on the amount of accumulated silver was analysed. The reaction-diffusion balance determines where the silver is deposited in the polymer. Although both polymers can be penetrated by Ag + ions, the highest amount of Ag is detected on the polymer surface, as laser ablation coupled with mass spectrometry experiments has shown.

Cover Picture: Fabrication and Characterization of Three-Dimensional Silver-Coated Polymeric Microstructures (Adv. Funct. Mater. 13/2006)

Kuebler and co-workers report on p. 1739 a method for preparing conductive and optically reflective silver-coated polymeric microstructures having virtually any 3D form. Shown are reflection images of a silvered five-layer simple-cubic lattice having a period of 2.4 μm (background) and a macroscopic silvered polymer film (inset). To prepare metallopolymeric microstructures, 3D polymeric scaffolds are first created by multiphoton direct laser writing, then functionalized with gold particles, and metallized using nucleated electroless silver deposition. A method is reported for fabricating complex 3D silver-coated polymeric microstructures. The approach is based on the creation of a crosslinked polymeric microscaffold via patterned multiphoton-initiated polymerization followed by surface-nucleated electroless deposition of silver. The conductivity and reflectivity of the resulting silver–polymer composites and the nanoscale morphology of the deposited silver are characterized. Sub-micrometer thick layers of silver can be controllably deposited onto surfaces, including those of 3D microporous forms without occluding the interior of the structure. The approach is general for silver coating crosslinked polymeric structures based on acrylate, methacrylate, and epoxide resins and provides a new path to complex 3D micrometer-scale devices with electronic, photonic, and electromechanical function.

Electrochemical investigation of the surface energy: Effect of the HF concentration on electroless silver deposition onto p-Si (1 1 1)

Electroless silver deposition onto p-silicon (111) from 0.005moll−1 AgNO3 solutions with different HF concentration was investigated by using an electrochemical direct current polarization method and open circuit potential-time (Ocp-t) technique. The fact that three-dimensional (3D) growth of silver onto silicon is favored with increasing the HF concentration was ascribed to the drop of the surface energy and approved by electrochemical direct current polarization, Ocp-t technique and atomic force microscopy (AFM). The drop slope of open-circuit potential, K−ΔE(OCP)/t, was educed from the mixed-potential theory. K−ΔE(OCP)/t as well as the deposition rate determined by an inductively coupled plasma atomic emission spectrometry (ICP-AES), increased with the HF concentration, yet was not a linear function. Results were explained by the stress generation and relaxation mechanisms.

Fabrication and Characterization of Three-Dimensional Silver-Coated Polymeric Microstructures

A method is reported for fabricating complex 3D silver-coated polymeric microstructures. The approach is based on the creation of a crosslinked polymeric microscaffold via patterned multiphoton-initiated polymerization followed by surface-nucleated electroless deposition of silver. The conductivity and reflectivity of the resulting silver-polymer composites and the nanoscale morphology of the deposited silver are characterized. Sub-micrometer thick layers of silver can be controllably deposited onto surfaces, including those of 3D microporous forms without occluding the interior of the structure. The approach is general for silver coating crosslinked polymeric structures based on acrylate, methacrylate, and epoxide resins and provides a new path to complex 3D micrometer-scale devices with electronic, photonic, and electromechanical function.

Morphology Investigation of Electrolessly Deposited Ag Film on Ag‐Activated p‐Type Silicon(111) Wafer

AbstractA method of electroless silver deposition on silver activated p‐type silicon(111) wafer was proposed. The silver seed layer was deposited firstly on the wafer in the solution of 0.005 mol/L AgNO3+0.06 mol/L HF. Then the silver film was electrolessly deposited on the seed layer in the electroless bath of AgNO3+NH3+acetic acid+NH2NH2 (pH 10.2). The morphology of the seed layer and the silver films prepared under the condition of the different bath composition was compared by atomic force microscopy. The reflectance of the silver films with different thickness was characterized by Fourier transform infrared spectrometry. The experimental results indicate that the seed layer possesses excellent catalytic activity toward electroless silver deposition and rotating of the silicon wafer during the electroless silver deposition could lead to formation of the smoother silver film.

Development of a periscopic confocal microscope for in situ observation under high magnetic fields

This article contains a description of a periscope system developed for in situ high-resolution observation under high magnetic fields in combination with a confocal scanning laser microscope. It fits a typical cryocooler-operated superconducting magnet with a 100mm diam room-temperature bore. To avoid the unwanted effect of magnetic fields, the laser scanning unit was positioned at sufficient distance from the field. The resolution obtained was several hundreds of nanometers. The observation area can be changed in situ by the xyz fine-motion stage. Processing of obtained images can be done in a manner nearly identical to that with a conventional confocal scanning laser microscope. Images of the in situ observation of electroless silver deposition under a 12T field are presented.

In situ microscopic observations of an electroless silver deposition process under high magnetic fields

The mechanism of the morphological effect of magnetic fields on electroless silver deposition was investigated through in situ microscopic observation by using a periscope system that was developed on the basis of a confocal scanning laser microscope. At the growth front of a silver dendrite, under a 12 T magnetic field applied perpendicularly to the sample plane, a silver branch was grown straightly for a while; then, a certain length of the branch at the neighbor of the tip started moving rapidly and was bent in an integrated manner. As a result of the process, a dense silver dendrite in the shape of a vortex was formed. When the sample space was narrowed, the branch did not bend due to the increase in the static friction between the branch and the glass plates. Judging from these observations, the mechanism of the formation of a dense vortex dendrite was thought to be the effect of a Lorentz force acting on the branch due to the electric current flowing through the branch itself accompanied by the silver deposition and the copper dissolution reactions.

Electroless deposition of Ag onto p-Si(100) surface under the condition of the centrifugal fields

A novel method of silver electroless deposition on p-Si(100) wafer under the condition of the centrifugal force was developed. The Ag seed layer was firstly prepared on the wafer in a solution of 0.005 mol/l AgNO 3 + 0.06 mol/l HF then the silver film was electrolessly deposited in another electroless Ag bath under the centrifugal fields. The morphology of the prepared silver film was characterized by atomic force microscopy. The crystal orientation of the film was characterized by X-ray diffraction. The experiment results show that the silver film obtained under the condition of the strong centrifugal force is smoother and denser.

Anodic oxidation of Co(II) complexes with amines on a rotating Au electrode: Ligand effects in relation to the application for autocatalytic metal deposition

For the comparison of the electrochemical activity of Co(II)–amine complexes, the electrochemical response of an Au rotating disk electrode in alkaline Co(II)–glycine solutions to six amines: ethylenediamine (en), propane-1,2-diamine (pn-1,2), propane-1,3-diamine (pn-1,3), cyclohexane-1,2-diamine (chn), butane-1,4-diamine (bn), diethylenetriamine (dien), was studied. Addition of amines tested (except for bn) in mM levels shifts the open-circuit potential to more negative values by up to 0.5 V and enhances dramatically the anodic Co(II) oxidation current, as a result of Co(II) complex transformation into more stable and electrochemically active Co(II)–amine species. The effect of amines on the open-circuit potential changes in the line: dien ∼ en > pn-1,2 ∼ chn > pn-1,3 ≫ bn, and on the anodic current in the sequence: dien ∼ en > pn-1,2 > chn > pn-1,3 ≫ bn. The procedure described helps to select ligands for Co(II) complexes used as reducing agents in electroless plating solutions. The amines of high electrochemical response: dien, en, pn-1,2, and possibly, chn, are suitable for electroless copper deposition, pn-1,3 (a lower response), for electroless silver deposition, and bn (no response), not suitable for electroless plating solutions.

From Si nanotubes to nanowires: Synthesis, characterization, and self-assembly

Through electroless silver deposition, we have successfully fabricated Si nanowires (SiNWs) in a conventional vessel containing aqueous HF and AgNO 3 solution. Their growth mechanisms are analyzed on the basis of a self-assembled localized microscopic electrochemical cell model. A series of scanning electron microscope observations reveal the detailed growth process of the SiNWs. The formation of intermediate Si nanostructures (undetached Si nanotubes) is suggested to be responsible for the growth of triangular shaped SiNWs. The shape and structure of the SiNWs and intermediate undetached Si nanotubes are promising characteristics for applications in interconnection and basic components for future nanoelectronic and optoelectronic devices.

Nanostructuring and nanoanalysis by scanning electrochemical microscopy (SECM)

The generation and application of nanodes in SECM experiments are described. Nanodes are ultramicroelectrodes with an active disk diameter in the submicrometer range. We investigated the behaviour of these electrodes by testing their properties with SECM applications which were previously performed at the micrometer scale. The active diameter of the nanodes was determined using cyclic voltammetry and SECM. The nanoanalysis was conducted at two nano interdigitated arrays. The nanostructuring was demonstrated by galvanic and electroless silver deposition from solution and from the surface, respectively. Experiments with nanodes illustrate that they exhibit the same behaviour as ultramicroelectrodes, but are more sensitive to adsorption and dirt particles in the electrolyte solution.