Thermodynamic studies of the surface and transport properties in Ag–In and Ag–Sb liquid alloys

The surface tension, surface concentration, viscosity and mutual diffusion co-efficients of the Ag–In and Ag–Sb liquid alloys have been calculated using energetics and derivables from a statistical mechanical framework which recognises the formation of atom clusters of self associates. Our calculations suggest the existence of some form of local order in the systems. Ag–In showed higher tendencies to heterocoordination in the bulk-manifested higher values of mutual diffusion coefficient throughout the concentration range. The viscosity values of Ag–In and Ag–Sb were calculated using the expression reported by Kucharsky which relates the viscosity of a liquid binary alloy to the activity coefficients of the liquid alloy components that are raised to some power m. This exponent m is a fitted parameter. The calculated viscosity values for Ag–Sb had some reasonable agreement with experiment above 0.5 atomic fraction of Sb, using a fitted parameter value of m = 4.5. The fitted parameter value for the viscosity of Ag–In is expected to be in the range 1.5 ≤ m ≤ 3.5.     

Adsorption and Diffusion of Hydrogen Atom on Low-index Ag Planes

1 INTRODUCTION The interaction of hydrogen with metal surfaces has been extensively investigated experimentally and theoretically[1] motivated by its technological im- portance as well as theoretical attractiveness. Studies have sought to identify and explain the induced struc- tural, electronic and chemical perturbations which accompany hydrogen physisorption and chemisorp- tion on well-characterized metal substrates. However, the interaction of hydrogen atoms with Ag surfaces has not r…     

Synthesis and Characterization of ZnS∶Ag Nanocrystals Surface-capped with Thiourea

IntroductionSemiconductor nanocrystals(NCs) exhibit uniquechemical and physical properties due to their quantumsize effect and surface effect. Researches on synthesis,self-assembly, and fluorescent characteristics of thesemiconductor nanocrystals have rec…     

Solvothermal preparation,and characterization,of Cu–Ag nanoparticles

Cu–Ag nanoparticles have been successfully synthesized by one-pot solvothermal treatment of a mixture of AgNO₃ and Cu(OAc)₂·H₂O in ethylene glycol solution at 180 °C for 10 h. The samples were characterized by UV–visible absorption, X-ray diffraction (XRD), and extended X-ray absorption fine structure (EXAFS) spectroscopy, transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDS). The results showed that Cu–Ag nanoparticles and a small amount of phase-separated Cu–Ag alloy nanoparticles with an average diameter of 100 ± 30 nm were synthesized by the solvothermal treatment procedure. The mechanism of formation is discussed.     

Synthesis and Characterization of ZnS：Ag Nanocrystals Surface-capped with Thiourea

Ag^＋ -doped ZnS nanocrystals surface-capped with thiourea （expressed as ZnS： Ag/thiourea） were synthesized through sol-gel method with thiourea as a surface modifier and characterized by X-ray diffraction（XRD）, transmission electron microscope（TEM）, X-ray fluorescence spectrum（XRF）, infrared spectrum （IR）, UV-Vis absorption spectrum（ UV-Vis）, and photoluminescence spectrum（PL）. The results show that Ag^＋ ions are doped in ZnS nanocrystals, and the sulfur atoms in thiourea molecules coordinate with metal ions on the surface of the nanocrystals. The spherical ZnS： Ag/thiourea nanocrystals with an average diameter of 5 nm have good fluorescent characteristics, and therefore have great potential for use in molecular assembly and novel luminescence materials.     

Adsorption and diffusion of propane and propylene in Ag+-impregnated MCM-41

Equilibrium data and diffusion characteristics of propane and propylene were determined on mesoporous adsorbents modified with an organic molecule (APTES) and/or impregnated with AgNO₃, in order to obtain a separation by adsorption via π-complexation. Adsorption capacities were determined by a gravimetric technique, while diffusion characteristics were evaluated by the ZLC technique. The equilibrium isotherms data showed that the modification with an organic molecule will weaken the π-interaction between Ag⁺ and double C=C bond. On the other hand slightly higher adsorption capacities for propylene (about 1.5 mol/kg) were obtained for the sample prepared by a direct impregnation with larger amounts of AgNO₃ (M4 sample). Diffusion runs confirmed that the propane desorption rate on M4 sample was much higher compared to propylene. This evidence leads to a potential application of that adsorbent material for a kinetic separation.     

Comparative toxicity study of Ag, Au, and Ag–Au bimetallic nanoparticles on Daphnia magna

A comparative assessment of the 48-h acute toxicity of aqueous nanoparticles synthesized using the same methodology, including Au, Ag, and Ag–Au bimetallic nanoparticles, was conducted to determine their ecological effect in freshwater environments through the use of Daphnia magna, using their mortality as a toxicological endpoint. D. magna are one of the standard organisms used for ecotoxicity studies due to their sensitivity to chemical toxicants. Particle suspensions used in toxicity testing were well-characterized through a combination of absorbance measurements, atomic force or electron microscopy, flame atomic absorption spectrometry, and dynamic light scattering to determine composition, aggregation state, and particle size. The toxicity of all nanoparticles tested was found to be dose and composition dependent. The concentration of Au nanoparticles that killed 50% of the test organisms (LC₅₀) ranged from 65–75 mg/L. In addition, three different sized Ag nanoparticles (diameters = 36, 52, and 66 nm) were studied to analyze the toxicological effects of particle size on D. magna; however, it was found that toxicity was not a function of size and ranged from 3–4 μg/L for all three sets of Ag nanoparticles tested. This was possibly due to the large degree of aggregation when these nanoparticles were suspended in standard synthetic freshwater. Moreover, the LC₅₀ values for Ag–Au bimetallic nanoparticles were found to be between that of Ag and Au but much closer to that of Ag. The bimetallic particles containing 80% Ag and 20% Au were found to have a significantly lower toxicity to Daphnia (LC₅₀ of 15 μg/L) compared to Ag nanoparticles, while the toxicity of the nanoparticles containing 20% Ag and 80% Au was greater than expected at 12 μg/L. The comparison results confirm that Ag nanoparticles were much more toxic than Au nanoparticles, and that the introduction of gold into silver nanoparticles may lower their environmental impact by lowering the amount of Ag which is bioavailable.     

Synthesis of fluorescent Ag nanoclusters and their application in α-l-fucosidase detection

Highly fluorescent Ag nanoclusters (NCs) were successfully prepared by a simple and nontoxic approach, and the as-prepared Ag NCs could be utilized for the AFu detection with a lower detection limit of 0.001 U L(-1).     

Effects of Ag–La codoping on structure and electrical properties of BaTiO3 powder

Ag–La codoped BaTiO₃ powders were prepared by sol–gel technology after the preparation of Ag-doped and La-doped BaTiO₃ powders. Variations in the structure, constitution, morphology, and electrical properties of the modified BaTiO₃ powders were characterized. It can be concluded that Ag–La codoping decreases the resistivity of the modified powders more significantly than Ag doping and La doping, respectively. The sample with the lowest resistivity was obtained by codoping with 0.1 at.% Ag and 0.3 at.% La, where the resistivity decreased to 7.13 × 10² Ω m from the value of 4.30 × 10⁹ Ω m of the undoped powder. X-ray diffractometry (XRD) and Fourier-transform infrared (FTIR) analyses indicate that the main phase of the codoped powders transitions from tetragonal to cubic with increasing La doping content. Scanning electron microscopy (SEM) observations illustrate that codoping makes the particles distribute more equably. The relationship between the resistivity and the structure of the doped BaTiO₃ powders is discussed based on defect chemistry.     

The role of Ag···O and Ag···Ag interactions in silver(I) supramolecular frameworks constructed from benzene multicarboxylate and nitrogen ligands

Using a hydrothermal synthesis method, two Ag(I) coordination polymers, {[Ag₂(bbbm)₂]·(Hbtc)} _n (1) and {[Ag₂(mbim)₂(Hsip)]·H₂O} _n (2) (bbbm = N,N’-(1,4-butanediyl)bis-(benzimidazole), mbim = N,N′-(1,1-methyl)-bis-(imidazole), H₃btc = 1,3,5-benzenetricarboxylic acid, H₃sip = 5-sulfoisophthalic acid) were synthesized and characterized by physicochemical and spectroscopic methods and single crystal diffraction. The complex 1 features a 2D supramolecular network formed by left- and right-handed cationic [Ag(bbbm)] _n helical chains and Hbtc ligands with the link of Ag···O interactions, displaying an unusual trinodal (3,3,4)-connected 3,3,4L12 topology net. The complex 2 has a left-handed and a symmetric right-handed double-stranded [Ag₂(mbim)₂(Hsip)] _n helical chains. The adjacent [Ag₂(mbim)₂(Hsip)] _n helical chains are further linked by Hsip ligands through the combination of weak Ag···O coordinative interactions and ligand-supported Ag···Ag interactions to generate a 3D supramolecular framework, exhibiting a new type of topology of a trinodal (4,5,5)-connected net. The solid-state fluorescence properties of the compounds 1 and 2 were investigated.     

SERS of 7-azaindole adsorbed on Ag doped sol–gel film and Ag sol: a comparative investigation

Surface enhanced Raman scattering (SERS) studies have been undertaken on Ag doped sol–gel derived film with 7-azaindole (7-AI) used as the reference compound. The enhancement factor in the film is comparable with the result of the chloride aggregated silver citrate sol. Along with the spectral observation and assignments of the frequencies, the significance of colloidal sol–gel film in which the size of the metal is in the dimensions of nanometers have been discussed.     

Facile Surfactant-, Reductant-, and Ag Salt-free Growth of Ag Nanoparticles with Controllable Size from 35 to 660 nm on Bulk Ag Materials

Morphologically and dimensionally controlled growth of Ag nanocrystals has long been plagued by surfactants or capping agents that complicate downstream applications, unstable Ag salts that impaired the reproducibility, and multistep seed injection that is troublesome and time-consuming. Here, we report a one-pot electro-chemical method to fast (∼2 min) produce Ag nanoparticles from commercial bulk Ag materials in a nitric acid solution, eliminating any need for surfactants or capping agents. Their size can be easily manipulated in an unprecedentedly wide range from 35 to 660 nm. Furthermore, the Ag nanoparticles are directly grown on the Ag substrate, highly desirable for promising applications such as catalysis and plasmonics. The mechanistic studies reveal that the concentration of Ag⁺ in the diffusion layer nearby the surface, controlled by the magnitude and duration of voltage, is critical in governing the nanoparticle formation (<1.3 mM) and its dimensional adjustability.     

Synthesis,Structure and Photochromism of a New Diarylethene and Its Ag(Ⅰ) Complex

A new symmetric diarylethene containing cyano group was synthesized and structurally characterized by elemental analysis,IR,1 H NMR and X-ray single-crystal diffraction.It belongs to the monoclinic system,space group C2/c with a = 18.848(6),b = 8.561(2),c = 16.875(5) ?,β = 100.398(6)o,V = 1344.6(11) ?~3,Z = 4,μ = 0.262 mm~(-1),Dc = 1.415 g/cm~3,M_r = 570.56,F(000) = 1160,the final R = 0.0808 and wR = 0.2107 with I 2σ(I).The two thienyls adopt reactive anti-parallel conformation and the carbon distance of photocyclization is 3.57 ?.The neighboring molecules are stacked closely with C–H…F hydrogen bonding.In addition,the photochromism of the new compound was investigated in solvents with different polarity and PMMA film.The alternative photo-irradiation of 254 nm light and ≥550 visible light can induce the reversible photo-cyclization and photo-reversion with the color interconversion between colorlessness and blue.In THF solution,the λ_(max) of diarylethene in PSS in visible band is 585 nm.The diarylethene further reacted with AgBF_4 in benzene to give rise to complex 1,which was structurally characterized by elemental analysis,IR,ESI-MS and TG.1 demonstrated reversible photochromism in both solution and PMMA film.The complexation of metal ions with diarylethene leads to a minor red-shift of the λ_(max) of 1 in THF in PSS to 590 nm.     

Effect of Ag addition on crystallization kinetics and thermal stability of As–Se chalcogenide glasses

Chalcogenide glasses of (As₅₀Se₅₀)_100?xAg_x (0 ≤ x ≤ 25) were prepared using the melt quenching technique under non-isothermal conditions. Differential scanning calorimetry curves measured at different heating rates (5 ≤ β ≤ 40 K min^?1) are used to characterize the as-quenched samples. The thermal stability was monitored through the calculation of the temperature difference T _c ? T _g, stability parameter S and crystallization rate factor K _p. The glass-forming ability (GFA) was investigated on the basis of Hurby parameter H _r which is a strong indicator of GFA. In addition, the activation energy of glass transition E _t, activation energy of crystallization E _c and Avrami exponent n of the studied compositions were determined. The mechanism of crystallization was found to be a combination of two- and three-dimensional crystal growth.     

Adsorption and Diffusion of O Atoms on Ag（210） Stepped Surface

The O-Ag(210)surface adsorption system was studied via the five-parameter Morse potential theory.Meanwhile,the 2O-Ag(210)system was investigated via the extended London-Eyring-Polanyi-Sato(LEPS)potential theory to learn the interaction between the adsorption states.Calculated results demonstrate that there are two stable on-surface adsorption sites(B and H)for O atoms on Ag(210)stepped surface.And the perpendicular vibrations are 30.3 and 42.9 meV,which are close to that observed in high resolution electron energy loss spectroscopy(HREELS).Also,there exists an octahedral subsurface adsorption state with a high vibrational frequency,and the interaction between the on-surface and subsurface O species is slight.The mode at 54.6 meV,which is close to that observed in HREELS(54-56 meV),is because of the vibration of the O atom on B site under the influence of that on H site.     

Assembly of Ag（I） Polymers with Thioether-S Binding and Homochiral Helices

A novel coordination polymer [Ag(pyta)]n (pyta^-=4-pyridylthioacetate) containing bound thioether sulfurs and single-stranded helical chains has been synthesized and structurally characterized.     

New Silver(I) Complexes of Pyridyl Dithioether Ligands with Ag–Ag Interactions: Effects of Anions and Ligand Spacers on the Framework Formations of Complexes

Three new silver(I) complexes existing Ag–Ag interactions, a trinuclear cluster complex [Ag₃(L ¹)₂(NO₃)₂](NO₃) 1, a dinuclear complex [Ag₂(L ¹)₂](PF₆)₂ 2 and a one-dimensional chain complex [Ag₂ L ²(NO₃)₂] 3, where L ¹ and L ² are two structurally related pyridyl dithioether ligands, bis(2-pyridylthio)methane (L ¹) and 1,3-bis(2-pyridylthio)-propane (L ²), have been synthesized and their structures were determined by single-crystal X-ray diffraction analysis. The striking structural differences of 1 and 2 suggest that counter anions have a profound effect upon the framework formations of silver complexes with pyridyl dithioether ligands, and the differences of 1 and 3 indicate that the subtle changes of the space groups have great influence on the coordination modes of the terminal pyridylsulfanyl groups and the geometries of Ag^I ion and therefore greatly influence the structures of their complexes. The weak AgO interactions in the trinuclear complex 1 and the one-dimensinoal chain complex 3 extend them into quasi two-dimensional networks, and the AgS weak interactions in the dinuclear complex 2 into one-dimensinoal chains, and such weak interactions further stabilized these complexes.     

Synthesis and Characterization of Compounds Containing 1,2,3-Triazole via Click Reaction and Ag(Ⅰ) Complex

In this work, 1,4-bis(4-phenyl-1,2,3-triazole)benzene, 1,3-bis(4-phenyl-1,2,3-triazole)propane, bis(1-phenyl-1,2,3-triazole)-methylphenylsilane, and 1-ally-4-phenyl-1,2,3-triazole have been designed and synthesized via Click reaction. Fourier transform infrared spectroscopy(FT-IR) and nuclear magnetic resonance spectroscopy(NMR) were used to confirm the compounds' structures. The effect of silicon atom on the optical properties has also been studied. The UV-vis absorption wavelength of silicon-containing compound is about ca. 10 nm red-shifted when compared with that of other three compounds. The fluorescence emission bands of the compounds in CHCl_3 solutions were observed around ca. 440 nm. And the luminescent coordination compound, namely [AgL1?NO_3?3H_2O]n, based on the ligand 1-allyl-4-phenyl-1,2,3-triazole has been prepared. In addition, this complex exhibits a 1 D chain structure. The crystal structure has been determined by single-crystal X-ray diffraction, and the optical properties have been investigated by fluorescence spectrum. In summary, our work may provide new materials with luminescent property which is potentially useful in material fields.     

Study and 3D modeling of the phase diagram of the Ag–Ge–Se system

In view of the contradictoriness of the literature data, phase equilibria in the Ag–Ge–Se system were restudied by differential thermal analysis and X-ray powder diffraction analysis. A number of polythermal sections and an isothermal section at room temperature of the phase diagram were constructed, and so was the projection of the liquidus surface. The primary crystallization fields of phases and the types and coordinates of in- and monovariant equilibria were determined. It was shown that, in the system, a single ternary compound, Ag₈GeSe₆, forms, which undergoes congruent melting at 1175 K and a polymorphic transformation at 321 K. The formation of the compounds Ag₂GeSe₃ and Ag₈GeSe₅, which was previously reported in the literature, was not confirmed. Based on the phase diagrams of boundary binary systems and the results of the differential thermal analysis of a number of samples of the ternary system, equations were obtained for calculation and 3D modeling of the liquidus and phase-separation surfaces.