Time‐Dependent Surface Plasmon Resonance Spectroscopy of Silver Nanoprisms in the Presence of Halide Ions

Herein, we find that the surface plasmon resonance (SPR) spectra of silver nanoprisms in the presence of halide ions change gradually with reaction time. The changes in the spectra correspond to the shape transformation of silver nanoprisms. There are threshold concentrations of halide ions that initiate the shape‐transformation reaction. The threshold concentrations for Cl^?, Br^?, and I^? are about 3×10^?4 M , 1×10^?6 M , and 1.5×10^?6 M , respectively. Any concentrations of the added halide ions above these thresholds can eventually etch the silver nanoprisms into nanodisks if the reaction time is long enough. The higher the concentration of the halide ions, the higher the etching rate will be. The kinetics of the shape transformation of the silver nanoprisms can be studied by recording their time‐dependent surface plasmon resonance (SPR) spectra on a commercial UV/Vis–NIR spectrometer. The peak positions of in‐plane dipole SPR bands of silver colloids in the presence of chloride and bromide ions can be fitted very well with the biexponential functions. We propose that the fast components of the biexponential behaviors should correlate to the truncating effect on the corners of silver nanoprisms, and the slow component should correlate to the redeposition of the truncated residues onto the basal plane of the nanoplates.     

Surface‐enhanced Raman scattering (SERS) spectra of hemoglobin on nano silver film prepared by electrolysis method

Nano silver films were prepared by the electrolysis method. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were employed to detect the morphology of the silver particles. The surface‐enhanced Raman scattering (SERS) spectra of the hemoglobin on nano silver film were recorded. It is seen from the SERS spectra that the nano silver films can enhance the Raman signals of the hemoglobin efficiently, and sodium citrate and phosphate buffered saline have no influence on the SERS spectra of hemoglobin. The electrolysis technique to fabricate this highly bioactive, stable, reusable, and low‐cost SERS substrate will be useful in the development of hemoglobin detection methods. Copyright © 2009 John Wiley & Sons, Ltd.     

Site‐specific deposition of Ag nanoparticles on ZnO nanorod arrays via galvanic reduction and their SERS applications

A controllable heterostructure consisting of ZnO nanorod arrays with attached Ag nanoparticles at only one end has been synthesized via a facile and convenient galvanic reduction method. Scanning electron microscopic images of these nanostructures showed good selectivity of Ag deposition on the tip of ZnO nanorod arrays. The formation of these regular Ag ZnO heterogeneous nanorod arrays can be explained by a localization of the electrons at the ends of the ZnO nanorods after the electron transfer step. By tuning the reaction time and the concentration of silver nitrate, the density of Ag nanoparticles on the tip of ZnO nanorods can be well controlled. Owing to the introduction of Ag nanoparticles with different densities, the resulting Ag ZnO heterogeneous nanorod arrays have been proved to be a versatile substrate for surface‐enhanced Raman scattering not only for common organic molecules but also for label‐free protein detection. Copyright © 2009 John Wiley & Sons, Ltd.     

A bi‐prism interferometer for hard X‐ray photons

Micro‐fabricated bi‐prisms have been used to create an interference pattern from an incident hard X‐ray beam, and the intensity of the pattern probed with fluorescence from a 30 nm‐thick metal film. Maximum fringe visibility exceeded 0.9 owing to the nano‐sized probe and the choice of single‐crystal prism material. A full near‐field analysis is necessary to describe the fringe field intensities, and the transverse coherence lengths were extracted at APS beamline 8‐ID‐I. It is also shown that the maximum number of fringes is dependent only on the complex refractive index of the prism material.     

Preparation and dispersive mechanism of highly dispersive ultrafine silver powder

Using ascorbic acid as the reducing agent, AgNO₃ as the source of Ag, the ultrafine silver powder was prepared by liquid-phase reduction method. The optimal conditions to prepare the ultrafine silver powder were obtained by studying the effects of following factors, such as the selection of dispersant, the doses of dispersant and pH, on the dispersibility of silver powder under other constant conditions. The pure ultrafine silver powder with quasi-spherical shape and mean size of 1.15 μm was synthesized under the optimal conditions of polyvinyl alcohol (PVA) as disperser, PVA/AgNO₃ mass ratio of 4:100 and pH 7 while maintaining other conditions exactly in the same circumstances, such as AgNO₃ concentration of 0.20 mol L⁻¹, ascorbic acid concentration of 0.15 mol L⁻¹ and reaction temperature of 40 °C. The ultrafine silver powder was characterized by SEM and XRD. And a PVA dispersive mechanism for preparing highly dispersive ultrafine silver powder, proved by the ultraviolet spectra, is that PVA absorbed on the surface of silver particles by coordination bond preventing the silver particles from diffusion and aggregation. In addition, the steric effect may help to reduce aggregation.     

Thermodynamic study of the Ag-As-Se and Ag-S-I systems using the EMF method with a solid Ag<Subscript>4</Subscript>RbI<Subscript>5</Subscript> electrolyte

The EMF method with a solid Ag₄RbI₅ superionic conductor was used to study the Ag-As-Se and Ag-S-I systems in the composition ranges of Ag₂Se-As₂Se₃-Se and Ag₂S-AgI-S, accordingly. Their solid-phase equilibrium diagrams are constructed or specified. The existence of ternary AgAs₃Se₅, AgAsSe₂, Ag₃AsSe₃, Ag₇AsSe₆, Ag₃SI compounds is confirmed. The standard partial and integral thermodynamic formation functions and also standard entropies were calculated for these compounds for the first time.     

Influence of silver nano‐additive amount on the supramolecular structure,porosity, and properties of polyacrylonitrile precursor fibers

This work examines the influence of the amount of silver nanoparticles added to polyacrylonitrile spinning solutions on their rheological properties as well as the structure and properties of the fibers produced. The influence of the amount of silver nanoparticles on the supramolecular structure of nanocomposite polyacrylonitrile precursor fibers, their porosity, as well as thermal and tensile strength properties was determined. The distribution of the nano‐ additive in fiber cross‐sections and on the surface was estimated. It was found that the addition of silver nanoparticles to polyacrylonitrile precursor fibers in an amount of up to 1.5% does not cause a decrease in the susceptibility of the fiber matter to deformation at the drawing stage. The produced fibers were characterized by an increased total volume of pores of 0.35 cm³/g and tenacity of more than 34 cN/tex. Copyright © 2009 John Wiley & Sons, Ltd.     

UV‐curing synthesis of sulfonated polyaniline‐silver nanocomposites by an in situ reduction method

Sulfonated polyaniline‐silver (SPAni‐Ag) hybrid nanocomposites have been synthesized by the in situ reduction using a UV‐curing polymerization method without using any reducing or binding agent. An aqueous solution of aniline and orthoanilinic acid (OA) comonomers, a free‐radical oxidant and silver metal salts were irradiated by UV rays. Reduction of the silver salt in aqueous aniline and OA leads to the formation of silver particles which in turn catalyze the oxidation of comonomers to sulfonated polyaniline (SPAni). The resultant SPAni‐Ag nanocomposites were characterized by using different spectroscopy analyses like UV–visible (UV–Vis), X‐ray diffraction (XRD) and infrared spectroscopy. The absorption bands were revealed to be optically active and the peaks blue‐shifted due to the presence of metallic silver within the SPAni matrix. The XRD patterns displayed both the broad amorphous polymeric and sharp metallic peaks. Scanning electron microscopy and transmission electron microscopy of the nanocomposites showed a uniform size distribution with spherical and granular morphology. Thermogravimetric analysis revealed that the nanocomposites had a better thermal stability than the bulk SPAni. Copyright © 2008 John Wiley & Sons, Ltd.     

Color Tunability and Electrochemiluminescence of Silver Nanoclusters

Colorful clusters : Silver nanoclusters consisting of only a few atoms exhibit large chemical‐environment‐responsive shifts of their optical absorption and emission bands, that is, large solvatochromism (see picture). The photophysical characteristics and electrochemiluminescence of the Ag clusters give them remarkable advantages over larger nanoparticles in applications such as molecular sensing.