Electroless versus electrodriven deposition of silver crystals in polyaniline: Role of silver anion complexes

Electrocrystallization of silver is studied at polyaniline-coated electrodes using silver cations and two silver anion complexes (silver thiosulfate and silver-EDTA) as reducing species. Use of the silver thiosulfate complex results in a significant shift of the silver deposition potential window in the negative direction and highly impeded metal crystallization. The silver cation and silver-EDTA plating solutions allow to perform both electrodriven and electroless metal deposition. Number and size of silver crystals obtained by the two deposition methods in the different plating solutions are compared. Electroless precipitation in the silver-EDTA solution results in the highest number (∼10⁸ cm⁻²) of small-sized crystals. This result is discussed in terms of the special role of the EDTA anions for the redox state of the polyaniline layers. It is demonstrated that factors such as polyaniline redox charge, concentration of reducing ions and dipping time allow effective control over the amount of electroless deposited metal.     

Electrochemical oxidation of glucose on silver nanoparticle-modified composite electrodes

Silver nanoparticle-modified composite electrodes were prepared by electroless forming silver nanoparticles in carbon black dispersed electroless silver plating solution, and then incorporating the silver nanoparticle/carbon black mixture in a polystyrene matrix. The electrooxidation of glucose in 0.1 M NaOH was studied by using cyclic voltammetry. The electrode has surface-confined nanoparicles showing effective catalytic behavior in the studies of glucose oxidation. It showed stepwise electrocatalytic oxidation behavior clearly without suppression by high background redox current caused by inner layer silver of disk-type silver electrodes. Initially the glucose was catalytically oxidized by AgO, and then the reaction glucose oxidation intermediates with Ag₂O were followed stepwisely. Based on the cyclic voltammetric results, pulsed amperometric detection parameters for flow injection analysis were optimized for sensitive detection of glucose.     

Electroless silver deposition on Si(100) substrate based on the seed layer of silver itself

A new method for silver electroless deposition on Si(100) wafer, based on the silver itself as the seed layer, was developed. The seed layer was first deposited onto the etched wafer surface in an acidic solution of 0.005 mol l⁻¹ AgNO₃+0.06 mol l⁻¹ HF. Then the silver thin film was electrolessly deposited upon the seed layer in the electroless bath of AgNO₃+NH₃+acetic acid+NH₂NH₂ (pH 10.2). The NH₂NH₂ was taken as the reducing agent. The morphology of the seed layer and the silver film were characterized by atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray analysis (EDX). The experimental results indicated that the seed layer showed excellent catalytic function for silver electroless deposition.     

Highly efficient and selective membrane transport of silver(I) using hexathia-18-crown-6 as a specific ion carrier

Hexathia-18-crown-6 (HT18C6) was used as a specific ion carrier for the transport of silver ion through a chloroform bulk liquid membrane. In the presence of thiosulfate ion as a suitable stripping agent in the receiving phase, the amount of silver transported across the liquid membrane after 60 min is 99.5±1.0%. The selectivity of Ag⁺ transport from the aqueous solutions containing other Mⁿ⁺ cations such as Tl⁺, Mg²⁺, Ca²⁺, Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Pb²⁺, Hg²⁺, and Cr³⁺ ions was investigated. Except with Hg²⁺ ion, non of the cations used interfere the silver transport, even at a Mⁿ⁺/Ag⁺ molar ratio of 500. The interfering effect of Hg²⁺ ion was successfully eliminated in the presence of EDTA at pH 5.     

Development of electroless silver plating on Para‐aramid fibers and growth morphology of silver deposits

The development of a conductive fiber with flame resistance is an urgent concern particularly in national defense and other specialized fields. Aramid fibers (para‐ or meta‐) exihibit high strength and excellent fire resistance. Electroless silver plating on para‐aramid fibers and growth morphology of silver deposits was investigated in the present work. The surface of para‐aramid fibers was roughened using sodium hydride/dimethyl sulfoxide to guarantee successful electroless plating. Two complexing agents (ethylene diamine/ammonia) and two reducing agents (glucose/seignette salt) were used for the electroless silver plating bath design. Structure and properties of the resulting silver‐deposited para‐aramid fibers were evaluated based on scanning electron microscopy, silver weight gain percentage calculation, electrical resistance measurement, crystal structure analysis, and mechanical properties test. The results showed that a higher silver weight gain was advantageous to the improvement of conductivity for the silver‐deposited para‐aramid fibers. The obtained silver deposit was homogenous and compact. Electroless silver‐plating deposits were considered to be three‐dimensional nucleation and growth model (Volmer–Weber). Black, silver gray, and white deposits appeared sequentially with progressive plating. The breaking strength of silver‐deposited para‐aramid fibers remained at value up to 44 N. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of silver on the photocatalytic degradation of humic acid

In this study, humic acid was mineralized and degraded photocatalytically in presence of bare TiO₂ and silver loaded TiO₂ (0.5–5.0 at.% Ag). X-ray diffraction (XRD) and inductive coupled plasma (ICP) analysis confirm the complete photodeposition of silver over TiO₂ by photodeposition method. X-ray photoemission spectroscopy (XPS) studies confirmed the presence of Ag⁰ in all Ag–TiO₂ samples and the absence of Ag⁺ ions. Silver loading over TiO₂ improved the rate of mineralization and degradation of humic acid with a maximum loading of 1.0 at.% Ag. Ninety percent carbon from humic acid was mineralized to CO₂ only after 60 min by using bare TiO₂ as a photocatalyst. However, this conversion was possible within 40 min by using 1.0 at.% Ag-loaded TiO₂. This observation verifies that coating of metals like silver over TiO₂ acts as an electron sink and can improve the redox reaction by preventing electron–hole recombination reaction. The optimum 1.0 at.% Ag loading in the current work is indicative that the blocking of the TiO₂ surface active sites by silver also plays an important role in the photocatalytic mineralization and degradation of humic acid. As the silver loading is increased, less number of active site are available over the surface of photocatalyst TiO₂ for redox reaction. This finding was supported by the TEM analysis of the photocatalyst samples.     

心电图仪用ABS塑料纽扣上化学镀银的大批量氯化

银/氯化银(Ag/AgCl)电极有多种应用,心电图仪用一次性Ag/AgCl电极便是其中之一。在带有一个直径3mm、长5mm的柄的ABS塑料钮扣(直径10 mm)的一个面上,尝试以二价钴为还原剂,化学镀一层1～2μm的银,然后在酸化的氯化物溶液中以化学镀银表面为阳极进行氯化处理。为了获得良好的Ag/AgCl电对,只有平面部分是氯化物而并非将整个覆银表面都转化。上述柄用作金属接点依次与探针连接。由于原材料是ABS塑料,且每毫克的覆银量只有1μm左右,因此损失降到最低。     

Polyaniline–silver composites prepared by the oxidation of aniline with silver nitrate in solutions of sulfonic acids

Aniline was oxidized with silver nitrate in aqueous solutions of sulfonic acids: camphorsulfonic, methanesulfonic, sulfamic, or toluenesulfonic acids. Polyaniline–silver composites were produced slowly in 4 weeks in good yield, except for the reaction, which took place in sulfamic acid solution, where the yield was low. Polyaniline in the emeraldine form was identified with UV–visible, FTIR, and Raman spectra. Thermogravimetric analysis was used to determine the silver content, which was close to the theoretical prediction of 68.9 wt.%. Transmission electron microscopy demonstrated the presence of silver nanoparticles of ca 50 nm average sizes as the dominating species, and hairy polyaniline nanorods having diameter 150–250 nm accompanied them. The highest conductivity of 880 S cm⁻¹ was found with the composite prepared in methanesulfonic acid solution. Its conductivity decreased with temperature increasing in the 70–315 K range, which is typical of metals such as silver. The conductivity of composites prepared in solutions of other acids was lower and increased with increasing temperature. Such dependence is typical of semiconductors, reflecting the dominating role of polyaniline in the conductivity behaviour. It is proposed that interfaces between the polyaniline matrix and dispersed silver nanoparticles play a dominating role in macroscopic level of conductivity.     

以次磷酸钠为还原剂的化学镀铜

研究了以次磷酸钠为还原剂的化学镀铜过程。确立了以硫酸铜为主盐,次磷酸钠为还原剂,乙二胺四乙酸二钠和柠檬酸钠为混合配位剂的碱性还原镀铜体系。在铸铁基体上实现了铜的连续自催化沉积,获得了较光亮、红黄色的铜镀层。     

涤纶织物化学镀Ni-Co-Fe-P的制备及性能表征

基于化学镀技术在涤纶织物表面进行了化学镀Ni-Co-Fe-P处理.在单因素实验的基础上对化学镀工艺进行了正交实验设计,筛选出沉积速率高、稳定性好的工艺配方.采用扫描电子显微镜(SEM)、X射线能谱仪(EDS)对镀层形貌、组分进行表征,并对镀后织物的电磁波屏蔽效能进行测定.结果表明:在缓冲剂的质量浓度为14 g/L,镀覆...     

Electroless recovery of silver by inherently conducting polymer powders, membranes and composite materials

A wide variety of inherently conducting polymers, including polypyrroles and polyanilines, were shown to reduce silver ion in aqueous solution, demonstrating that these materials may form the basis of a novel approach to silver recovery. The effect of varying the polymer, dopant, and underlying substrate (reticulated vitreous carbon or fabric) was investigated, as was the effect of changing the pH of the solution containing silver. Silver recovery was found to proceed more readily from solutions with near neutral pH than from solutions with strongly acidic pH, and to occur selectively from solutions containing both silver and iron. Scanning electron microscopy (SEM) showed deposits that formed on polymeric materials after prolonged exposure to concentrated silver nitrate solutions were partially crystalline in nature. XPS spectra provided support for a mechanism of silver recovery involving a redox reaction between the polymer and silver ions leading to the formation of silver metal.     

化学镀银在材料表面金属化中的应用

介绍了化学镀银法制备导电填料、屏蔽材料、电子元件等的工艺,分析了影响化学镀银速度和镀层质量的因素,如表面预处理、镀液配方、操作工艺条件等。指出了工艺中存在的问题,并对发展前景进行了展望。     

Electroless silver plating on the PET fabrics modified with 3‐mercaptopropyltriethoxysilane

The feasibility of adherent silver layers onto PET fabrics by electroless plating was explored and its optimal technology for modification and electroless plating was investigated. Morphology, structure, and thermal stability of silver plating PET fabrics were characterized by scanning electric microscope (SEM), X‐ray diffraction (XRD) and thermogravitric (TG) analysis. As the silver weight on the modified fabric is 25 g/m², the electromagnetic shielding effectiveness (SE) of silver plating PET fabric is more than 30dB at the frequency ranging from 1MHz to 5000 MHz. The results show that the silver plating PET fabric has good electrical conductivity and electromagnetic shielding property. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

The oxidation of aniline with silver nitrate to polyaniline-silver composites

Silver nitrate oxidizes aniline in the solutions of nitric acid to conducting nanofibrillar polyaniline. Nanofibres of 10-20 nm thickness are assembled to brushes. Nanotubes, having cavities of various diameters, and nanorods have also been present in the oxidation products, as well as other morphologies. Metallic silver is obtained as nanoparticles of ∼50 nm size accompanying macroscopic silver flakes. The reaction in 0.4 M nitric acid is slow and takes several weeks to reach 10-15% yield. It is faster in 1 M nitric acid; a high yield, 89% of theory, has been found after two weeks oxidation of 0.8 M aniline. The emeraldine structure of polyaniline has been confirmed by FTIR and UV-vis spectra. The resulting polyaniline-silver composites contain 50-80 wt.% of silver, close to the theoretical expectation of 68.9 wt.% of silver. The highest conductivity was 2250 S cm⁻¹. The yield of a composite is lower when the reaction is carried out in dark, the effect of daylight being less pronounced at higher concentrations of reactants.     

涤纶织物上化学镀银的晶体结构与性能

利用化学镀,在涤纶织物上制备了金属银薄膜.化学镀银液配方及工艺条件为:硝酸银3.0g/L,氢氧化钠2.0g/L,葡萄糖2.0 g/L,氨水适量,温度25℃,pH=11.采用扫描电镜和X射线衍射研究了薄膜的表面形貌和晶体结构,采用紫外分光光度计和静电伏特计分析了镀银涤纶的抗紫外及抗静电特性.结果表明,化学镀银后涤纶织物的抗紫外和抗静电性能有了很大提高.     

非金属粉体化学镀银的研究进展

介绍了非金属粉体化学镀银的发展趋势和特点。综述了非金属粉体如空心玻璃微珠、SnO2、A l2O3、纤维、碳纳米管、石墨、BaTiO3等粉体化学镀银的工艺研究现状及应用。讨论了非金属粉体化学镀银的影响因素,包括前处理、表面活性剂、主盐浓度、温度、银离子滴加的速度等。     

Direct evidence for purely silver ion conduction in CuI-doped silver oxysalt superionic systems: Combined electrolysis and EDS studies

Maiden attempt has been made for the direct estimation of the contributions of silver and copper ions to the ionic conductivity in superionic solids obtained in CuI-doped silver oxysalt systems. The application of the combined electrolysis and EDS techniques towards qualitative and quantitative analyses of the mobile ionic species in solid electrolyte systems having more than one possible mobile ion is reported. These studies confirmed that these electrolyte materials are purely Ag⁺ conducting up to 50 mol% CuI in xCuI–(100 − x)[2Ag₂O–0.7V₂O₅–0.3B₂O₃] and xCuI–(100 − x)[Ag₂O–0.7MoO₃–0.3WO₃] systems and small fraction of t_Cu+ exists above 60 mol% CuI. These solid electrolyte materials exhibited a high ionic transport numbers (t_i) of >0.985 and the t_i increases when two glass formers are used.     

Kinetics of electroless silver deposition using cobalt(II)-ammonia complex compounds as reducing agents

The kinetics of electroless silver deposition from solutions containing Co(II)-ammonia complex compounds as reducing agents was studied at 20 and 50 °C. The process rate depends on the solution pH and the concentration of Ag(I), Co(II) and ammonia species. Under optimum operating conditions selected a silver deposition rate up to 1.2 m h^–1 can be obtained at 20 °C with high solution stability. At elevated temperature (50 °C) the rate increases and reaches 3 m h^–1. The silver coatings obtained are of high quality, compact and bright.     

Region-selective electroless gold plating on polycarbonate sheets by UV-patterning in combination with silver activating

A simple, time- and cost-effective approach for region-selective metalization of polycarbonate (PC) surface has been established by combining photoresist-free UV-patterning with tin- and amine-free silver activating and electroless gold plating. The surface of PC sheets was exposed to the UV lights emitted from a low-pressure mercury lamp through a photomask, the micro pattern on the mask being transferred to the PC surface due to the photochemical generation of carboxyl groups on the UV-exposed region. The UV-exposed PC sheets were then treated with an ammoniacal AgNO₃ solution, so that the silver ions were chemisorbed by the photochemically generated carboxyl groups. When the Ag⁺-adsorbed PC sheet was immersed into an electroless gold plating bath, shiny gold film quickly deposited on the UV-exposed region, resulting in the formation of a micro gold devices on the PC surface. The whole plating process including UV-exposure, surface activating and gold plating can be completed in about 3-4 h. Attenuated total reflection Fourier transformation infrared spectrometer (ATR-FT-IR), X-ray photoelectron spectroscopy (XPS), atomic force microscope (AFM) and scanning electron microscope (SEM) were employed to trace the surface change during the plating process. Cyclic voltammetry (CV) and Scotch^®-tape test were employed to characterize the electrochemical properties and adhesion strength of the prepared micro gold devices, respectively. The prepared micro gold electrodes were demonstrated for amperometric detection of hydrogen peroxide.     

Electrodeposition of palladium–silver in a Lewis basic 1-ethyl-3-methylimidazolium chloride-tetrafluoroborate ionic liquid

The electrodeposition of palladium–silver alloys was investigated in a basic 1-ethyl-3-methylimidazolium chloride/tetrafluoroborate ionic liquid containing Pd(II) and Ag(I). Cyclic voltammetry experiments showed that the reduction of Ag(I) occurs prior to the reduction Pd(II). Both electrodeposition processes require nucleation overpotential. Energy-dispersive spectroscopy data indicated that the composition of the Pd–Ag alloys could be varied by deposition potential and concentrations of Pd(II) and Ag(I) in the solution. The Pd content in the deposited Pd–Ag alloy increased with decreasing deposition potential and the Pd mole fraction in the plating bath. At potentials where the deposition of both Pd and Ag was mass-transport limited, the Pd/Ag ratio in the electrodeposited alloys was slightly less than the Pd(II)/Ag(I) ratio in the ionic liquid due to the smaller diffusion coefficient of Pd(II). Scanning electron micrographs of the electrodeposits showed that in general, the Pd–Ag alloys were nodular and become more compact upon increasing the temperature up to 120 °C.