Strain distributions of confined Au/Ag and Ag/Au nanoparticles

The strain distributions of Au/Ag and Ag/Au nanoparticles confined in the Al2O3 matrix with different core sizes are investigated by using the finite element method, respectively. The simulation results clearly indicate that the compressive strains exerted on the Au/Ag and Ag/Au nanoparticles can be induced by the Al2O3 matrix. Moreover, it can be found that the strain gradient existing in a Au/Ag nanoparticle is much larger than that in a Ag/Au nanoparticle, which could be due to the larger Young's modulus of Au than that of Ag. With the core size increasing, the strain gradient existing in the Au/Ag nanoparticle becomes larger, while the strain gradient existing in the Ag/Au nanoparticle keeps constant. These different strain distributions may have significant influences on the structures and morphologies of the Au/Ag and Ag/Au nanoparticles, leading to the different physical properties for potential applications.     

Unexpected high stiffness of Ag and Au nanoparticles

We studied the compressibility of silver (10 nm) and gold (30 nm) nanoparticles, n-Ag and n-Au, suspended in a methanol-ethanol mixture by x-ray diffraction (XRD) with synchrotron radiation at pressures up to 30 GPa. Unexpectedly for that size, the nanoparticles show a significantly higher stiffness than the corresponding bulk materials. The bulk modulus of n-Au, K(0)=290(8) GPa, shows an increase of ca. 60% and is in the order of W or Ir. The structural characterization of both kinds of nanoparticles by XRD and high-resolution electron microscopy identified polysynthetic domain twinning and lamellar defects as the main origin for the strong decrease in compressibility.     

Investigation of ultra-thin and flexible Au–Ag–Au transparent conducting electrode

The performance of ultra-thin Au–Ag–Au tri-layer film deposited thermally over a flexible substrate is investigated using structural, optical, mechanical and electrical-transport measurements. The optimum total thickness of the tri-layer for high transparency and conductivity is determined to be around 8 nm using a theoretical model. The Au–Ag–Au tri-layer shows maximum transmittance (≅ 62%) at wavelength 500 nm. XRD pattern shows peak corresponding to (111) plane of Au and/or Ag. Sheet resistance (≅ 10.42 Ω/□) measured at 300 K using four probe technique is stable up to 150 °C. Hall effect measurements show high conductivity (1.34 × 10⁵ (Ω cm)⁻¹), carrier concentration (2.48 × 10²³/cm³), and mobility (3.4 cm²/Vs). Scotch tape test confirms good adhesion of the film onto PET substrate. Bending-twisting tests using an indigenous apparatus indicate high resistance-stability even after 50,000 cycles. These results imply the viability of Au–Ag–Au tri-layer film as a transparent conducting electrode worth exploring for optoelectronic applications.     

Electronic structure of Ag x Au1-x

The fully relativistic version of the Korringa-Kohn-Rostoker-Coherent Potential Approximation (KKR-CPA) method has been used to study the electronic structure of the alloy system Ag _x Au_1-x forx=0.20, 0.40, 0.60 and 0.80. The results of these calculations are discussed in terms of densities of states and Bloch spectral functions and are compared with experimental data.     

Preparation of large-area surface-enhanced Raman scattering active Ag and Ag/Au nanocomposite films

Ag films on tinning glass substrates were fabricated by modified silver-mirror (Tollen’s) reaction with the advantage of low-cost, simple and quick fabrication process. The obtained Ag films were served as sacrificial materials for preparation of Ag/Au nanocomposite films by immersing in a chlorauric acid (HAuCl₄) solution at room temperature. After a short time of galvanic replacement reaction, Ag/Au bimetallic nanostructures were synthesized with “concave” structures. The morphology, properties and composition of the Ag and Ag/Au nanocomposite films were analyzed by using scanning electron microscopy (SEM), UV-visible spectroscopy, X-ray diffraction (XRD), energy-dispersive X-ray spectrometry (EDS) and surface enhanced Raman scattering (SERS). SEM images displayed that the large area of Ag film and Ag/Au bimetallic nanostructures experienced structural evolution process during galvanic reaction. The UV-Vis spectra showed the absorbencies characterization of Ag film and Ag/Au nanocomposite films. SERS measurements using methylene blue as an analyte showed that SERS intensities of bimetallic films were enhanced significantly compared with that of pure Ag films. The SERS enhancement ability of Ag/Au bimetallic films was dependent on the immersion time for galvanic replacement reaction.     

Calculations of Electrical Conductivity of Ag and Au Plasma

The conductivity of silver and gold plasma is calculated within the relaxation‐time approximation at T ≥ 10 kK. The most accurate at present time momentum cross‐section for electron‐atom scattering was used. The ionic composition of plasma was calculated by means of generalized chemical model (GCM). The results of calculation were compared with the available data of others researchers (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Alloying behaviors of AgMg,AuMg and AgAl alloys

An expression of the structure-dependent energy of simple metal-noble metal binary alloy is given on the basis of the pseudopotential method. The energy is expressed as a sum of three parts; a band-structure energy, an electrostatic energy and a repulsive overlap energy, each of which is characterized by the usual long-range and short-range order parameters.The energy in a disordered state and the ordering energy are calculated for the AgMg, AuMg and AgAl systems, using the pseudopotential form factors and the overlap potentials of noble metals given by Moriarty. The numerical results reproduce qualitatively the observed phase diagrams; the existences of β- and ?-phases in the AgMg system, of β-phase in AuMg and of β- and ζ-phases in AgAl. The L2₀-type ordered phase (β′-phase) of AgMg alloy which remains ordered up to the melting point is well explained. Further, an estimation of the local ordering energy suggests that a clustering appears in the Al-rich region of AgAl alloy. However, the calculations fail to interpret the ordering behavior of β′-phase in the AuMg system and the short-range order of Ag-rich AgAl alloy. The role of individual terms of the structure-dependent energy on alloying is discussed.     

Electron energy loss spectroscopy of the vibration modes of water on Ag(100) and Ag(115) surfaces and comparison to Au(100), Au(111) and Au(115)

Motivated by rather similar behavior of the Helmholtz capacitances of stepped Au(11n) and Ag(11n) electrodes we have extended a previous study on the vibration spectrum of water adsorbed at low temperatures on stepped gold surfaces to Ag(100), Ag(115) and Au(111) surfaces. On Ag(100) surfaces, the spectra show the presence of the typical H-bonded network of water molecules. The rather weak intensity, the absence of non-hydrogen bonded hydrogen atoms, the similarity to the infrared spectrum of ice crystallites, and the increase in the angular spread of the elastic peak are indicative of adsorption in form of three-dimensional clusters. This is stark contrast to Au(100) and Au(111) where the spectra match to a model involving stacks of water bilayers. The low coverage spectra on Ag(115) resemble the results on Au(115): A considerable fraction of the H-atoms remains in the non-H-bonded state and spectral features of water adsorbed at step-sites are identified. The first layer of water on Ag(115) surfaces should therefore have a similar structure as recently proposed in a theoretical study concerning water on Au(115). For larger doses, the experimental results on Ag(115) suggests the formation of three-dimensional clusters. This is contrary to Au(115) where the layered structure with a constant fraction of non-hydrogen-bonded H-atoms persists at higher doses.     

The recovery of Ag and the formation of mixed dumbells in Ag alloyed with Au after thermal-neutron irradiation

The recovery spectrum of Ag and AgAu between 10K and 400K is discussed. In AgAu the recovery observed near 110K and in stage III indicates that not all the Ag interstitials form a mixed dumbbell configuration with Au. The defect concentration dependence of the 110K substage confirms that this substage is due to detrapping of self-interstitials from single Au impurities.     

在银、金和铂基底上银纳米粒子诱导的单层有机分子的表面增强拉曼散射(英文)

Noble metallic nanostructures exhibit a phenomenon known as surface-enhanced Raman scattering （SERS） in which the scattering cross sections are dramatically enhanced for molecules adsorbed thereon. Thanks to the enormously large enhancement factor on the order of 106～1015, one can readily acquire thevibrational spectra from adsorbates on roughened surfaces of Ag, Au, and Cu. However, SERS has not developed to be as powerful a surface technique as many people had hoped initially because of two specific obstacles.     

Broadband visible reflectors using Au and Ag elliptic cylinder pattern

Broadband terahertz reflector is suggested based on the shape of circular- and elliptic-cylinder metamaterials. We periodically arrange the structural pattern with gold and silver thin films on the FR4 substrate and optimize to operate in the wavelength range of 300–750 THz. Comparing the spectral responses of metamaterials with changes in shape and material, the ellipse shape greatly increased the reflection, and the silver pattern led to induce a broadening of the reflection band. Also, we identify the underlying physics necessary to design broadband reflector at any wavelength band of interest. Our results show that we can obtain broad reflection with 126 THz bandwidth at normal incidence, these results have high potential in large area photonic applications and can serve as reflectors in thin active film.     

Ag–Au alloy nanoparticles prepared by electro-exploding wire technique

Homogenous Ag–Au alloy nanoparticles having an average size of 12 ± 2 nm were successfully prepared by the exploding wire technique comprising of a wire–plate system and using 12 V batteries. The X-ray photoelectron spectroscopy data reveal the formation of alloy nanoparticles with Ag80-Au20 composition, which agrees with the absorption data, obtained using UV-Visible spectroscopy. XPS also reveals a thin metal-oxide shell on the metallic alloy core. These alloy nanoparticles show visible fluorescence emission that was compared with the observed fluorescence from pure Ag nanoparticles. A mechanism for the observed fluorescence is also provided.     

Adsorption of Ag and Au atoms on wurtzite ZnO (0001) surface

We perform first-principles calculations to investigate various surface structures in the absorption of Ag and Au atoms on wurtzite ZnO (0001) surface. The results show that both Ag and Au atoms prefer to be absorbed on the H₃ sites (the center of Zn–O ring) of the surface, and the most favorable monolayer (ML) coverage is 1. The calculated electron structure shows that the Ag- and Au-adsorbed ZnO (0001) surfaces exhibit metallic characteristics even the ML coverage of the adatoms is very low. Finally, the work functions of Ag- and Au-adsorbed ZnO (0001) surfaces are calculated and discussed for the first time in the present work.     

Sers Spectra of Mono and Bisphthalocyanine Complexes Deposited on Ag and Au Supports

In this letter, we present a study of surface-enhanced Raman spectra of thin layers of phthalocyanine (Pc) complexes deposited on Ag and Au rough surfaces. the materials of this work are MgPc (monophthalocyanine) and the asymmetrical lutetium bisphthalocyanine (tBu)₄PcLuPcCl₈ (Pc'LuPc') under three oxidation states. Enhancement of specific bands is observed depending on the surface and the oxidation state. SERS signatures of neutral, oxidised and reduced Pc'LuPc' are identified.     

Virtual bound states of Pd in Cu,Ag and Au and of Pt in Ag

The positions and widths of the virtual bound states of 5 and 10% Pd in Cu, Ag and Au and of 5 and 10% Pt in Ag have been measured by XPS. The spin—orbit splitting of the Pt state in Ag is reduced from the theoretical value, but comparable to the spectroscopic atomic value. The host lattice d-band structure is perturbed in the alloys.