Electroless Deposition Of Silver Research Articles

Multifunctional carbon nanotubes for direct electrochemistry of glucose oxidase and glucose bioassay

Polydopamine (Pdop) has recently been shown to adsorb to a wide variety of surfaces and serves as an adhesion layer to immobilize biological molecules. In this work, the multifunctional carbon nanotube (CNT) composites were prepared though the oxidation of dopamine at room temperature and subsequent electroless silver deposition by mildly stirring. The stable immobilization and direct electron transfer of glucose oxidase were achieved on the composite film modified glassy carbon electrode. The resulting electrode gave a well-defined redox peaks with a formal potential of about −482 mV (vs. SCE) in pH 7.0 buffer. The electron transfer rate constant was estimated to be 3.6 s −1, due to the combined contribution of Pdop, CNTs and Ag nanoparticles with the help of Nafion. Furthermore, the method for detecting of glucose was proposed based on the decrease of oxygen caused by the enzyme-catalyzed reaction between glucose oxidase (GOD) and glucose. The linear response to glucose ranging from 50.0 μM to 1.1 mM ( R 2 = 0.9958), with a calculated detection limit of 17.0 μM at a signal-to-noise ratio of 3. The low calculated apparent Michaelis–Menten constant ( K M app ) was 5.46 mM, implying the high enzymatic activity and affinity of immobilized GOD for glucose. It can reasonably be expected that this observation might hold true for other noble metal nanostructure-electroactive protein systems, providing a promising platform for the development of biosensors and biofuel cells.

Connecting the Nanodots: Programmable Nanofabrication of Fused Metal Shapes on DNA Templates

We present a novel method for producing complex metallic nanostructures of programmable design. DNA origami templates, modified to have DNA binding sites with a uniquely coded sequence, were adsorbed onto silicon dioxide substrates. Gold nanoparticles functionalized with the cDNA sequence were then attached. These seed nanoparticles were later enlarged, and even fused, by electroless deposition of silver. Using this method, we constructed a variety of metallic structures, including rings, pairs of bars, and H shapes.

Electrically conductive acrylonitrile–butadiene rubber elastomers prepared by dopamine‐induced surface functionalization and metallization

A novel method for the preparation of electrical conductive surface silvered acrylonitrile–butadiene rubber (NBR) was developed. Dopamine was spontaneously oxide polymerized and deposited onto the surface of NBR. Electroless plating of silver was carried out on the poly(dopamine) (PDA)‐functionalized NBR surface. The composition of the NBR surface was studied by X‐ray photoelectron spectroscopy (XPS). XPS results showed that PDA was successfully deposited onto the NBR surface. The morphology of the NBR surface was observed by scanning electron microscopy (SEM). The SEM images showed that PDA had formed a distinctive layer ready for electroless deposition of silver. The catechol/quinone groups on the PDA molecular structure can be used as binding sites for silver ions. The silvered NBR showed high surface conductivity of 1.4 Ω. Copyright © 2011 John Wiley & Sons, Ltd.

Silver particles-modified polysulfonic acid-doped polyaniline layers: electroless deposition of silver in slightly acidic and neutral solutions

Polyaniline layers are produced by electrochemical polymerisation of aniline in the presence of small amounts of poly(2-acryalamido-2-methyl-propane-sulfonic acid) in an inorganic acid solution. Electroactivity and in situ conductance of the obtained polysulfonic acid-doped layers are studied in slightly acidic and neutral solutions. Electroless deposition of silver particles is carried out in silver-EDTA complex ion solutions at pH = 4.2 and pH = 6.6 by using the polyaniline layers as reductant. The amount of electroless-deposited silver is studied depending on: polymerisation charge used to synthesize the polymer layer, pH of the plating solution, metal ion concentration and dipping time. SEM shows in all cases a highly non-homogeneous distribution of the metallic phase over the surface, the most protruding fibrillar polymer structures favouring the electroless silver deposition. A linear dependence between amount of the polyaniline material and amount of deposited silver is found for the silver plating solutions with the highest investigated concentration (10 mmol l−1). At lower concentrations (2.0 and 0.4 mmol l−1), the same amount of silver becomes deposited on polymer layers with markedly different charges. The electroless deposition of silver in the solutions with lower acidity results in lower amounts of deposited silver at otherwise identical conditions. Effects such as charge transfer within the polymer phase and mass transport in the solution are addressed to explain the observed dependencies of the amount of deposited silver on concentration and pH in the different plating solutions.

Electroless Deposition of Silver on Multiwalled Carbon Nanotubes Using Iodide Bath

Electroless deposition of silver on multiwalled carbon nanotubes (MWCNTs) was investigated using an iodide bath. Prior to electroless deposition of silver, the MWCNTs were chemically oxidized and then pre-treated using a typical two-step method (sensitization and activation) to form catalytic palladium nuclei on the MWCNTs. Dimethylaminoborane (DMAB) was used to reduce silver ions. Electroless deposition of silver was carried out at 25°C with variation of the pH. The microstructure of the deposits was evaluated using field emission-scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The silver iodide complex ion species present was determined to be AgI43− from equilibrium potential measurements. Silver was selectively deposited on palladium nuclei on the surface of the MWCNTs and continuous diffusion of deposited silver and palladium nuclei resulted in a solid solution of Ag-Pd alloy particles on the MWCNTs at pH = 7.5.

Mechanistic Study of Silver Nanoparticle Formation on Conducting Polymer Surfaces

Conducting polymer (polyaniline) sheets are shown to be active substrates to promote the growth of nanostructured silver thin films with highly tunable morphologies. Using the spontaneous electroless deposition of silver, we show that a range of nanostructured metallic features can be controllably and reproducibly formed over large surface areas. The structural morphology of the resulting metal-polymer nanocomposite is demonstrated to be sensitive to experimental parameters such as ion concentration, temperature, and polymer processing and can range from densely packed oblate nanosheets to bulk crystalline metals. The deposition mechanisms are explained using a diffusion-limited aggregation (DLA) model to describe the semi-fractal-like growth of the metal nanostructures. We find these composite films to exhibit strong surface-enhanced Raman (SERS) activity, and the nanostructured features are optimized with respect to SERS activity using a self-assembled monolayer of mercapto-benzoic acid as a model Raman reporter. SERS enhancements are estimated to be on the order of 10(7). Through micro-Raman SERS mapping, these materials are shown to exhibit uniform SERS responses over macroscopic areas. These metal-polymer nanocomposites benefit from the underlying polymer's processability to yield SERS-active materials of almost limitless shape and size and show significant promise for future SERS-based sensing and detection schemes.

Dopamine-Induced Surface Functionalization for the Preparation of Al–Ag Bimetallic Microspheres

A novel method for the preparation of highly conductive silver-plated aluminum (Al) microspheres was demonstrated. The surface of the aluminum microspheres was functionalized by a bioinspired polydopamine (PDA) coating. Electroless plating of silver was then carried out on the functionalized aluminum microspheres. An aqueous solution of silver nitrate is used as silver precursor and glucose is used as reducing reagent. The overall procedure is fast, simple, nontoxic, and controllable. The surface compositions and the crystalline structure of the modified aluminum microspheres were studied by x-ray photoelectron spectroscopy (XPS) and x-ray diffraction, respectively. XPS results show that the Al-PDA surfaces were successfully deposited with polydopamine and were ready for electroless deposition of silver. Scanning electron microscopy (SEM) was used to study the morphology of the Al–Ag bimetallic particles. SEM results show that the silver-plated aluminum core–shell microspheres have a continuous, uniform, and compacted silver layer. The as-prepared Ag/Al particles possess high electrical conductivity.

Emerging fabrication techniques for 3D nano-structuring in plasmonics and single molecule studies

The application of new methods and techniques to fields such as biology and medicine is becoming more and more demanding since the request of detailed information down to single molecules is a scientific necessity and a technical realistic possibility. In this effort a key role is played by emerging fabrication techniques. One of the hardest challenges is to incorporate the third dimension in the design and fabrication of novel devices. Significantly, this means that conventional nano-fabrication methods, intrinsically useful for planar structuring, have to be substituted or complemented with new approaches. In this paper we show how emerging techniques can be used for 3D structuring of noble metals down to nanoscale. In particular, the paper deals with electroless deposition of silver, ion and electron beam induced deposition, focused ion beam milling, and two-photon lithography. We exploited these techniques to fabricate different plasmonics nanolenses, nanoprobes and novel beads for optical tweezers. In the future these devices will be used for the manipulation and chemical investigation of single cells with sensitivity down to a few molecules in label free conditions and native environment. Although this paper is only devoted to nanofabrication, we foresee that the fields of biology and medicine will directly gain substantial advantages from this approach.

Preparation and Characterization of Porous Silicon in HF-AgNO3 Solution

Porous silicon (PS) of uniform structure was prepared by electroless silver deposition on surface of silicon at near room temperature in HF-AgNO3 system solution. Morphology of PS was characterized by scanning electron microscopy. The results showed that the diameter of hole was 1-2μm and holes distributed regularly. The ethylene diamine tetra acetic acid (EDTA) was an important additive to control the etching rate of silicon, which is of great significance to research the mechanism of porous silicon formation. Furthermore, photoluminescence property of PS was characterized.

Deposition and wettability of silver nanostructures on Si(1 0 0) substrate based on galvanic displacement reactions

A new route for silver electroless deposition on Si(1 0 0) substrate is developed based on the galvanic displacement process. The basic electroless bath contains NaF and AgNO 3 with different concentrations. The morphologies of electrolessly deposited silver nanostructures, including silver nanowires and nanoparticles, are strongly dependent on the electrolyte composition. Adding an excess dosage of polyvinylpyrrolidone into the basic electrolyte yields final silver films of porous structures composed by multitudinous Ag nanoparticles. The porous silver films possess the surface hydrophobic property after the modification with n-dodecanethiol. Unidirectional wetting and spreading of a water droplet are also demonstrated on the patterned porous Ag films.

Magnetic Silver-Coated Ferrite Nanoparticles and Their Application in Thick Films

Magnetic silver-coated ferrite nanoparticles with 39.8% weight gain (relative to ferrite nanopowder coated by a silver layer) were synthesized by electroless deposition of silver on ferrite nanopowder. The mechanism of the electroless deposition was explored in terms of pretreatment, sensitization, activation, and the reduction of silver–ammonia complexes. Experiments showed that the optimal deposition conditions were a temperature of 50°C, pH value of 10 to 12, duration of 65 min with ethanol plus polyethylene glycol as additives, and ultrasonic vibration as a method of dispersing the nanoparticles. From transmission electron microscopy (TEM) images, it was observed that as-synthesized nanoparticles had a core–shell structure with a particle size of 35 nm to 90 nm and a shell thickness of 5 nm to 20 nm. X-ray diffraction (XRD) analysis confirmed that only ferrite and metallic silver were present in the product. Electrical resistance and magnetic hysteresis measurements demonstrated that the nanoparticles were both electrically conductive (volume electrical resistivity on the order of 10−4 Ω cm to 10−3 Ω cm when compressed to pressure of 2 × 10 6 Pa) and possessed ferrimagnetic properties. After a thick-film paste, obtained with the nanoparticles as the functional phase, was directly written and sintered, scanning electron microscopy (SEM) analysis and electrical resistance measurements of conductive lines in the acquired array pattern showed that an electrically conductive network with some defects and cavities was formed, with a volume electrical resistivity of 1 × 10−4 Ω cm to 1 × 10−3 Ω cm.

Optical Properties of Silicon Nanowires Fabricated by Electroless Silver Deposition

Vertically aligned silicon nanowires are fabricated on silicon substrates by electroless silver deposition, and their optical properties are investigated. The diameter of the nanowires ranges from 100 to 500 nm and their length ranges from 30 to 100 µm. Red photoluminescence appears at approximately 700 nm at room temperature. Its peak and intensity vary along the wire positions in Raman microscopy measurements. The photoluminescence intensity is high at the top of the wire. In this region, oxidation is enhanced and the Raman scattering spectra of the optical phonon mode tend to be broadened. The origin of the red photoluminescence is assumed to be defect states located at the interface between the core of the silicon nanowires and the surrounding silicon oxide.

Carbon fiber coating with silver using intervening Au/Pd nanoparticle films produced using a spark discharge

A low roughness conductive silver film on a fiber substrate was fabricated via a catalytic surface activation (needed to initiate electroless silver deposition) with spark produced gold aerosol nanoparticles. Gold had a similar lattice parameter with silver in crystallinity and thus a crystallographic misfit between gold activated substrate and silver was minimized during the deposition, resulting in formation of a flat silver film. Properties were compared with those obtained with palladium aerosol activation, the gold activation enhanced thin-metallic film properties in surface root-mean-square roughness (nm: 8, gold vs 44, palladium) and electrical resistivity (μΩ cm: 64, gold vs 498, palladium) at 88 mg/g (silver/substrate) in deposition amount.

Electroless silver deposition on ABS plastic using Co(II) as reducing agent

An unconventional way of plating Ag by electroless means is by using the oxidation process of Co(II) to Co(III) in an ammonia complex to reduce the ionic Ag to metal. The present work deals with electroless Ag deposition on acrylonitrile butadiene styrene (ABS) plastic. Detailed studies on the effect of bath constituents, bath operating conditions and addition agents on the deposition rate, quality of the Ag deposit and crystalline nature of the deposit on ABS plastic discs were carried out and the results discussed.

Electroless Deposition of Silver onto Silicon as a Method of Preparation of Reproducible Surface-Enhanced Raman Spectroscopy Substrates and Tip-Enhanced Raman Spectroscopy Tips

A simple method for the production of silver nanoparticles on a silicon substrate that is suitable for surface-enhanced Raman spectroscopy (SERS) is presented. The method is based on spontaneous reduction of Ag(+) ions by elemental silicon. The oxide layer is removed from the surface of a silicon disk by etching with dilute HF that is present in the same dilute solution of silver nitrate that is used to form the silver nanoparticles. By controlling the concentrations of HF and AgNO(3), the morphology of the deposited silver nanostructures can be varied dramatically. The reproducibility of SERS measurements for substrates produced with a given concentration of HF and AgNO(3) is good (relative standard deviation approximately 10%). The application was extended to coating the tips of silicon cantilevers designed for atomic force microscopy (AFM) with silver nanoparticles to permit measurements of tip-enhanced Raman spectra (TERS). The feasibility of TERS measurements with AFM tips prepared in this way is demonstrated.

The Influence of Electroless Silver Deposition on Electrochemical Properties of the Steel Cathode Current Collector of Alkaline Batteries

The Influence of Electroless Silver Deposition on Electrochemical Properties of the Steel Cathode Current Collector of Alkaline Batteries

Fabrication of high adhesive silver-coated PET electrode challenged by simulated body fluid (SBF) soaking

Ultrasonic assisted electroless deposition of silver on poly(ethylene terephthalate) (PET) modified with silanes was investigated. Mercapto groups were linked to the PET film as an active layer, which was proved by Raman spectra and EDX analysis. The composition, structure, thermal decomposing behavior of silver-coated PET films after simulated body fluid (SBF) treatment were characterized by scanning electron scopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), thermogravimetric analysis (TG), and ATR-FTIR spectra respectively. Silver plating on modified PET films has good adherence stability (>40 N/cm) and high electric conductivity (∼0.03 Ω/□) before and after SBF soaking. The practical implication of these results is that this silver-coated polymer can be applied to the flexible conductive electrodes for interventional therapy because of its firmness and improved mechanical property.

Selective microfabrication of silver electrodes inside a microchannel by multiphase laminar flow with density difference

In this paper, we propose a selective microfabrication technique of metal electrodes in a microchannel. The technique is based on the chemical deposition and the interface rotation of laminar flows among three multiphase fluids. Silver electrodes were patterned by electroless silver deposition only on the wall of the microchannel where the interface between a silver electroless plating solution and a reducer solution makes contact with the wall. A third fluid having a lower (or higher) density compared to the two solutions was introduced into the microchannel at the same time. The density difference between the two solutions and the third fluid induced the stable rotations of the interfaces between two among the three fluids. The third fluid having a different density, therefore, enabled us to selectively position the interfaces between the electroless plating and reducer solutions on the wall of the microchannel. We have demonstrated the fabrication of a single electrode and double electrodes on the bottom walls of microchannels based on the suggested microfabrication technique by changing number of streams, injection locations, flow rates, and flow duration time.

A facile method for preparing highly conductive and reflective surface-silvered polyimide films

A novel method was developed for the preparation of reflective and electrically conductive surface-silvered polyimide (PI) films. The polyimide films were functionalized with poly(dopamine), simply by dipping the PI films into aqueous dopamine solution and mildly stirring at room temperature. Electroless plating of silver was readily carried out on the poly(dopamine) deposited PI (PI-DOPA) surface. The surface compositions of the modified PI films were studied by X-ray photoelectron spectroscopy (XPS). XPS results show that the PI-DOPA surfaces were successfully deposited with ploy(dopamine) and were ready for electroless deposition of silver. The poly(dopamine) layer was used not only as the chemi-sorption sites for silver particles during the electroless plating of silver, but also as an adhesion promotion layer for the electrolessly deposited silver. The as-prepared silvered PI films show high conductivity and reflectivity, with a surface resistance of 1.5 Ω and a reflectivity of 95%, respectively.

Electroless deposition of silver on synthesized calcite via surface modification

Metallic silver was deposited on the surface of synthesized calcite via a simple electroless deposition method. Calcite with cubic morphology was prepared first by homogeneous precipitation and it was subsequently surface modified using ammonium oxalate. The electroless deposition was carried out using formaldehyde as the reducing agent and silver nitrate as the silver source. Both calcite and the silver deposited calcite were characterized by different techniques. Surface modification of calcite with ammonium oxalate is necessary for the deposition of silver and the size of the deposited silver particles could be controlled by changing the deposition parameters such as concentration of the reagents and the deposition time. Lower concentration of silver ions (e.g. 0.01 M AgNO 3) and shorter deposition times (e.g. 30 min) lead to the formation of silver nanoparticles on calcite.