The first measured Ag I, Ag II and Ag III Stark broadening parameters

The Stark widths (W) and shifts (d) of two neutral (520.908 and 546.550 nm), eleven singly (211.382, 224.643, 224.874, 232.029, 232.468, 233.140, 241.141, 241.323, 243.781, 244.793 and 276.754 nm) and three doubly (216.189, 231.004 and 239.569 nm) ionized silver (Ag I, Ag II and Ag III, respectively) spectral lines have been measured in nitrogen plasma at about 18,000 K electron temperature and electron density ranged between 0.65 × 10²³ and 1.15 × 10²³ m^− 3. They are the first measured W and d values while those of the Ag II and Ag III lines are the first published data in these spectra. The modified version of the linear, low-pressure, pulsed arc was used as a plasma source operated in nitrogen with silver atoms, as impurities, evaporated from silver cylindrical plates located in the homogeneous part of the discharge. No theoretical predictions exist for W and d values of above mentioned spectral lines. Besides, we have checked the transition probability ratio of two investigated Ag I lines. An agreement with theoretical predictions was found.     

Real and Hypothetical Intermediate-Valence Ag(II)/Ag(III) and Ag(II)/Ag(I) Fluoride Systems as Potential Superconductors

With the aim of gauging their potential as conducting or superconducting materials, we examine the crystal structures and magnetic properties of the roughly one hundred binary, ternary, and quaternary Ag(II) and Ag(III) fluorides in the solid state reported up to date. The Ag(II) cation appears in these species usually in a distorted octahedral environment, either in an [AgF](+) infinite chain or as [AgF(2)] sheets. Sometimes one finds discrete square-planar [AgF(4)](2-) ions. The Ag(III) cation occurs usually in the form of isolated square-planar [AgF(4)](-) ions. Systems containing Ag(III) (d(8)) centers are typically diamagnetic. On the other hand, the rich spectrum of Ag(II) (d(9)) environments in binary and ternary fluorides leads to most diverse magnetic properties, ranging from paramagnetism, through temperature-independent paramagnetism (characteristic for half-filled band and metallic behavior) and antiferromagnetism, to weak ferromagnetism. Ag(II) and Ag(III) have the same d-electron count as Cu(II) (d(9)) and Cu(III) (d(8)), respectively. F(-) and O(2-) ions are isoelectronic, closed-shell (s(2)p(6)) species; both are weak-field ligands. Led by these similarities, and by some experimental evidence, we examine analogies between the superconducting cuprates (Cu(II)/Cu(III)-O(2-) and Cu(II)/Cu(I)-O(2-) systems) and the formally mixed-valence Ag(II)/Ag(III)-F(-) and Ag(II)/Ag(I)-F(-) phases. For this purpose we perform electronic-structure computations for a number of structurally characterized binary and ternary Ag(I), Ag(II), and Ag(III) fluorides and compare the results with similar calculations for oxocuprate superconductors. Electronic levels in the vicinity of the Fermi level (x(2)-y(2) or z(2)) have usually strongly mixed Ag(d)/F(p) character and are Ag-F antibonding, thus providing the potential of efficient vibronic coupling (typical for d(9) systems with substantially covalent bonds). According to our computations this is the result not only of a coincidence in orbital energies; surprisingly the Ag-F bonding is substantially covalent in Ag(II) and Ag(III) fluorides. The electron density of state at the Fermi level (DOS(F)) for silver fluoride materials and frequencies of the metal-ligand stretching modes have values close to those for copper oxides. The above features suggest that properly hole- or electron-doped Ag(II) fluorides might be good BCS-type superconductors. We analyze a comproportionation/disproportionation equilibrium in the hole-doped Ag(II) fluorides, and the possible appearance of holes in the F(p) band. It seems that there is a chance of generating an Ag(III)-F(-)/Ag(II)-F(0) "ionic/covalent" curve crossing in the hole-doped Ag(II)-F(-) fluorides, significantly increasing vibronic coupling.     

Disc-Like Silver Nanocluster Ag93 Built with Bicapped Hexagonal Prismatic Ag15 and Ino Decahedral Ag13 Units

The reduction of alkynyl-silver and phosphine-silver precursors with a weak reducing reagent Ph₂SiH₂ led to the formation of a novel silver nanocluster [Ag₉₃(PPh₃)₆(C≡CR)₅₀]³⁺ (R=4-CH₃OC₆H₄), which is the largest structurally characterized cluster of clusters. This disc-shaped cluster has a Ag₆₉ kernel consisting of a bicapped hexagonal prismatic Ag₁₅ unit wrapped by six Ino decahedra through edge-sharing. This is the first time that Ino decahedra are used as a building block to assemble a cluster of clusters. Moreover, the central silver atom has a coordination number of 14, which is the highest in metal nanoclusters. This work provides a diverse metal packing pattern in metal nanoclusters, which is helpful for understanding metal cluster assembling mechanisms.     

Ligand and counterion control of Ag(I) architectures: assembly of a {Ag8} ring cluster mediated by hydrophobic and Ag...Ag interactions

A strategy combining ligand design and counterion variation has been used to investigate the assembly of silver(I) complexes. As a result, dinuclear, octanuclear, and polymeric silver(I) species have been synthesized by complexation of the rigid aliphatic amino ligands cis-3,5-diamino-trans-hydroxycyclohexane (DAHC), cis-3,5-diamino-trans-methoxycyclohexane (DAMC), and cis-3,5-diamino-trans-tert-butyldimethylsilylanyloxycyclohexane (DATC) with silver(I) triflate, nitrate, and perchlorate. The compositions of these aggregates, established by X-ray crystallography and elemental analysis, are [{Ag(DAHC)}2](CF3SO3)2 (1), [{Ag(DAMC)}2](CF3SO3)2 (2), [{Ag(DAMC)}2](NO3)2 (3), [{Ag(DATC)}6{Ag(DAHC)}2](NO3)8 (4), and [{Ag(DATC}n](NO3)n (5), where the DAHC present in 4 is formed by in situ hydrolysis of the acid labile silyl ether group. The type of aggregate formed depends both upon the noncoordinating O-substituent of the ligand and the (also noncoordinating) counterion, with the normal preference of the ligand topology for forming Ag2L2 structures being broken by introduction of the bulky, lipophilic O-tert-butyldimethylsilyl (TBDMS) group. Of particular note is the octanuclear silver ring structure 4, which is isolated only when both the O-TBDMS group and the nitrate counteranion are present and is formed from four Ag2L2 dimers connected by Ag...Ag and hydrogen-bonding interactions. Diffusion rate measurement of this {Ag8} complex by 1H NMR (DOSY) indicates dissociation in CD3OD and CD3CN, showing that this supramolecular ring structure is formed upon crystallization, and establishing a qualitative limit to the strength of Ag...Ag interactions in solution. When solutions of the {Ag8} cluster in methanol are kept for several days though, a new UV-vis absorption is observed at around 430 nm, consistent with the formation of silver nanoparticles.     

Phase equilibria in the Ag2Te-ZnTe and Ag2Te-Zn systems

The state diagrams (T-x) of the systems Ag₂Te-ZnTe(I) and Ag₂Te-Zn(II) are offered on the ground of data obtained by differential thermal analysis, X-ray phase analysis, microstructural analysis and measurements of the density and the microhardness of samples synthesized. The systems studied are quasibinary sections of the ternary system Ag-Zn-Te. System I is characterized by two eutectic and three eutectoidal non-variant equilibria as well as by an intermediate compound Ag₂ZnTe₂, which melts congruently at 880°C. The latter exists in the range from 120 to 880°C in two polymorphic modifications (T_ʅ→β=515°C). System II is characterized by one eutectic, two eutectoidal and one peritectic nonvariant equilibria, boundary solid solutions on the ground of Ag₂Te and Zn and one intermediate phase of the composition Ag₄Zn₃Te₂, which melts congruently at 880°C.     

Alternating Array Stacking of Ag26Au and Ag24Au Nanoclusters

An assembly strategy for metal nanoclusters using electrostatic interactions with weak interactions, such as C?H???π and π???π interactions in which cationic [Ag₂₆Au(2‐EBT)₁₈(PPh₃)₆]⁺ and anionic [Ag₂₄Au(2‐EBT)₁₈]^? nanoclusters gather and assemble in an unusual alternating array stacking structure is presented. [Ag₂₆Au(2‐EBT)₁₈(PPh₃)₆]⁺ [Ag₂₄Au(2‐EBT)₁₈]^? is a new compound type, a double nanocluster ion compound (DNIC). A single nanocluster ion compound (SNIC) [PPh₄]⁺ [Ag₂₄Au(2‐EBT)₁₈]^? was also synthesized, having a k‐vector‐differential crystallographic arrangement. [PPh₄]⁺ [Ag₂₄Au(2,4‐DMBT)₁₈]^? adopts a different assembly mode from both [Ag₂₆Au(2‐EBT)₁₈(PPh₃)₆]⁺ [Ag₂₄Au(2‐EBT)₁₈]^? and [PPh₄]⁺ [Ag₂₄Au(2‐EBT)₁₈]^?. Thus, the striking packing differences of [Ag₂₆Au(2‐EBT)₁₈(PPh₃)₆]⁺ [Ag₂₄Au(2‐EBT)₁₈]^?, [PPh₄]⁺ [Ag₂₄Au(2‐EBT)₁₈]^? and the existing [PPh₄]⁺ [Ag₂₄Au(2,4‐DMBT)₁₈]^? from each other indicate the notable influence of ligands and counterions on the self‐assembly of nanoclusters.     

Ag, Ag2S, and Ag2Se nanocrystals: synthesis, assembly, and construction of mesoporous structures

Synthesis of mesoporous materials has become more and more important due to their wide application. Nowadays, there are two main ideas in their preparation. One is focused on the templating method. The other is based on metal-organic frameworks (MOFs) constructed from molecular building blocks. Herein, we exploit a new idea for their facile and general synthesis, namely, using "artificial atoms" (monodisperse nanoparticles) as uniform building blocks to construct ordered mesoporous materials. Mesoporous Ag, Ag2S, and Ag2Se have been obtained to demonstrate this concept. On the other hand, we also describe a facile method to prepare the "building blocks". Ag nanoparticles were obtained by direct thermal decomposition of AgNO3 in octadecylamine, and Ag2S/Ag2Se nanoparticles were synthesized by reaction between sulfur or selenium powder and Ag nanoparticles formed in situ. This approach for Ag, Ag2S, and Ag2Se nanoparticles is efficient, economical, and easy to scale up in industrial production.     

Ag、Ag2O纳米粒子对Pb电极的电催化作用

Ag、Ag2O纳米粒子对Pb电极的电催化作用;银溶胶;纳米氧化银;电催化;吸附;循环伏安     

Ag nanoparticles from the mechanochemical decomposition of Ag oxalate

The present work focuses on the chemical reactivity of Ag oxalate powders under mechanical processing conditions. The powders were submitted to mechanical loads in the presence of an aqueous solution containing a polymeric surfactant. A gradual decrease of the total mass of powders was observed, ascribable to the occurrence of a decomposition process. X-ray diffraction and UV-vis spectrophotometric analyses indicated that the Ag oxalate decomposes into metallic Ag and gaseous carbon dioxide. Transmission electron microscopy showed that metallic Ag exists in the form of particles with average size of about 5 nm. The formation of nanometer-sized Ag particles can be related to the plastic deformation and attrition processes taking place at the points of contacts between neighboring particles during the mechanical loading at collision.     

X-ray diffraction investigations of Ag2ReCl6 and Ag2OsCl6

Complex salts Ag₂ReCl₆ and Ag₂OsCl₆ were synthesized and characterized by X-ray powder diffraction analysis, elemental analysis, and IR spectroscopy. The resulting compounds were demonstrated to be isostructural. It was found that the principal structural motif of the compounds under study is similar to that of K₂ReCl₆. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1314–1316, July, 2000.     

Microstructure and Magnetic Properties of Ag/Fe/Ag Pseudo-Sandwich Nanogranular Films

"Nanogranular Ag/Fe/Ag films were prepared by magnetron sputtering from a silver and an iron target onto glass substrates at room temperature and subsequent in situ annealing. The structural and magnetic properties of the films were investigated as a function of silver layer thickness and annealing temperature. X-ray diffraction shows the Fe(110) peak is formed in all the samples. Vibrating sample magnetometer measurements indicate that the magnetic moments lie well perpendicular to the film plane. Coercivityreaches the maximum in the sample annealed at 500 oC for 30 min with 3 nm Ag layer. A scanning probemicroscope was used to scan surface morphology and magnetic domain structures. In as-deposited samplesthe average grain size and the average roughness is smaller than that the annealing samples. After annealing,the grain size is larger and the contrast of domains increases, but the domain size becomes smaller."     

Ag2 and Ag3 Clusters: Synthesis,Characterization, and Interaction with DNA

Subnanometric samples, containing exclusively Ag₂ and Ag₃ clusters, were synthesized for the first time by kinetic control using an electrochemical technique without the use of surfactants or capping agents. By combination of thermodynamic and kinetic measurements and theoretical calculations, we show herein that Ag₃ clusters interact with DNA through intercalation, inducing significant structural distortion to the DNA. The lifetime of Ag₃ clusters in the intercalated position is two to three orders of magnitude longer than for classical organic intercalators, such as ethidium bromide or proflavine.     

Ag2 and Ag3 Clusters: Synthesis,Characterization, and Interaction with DNA

Subnanometric samples, containing exclusively Ag₂ and Ag₃ clusters, were synthesized for the first time by kinetic control using an electrochemical technique without the use of surfactants or capping agents. By combination of thermodynamic and kinetic measurements and theoretical calculations, we show herein that Ag₃ clusters interact with DNA through intercalation, inducing significant structural distortion to the DNA. The lifetime of Ag₃ clusters in the intercalated position is two to three orders of magnitude longer than for classical organic intercalators, such as ethidium bromide or proflavine.     

Controlled synthesis and self-assembly of highly monodisperse Ag and Ag(2)S nanocrystals

A facile method to control the synthesis and self‐assembly of monodisperse Ag and Ag₂S nanocrystals with a narrow‐size distribution is described. Uniform Ag nanoparticles of less than 4 nm were obtained by thermolysis of Ag–oleate complexes in the presence of oleic acid and dodecylamine, and monodisperse Ag nanoparticles of less than 10 nm were also prepared in one step by using dodecylamine and oleic acid as capping agents. Moreover, the surface‐enhanced Raman scattering (SERS) properties of the Ag substrates have also been investigated. It is worth mentioning that these Ag nanoparticles and assemblies show great differences in the SERS activities of Rhodamine B dye. In addition, the superlattices of Ag₂S nanocrystals were synthesized with Ag–oleate complexes, alkanethiol, and sulfur as the reactants. The resulting highly monodisperse nanocrystals can easily self‐assemble into interesting superstructures in the solution phase without any additional assembly steps. This method may be extended to the size‐controlled preparation and assembly of many other noble‐metal and transition‐metal chalcogenide nanoparticles. These results will aid the study of the physicochemical properties of the superlattice assemblies and construction of functional macroscopic architectures or devices.     

Ag+ Selective Macrocycles Containing Soft Ligating Moieties and Regulation of Ag+ Binding

Strategies are discussed for the design of Ag+ selective macrocyclic molecules, together with the structures of the Ag+ complexes. One of the most useful and basic methods is to incorporate heteroatoms, such as nitrogens and sulfurs, and heterocycles into the macrocyclic framework. A side arm containing the heteroatom also enhances Ag+ selectivity tremendously. A sulfide chain outside or inside the macroring contributes to highly selective Ag+ binding. Soft alkenyl and alkynyl carbons arranged in a macrocyclic fashion bind Ag+ preferentially. Regulation of Ag+ binding by redox reactions and by metal ligation is also described.     

银纳米粒子修饰的银电极测定酪氨酸

通过Na BH4还原Ag NO3得到胶体银纳米粒子,制作了以该纳米粒子修饰的银电极,研究了其在电催化中的应用,并对相关机理进行了探讨。基于酪氨酸对纳米银的还原信号有明显抑制作用,建立了胶体银纳米粒子修饰银电极在Na Ac-HAc缓冲溶液中用差分脉冲法检测酪氨酸的方法,并讨论了优化工作条件。结果表明,在p H=5.5时,峰电流与酪氨酸的浓度在1.0×10-8~1.0×10-3mol/L范围内呈良好的线性关系,检出限为4.2×10-9mol/L,峰电流Ip与酪氨酸浓度的负对数p C的线性回归方程为Ip(μA)=7.64 p C-15.69(R=99.73%)。用该方法检测氨基酸注射液中酪氨酸的含量,加标回收率在95.2%~107.8%之间。     

Ag(+)-enhanced fluorescence of lanthanide/nucleotide coordination polymers and Ag(+) sensing

The weak fluorescence of lanthanide/nucleotide coordination polymers was greatly enhanced by Ag(+) in aqueous solution, which has been used for highly sensitive sensing of Ag(+).     

CO adsorption on Ag(100) and Ag/MgO(100)

Theoretical studies of CO adsorption on a two-layer Ag(100) film and on a two-layer Ag film on a MgO(100) support are reported. Ab initio calculations are carried at the configuration interaction level of theory using embedding methods to treat the metal-adsorbate region and the extended ionic solid. The metal overlayer is considered in two different structures: where Ag-Ag distances are equal to the value in the bulk solid, and for a slightly expanded lattice in which the Ag-Ag distances are equal to the O-O distance on the MgO(100) surface. The calculated adsorption energy of Ag(100) on MgO(100) is 0.58 eV per Ag interfacial atom; the Ag-O distance is 2.28 A. A small transfer of electrons from MgO to Ag occurs on deposition of the silver overlayer. CO adsorption at an atop Ag site is found to be the most stable for adsorption on the two-layer Ag film and also for adsorption on Ag deposited on the oxide; CO adsorption energies range from 0.12 to 0.19 eV. The CO adsorption energy is reduced for the Ag/MgO system compared to adsorption on the unsupported metal film thereby providing evidence for a direct electronic effect of the oxide support at the metal overlayer surface. Expansion of the Ag-Ag distance in the two-layer system also reduces the adsorption energy.