室温离子液体中银纳米微粒的制备与结构表征

利用化学还原方法在室温离子液体1-甲基-3-丁基咪唑四氟硼酸盐中制备了金属银纳米微粒,采用X射线衍射,透射电子显微镜,傅立叶红外光谱和热分析对所制备的样品进行了结构表征.结果表明,所制备的银纳米微粒具有立方相结构,粒径约为20 nm.离子液体不但作为反应的溶剂而且作为修饰剂修饰在银纳米微粒的表面,从而有效地阻止了银纳米微粒的团聚.     

Cobalt‐Bridged Ionic Liquid Polymer on a Carbon Nanotube for Enhanced Oxygen Evolution Reaction Activity

By taking inspiration from the catalytic properties of single‐site catalysts and the enhancement of performance through ionic liquids on metal catalysts, we exploited a scalable way to place single cobalt ions on a carbon‐nanotube surface bridged by polymerized ionic liquid. Single dispersed cobalt ions coordinated by ionic liquid are used as heterogeneous catalysts for the oxygen evolution reaction (OER). Performance data reveals high activity and stable operation without chemical instability.     

Preparation of metallodielectric composite particles with multishell structure

In this article, we demonstrated the synthesis of metallodielectric composite particles comprising a metal shell on a dielectric core and an outer coating of an insulating dielectric layer by depositing silver on silica supporting cores followed by coating of titania. A combination of surface reaction and surface seeding techniques is exploited for the formation of a complete silver shell on silica spheres. The additional outer coating of titania on silver shell particles is then performed by hydrolyzing tetra-n-butyl titanate in ethanol at room temperature. The morphologies of silver shells and titania coating are studied with electron microscopy, and their existences are confirmed with X-ray diffraction and energy-dispersive X-ray measurement.     

Features of light absorption of gold nanoparticles bound to the surface of silver by a bridge structure containing Zr(IV) ions

A study was carried out on the optical properties of multilayered surface structures obtained by the coordination binding of gold nanoparticles to a silver surface by Zr(IV) ions. Such a system displays high absorption capacity in a broad spectral range (200-2000 nm), which is observed visually as an ultra-black coating. A physical interpretation of this effect is attributed to an interaction between plasmon excitations on the silver surface and the gold nanoparticle film separated by a dielectric bridge structure consisting of d-metal ions.     

Synthesis of Silver Nanoparticles Using Ionic‐Liquid‐Based Microwave‐Assisted Extraction from Polygonum minus and Photodegradation of Methylene Blue

A green biogenic, nontoxic, high‐yielding synthetic method is introduced for the synthesis of silver nanoparticles (AgNPs) using ionic‐liquid‐based, microwave‐assisted extraction (ILMAE) from Polygonum minus . The aqueous ionic liquid (1‐butyl‐3‐methylimidazolium chloride [BMIM]Cl)‐based plant extract was used as reducing agent to reduce silver ions to AgNPs. The synthesis of AgNPs was confirmed by UV–visible spectrophotometry. Fourier transforms infrared (FTIR) spectra showed that the plant bioactive compounds capped the AgNPs. The particle size and morphology of Ag NPs were characterized by dynamic light scattering (DLS) and field emission scanning electron microscopy (FESEM), respectively. Elemental analysis was carried out by energy‐dispersive X‐ray (EDX) spectroscopy. Photodegradation studies showed that the AgNPs degraded 98% of methylene blue in 12 min.     

Microwave-Assisted Coating of PMMA beads by silver nanoparticles

Microwave (MW) irradiation was found to be a new technique for coating silver nanoparticles with an average size of approximately 31 nm onto the surface of poly(methyl methacrylate) PMMA beads (3 mm diameter). The microwave polyol reduction was carried out under an argon atmosphere. Silver nanoparticles were obtained by the MW irradiation of a solution mixture containing silver nitrate (or silver acetate), poly(ethylene glycol), ethanol, water, and 24 wt % aqueous ammonia for 5 min in the presence of PMMA beads, yielding a PMMA-nanosilver composite. By controlling the atmosphere and reaction conditions, we could achieve the deposition of silver nanoparticles onto the surface of poly(methyl methacrylate) and vary the amount of the silver anchored to the surface. The resulting silver-deposited PMMA samples were characterized using X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray analysis, high-resolution scanning electron microscopy, X-ray photoelectron spectroscopy, and volumetric titration with potassium thiocyanate (KSCN) according to the Folgard method.     

Surface-enhanced Raman scattering from oleate-stabilized silver colloids at a liquid/liquid interface.

Oleate-stabilized silver colloids of 5-nm-diameter were adsorbed to a toluene/water interface, and surface enhanced Raman scattering (SERS) spectra from these colloids were measured under the total internal reflection (TIR) condition. From the observed spectra, we examined the states of oleate ions and toluene molecules on silver colloids at the liquid/liquid interfacial region. The TIR-SERS spectra of oleate ions showed stronger peaks of the carboxylate group and the ethylene group than those of alkyl chains. From these results, it was found that the oleate ions were adsorbed on the silver surface in two different ways at the liquid/liquid interface; the carboxylate group adsorbed in the organic phase side, while the ethylene group adsorbed in the aqueous phase side. The shifts of the toluene in the interfacial SERS spectra were identical to those of bulk toluene, though the relative intensities among the peaks were not same. This result suggested that the toluene was adsorbed with a weak interaction, but was significantly enhanced by the local electromagnetic field at the colloid surface.     

One-step synthesis of monodisperse silver nanoparticles beneath vitamin E Langmuir monolayers

The monodisperse silver nanoparticles were synthesized by one-step reduction of silver ions in the alkaline subphase beneath vitamin E (VE) Langmuir monolayers. The monolayers and silver nanocomposite LB films were characterized by surface pressure-area (pi-A) isotherms, transmission electron microscopy (TEM), ultraviolet-visible spectroscopy (UV-vis), selected area electron diffraction (SAED), Fourier transform infrared transmission spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS), respectively. The results showed that the limiting area/VE molecule on different subphases varied. The phenolic groups in the VE molecules were converted to a quinone structure, and the silver ions were mainly reduced to ellipsoidal and spherical nanoparticles. The arrangement of the nanoparticles changed from sparseness to compactness with reaction time. The electron diffraction pattern indicated that the silver nanoparticles were face-centered cubic (fcc) polycrystalline. Silver nanocomposite LB films with excellent quality could be formed on different substrates, indicating that the transfer ratio of monolayer containing silver nanoparticles is close to unity. The dynamic process of reduction of silver ions by VE LB films was also studied through monitoring the conductivity of an Ag2SO4 alkaline solution.     

硬脂酸单分子膜上电沉积Ag膜的研究

通过电沉积方法,以气/液界面上形成的硬脂酸单分子膜为模板诱导沉积金属银膜.考察了镀液pH值、单分子膜表面压及沉积电位对银膜形貌及结构的影响.实验发现,酸性镀液的气/液界面上形成的单分子膜不能诱导沉积银,而在中性和碱性镀液的气/液界面上可以诱导银膜的生长.当单分子膜处于液态或固态时,气/液界面有银膜形成;液态单分子膜上的银膜生长速度较快,且银膜的结构一致.随着电极电位的升高,银膜沉积的速度加快,呈环状向外生长的圆形银膜逐渐变得不规则.将不同实验条件下的银膜转移出来,采用扫描电镜(SEM)、透射电镜(TEM)对银膜的结构与形貌进行了表征.研究表明,银首先在单分子膜上异相成核,由八面体构型逐渐发展成星型,最终在气/液界面形成具有松枝状微观结构的光亮银膜.     

Synthesis of highly stable silver nanoparticles using imidazolium-based ionic liquid

Highly stable, aqueous dispersions, and hydrophilic ionic liquid-capped silver nanoparticles with positive surface charge were synthesized by in situ reduction of AgNO₃ with NaBH₄ in the presence of an imidazolium-based ionic liquid, viz., 1-dodecyl-3-methylimidazolium chloride ([C₁₂mim][Cl]) at room temperature. Prepared silver nanoparticles were characterized by UV–vis spectra, transmission electron microscopy (TEM), and zeta potential. UV–visible spectrum of the aqueous medium peaked at 407 nm corresponding to the plasmon absorbance of silver nanoparticles. TEM analysis revealed the spherical shape of the particles with sizes about 9 nm and low polydispersed. The surface charge of the synthesized silver nanoparticles was determined as +5.0 mV. The ionic liquid ([C₁₂mim][Cl]) capped silver nanoparticles were stable for at least 8 months.     

Formation of porous silver by electrochemical alloying/dealloying in a water-insensitive zinc chloride-1-ethyl-3-methyl imidazolium chloride ionic liquid

This paper describes the formation of a porous silver surface by a convenient two-step process involving electrochemical formation of a binary silver-zinc alloy film on a silver surface followed by electrochemical etching of the zinc from the alloy. Both the deposition and the dealloying steps were performed in a single bath of low-temperature zinc chloride-1-ethyl-3-methylimidazolium chloride ionic liquid at temperatures below 150 degrees C without using any other corrosive acids or bases. The effects of the deposited zinc quantity, deposition potential, current, and temperature on the structures and morphologies of the porous silver film were examined. In comparison with conventional molecular electrolyte solutions, ionic liquids provide a more versatile environment for fabricating porous metals. Because the zinc(II) species consumed during the deposition step was recovered during the dealloying step, the ionic liquid is reusable.     

Comparing π-complexation capabilities of ionic liquids containing silver(I) and copper(I) ions by headspace single drop microextraction in combination with high-performance liquid chromatography

Selective π-complexation capabilities of silver(I) and copper(I) ions can be effectively facilitated in ionic liquids. To understand the effects of environmental factors that influence the π-complexation of these metal ions with analytes, techniques that employ small volumes of ionic liquid that can be readily analyzed are desired. In this study, headspace single drop microextraction coupled with HPLC is used to investigate a diverse set of environmental factors on the metal ion-mediated complexation with aromatic compounds in ionic liquid media. Silver(I) and copper(I) bis[(trifluoromethyl)sulfonyl]imide salts were both studied by dissolving them in the 1-decyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ionic liquid and employing the mixture as extraction media for aromatic compounds. Water and acetonitrile within the sample solution were observed to interfere with the complexation of silver(I) ions and aromatic compounds, while ethylene glycol and triethylene glycol did not. The temperature and extraction times were optimized to fully facilitate the π-complexation capabilities of metal ions in ionic liquid media. Partition coefficients between the sample headspace and metal ion were determined using a three-phase equilibria model. Although no discernable difference in analyte partitioning between the headspace and ionic liquid solvent was observed, analyte partition coefficients to silver(I) ion tended to be greater compared to copper(I) ion.     

Modification of catheter materials by coating with polymer layers containing silver

The surface of polyurethane based catheter material or of silicon wafers as model surfaces were modified by spin coating of solutions of poly(ethylene oxide) or poly(vinyl alcohol) in water. For the incorporation of silver ions, silver nitrate was added to some of the solutions or the as-cast surfaces were dipped into AgNO₃ solution. Furthermore, samples coated with a thin layer of metallic silver were prepared by deposition of silver vapor in vacuum. The as-prepared surfaces were studied by atomic force microscopy and X-ray photoelectron spectroscopy. During the spin coating of the solutions containing AgNO₃, clusters of the silver component were formed. They were well dispersed in a poly(vinyl alcohol) matrix but act as nucleation agents in poly(ethylene oxide) where then large spherulites are formed. The surface compositions of coated samples and the depth profiling were carried out by angle dependent X-ray photoelectron spectroscopy.     

Relating chromatographic retention and electrophoretic mobility to the ion distribution within electrosprayed droplets

Ions that are observed in a mass spectrum obtained with electrospray mass spectrometry can be assumed to originate preferentially from ions that have a high distribution to the surface of the charged droplets. In this study, a relation between chromatographic retention and electrophoretic mobility to the ion distribution (derived from measured signal intensities in mass spectra and electrospray current) within electrosprayed droplets for a series of tetraalkylammonium ions, ranging from tetramethyl to tetrapentyl, is presented. Chromatographic retention in a reversed-phase system was taken as a measure of the analyte’s surface activity, which was found to have a large influence on the ion distribution within electrosprayed droplets. In addition, different transport mechanisms such as electrophoretic migration and diffusion can influence the surface partitioning coefficient. The viscosity of the solvent system is affected by the methanol content and will influence both diffusion and ion mobility. However, as diffusion and ion mobility are proportional to each other, we have, in this study, chosen to focus on the ion mobility parameter. It was found that the influence of ion mobility relative to surface activity on the droplet surface partitioning of analyte ions decreases with increasing methanol content. This effect is most probably coupled to the decrease in droplet size caused by the decreased surface tension at increasing methanol content. The same observation was made upon increasing the ionic strength of the solvent system, which is also known to give rise to a decreased initial droplet size. The observed effect of ionic strength on the droplet surface partitioning of analyte ions could also be explained by the fact that at higher ionic strength, a larger number of ions are initially closer to the droplet surface and, thus, the contribution of ionic transport from the bulk liquid to the liquid/air surface interface (jet and droplet surface), attributable to migration or diffusion will decrease.     

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.     

Development of in situ scanning electron microscope system for real time observation of metal deposition from ionic liquid

Based on our previous finding that room temperature ionic liquid (RTIL) can be observed by scanning electron microscopy (SEM) without charging of the liquid, a specifically designed electrochemical cell has been developed to observe electrochemical metal deposition from RTIL in real time by SEM. The cell was fabricated employing a fluorine doped tin oxide transparent glass, whose surface was divided into three electrodes. Then, the effectiveness of the fabricated cell was confirmed by demonstrating silver deposition form RTIL of 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (BMI-TFSI) containing Ag-TFSI, which gave growth of granular and dendritic forms of Ag deposit.     

Silver Hollow Microspheres: Large-scale Synthesis, Characterization and Electromagnetic Shielding Property

A facile and large-scale synthesis method to fabricate silver hollow microspheres with controllable morphologies and shell thickness is described using low-cost glass microspheres as templates. The method mainly involves two steps of the preparation of silver-coated glass microsphere core-shell particles by a controllable liquid reduced reaction of Ag[(NH3)2]+ solution, which only produces silver nanoparticles anchored on the surface of the thiolated glass microsphere templates, and the removal of glass microspheres by wet chemical etching with HF solution. The products are well characterized by field emitted scanning electron microscopy (SEM), transmitted electron microscopy (TEM), X-ray photoelectron spectra (XPS), X-ray diffraction (XRD) and energy dispersive X-ray (EDX) etc. The as-prepared core-shell particles and hollow particles have even and compact silver shells. The electromagnetic shielding coatings based on the silver hollow microspheres are demonstrated to have high conductivity, excellent shielding effectiveness and long durability, suggesting that the silver hollow microspheres obtained here are a novel light-weight electromagnetic shielding filler and will have extensive applications in the electromagnetic compatibility fields.     

A study of the silver form of a natural zeolitic material of the clinoptilolite type

The silver forms of a natural zeolitic material (from the East Slovakian deposit) on the clinoptilolite type has been prepared. The silver forms of the natural zeolitic material were investigated by X-ray powder diffractometry, IR spectroscopy, ESCA measurements, scanning electron microscopy and conductivity measurements. Depending on the preparation conditions, the content of silver ions in the zeolitic products was found to be in the range from 16 to 24%. In the sample with a silver loading of 18.6%, the silver uptake is due to an ion exchange process, mostly involving Na(I), Ca(II) and Mg(II) ions.     

片状卤化银晶体的制备、结构与性能的研究——Ⅱ.pAg对片状颗粒的尺寸、纵横比、碘离子分布及离子电导率的影响

本文研究了双注法制备片状卤化银微晶时,pAg值对所形成的卤化银片状颗粒的尺寸、纵横此、碘离子分布以及离子电导率的影响。随着pAg值的升高,片状颗粒的尺寸和纵横比都相应地增大和升高,且越来越多的碘离子从颗粒中心向外层迁移,直至到达表层,这说明存在晶体的重结晶过程。表面层的溴碘原子比是用X射线光电子能谱仪(XPS)测定的,并测量了不同pAg值下制备的不同尺寸的片状卤化银乳剂的介电损耗频谱。其结果表明,片状颗粒的尺寸影响其离子电导率,表层碘含量的影响不明显。     

Extraction of silver(I) from aqueous solutions in the absence and presence of copper(II) with a methimazole-based ionic liquid

The ionic liquid (IL) 2-butylthiolonium bis(trifluoromethanesulfonyl)amide, [mimSBu][NTf(2)], facilitates the efficient extraction of silver(I) from aqueous media via interaction with both the cation and anion components of the IL. Studies with a conventional aqueous-IL two phase system as well as microextraction of silver(I) by a thick IL film adhered to an electrode monitored in situ by cyclic voltammetry, established that [mimSBu][NTf(2)] can extract electroactive silver(I) ions from an aqueous solution. The pH of the aqueous phase decreases upon addition of [mimSBu](+), which is attributed to partial release of the hydrogen attached to the N(3) nitrogen atom of the imidazolium ring. The presence of silver(I) further increase the acidity of the aqueous phase as a consequence of coordination with the IL cation component. Voltammetric and (1)H and (13)C NMR techniques have been used to establish the nature of the silver(I) complexes extracted, and show that the form of interaction with the IL differs from that outlined previously for the extraction of copper(II). Insights on the competition established when silver(I) is extracted in the presence of copper(II) are provided. Finally, it is noted that metallic silver can be directly electrodeposited at the electrode surface after extraction of silver(I) into [mimSBu][NTf(2)] and that back extraction of silver(I) into aqueous media is achieved by addition of an acidic aqueous solution.