Polyaniline‐Modified Silver and Binary Silver‐Cobalt Catalysts for Oxygen Reduction Reaction

Novel dendrite‐like silver particles were electrodeposited on Ti substrates from a supporting electrolyte‐free 30 mmol L^?1 Ag(NH₃)₂⁺ solution, to synthesize the den‐Ag/Ti electrode. Binary Ag_xCo_y/Ti electrodes with different Ag:Co atomic ratios were further obtained by electrodeposition of Co particles on the den‐Ag/Ti electrode. Polyaniline (PANI) modified den‐Ag/Ti and Ag_xCo_y/Ti electrodes, PANI(n)‐den‐Ag/Ti and PANI(n)‐Ag_xCo_y/Ti, were also obtained by cyclic voltammetry at different numbers of cycles (n) in acidic and alkaline solutions containing aniline, respectively. All these electrodes exhibit high electroactivity for oxygen reduction reaction (ORR) in alkaline solution and their electroactivities follow the order: PANI(15)‐Ag₃₁Co₆₉/Ti>Ag₃₁Co₆₉/Ti>PANI(20)‐den‐Ag/Ti>den‐Ag/Ti. Among them, PANI(15)‐Ag₃₁Co₆₉/Ti displays the highest electrocatalytic activity for ORR with a much positive onset potential of 0 V (vs. Ag/AgCl) and a high ORR current density of 1.2 mA cm^?2 at ?0.12 V (vs. Ag/AgCl). The electrocatalysts are electrochemically insensitive to methanol and ethanol oxidation, and, as cathode electrocatalysts of direct alcohol fuel cells, can resist poisoning by the possible alcohol crossover from the anode.     

Two 3D Polyoxometalate‐based Frameworks Constructed from Silver(I)‐triazole/tetrazole Units: Hydrothermal Syntheses,Crystal Structure and Properties

Two polyoxometalate‐based compounds constructed by Keggin/Ag/ L , namely [Ag₁₀( L₁ )₆(H L₁ )₂][HPMo₂^VMo^VI₁₀O₄₀] ( 1 ) and [Ag₁₀( L₂ )₈(H₂SiMo₁₂O₄₀)] ( 2 ) ( L₁ = 1,2,4‐1H‐triazole and L₂ = 1H‐tetrazole), were synthesized under hydrothermal conditions and characterized by single‐crystal X‐ray diffraction, elemental analyses, and IR spectroscopy. In compound 1 , the tetra‐nuclear Ag cycles constructed by four L₁ ligands, two Ag1 ions, and two Ag2 ions. Compound 1 exhibits a two dimensional (2D) metal‐organic layer containing adjacent tetra‐nuclear Ag cycles. Furthermore, the adjacent 2D layers are further extended by Ag ions to form a three dimensional (3D) channel‐like framework, with Keggin anions embedding in the channels. Compound 2 is isostructural with 1 . Additionally, the electrochemical and photocatalytic properties of the title compounds were investigated.     

A Cryptate Reference Electrode for Ionic Liquids

The cryptate electrode (Ag/Ag⁺222), prepared by immersing silver wire in a solution of silver(I) salt and the cryptand 222 (4,7,13,16,21,24‐hexaoxa‐1,10‐diazabicyclo[8.8.8]hexacosane) in ionic liquids have been studied. The potential of the electrode is stabilized by the equilibrium of the Ag⁺ ion complexation by the cryptand, similarly to the potential stabilization by the ionic product of slightly soluble salts, used in aqueous electrodes of the second kind. The Ag/Ag⁺222 cryptate electrode (concentration of the cryptate was much higher than the silver(I) cation concentration, [222]>[Ag⁺]) may be used as a reference electrode in room temperature ionic liquids. The potential of the Ag/Ag⁺222 electrode is less sensitive to the presence of impurities, such as halides or water, in comparison to the Ag/Ag⁺ electrode. After anodic or cathodic polarization, the potential of the Ag/Ag⁺222 electrode comes back to the initial open circuit potential quickly. Preparation of the Ag/Ag⁺222 reference electrode is very easy: a silver wire is immersed in a solution of Ag⁺ salt and cryptand 222 (both available commercially) in the ionic liquid under study.     

反应性模板法合成硫化银中空球-银纳米粒子异质结构

以Cu₂S中空球为反应性模板, 通过在水溶液中与银离子的阳离子交换和氧化还原反应制备了大小均匀的Ag₂S中空球-Ag纳米粒子异质结构, 即Ag₂S-Ag异质中空球. 该异质结构中每个Ag₂S中空球的直径约为600 nm, 壁厚约20–30 nm, 其表面均附着一个Ag纳米粒子. 采用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线衍射(XRD)和能量色散X射线谱(EDS)对所得Ag₂S-Ag异质中空球的结构和组成进行了表征. 若以CuS中空球为反应性模板, 在相似转化条件下则主要得到不含Ag粒子的Ag₂S中空球. 该结果表明, Cu₂S中的Cu(I)的还原性在Ag₂S-Ag异质中空球的形成中发挥了重要作用. 通过对所制备的Ag₂S-Ag异质中空球进行二次生长, 还可以得到Ag₂S中空球的半球表面均被Ag膜所包覆的Ag₂S-Ag异质中空球.     

A Three-dimensional Heteronuclear Polymer of [Ag2Fe（SCN）5（DMF）]n Containing Channels and One-dimensional Ag2S2-S-Ag2S2 Chains with Ag…Ag Interaction

Introduction So far, considerable attention has been paid to mag-netic interaction between two different metal ions.1-3 As a potential bridging ligand, thiocyanate can coordinate to a harder metal center with N atom and softer ones with S atom at the same time, resulting in the formation of small ferromagnetic coupling.2 On the other hand, the Fe(III) atom is a good candidate as a hard acid and Ag(I) is a good candidate as a soft acid, so that the Fe(III) centers could be expected to conn…     

Anodic Stripping Voltammetric Determination of Lead（Ⅱ） Using Glassy Carbon Electrode Modified with Novel Calix[4] arene

A new glassy carbon electrode modified with novel calix[4]‐arene derivative was prepared and then applied to the selective recognition of lead ion in aqueous media by cyclic and square wave voltammetry. A new anodic stripping peak at ? 0.92 V (vs. Ag/Ag⁺) in square wave voltammogram can be obtained by scanning the potential from ? 1.5 to ? 0.6 V, of which the peak current is proportional to the concentration of Pb²⁺. The modified electrode in 0.1 mol/L HNO₃ solution showed a linear voltammetric response in the range of 2.0 × 10–⁸–1.0 × 10–⁶ mol/L and a detection limit of 6.1 × 10–⁹ mol/L. In the modified glassy carbon electrode no significant interference occurred from alkali, alkaline and transition metal ions except Hg²⁺, Ag⁺ and Cu²⁺ ions, which can be eliminated by the addition of KSCN. The proposed method was successfully applied to determine lead in aqueous samples.     

Octahedral and Cyclic [Ag6] Cluster Cores Stabilized by {Ag3(Spz)3(N‐triphos)3} Motifs [HSpz = Pyrazine‐2‐thiolate,N‐triphos = Tris((diphenylphosphanyl)methyl)amine]: Ag···Ag Interactions

The complexes [Ag₁₂(Spz)₁₂(N‐triphos)₂][Ag₃(Spz)₃(N‐triphos)]₂ · (DMF)₆ ( 1 ) and [Ag₁₈(Spz)₁₂(N‐triphos)₄(CF₃CO₂)₆] ( 2 ) were synthesized and structurally characterized by X‐ray diffraction [HSpz = pyrazine‐2‐thiolate, N‐triphos = tris((diphenylphosphanyl)methyl)amine]. The central [Ag₆] ring with chair‐conformation in 1 and the ideally octahedral [Ag₆] cluster core in 2 are both stabilized by the tripodal building units of neutral [Ag₃(Spz)₃(N‐triphos)] compound. The Ag ··· Ag distances of the [Ag₆] moieties in 1 and 2 are 3.07 and 2.81 Å, respectively, exhibiting intermetallic interactions, which can enhance the stability of [Ag₆] conformations. In addition, the π ··· π interactions between parallel pyrazine rings could impose on the building and the Ag ··· Ag interactions of these Ag–S clusters.     

A 3D Polyoxometalate‐Based Framework Constructed from Ag/trz Metal‐Organic Ribbons and P2W18 Polyoxoanions: Synthesis,Structure and Electrochemical Properties

A Wells‐Dawson Polyoxometalate‐based hybrid, Ag₉(trz)₃(Htrz)₄ (H₂O)(P₂W₁₈O₆₂)·3H₂O ( 1 ) (Htrz = 1,2,4‐1H‐triazole) was hydrothermally synthesized through using trz ligand and silver nitrate in the presence of [P₂W₁₈O₆₂]^6– polyoxoanion. In the 3D framework structure of compound 1 , two kinds of wave‐like Ag/trz chains originated from trz ligands and silver cations are aggregated in a “2+1” mode by {Ag₂/trz} linkages to result in a 1D Ag/trz metal‐organic ribbon, which is further extended into a 3D framework structure by [P₂W₁₈O₆₂]^6– polyoxoanions through Ag‐O covalent bonds. Additionally, the electrochemical properties of compound 1 have also been investigated.     

Core Modulation of 70‐Nuclei Core‐Shell Silver Nanoclusters

The reaction of {(HNEt₃)₂[Ag₁₀(tBuC₆H₄S)₁₂]}_n, Ag₂O, Na₂MoO₄, and m‐methoxybenzoic acid (Hmbc) in CH₃OH/CH₂Cl₂ led to yellow crystals of [Ag₄S₄ (MoO₄)₅@Ag₆₆] (SD/Ag70b; SD=SunDi) only, while in the presence of DMF, additional dark‐red crystals of [Ag₁₀@ (MoO₄)₇@Ag₆₀] (SD/Ag70a) were obtained. SD/Ag70b consists of five MoO₄^2? ions wrapped by a shell of 66 Ag atoms, while SD/Ag70a contains a rare Ag₁₀ kernel consisting of five tetrahedra sharing faces and edges, surrounded by seven MoO₄^2? ions enclosed in a shell of 60 Ag atoms. The formation of the Ag₁₀ kernel originates from a reduction reaction during the self‐assembly process that involves DMF. This work provides the structural information of a unique Ag₁₀ kernel (five fused Ag₄ tetrahedra) and paves an avenue to trap elusive silver species with hierarchical multi‐shell silver nanocluster assemblies with the help of anion templates.     

Electro-chromatography in the separation of ions : Part III. Separation of silver group metals

The migration sequences of silver group ions Ag⁺, Hg₂⁺², Pb⁺²and Ti⁺ have been studied in a number of complex-forming electrolytes. Based on the migration sequences, the ions in a mixture can be separated into distinct zones using a decinormal solution of sodium chloride, potassium chloride or potassium cyanide as the electrolyte. The sequence is Hg — Ag— Pb—Ti, while in KCN at pH 7.0 the sequence becomes Ag—Hg—Pb—Ti.     

Synthesis and Characterization of Silver Sulfide Nanoparticles Containing Sol-Gel Derived HPC-Silica Film for Ion-Selective Electrode Application

Silver sulfide nanoparticles dispersed in sol-gel derived hydroxypropyl cellulose (HPC)-silica films have been successfully synthesized using H₂S gas diffusion method. This is the first attempt to produce silver sulfide nanoparticles using this technique. Ag₂S nanoparticles are generated through reaction of H₂S gas with AgNO₃ precursor dissolved in the HPC-silica matrix. Transmission electron microscope (TEM) and atomic force microscope (AFM) analysis reveal nanoparticles size distribution from 2.5 nm to 56 nm for H₂S gas exposed sample. The surface chemistry of Ag₂S nanoparticles and sol-gel derived HPC-silica matrix is confirmed by X-ray photoelectron spectroscopy (XPS). The negative shifts in the core-level XPS Ag (3d) binding energy of Ag₂S nanoparticles are attributed to Ag : S surface atomic ratio exhibited by these nanoparticles with varying processing conditions. Following processing and characterization, suitability of the present method to produce silver sulfide ion-selective electrode is demonstrated by depositing Ag₂S nanoparticles on a graphite rod. The high reponse function of the electrode is due to the presence of nanoparticles.     

Extraction of silver(I) in the system tetrabutyl S-dithiopyrophosphate (TBDTPP)—electrolyte

The extraction of Ag⁺ ions was studied in the systems tetra-n-butyl S-dithiopyrophosphate [(BuO)₂P(S)(O)P(S)(BuO)₂]—TBDTPP in CCl₄/HNO₃ and TBDTPP/LiNO₃. The extraction coefficients were determined as a function of the electrolyte and TBDTPP concentration. Infrared absorption studies have been undertaken to obtain information on the changes in the organic phase during the extraction of Ag(I). Analysis of the spectra has shown a shift of the P=S stretching band in the direction of lower frequencies. This is indicative of bond weakening and a decrease in the double bond character of P=S, due to withdrawal of electron density by the metal ion, and constitutes evidence for the coordination of Ag⁺ by thiophosphoryl groups of TBDTPP.     

Silver(I) Complexes with a Bulky Anthracene‐Based Dicarboxylic Ligand: Syntheses,Crystal Structures,and Luminescent Properties

To explore the influence of anthracene skeleton with a larger conjugated π‐system on the structures and properties of its complexes, two Ag^I–carboxylate complexes based on anthracene‐9,10‐dicarboxylate (L) were synthesized and characterized: [{[Ag(L)][Ag(dmpy)₂]}_∞] ( 1 ) and [{[Ag₂(L)(bipy)₂]}_∞] ( 2 ) (dmpy = 2,6‐dimethylpyridine and bipy = 4,4′‐bipyridine). Complex 1 has an interesting framework consisting of anionic chains {[Ag(L)]^–}_∞ and the mononuclear cationic units [Ag(dmpy)₂]⁺, which is further assembled to form networks along the different crystallographic directions by the intermolecular C–H ··· Ag hydrogen‐bonding interactions. Complex 2 takes a ladder‐like chain structure by incorporating 4,4′‐bipyridine (bipy) as a bridging co‐ligand, which is further interlinked to generate a planar network through interchain Ag–Ag bonding contacts. The steric bulk of anthracene ring in L may play an important role in the formation of 1 and 2 . Moreover, the luminescent properties of the 1 and 2 were investigated in detail.     

Improved Photocatalytic Activity and Stability of Nano‐sized Ag/Ag2CO3 Plasmonic Photocatalyst by Surface Modification of Fe(III) Nanocluster

The surface modification of Ag/Ag₂CO₃ with Fe(III) ions has been achieved through simply photoreduction‐impregnation method. The obtained products were characterized by means of X‐ray diffraction (XRD), scanning electron microscopy (SEM), X‐ray photoelectron spectroscopy (XPS), and UV‐vis absorption spectroscopy. Under visible‐light irradiation (γ>420 nm), the Fe(III)/Ag/Ag₂CO₃ sample displays a higher photocatalytic activity and stability than pure Ag₂CO₃ and Ag/Ag₂CO₃ samples for the degradation of methyl orange (MO). The improved photocatalytic activity and stability of this ternary system could be ascribed to the synergetic effect between Ag nanoparticles and Fe(III) nanocluster. The metallic Ag nanoparticles cause an obviously enhanced visible‐light absorption to produce more photogenerated charges, while the Fe(III) works as an active site for the following oxygen reduction to reduce the recombination rate of photogenerated electrons and holes.     

Trifluoroborate-substituted polythiophene as a novel conjugated polymer promising for sensing and solid-state reactions

The anodic oxidation of trifluoroborate-substituted thiophene 1 in CH₃CN without added electrolyte yielded at ca. 1.0 V (vs. Ag⁺|Ag) a conjugated polymer film showing electroactivity both in water and organic media. The electrochemical and UV–visible spectroscopic responses of such a material were found to be dependent on the nature of cation.     

Synthesis,crystal structure and studies on the interaction with albumin of a new silver(I) complex based on 2‐(4‐nitrobenzenesulfonamido)benzoic acid

In the present work, the two‐dimensional (2D) polymer poly[[μ₄‐2‐(4‐nitrobenzenesulfonamido)benzoato‐κ⁴O¹:O¹:O^1′:N⁶]silver(I)] (AgL), [Ag(C₁₃H₉N₂O₆S)]_n, was obtained from 2‐(4‐nitrobenzenesulfonamido)benzoic acid (HL), C₁₃H₁₀N₂O₆S. FT–IR, ¹H and ¹³C{¹H} NMR spectroscopic analyses were used to characterize both compounds. The crystal structures of HL and AgL were determined by single‐crystal X‐ray diffraction. In the structure of HL, O—H…O hydrogen bonds between neighbouring molecules result in the formation of dimers, while the silver(I) complex shows polymerization associated with the O atoms of three distinct deprotonated ligands (L^?). Thus, the structure of the Ag complex can be considered as a coordination polymer consisting of a one‐dimensional linear chain, constructed by carboxylate bridging groups, running parallel to the b axis. Neighbouring polymeric chains are further bridged by Ag—C monohapto contacts, resulting in a 2D framework. Fingerprint analysis of the Hirshfeld surfaces show that O…H/H…O hydrogen bonds are responsible for the most significant contacts in the crystal packing of HL and AgL, followed by the H…H and O…C/C…O interactions. The Ag…Ag, Ag…O/O…Ag and Ag…C/C…Ag interactions in the Hirshfeld surface represent 12.1% of the total interactions in the crystal packing. Studies of the interactions of the compounds with human serum albumin (HSA) indicated that both HL and AgL interact with HSA.     

Two AgI–Carboxylate Polymers Involving Ag–Ag Interactions: Syntheses,Structures and Fluorescent Properties

Two novel silver complexes [Ag₂(Hsal)₂]_n ( 1 ) and [Ag₂(oda)]_n ( 2 ) (H₂sal = salicylic acid, H₂oda = oxydiacetatic acid) were synthesized hydrothermally by reaction of AgNO₃ with H₂sal or H₂oda and characterized by IR spectroscopy, elemental analysis, and single‐crystal X‐ray diffraction. Compound 1 shows a 2D metal‐organic architecture connected by μ₃‐η¹:η¹:η¹‐salicylato ligands and Ag–Ag interactions. Compound 2 displays a 3D metal‐organic network formed by μ₇‐(η²:η¹)‐(η²:η¹)‐η¹‐oxydiacetato ligands and Ag–Ag interactions. The photoluminescence properties of both complexes were also investigated.     

Coordination Chemistry of Diiodine and Implications for the Oxidation Capacity of the Synergistic Ag+/X2 (X=Cl,Br, I) System

The synergistic Ag⁺/X₂ system (X=Cl, Br, I) is a very strong, but ill‐defined oxidant—more powerful than X₂ or Ag⁺ alone. Intermediates for its action may include [Ag_m(X₂)_n]^m+ complexes. Here, we report on an unexpectedly variable coordination chemistry of diiodine towards this direction: ( A )Ag‐I₂‐Ag( A ), [Ag₂(I₂)₄]²⁺( A ⁻)₂ and [Ag₂(I₂)₆]²⁺( A ⁻)₂⋅(I₂)_x≈0.65 form by reaction of Ag( A ) ( A =Al(OR^F)₄; R^F=C(CF₃)₃) with diiodine (single crystal/powder XRD, Raman spectra and quantum‐mechanical calculations). The molecular ( A )Ag‐I₂‐Ag( A ) is ideally set up to act as a 2 e⁻ oxidant with stoichiometric formation of 2 AgI and 2 A ⁻. Preliminary reactivity tests proved this ( A )Ag‐I₂‐Ag( A ) starting material to oxidize n‐C₅H₁₂, C₃H₈, CH₂Cl₂, P₄ or S₈ at room temperature. A rough estimate of its electron affinity places it amongst very strong oxidizers like MF₆ (M=4d metals). This suggests that ( A )Ag‐I₂‐Ag( A ) will serve as an easily in bulk accessible, well‐defined, and very potent oxidant with multiple applications.     

Coordination Chemistry of Diiodine and Implications for the Oxidation Capacity of the Synergistic Ag+/X2 (X=Cl,Br, I) System

The synergistic Ag⁺/X₂ system (X=Cl, Br, I) is a very strong, but ill‐defined oxidant—more powerful than X₂ or Ag⁺ alone. Intermediates for its action may include [Ag_m(X₂)_n]^m+ complexes. Here, we report on an unexpectedly variable coordination chemistry of diiodine towards this direction: ( A )Ag‐I₂‐Ag( A ), [Ag₂(I₂)₄]²⁺( A ^?)₂ and [Ag₂(I₂)₆]²⁺( A ^?)₂?(I₂)_x≈0.65 form by reaction of Ag( A ) ( A =Al(OR^F)₄; R^F=C(CF₃)₃) with diiodine (single crystal/powder XRD, Raman spectra and quantum‐mechanical calculations). The molecular ( A )Ag‐I₂‐Ag( A ) is ideally set up to act as a 2 e^? oxidant with stoichiometric formation of 2 AgI and 2 A ^?. Preliminary reactivity tests proved this ( A )Ag‐I₂‐Ag( A ) starting material to oxidize n‐C₅H₁₂, C₃H₈, CH₂Cl₂, P₄ or S₈ at room temperature. A rough estimate of its electron affinity places it amongst very strong oxidizers like MF₆ (M=4d metals). This suggests that ( A )Ag‐I₂‐Ag( A ) will serve as an easily in bulk accessible, well‐defined, and very potent oxidant with multiple applications.     

Electrochemistry and Ion Sensing Properties of Conducting Hydrogel Layers Based on Polypyrrole and Alkoxysulfonated Poly(3,4‐ethylenedioxythiophene) (PEDOT‐S)

Acidic aqueous solutions containing pyrrole and alkoxysulfonated PEDOT derivative (PEDOT‐S) were found to undergo polymerization in the absence of an external oxidizing agent. The product was a nearly black‐colored conducting hydrogel that after separation could be dispersed in water or acetone. The suspensions could be used to deposit cast films on a polycrystalline gold electrode. The polymer modified electrode showed a nearly Nernstian potentiometric response to Ag⁺ cations in the concentration range of 10^?5–10^?1 M with the slope of 54 mV/decade. The response was specific to Ag⁺ compared to a series of alkali and transition‐metal cations (pK_Ag/M>3.7).