Size-controlled synthesis of monodispersed silver nanoparticles capped by long-chain alkyl carboxylates from silver carboxylate and tertiary amine

Monodispersed silver nanoparticles capped by long-chain alkyl carboxylates were prepared by the reaction of silver carboxylate with tertiary amine at 80 degrees C for 2 h. This approach is a unique, size-controlled synthetic method for the large-scale preparation of silver nanoparticles. Long-chain alkyl carboxylate derived from a precursor acts as a stabilizer to avoid the aggregation of silver nanoparticles and to control particle size. In addition, amine plays an important role both as a reagent to form a thermally unstable, amine-coordinated intermediate, bis(amine)silver(I) carboxylate, and as a mild reducing agent for the intermediate to produce nanoparticles at a low temperature. The silver core and carboxylate-capping ligand of silver nanoparticles were characterized by various techniques such as transmission electron microscopy, optical absorption spectroscopy, powder X-ray diffraction, X-ray photoelectron spectroscopy, gas chromatograph mass spectroscopy, and thermogravimetric and differential thermal analysis. The diameter of the nanoparticles can be strongly influenced by the alkyl chain length and the structure of the carboxylate. The average diameters of the silver nanoparticles were controlled to less than 5 nm in the case of silver carboxylate with a single alkyl chain length of 13 or 17 carbon atoms. On the contrary, the average diameters of silver nanoparticles became large and polydisperse in the case of silver carboxylate with a chain length of 7 carbon atoms or a branched chain. In comparing triethylamine with trioctylamine, there was no obvious effect to regulate the size distribution of the nanoparticles because they could not function as a capping ligand of the nanoparticles due to their weak coordination to silver. In addition, the heat treatment of silver nanoparticles in solution rather than in the solid state was effective for the growth of particles while maintaining narrow size distributions.     

Crystallization of silver stearate from sodium stearate dispersions

Silver carboxylates, the common silver source used for photothermographic imaging materials, are normally obtained from the reaction between sodium soap (e.g., sodium stearate) and silver nitrate. They form platelet-like crystals with a lamellar structure in water at room temperature. Light microscopy investigations reveal that the formation of silver stearate (AgSt) crystals follows a diffusion-controlled mechanism. The reaction between the sodium soap and silver nitrate preferentially occurs in solution rather than on the soap fiber solid interface. Cryogenic transmission electron microscopy, together with an on-the-grid reaction technique, provides a useful tool to directly image silver stearate microstructures at the initial stages of AgSt precipitation. The AgSt reaction product first forms particles about 5 nm in size, which is similar to the d-spacing of final AgSt crystals. Those particles aggregate to produce larger and loosely packed embryonic crystals, the precursors to the ultimate silver stearate crystals.     

Perfluorocarbon-stabilized silver nanoparticles manufactured from layered silver carboxylates

Perfluorocarboxylate-stabilized silver nanoparticles have been prepared uniformly via the thermal decomposition of layered silver perfluorocarboxylates (AgCO2(CF2)nCF3, n = 10, 12, 14 and 16).     

Thermal decompositions of silver carboxylates

The thermal decompositions of the even silver dicarboxylates from silver oxalate to silver sebacate were studied. In vacuum, the dicarboxylates decomposed to give metallic silver, CO₂ and organic diradicals as primary products, and polymers as secondary products. The higher silver dicarboxylates were much more stable to thermal treatment than silver oxalate, probably due to the initiation of decomposition of all carboxylates except silver oxalate by the rupture of a Ag-O and not a C-C bond.

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Zusammenfassung Die thermische Zersetzung der geradzahligen Silberdicarboxylate Silberoxalat bis-sebacinat wurde untersucht. Unter Vakuum zersetzen sich die Dicarboxylate zu metallischem Silber, CO₂ und organischen Diradikalen als Primärprodukt und Polymeren als Sekundärprodukt. Die höheren Silberdicarboxylate sind wesentlich stabiler als das Oxalat, wahrscheinlich weil bei ihnen die Zersetzung von der Spaltung einer Ag-O-Bindung und nicht einer C-C-Bindung wie beim Oxalat ihren Anfang nimmt.

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, . , — . , . , , , Ag-O, -.

     

Self-assembly, foaming, and emulsifying properties of sodium alkyl carboxylate/guanidine hydrochloride aqueous mixtures

Unsaturated fatty acids may be extracted from various agricultural resources and are widely used as soaps in the industry. However, there also exist a large variety of saturated and hydroxy fatty acids in nature, but their metal salts crystallize at room temperature in water, hampering their use in biological and chemical studies or for industrial applications. Addition of guanidine hydrochloride (GuHCl) to sodium salt of myristic acid has been shown to prevent its crystallization in water, forming stable flat bilayers at room temperature. Herein, we extend this finding to two other saturated fatty acids (palmitic and stearic acids) and two hydroxyl fatty acids (juniperic and 12 hydroxy stearic acids) and study more deeply (by using small angle neutron scattering) the supramolecular assemblies formed in both saturated and hydroxyl fatty acid systems. In addition, we take the advantage that crystallization no longer occurs at room temperature in the presence of GuHCl to study the foaming and emulsifying properties of those fatty acid dispersions. Briefly, our results show that all fatty acids, even juniperic acid, which is a bola lipid, are arranged in a bilayer structure that may be interdigitated. Depending on the nature of the fatty acid, the systems exhibit good foamability and foam stability (except for juniperic acid), and emulsion stability was good. Those findings should be of interest for using saturated long chain (and hydroxyl) fatty acids as surfactants for detergency or even materials chemistry.     

Morphology of solid photochemical decomposition products of silver carboxylates

The formation of solid photochemical decomposition products of silver carboxylates with long linear hydrocarbon chains and its variation in the course of reaction was investigated. At the initial stage of photolysis, particles of silver are formed with the overall situation analogous to that in the case of other silver salts. After the degree of decomposition has reached 20%, the formation of a space-ordered structure of solid products in the form of alternating volume lamellae of paraffin and silver is observed. The average distance from one lamella edge to the next lamella edge is dependent upon the length of the methylene chains of silver carboxylates and the intensity of irradiation. The results obtained are discussed from the point of view of possible spinodal character of decomposition of intermediate solid solution paraffin-silver carboxylate.     

The separation of silver from mixtures by cation-exchange chromatography

Summary The cation-exchange behaviour of milligram amounts of silver on Dowex 50 W-X 8 has been studied, with nitric acid, sulphuric acid, ammonium acetate, ammonium nitrate, sodium nitrate, citric acid, tartaric acid, and acetic acid as eluents. A volume of 200–300 ml of 3M nitric acid, sulphuric acid, ammonium acetate, ammonium nitrate, or sodium nitrate was adequate for quantitative removal of 26 mg of silver from a 1.4×19 cm column of resin. Methods are described for the separation of silver from Ce, Zr, Th, Bi, and Fe by conversion of these elements into anionic complexes; from Cu, U, Al, and Zn by selective elution with nitric acid; from Ba, Sr, Sb, and As by elution with specific eluents.

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Zusammenfassung Das Verhalten von Milligrammengen Silber am Kationenaustauscher Dowex 50 W-X 8 bei Verwendung von Salpetersäure, Schwefelsäure, Ammoniumacetat, Ammoniumnitrat, Natriumnitrat, Zitronensäure, Weinsäure und Essigsäure als Eluenten wurde untersucht. 200 bis 300 ml 3-m Salpetersäure, Schwefelsäure, Ammoniumacetat, Ammoniumnitrat oder Natriumnitrat waren hinreichend für die quantitative Elution von 26 mg Silber aus einer Harzsäule von 1,4×19 cm. Methoden zur Trennung des Silbers von Ce, Zr, Th, Bi und Fe durch Überführung dieser Elemente in Komplexanionen wurden beschrieben. Die Trennung von Cu, U, Al und Zn gelingt durch selektive Elution mit Salpetersäure, von Ba, Sr, Sb und As durch Elution mit spezifischen Eluenten.

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Résumé On a étudié le comportement de quantités d'argent de l'ordre du milligramme du point de vue échange cationique sur Dowex 50 W-X 8, avec différents éluants: acide nitrique, acide sulfurique, acétate d'ammonium, nitrate d'ammonium, nitrate de sodium, acide citrique, acide tartrique et acide acétique. Un volume de 200–300 ml d'acide nitrique 3M, d'acide sulfurique, d'acétate d'ammonium, de nitrate d'ammonium ou de nitrate de sodium est nécessaire pour l'élimination quantitative de 26 mg d'argent d'une colonne en résine de 1,4×19 cm. On décrit des méthodes de séparation de l'argent d'avec Ce, Zr, Th, Bi et Fe par conversion de ces éléments en complexes anioniques; d'avec Cu, U, Al et Zn par élution sélective par l'acide nitrique; d'avec Ba, Sr, Sb et As par élution avec des éluants spécifiques.

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We wish to thank Dr.R. A. Chalmers for helpful discussion and suggestions.     

The effect of carboxylate anions on the formation of clathrate hydrates of tetrabutylammcnium carboxylates

The solid-liquid phase diagrams of binary mixtures of water with tetrabutylammonium carboxylate having an unsaturated alkyl group in the carboxylate anion ((n-C₄H₉)₄NOOCR; R=C₂H₃–C₉H₁₇) were examined in order to confirm the formation of clathrate-like hydrates. The results are summarized as follows: (1) the formation of a clathrate-like hydrate is newly confirmed for all the 13 carboxylates examined; (2) these hydrates are classified into three groups I, II, and III on the basis of the hydration numbers; (3) the group I hydrates, which are formed by the carboxylates with R=C₂ and R=C₃, have hydration numbers around 30 and are the most stable hydrates among those examined in this study; (4) the group II hydrates, with hydration numbers around 39, are formed by all the carboxylates with R=C₄ and C₅ including sorbate and are less stable than the group I hydrates; (5) the group III hydrates, with hydration numbers around 30 like the group I hydrates, are formed by carboxylates with long alkyl chains such as 2-octenoate and 2-decenoate and are generally unstable.     

Enthalpies and heat capacities of transfer of sodium carboxylates and sodium dodecylsulfate from water to aqueoustert-butyl alcohol solutions

Integral enthalpies of solution at very low concentrations of sodium carboxylates and sodium dodecylsulfate in aqueous tert-butyl alcohol solutions at 25°C and 35°C were measured with an isoperibol submarine calorimeter. The enthalpies and heat capacities of transfer of these surfactants from water to aqueous tertbutyl alcohol solutions were derived from integral enthalpies of solution. The results are explained in terms of the structural alteration effect of the constituent hydrophobic and hydrophilic groups of the solute.     

Argentophilicity and solvent-induced structural diversity in double salts of silver acetylide with silver perfluoroalkyl carboxylates

A series of novel double salts of silver(I) were isolated by dissolving Ag(2)C(2) in a concentrated aqueous solution of R(F)CO(2)Ag (R(F) = CF(3), C(2)F(5)) and AgBF(4). Different ancillary solvento ligands such as H(2)O, CH(3)CN, and C(2)H(5)CN were found to affect the crystallization process that led to the assembly of various silver(I) cages with embedded C(2)(2-) ions. 2Ag(2)C(2) x 12CF(3)CO(2)Ag x 5H(2)O (1) consists of two independent C(2)@Ag(7) cages, each having the shape of a basket with a square base. Ag(2)C(2) x 6CF(3)CO(2)Ag x 3CH(3)CN (2) contains a zigzag chain of edge-sharing triangulated dodecahedra, and 4Ag(2)C(2) x 23CF(3)CO(2)Ag x 7C(2)H(5)CN x 2.5H(2)O (3) features an unusual double-walled silver column constructed from the fusion of four different kinds of irregular polyhedra. Ag(2)C(2) x 10C(2)F(5)CO(2)Ag x 9.5H(2)O (4), Ag(2)C(2) x 9C(2)F(5)CO(2)Ag x 3CH(3)CN x H(2)O (5), and Ag(2)C(2) x 6C(2)F(5)CO(2)Ag x 2C(2)H(5)CN (6) all contain an edge-sharing double cage with each single cage in the shape of a square antiprism, a capped square antiprism, and a triangulated dodecahedron, respectively.     

Phosphane/phosphite silver(I) carboxylates as CVD precursors

The preparation of [L_mAgO₂CR] (L = PⁿBu₃, P(OMe)₃, P(OEt)₃; m = 1, 2; R = singly-bound organic group) and [L_mAg–E–AgL_m] (L = PⁿBu₃; E = oxalate; m = 1, 2, 3) is described. Their use as spin-on and CVD precursors is reported. SEM and EDX studies show that closed and homogeneous silver films with admirable conductivity could be obtained.     

2-吡嗪羧酸银的合成、晶体结构及热化学性质

以二次蒸馏水为溶剂,合成了2-吡嗪羧酸银(Ag(pyza)(s)),并利用X-射线单晶衍射法表征了其晶体结构.根据晶体结构数据计算得到2-吡嗪羧酸银的晶格能为554.10 kJ/mol.利用TG/DSC热分析技术研究了该化合物的热分解过程;用精密自动绝热热量计测量了其在78~378 K温区的低温热容;通过最小二乘法拟合得到了摩尔热容随折合温度变化的多项式方程,利用此方程计算出该化合物的舒平热容和各种热力学函数.通过设计合理的热化学循环,利用等温环境溶解-反应热量计分别测定了所设计热化学反应的反应物和产物在选定溶剂中的溶解焓,通过计算得到反应的反应焓为:?(31.919±0.526)kJ/mol.利用Hess定律计算出2-吡嗪羧酸银的标准摩尔生成焓为:?(243.659±1.298)kJ/mol.利用紫外-可见光谱仪对反应物和产物溶解所得溶液分别进行测量,从而证实了所设计热化学循环的可靠性.     

A series of silver coordination polymers constructed from flexible bis(benzimidazole) ligands and different carboxylates

In this article, eight new silver coordination polymers constructed from two structurally related ligands, 1,1′-(1,4-butanediyl)bis(2-methylbenzimidazole) (bbmb) and 1,1′-(1,4-butanediyl)bis(2-ethylbenzimedazole) (bbeb), have been synthesized: [Ag(L1)(bbmb)]·C₂H₅OH·H₂O (1), [Ag(L2)(bbmb)]·C₂H₅OH (2), [Ag(L3)(bbmb)] (3), [Ag₂(L4)(bbmb)₂]·C₂H₅OH (4), [Ag(L2)(bbeb)]·C₂H₅OH (5), [Ag(L5)(bbeb)]·CH₃OH (6), [Ag₂(L6)₂(bbeb)]·H₂O (7), and [Ag₂(L7)(bbeb)₂]·4(H₂O) (8), where L1 = benzoate anion, L2 = p-methoxybenzoate anion, L3 = 2-amino-benzoate anion, L4 = oxalate anion, L5 = cinnamate ainon, L6 = 3-amino-benzoate anion, and L7 = fumaric anion. In 1-3, 5 and 6, the bidentate N-donor ligands (bbmb and bbeb) in trans conformations bridge neighboring silver centers to form 1D single chain structures. The carboxylate anions are attached on both sides of the chains. Moreover, 1 and 3 are extended into 2D layers, while 2 and 6 are extended into 3D frameworks through π-π interactions. In 4, the bbmb ligands bridge adjacent Ag(I) centers to form -Ag-bbmb-Ag- chains, which are further connected by L4 anions to form a 2D layer. The resulting layers are extended into 3D frameworks through strong π-π interactions. In 7, the N-donor ligands (bbeb) in trans conformations bridge two silver centers to generate a [Ag₂(bbeb)]²⁺ unit. The adjacent [Ag₂(bbeb)]²⁺ units are further connected via the L6 anions to form a 1D ladder chain. Moreover, the structure of compound 7 is extended into a 3D framework through hydrogen bonding and π-π interactions. In 8, two Ag(I) cations are bridged by two bbeb ligands in cis conformations to form a [Ag₂(bbeb)₂]²⁺ ring, which are further linked by L7 anions to generate a 1D string chain. Furthermore, the hydrogen bonding and π-π interactions link L7 anions to form a 2D supramolecular sheet. Additionally, the luminescent properties of these compounds were also studied.     

Review: Antibacterial behavior of carboxylate silver(I) complexes

Since ancient times, silver ions have been known to be effective against a broad range of micro-organisms but in the last decade, this metal has been greatly studied because of their antimicrobial capability against a wide range of bacteria, viruses, and fungi. For the same reason, it is the most extensively studied metal with antibacterial applications in medicine. Besides applications, the antimicrobial activity is associated with high effectiveness, low toxicity, and virtually no resistance of micro-organisms to the presence of this metal. The appearance of new bacterial strains resistant to antibiotics is a serious health problem; so, there is a strong incentive to develop new bactericides. This makes current research in bactericidal silver complexes particularly important. This review summarizes the most important aspect related to coordination chemistry of Ag(I) carboxylate complexes and their influence as antibacterial agents.     

Crystallization of X-type zeolite from concentrated sodium silicate and aluminate solutions

Crystallization of an X-type zeolite from concentrated solutions of sodium aluminate (Al₂O₃ 90–330 g l^?1) and silicate (SiO₂ 110–180 g l^?1) was studied.     

Thermal decomposition of some silver(I) carboxylates under nitrogen atmosphere

The thermal decomposition reactions of CH₃CH₂C(CH₃)₂COOAg (1), (CH₃)₃SiCH₂COOAg (2), CF₃COOAg (3), (CH₃)₃CCOOAg (4), C₂H₅COOAg (5), C₃F₇COOAg (6), C₆F₁₃COOAg (7) and (CF₂)₃(COOAg)₂ (8) were studied in N₂ atmosphere using thermogravimetry (TG), derivative thermogravimetry and differential thermal analysis. Characterized compounds decomposed in one- or multi-step processes with metallic silver formation in the range 215–465 °C. TG-IR studies of gases evolved during thermolysis revealed products of decomposition, such as carboxylic acids, CO₂ and recombination reactions.     

Crystallization of silver chloride in crazed porous polymers

During this study the formation and growth of silver chloride crystals in crazed porous polymeric matrixes of poly(ethylene terephthalate) (PET) and polypropylene (PP) were under investigation. The rate of formation and dispersity and the way AgCl particles aggregate in porous polymers were shown to be dependent on the effective volume porosity, pore dimension, and physical state of the polymer. Methods of the determination of diffusion and distribution constants for low-molecular substances in porous polymers were suggested, and a mechanism of silver chloride crystallization in porous medium was proposed.     

Dielectric properties of sols of silver nanoparticles capped by alkyl carboxylate ligands

Sols of silver nanoparticles in toluene were studied by broadband dielectric spectroscopy (10⁻³–10⁵ Hz). The frequency dependences of the specific alternating current (ac) conductivity and the complex electric modulus were used to estimate the temperature/frequency intervals of long- and short-range charge transfer occurs, respectively. A considerable increase (by more than 30 °C) in the Vogel temperature T ₀ and the glass transition temperature T _g in sols compared with the pure solvent was found. It can be hypothesized that these cooperative effects reflect the initial stage of the superlattice formation. Although the dielectric characteristics of sols are generally controlled by the conductivity relaxation, the dielectric response was observed in the high-frequency range (1–10³ Hz) at low temperatures (from −50 to +10 °C). This response results from the presence of nanoparticles in solution. It is supposed that the relaxation is caused by the motion of ion impurities on the Ag nanoparticle surface within the carboxylate ligands shell. The dielectric properties of films strongly depend on both the characteristics of nanoparticles and the conditions of the film preparation. Like in sols, the direct current (dc) conductivity and the dielectric response of Ag nanoparticles in films are due to ion impurities.