Synthesis, reaction and structure of a highly light-stable silver(I) cluster with an Ag4S4N4 core having a tridentate 4N-morpholyl 2-acetylpyridine thiosemicarbazone ligand: use of water-soluble silver(I) carboxylates as a silver(I) source

A novel neutral tetrameric silver(I) cluster [Ag(mtsc)](4) was obtained from reactions of a tridentate (4)N-morpholyl 2-acetylpyridine thiosemicarbazone ligand (N'-[1-(2-pyridyl)ethylidene] morpholine-4-carbothiohydrazide, Hmtsc) and silver(I) sources containing Ag-O bonds (Ag(2)O, Ag(OAc), silver(I) 2-pyrrolidone-5-carboxylate (infinity){[Ag(Hpyrrld)](2)}, silver(I) 5-oxo-2-tetrahydrofurancarboxylate (infinity){[Ag(othf)](2)}, and silver(I) complexes with camphanic acid (infinity){[Ag(ca)]} and (infinity){[Ag(ca)(Hca)]}). The cluster was characterized by elemental analysis, TG/DTA, FTIR and single-crystal X-ray analysis in the solid state. The solution properties of the complexes were investigated using solution molecular weight measurement, ESI-MS and solution ((1)H, (13)C and (31)P) NMR spectroscopy. The obtained cluster is a novel example of a light-stable Ag(I) cluster with a tridentate thiosemicarbazone ligand and the second report of a crystal structure of a thiosemicarbazone silver(I) complex. The reaction of the tetramer with a large excess of PPh(3) gave dimeric complexes, namely, [Ag(micro(S)-mtsc)(PPh(3))](2) and [(PPh(3))(2)Ag(micro(S)-mtsc)(2)Ag]. The chloroform solution of the tetrameric complex showed modest and effective activities against selected bacteria (Bacillus subtilis, Staphylococcus aureus and Pseudomonas aeruginosa) and yeasts (Candida albicans and Saccharomyces cerevisiae), respectively, but it did not inhibit the growth of any selected microorganisms in a water-suspension system.     

2,2'-Biquinolines as test pilots for tuning the colour emission of luminescent mesomorphic silver(I) complexes

The synthesis and characterization of a series of 2,2'-biquinolines differently substituted in the 4,4'-position and their corresponding silver(I) derivatives obtained through reaction with silver triflate in a 1 : 1 stoichiometric ratio are reported. In order to perform a systematic investigation on the role played by the substituents on the coordination to the silver(I) centre, structural studies through single crystal X-ray diffraction have been performed on two Ag(I) model complexes. Unlike their analogous 2,2'-bipyridine ligands, the biquinolines have been found to behave only as chelated ligands towards the silver(I) ion, irrespective of the substituents. The coordination sphere of the Ag(I) is filled by a solvent molecule and, depending on the presence and nature of the substituents on the organic ligand, by an oxygen atom coming from a coordinated triflate or from a carboxylic group of a symmetrically related molecule, giving rise to neutral or ionic species. For the highest Ag(I) triflate homologues the presence of long and flexible peripheral tails makes it possible to achieve liquid crystalline properties with columnar organization whose high order is due to the large and rigid core. Moreover, the metal coordination induces in all the Ag(I) species interesting emission properties both in solution and condensed states, giving rise to blue or green emitters, depending on the nature of the substituents on the biquinoline units.     

Fabrication of a Simple and Cheap Screen-printed Silver/Silver Chloride (Ag/AgCl) Quasi-reference Electrode

In this work, a silver/silver chloride ink is fabricated using two steps. First the silver ink is prepare using silver, nail polish and acetone. Then the silver ink is painted in a paper substrate and a silver chloride layer is deposited using a bleach solution. The result is the silver/silver chloride conductive ink. The silver ink is cheap ($2.49/g), well-dispersive and very easy to fabricate. The materials were characterized by SEM and XRD. The Ag ink showed the formation of a continuous network throughout the silver ink film with fewer agglomeration. The effective chlorination process was also observed in the Ag/AgCl characterization. Since the Ag/AgCl substrate will be used as a quasi-reference electrode, it is important to investigate the electrical properties. The Ag ink showed an average ohmic resistance of 2.27 Ω. The addition of the AgCl layer decreases the conductivity, as expected. In summary, the Ag/Ag/Cl ink developed is simple, well-dispersed, cheap and with good conductivity. Therefore, it can be used as a conductive ink in the fabrication of quasi-reference electrodes.     

N,N-bis-(2-benzimidazolylmethyl)L-methionine: An efficient Ag(I) extractant

A new ligand N,N-bis-(2-benzimidazolylmethyl)L-methionine has been synthesized and well characterized by different analytical techniques. The ligand has a very strong affinity for silver(I) and is used for the selective extraction of silver ions from aqueous solution into 1-butanol. The effect of concentration of Ag(I), pH, diverse ions, and temperature on the extraction is reported. The developed method has success-fully been applied to the determination of silver in different samples. Radiotracer technique, using ^110mAg(I) as a tracer, has been used for monitoring the concentration of silver ion.     

Influence of neutral ligands on the structures of silver(I) sulfonates

This article represents a systematical examination of the structures of silver(I) sulfonates incorporating neutral ligands. To survey the influence of the properties of neutral ligands on the structures of silver(I) sulfonates, three kinds of sulfonate anions (L1=1-naphthalenesulfonate, L2=p-toluenesulfonate, and L3=1, 3, 6, 8-pyrenetetrasulfonate) and three kinds of neutral ligands (pyrazine, Pyr, a divergent bidentate ligand; hexamethylenetetramine, hmt, a divergent tetradentate ligand; and beta-picoline, Pic, a monodentate ligand) were selected for study, and five novel silver(I) sulfonates containing neutral ligands have been synthesized: [Ag(L1)(Pyr)].H2O, Ag(L2)(Pyr), Ag4(L3)(Pyr)4(H2O)2, [Ag(L1)(hmt)].H2O, and Ag(L1)(Pic)2. The crystal structures have been determined by single-crystal X-ray diffraction, and these compounds show a variety of structures with different dimensionalities. Moreover, the luminescent properties of compounds and are also discussed.     

Controlled formation of optically reflective and electrically conductive silvered surfaces on polyimide film via a direct ion-exchange self-metallization technique using silver ammonia complex cation as the precursor

Double-surface-silvered polyimide films have been successfully fabricated using silver ammonia complex cation ([Ag(NH3)2]+) as the silver precursor and 3,3',4,4'-benzophenonetetracarboxylic dianhydride/4,4'-oxidianile- (BTDA/ODA-) based poly(amic acid) (PAA) as the polyimide precursor via a direct ion-exchange self-metallization technique. The process has been clarified to involve the loading of silver(I) into PAA via ion exchange, the thermally induced reduction of silver(I) to silver(0) and the concomitant imidization of PAA to polyimide upon thermal treatment, the subsequent silver-catalyzed and oxygen-assisted decomposition of the polyimide overlayer, and the self-accelerated aggregation of silver clusters on the film surface to produce well-defined surface silver layers. By employing [Ag(NH3)2]+ solution with a concentration of only 0.01 M and an ion-exchange time of no more than 10 min, the controlled formation of highly reflective and conductive silver surfaces upon thermal treatment at 300 degrees C for less than 4.5 h indicates that the present work provides an efficient route and an effacious silver species for polyimide surface metallization. Although the alkaline characteristics of [Ag(NH3)2]+ have a strong hydrolysis effect on the polyimide precursor chains, the final metallized films retain the key mechanical and thermal properties of the pure polyimide. Films were characterized by ATR-FTIR, XPS, ICP-AES, SEM, TEM, DSC, TGA, reflectivity, conductivity, and mechanical measurements.     

Polynuclear Silver(I) Triazole Complexes: Ion Conduction and Nanowire Formation in the Mesophase

Examples of polynuclear metallomesogens are few. Herein,1,2,4‐triazole ligands were used to prepare mono‐ and polynuclear silver(I) triazole metallomesogens. Besides showing an SmA phase in the mesophase, two interesting properties were observed. First, higher ion conductivity is always found for the polynuclear complexes than for the mononuclear complexes with the same anion, an observation contrary to the knowledge that migration of a monomeric cation should be faster than that of a polymeric cation. Second, thermolysis of the polynuclear silver(I) triazole complexes in the assembled mesophase yielded Ag nanowires, in an excellent demonstration of the assembled nature of the polynuclear silver(I) ions in the thermolysis process.     

On a new phase of elemental silver,appearing on its “reprecipitation” in Ag-gelatin-immobilized matrix systems

The process of transformation of elemental silver according to the scheme Ag→AgHlg→Ag in gelatin-immobilized matrices is studied. The process includes two steps: keeping the matrix in an aqueous solution containing potassium hexacyanoferrate(III) and any potassium halide and keeping in an aqueous solution containing tin(II) chloride and an organic or inorganic compound that forms a sufficiently strong soluble complex with Ag(I). It is established that thus formed gelatin-immobilized substance is a practically pure elemental silver in two structural modifications with different optical and X-ray diffraction parameters.     

Gas phase synthesis, structure and unimolecular reactivity of silver iodide cluster cations, Ag(n)I(m)(+) (n = 2-5, 0 < m < n)

Multistage mass spectrometry (MS(n)) experiments reveal that gas phase silver iodide cluster cations, Ag(n)I(m)(+), are readily built up in a stepwise fashion via ion-molecule reactions between mass selected silver (Ag(3)(+) and Ag(5)(+)) or silver hydride (Ag(2)H(+) and Ag(4)H(+)) cluster cations and allyl iodide, in contrast to their reactions with methyl iodide, which solely result in ligation of the clusters. The stoichiometries of these clusters range from 1 < or = n < or = 5 and 1 < or = m < or = 4, indicating the formation of several new subvalent silver iodide clusters. Collision induced dissociation (CID) experiments were carried out on each of these clusters to shed some light on their possible structures. The products arising from CID of the Ag(n)I(m)(+) clusters are highly dependent on the stoichiometry of the cluster. Thus the odd-electron clusters Ag(4)I(2)(+) and Ag(5)I(+) fragment via loss of a silver atom. In contrast, the even-electron cluster ions all fragment via loss of AgI. In addition, Ag(2)I(2) loss is observed for the Ag(4)I(3)(+) and Ag(5)I(2)(+) clusters, while loss of Ag(3)I(3) occurs for the stoichiometric Ag(5)I(4)(+) cluster. DFT calculations were carried out on these Ag(n)I(m)(+) clusters as well as the neutrals associated with the ion-molecule and CID reactions. A range of different isomeric structures were calculated and their structures are described. A noteworthy aspect is that ligation of these silver clusters by I can have a profound effect on the geometry of the silver cluster. For example, D(3h) Ag(3)(+) becomes C(2v) Ag(3)I(+), which in turn becomes C(2h) Ag(3)I(2)(+). Finally, the DFT predicted thermochemistry supports the different types of reaction channels observed in the ion-molecule reactions and CID experiments.     

Evidence for the involvement of silver nanoclusters during the Wolff rearrangement of alpha-diazoketones

In situ-generated silver nanoclusters(Ag(n)) during the reduction of either silver(I) oxide or other salts presumably catalyze the Wolff rearrangement of alpha-diazoketones. Their optical, physical, and catalytic properties depend on the starting silver(I) compound and the reaction conditions. [reaction: see text]     

Silica Gels and Gel Glasses Containing Silver and Platinum Metal Particles

Silica gels containing between 0.05 and 20.0 mol% Ag2O and between 0.1 and 1.0 mol% PtO2 have been synthesized using TEOS, C2H5OH, H2O, HNO3, HCl, AgNO3 and PtCl4 as precursors. The gels obtained with Ag2O are colorless, while the gels containing PtO2 are yellow. The gels have been heat treated in the 25–1000°C temperature range. The processes of structural evolution of gels have been studied by means of IR-spectroscopy, X-ray diffraction analysis, transmission electron microscopy (TEM) and transmission electron microdiffraction (TEMD). It has been established that the temperature of gel to gel-glass transition decreases when the Ag2O content of the gels increases. The same tendency was established for the gel to gel-glass transition in the SiO2-PtO2 system.Special attention was paid to the formation of silver and platinum metallic particles in amorphous materials. The microstructure of the gels has been observed and the sizes of the metal particles were determined to be from 3 to 25 nm.The crystallization processes in the gels heat treated at 1000–1200°C have been examined and besides the silver and platinum particles -cristobalite was formed.It has been shown that nanocomposite materials containing ultrafine silver and platinum particles in SiO2 amorphous or polycrystalline matrixes can be obtained.     

超细Ag颗粒对葡萄糖氧化酶生物传感器响应灵敏度的增强效应

生物传感器在临床医学、环境和食品工业等方面都有重要的用途［１］,且由于其具有体积小、精度高、灵敏度好和便于现场测定等优点,已成为当前研究的热点课题之一．其中研究得较多的是氧化酶电流型生物传感器,特别是介体型,由于其响应快,灵敏而倍受重视．现已报道的可...     

Synthesis and ligand properties of thianthrenophane

Thianthrenophane 1 has a cavity which offers enough room to potentially enable endohedral coordination to small ions or molecules. For the complexation of silver(I) perchlorate the complex stability constants of 1 logK1=5.45 +/- 0.13 and of thianthrene logK2=9.16 +/- 0.10 were determined by UV/Vis titration. Single competition transport experiments with ten metal salts demonstrate a very high selectivity of 1 as a carrier for silver(I) and a distinctly higher transport rate compared to carriers such as thianthrene and 1,4,8,11-tetrathiacyclotetradecane (14-ane-S4). Although the X-ray crystal structure analysis of the polymeric [Ag(1)]ClO4.(dioxane)7 complex shows an exohedral coordination to silver(I) we suggest that the formation of an endohedral [Ag(1)]+ complex is the explanation for the unusual carrier selectivity of silver(I) by 1 in bulk liquid membrane.     

Review: Multimetallic silver(I)–pyridinyl complexes: coordination of silver(I) and luminescence

This review highlights some structural features and luminescent properties of homo- and hetero-multinuclear silver(I)–pyridinyl complexes. It focuses on the coordination and geometry of the silver(I) ions to the pyridinyl-nitrogen. For this reason, we have considered only pyridinyl-N–Ag(I) complexes whose crystal data are available. In addition, this review does not consider mononuclear silver(I)–pyridinyl complexes as these have been reviewed elsewhere. This is motivated by the fact that multinuclear silver(I)–pyridinyl complexes have been shown to be more stable in solution, possess enhanced properties, and have fascinating structures compared to their mononuclear counterparts. The introduction highlights pyridinyl ligands used in complexation of silver(I) ions. The main body highlights complexation of silver(I) through pyridinyl nitrogen and the interactions found in the multinuclear silver(I)–pyridinyl complexes as well as the coordination number and geometry of silver(I) centers. Though silver(I) has been flaunted to prefer linear twofold coordination geometry, from this review, it is clear that higher coordination numbers in varied geometries are possible. These include distorted trigonal planar, T-shaped, distorted tetrahedral, trigonal bipyramidal, and octahedral geometries. Coordination of silver(I) to pyridinyl ligands and their metalloligands has been observed to impart or enhance luminescent properties in the ensuing complexes.     

氧化铁和羟基氧化铁光催化还原银离子

在波长λ≥320 nm的紫外灯照射下, 水溶液中的银离子能在氧化铁和羟基氧化铁催化剂表面发生还原反应而生成颗粒银. 在这些催化剂上, Ag(I)的等温吸附线都符合Langmuir吸附方程; Ag(I)的初始还原速率均随其初始吸附量的增加而线性增大, 并且增大的幅度依α-Fe2O3>α-FeOOH>γ-Fe2O3>γ-FeOOH>δ-FeOOH的顺序降低. 但是, 在前三种催化剂上, 只有当Ag(I)的吸附量达到其饱和吸附量的一半时, Ag(I)的还原才能发生, 并且几乎不受氮气的影响. 在δ-FeOOH和TiO2体系中通入氮气, 能显著加快Ag(I)的光催化还原. 这说明O2与Ag(I)竞争催化剂上的吸附位点和还原物种, 且与催化剂的性质有关. XRD分析表明, α-Fe2O3和δ-FeOOH分别具有较好和较差的结晶度. 这说明氧化铁和羟基氧化铁的结晶度越高, 越有利于光生载流子的分离及其与表面目标物种发生氧化还原反应.     

Wolff rearrangement of alpha-diazoketones using in situ generated silver nanoclusters as electron mediators

[reaction: see text] We report Wolff rearrangement of alpha-diazoketones by in situ generated silver nanoclusters (Ag(n)(), 2-4 nm) from silver(I) oxide (Ag(2)O) involving a nonclassical electron-transfer process. Our results show that Ag(n)()(+)/Ag(n)()(0) redox couple allows the initial removal of an electron from alpha-diazoketone and its back-donation after chemical reaction(s). Controlled potential coulometry (CPC) of various alpha-diazoketones results in the realization of Wolff-rearranged carboxylic acids in excellent yields.     

Controlled synthesis of double- and multiwall silver nanotubes with template organogel from a bolaamphiphile

Double- and multiwall silver nanotubes were synthesized by using the uniform low-molecular-mass organogel nanotubes self-assembled from an L-glutamic-acid-based bolaamphiphile, N,N-eicosanedioyl-di-L-glutamic acid (EDGA). The EDGA could gel a mixed water/ethanol solvent and form helical nanotubes. When the gel thus formed was mixed with AgNO3 in water/ethanol, the silver(I) cations could be coordinated with both the inner and outer surfaces of the EDGA nanotubes. The reduction of the silver cation under the photoirradiation yielded double-wall silver nanotubes, where two silver layers were separated by one EDGA layer. Elongations of the reduction time of the mixed gels and AgNO3 in the solution lead to the formation of three-, four-, and five-wall silver nanotubes. In these multiwall silver nanotubes, each wall was separated at a distance of about 2.7 nm, which was just the molecular length of the bolaamphiphile. It was suggested that the dissolved EDGA molecules and excess Ag(I) cations were further assembled onto the surface of the formed double-wall silver nanotubes and, as a consequence, the photoreduction caused the formation of the third-wall silver nanotubes. The multiwall silver nanotubes were further formed in a similar way. The factors affecting the formation of the silver wall nanotubes such as the relative amount of AgNO3 to EDGA and the synthetic conditions were discussed.     

Toward monodispersed silver nanoparticles with unusual thermal stability

A novel in situ autoreduction route has been developed, by which monodispersed silver nanoparticles with tunable sizes could be easily fabricated on silica-based materials, especially inside the channels of mesoporous silica (MPS). 13C CP/MAS NMR spectroscopy was employed to monitor the whole assembly process. It was demonstrated that the amino groups of APTS (aminopropyltriethoxyl silane)-modified MPS can be used to anchor formaldehyde to form novel reducing species (NHCH2OH), on which Ag(NH3)2NO3 could be in situ reduced. Monodispersed silver nanoparticles were thus obtained. In situ XRD and in situ TEM experiments were used to investigate and compare the thermal stabilities of silver nanoparticles on the external surface of silica gels (unconfined) and those located inside the channels of SBA-15 (confined). It was observed that unconfined silver nanoparticles tended to agglomerate at low temperatures (i.e., lower than 773 K). The aggregation of silver nanoparticles became more serious at 773 K. However, for those confined silver nanoparticles, no coarsening process was observed at 773 K, much higher than its Tammann temperature (i.e., 617 K). Only when the treating temperature was higher than 873 K could the agglomeration of those confined silver nanoparticles happen with time-varying via the Ostwald ripening process. The confinement of mesopores played a key role in improving the thermal stabilities of silver nanoparticles (stable up to 773 K without any observable coarsening), which is essential to the further investigations on their chemical (e.g., catalytic) properties.     

The Oxidation of Aliphatic Hydrocarbons in the Presence of Higher Oxidation States of Silver

Abstract

The compound silver “peroxide”? has been known for some time and its preparation is described in the literature.¹ The structure of this compound has been in dispute; however it appears to have been resolved using neutron diffraction techniques. Scatturin, Bellon and Salkind² have shown that silver “peroxide” is a rather complex material in which silver is present in two different oxidation states, namely Ag(I) and Ag(III). In the crystal, Ag(III) atoms are coordinated to oxygen in a square planar array and the Ag(I) atoms are linearly coordinated. There are no peroxide oxygens. Hence the formula for silver “peroxide” is more properly written Ag(I)Ag(III)02.     

Sorption of Copper(II) and Silver(I) by Four Bacterial Exopolysaccharides

Metal remediation was studied by the sorption of analytical grade copper Cu(II) and silver Ag(I) by four exopolysaccharides (EPS) produced by marine bacteria. Colorimetric analysis showed that these EPS were composed of neutral sugars, uronic acids (>20 %), acetate, and sulfate (29 %). Metal sorption experiments were conducted in batch process. Results showed that the maximum sorption capacities calculated according to Langmuir model were 400 mg g^?1 EPS (6.29 mmol g^?1) and 333 mg g^?1 EPS (3.09 mmol g^?1) for Cu(II) and Ag(I), respectively. Optimum pH values of Ag(I) sorption were determined as 5.7. Experiment results also demonstrated the influence of initial silver concentration and EPS concentrations. Microanalyzing coupled with scanning electron microscopy demonstrated the presence of metal and morphological changes of the EPS by the sorption of metallic cations. The Fourier transform infrared spectroscopy analysis indicated possible functional groups (e.g., carboxyl, hydroxyl, and sulfate) of EPS involved in the metal sorption processes. These results showed that EPS from marine bacteria are very promising for copper and silver remediation. Further development in dynamic and continuous process at the industrial scale will be established next.