Preparation of monodisperse polystyrene/silver composite microspheres and their catalytic properties

This article presents a facile method for the preparation of polystyrene/silver (PS/Ag) composite microspheres. In this approach, monodisperse PS spheres were synthesized via dispersion polymerization and modified by sulfonation to obtain sulfonated PS spheres with sulfonic acid groups on the surfaces, and then adsorbed Sn²⁺ ions by electrostatic interaction and used as templates. PS/Ag composite microspheres were prepared successively by addition of [Ag(NH₃)₂]⁺ complex ions to the templates dispersion, adsorbing to the surfaces of templates, and then reduction of [Ag(NH₃)₂]⁺ complex ions to Ag nanoparticles by sodium potassium tartrate. The results showed that monodisperse PS spheres with sulfonic acid groups on the surfaces were coated by an incomplete and nonuniform coverage of Ag nanoparticles in the absence of Sn²⁺ ions. In the presence of Sn²⁺ ions, however, complete and uniform Ag nanoparticles coatings were obtained on the entire PS sphere. And the deposition density and size of Ag nanoparticles can be controlled by [Ag(NH₃)₂]⁺ concentration. The resulting PS/Ag composite microspheres were characterized by SEM, TEM, XRD, TGA, and UV-vis. Preliminary catalytical tests indicated these PS/Ag composite microspheres showed good catalytic properties.     

Coating sulfonated polystyrene microspheres with highly dense gold nanoparticle shell for SERS application

The fabrication of highly dense gold nanoparticles (NPs)-coated sulfonated polystyrene (PS) microspheres and their application in surface-enhanced Raman spectroscopy (SERS) were reported. After the preparation of PS microsphere using dispersion polymerization and subsequent sulfonation, [Ag(NH₃)₂]⁺ ions were adsorbed on the surfaces of the sulfonated PS microspheres and then reduced to silver nanoseeds for further growth of gold NPs shell by seeded growth approach. Reaction conditions such as the concentration of the growth solution and growth time were adjusted to achieve nonspherical gold NPs-coated PS microspheres with different coverage degree. The application of the as-prepared spiky gold NPs-coated PS microsphere hybrid composite in SERS was finally investigated by using 4-aminothiophenol as probe molecules. The results showed that as-prepared gold NPs-coated PS microspheres could be used as functional hybrid materials to exhibit excellent enhancement ability in SERS.

Accumulation of Silver(I) Ion and Diamine Silver Complex by <Emphasis Type="Italic">Aeromonas</Emphasis> SH10 biomass

The biomass of Aeromonas SH10 was proven to strongly absorb Ag⁺ and [Ag(NH₃)₂]⁺. The maximum uptake of [Ag(NH₃)₂]⁺ was 0.23 g(Ag) g⁻¹(cell dry weight), higher than that of Ag⁺. Fourier transform infrared spectroscopy spectra analysis indicated that some organic groups, such as amide and ionized carboxyl in the cell wall, played an important role in the process of biosorption. After SH10 cells were suspended in the aqueous solution of [Ag(NH₃)₂]⁺ under 60°C for more than 12 h, [Ag(NH₃)₂]⁺ was reduced to Ag(0), which was demonstrated by the characteristic absorbance peak of elemental silver nanoparticle in UV-VIS spectrum. Scanning electron microscopy and transmission electron microscopy observation showed that nanoparticles were formed on the cell wall after reduction. These particles were then confirmed to be elemental silver crystal by energy dispersive X-ray spectroscopy, X-ray diffraction, and UV-VIS analysis. This study demonstrated the potential use of Aeromonas SH10 in silver-containing wastewater treatment due to its high silver biosorption ability, and the potential application of bioreduction of [Ag(NH₃)₂]⁺ in nanoparticle preparation technology.     

Two New Silver(I) Ammine Complexes by Displacement Reaction Between [Ag(NH3)2]+ Ions and Different Pyridine‐4,5‐Imidazoledicarboxylic Acids

[Ag(NH₃)₂]⁺ ions are chosen as an initial reaction precursor because of its simple displacement reaction and intrinsic arrangement as well as specific coordination directionality. Two new silver(I) ammine complexes, Ag₂(NH₃)HL² ( 2 ) and Ag₂(NH₃)₂HL³ ( 3 ), were obtained by a simple substitution reaction between [Ag(NH₃)₂]⁺ ions and pyridine‐4,5‐imidazoledicarboxylic acid [H₃L² = 2‐(3′‐pyridyl) 4,5‐imidazoledicarboxylic acid and H₃L³ = 2‐(4′‐pyridyl) 4,5‐imidazoledicarboxylic acid]. Silver dimers are connected into a 2D layer and 1D chain in complexes 2 and 3 , respectively. In complex 2 two kinds of displacement reactions (mono‐substituting and bis‐substituting) occurred between the ammine molecules in [Ag(NH₃)₂]⁺ ions and H₃L², however, only the mono‐substituting reaction occurs in complex 3 .     

Preparation and characterization of stable monodisperse silver nanoparticles via photoreduction

Silver nanoparticles were synthesized by UV irradiation of [Ag(NH₃)₂]⁺ aqueous solution using poly(N-vinyl-2-pyrrolidone) (PVP) as both reducing and stabilizing agents. The formation of silver nanoparticles was confirmed from the appearance of surface plasmon absorption maxima around 420 nm. It was found that the formation rate of silver nanoparticles from Ag₂O was much quicker than that from AgNO₃, and the absorption intensity increased with PVP concentration as well as irradiation time. The maximum absorption wavelength (λ_max) was blue shift with increasing PVP content until 8 times concentration of [Ag(NH₃)₂]⁺ (wt%). The transmission electron microscopy (TEM) showed the resultant particles were 4–6 nm in size, monodisperse and uniform particle size distribution. X-ray diffraction (XRD) demonstrated that the colloidal nanoparticles were the pure silver. In addition, the silver nanoparticles prepared by the method were stable in aqueous solution over a period of 6 months at room temperature (25 °C).     

Preparation of Silica Microspheres Containing Ag Nanoparticles

Two sol-gel fabrication processes were investigated to make silica spheres containing Ag nanoparticles: (1) a modified Stöber method for silica spheres below 1 m size, and (2) a SiO₂-film formation method on spheres of 3–;7 m size. The spheres were designed to incorporate silver nanoparticles of high ⁽³⁾ in a spherical optical cavity structure for the resonance effect. For the incorporation, interaction between [Ag(NH₃)₂]⁺ ion and Si-OH was important. In the Stöber method, the size of the silica spheres was determined by a charge balance of plus and minus ions on the silica surface. In the film formation method, the capture of Ag complex ion on the silica surface depended on whether the surface was covered with OH groups or not. After doping [Ag(NH₃)₂]⁺ into silica particles or SiO₂ films on the spheres, these ions w ere reduced by NaBH₄ to form silver nanoparticles. From plasma absorption at around 420 nm wavelength and TEM photographs of nanometer-sized silver particles, their formation inside the spherical cavity structures was confirmed.     

Coulometric argentometry of microgram amounts of sulphide

Summary The voltammetric behaviour of the silver sulphide-silver electrode in pure ammoniacal-alkaline electrolytes as well as in the presence of sulphide and the complex cation [Ag(NH₃)₂]⁺ have been investigated. It has been found that the silver sulphide-silver electrode behaves slightly irreversibly in ammoniacal-alkaline solutions of sulphide. On the basis of the results obtained the use of the silver sulphide-silver electrode for constant-current bipotentiometric and biamperometric end-point detection techniques appears to be convenient in the argentometric determination of sulphide.

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Zusammenfassung Das voltammetrische Verhalten der Silbersulfid-Silber-Elektrode wurde in Ammoniak und Natronlauge enthaltenden Lösungen, auch in Anwesenheit von Sulfid und von komplexem Kation [Ag(NH_{3 2}]⁺, untersucht. Es wurde festgestellt, da\ sich die Silbersulfid-Silber-Elektrode in Sulfid enthaltenden Lösungen schwach irreversibel verhÄlt. Die gewonnenen Resultate zeigen die Möglichkeit, die genannte Elektrode zur bipotentiometrischen oder biamperometrischen Endpunktbestimmung bei der argentometrischen Sulfidbestimmung anzuwenden.

     

Efficient silver modification of TiO2 nanotubes with enhanced photocatalytic activity

In this paper, Ag(CH₃NH₂)₂⁺, Ag(NH₃)₂⁺ and Ag⁺ with different radii have been used as silver sources to find out the distribution of Ag ions on the H-TNT surface, which is critical to the final performance. The influence of this distribution on visible photocatalytic activity is further studied. The results indicate that, when Ag⁺ used as silver source with low concentration, these small sized silver ions mainly distribute on interlayer spacing of H-TNT. After heat-treatment and photo-reduction, the generated silver nanoparticles uniformly embed in the anatase TiO₂ nanotube walls, and bring large interfacial area between Ag particles and TiO₂ nanotubes. The separation effect of photogenerated electron-hole pair in TiO₂ is enhanced by Ag particles, and achieves the best at 0.15 g/L, much higher than P25, TiO₂/0, Ag-N@TiO₂ and Ag-C-N@TiO₂. This paper provides new ideas for the modification of TiO₂ nanotubes.     

Nanoparticle‐enhanced bamboo‐like tubular nanofibers for active capture of particulate matter

We proposed a thought of active capture of particles by improving the interaction force between fibers and particles. Nanoparticle‐enhanced tubular nanofibers (Ag‐SPNTs) were prepared by template‐free cationic polymerization followed by surface modification. Ag‐SPNTs have coarse surface and bamboo‐like tubular structure with a diameter of approximately 80‐150 nm. Ag nanoparticles were embedded on the nanofibers surface, and the content of Ag nanoparticles in the nanofibers could be tuned by changing the concentration of [Ag(NH₃)₂]⁺ in the preparation process. f‐d curve measured by AFM showed that increasing the content of Ag nanoparticles in the nanofibers resulted in the enhanced interaction force between the nanofiber surface and particles. Particle matter capture test showed that the number of captured microscaled/naonoscaled particles on the fiber surface increased obviously for the nanoparticle‐enhanced tubular nanofibers (Ag‐SPNTs) compared to the nanofibers without nanoparticle (SPNTs), probably due to the increased interaction force and adhesion energy between fiber surface and particles. Filtration property test showed that the Ag‐SPNTs fiber films had a better filtration performance with a higher filter efficiency and QF value than that of SPNTs. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019     

Spontaneous Growth of 3D Silver Mesoflowers on Poly(4-vinylpyridine) Brushes-Grafted-Graphene Oxide Films and Facile Creation of Nanoporosities over their Surface

Fabricating three-dimensional (3D) hierarchical noble-metal particles by spontaneous redox reactions between graphene and noble-metal salts still remains a great challenge. Herein, the fact that graphene oxide (GO) itself acts as both a platform for grafting polymer brushes and a reducing agent to reduce [Ag(NH₃)₂]⁺ ions is taken advantages of. 3D flower-like Ag mesoparticles (Ag mesoflowers, Ag MFs) with tunable size and shapes can spontaneous grow on poly(4-vinylpyridine) brushes-grafted-graphene oxide (P4VP-g-GO) films in Ag(NH₃)₂OH solution without the use of any additional reducing agent. The residual Ag(NH₃)₂OH on 3D Ag MFs surface can be further reduced by NaBH₄, causing abundant nanoporosities over the entire Ag MFs. The resulting Ag nanoporous MFs (Ag NMFs) with larger surface-to-volume ratio and higher nanoscale roughness exhibit ultrasensitivity in surface-enhanced Raman spectroscopy (SERS) detection, and the detection limit for 4-aminothiophenol is as low as 10⁻¹³ m .     

Synthesis,Characterization, and Crystal Structures of Cu,Ag, and Pd Dinitramide Salts

The literature known, but not fully characterized, silver dinitramide transfer reagents AgN(NO₂)₂ ( 1 ), [Ag(NCCH₃)][N(NO₂)₂] ( 2 ), and [Ag(py)₂][N(NO₂)₂] ( 3 ) have been investigated by ¹⁰⁹Ag, ¹⁴N NMR and vibrational spectroscopy (IR, Raman). In addition, the poorly understood [Cu(NH₃)₄][N(NO₂)₂)]₂ ( 4 ) and [Pd(NH₃)₄][N(NO₂)₂]₂, ( 5 ) have also been prepared and characterized by ¹⁴N NMR and vibrational spectroscopy (IR, Raman). The structures of 2 — 5 have also been determined by X‐ray diffraction.     

[Ag(NH3)2]Ag(OsO3N)2: a new nitridoosmate(VIII)

Dark brown single crystals of [Ag(NH₃)₂]Ag(OsO₃N)₂ were obtained from the reaction of Ag₂CO₃, OsO₄, and NH₃ in aqueous solution. The crystal structure was solved in the monoclinic space group C2/m, with the following unit-cell dimensions: a=1962.5(3), b=633.1(1), c=812.6(1) pm, β=96.71(1)°. The final reliability factor was R=0.0256 for 1034 reflections with I>2σ(I). Linear [Ag(NH₃)₂]⁺ ions are present oriented perpendicular to the [010] direction, leading to short Ag⁺-Ag⁺ distances of 316 pm. A second type of Ag⁺ ions in the crystal structure present coordination number “6+1” and are surrounded by oxygen and nitrogen atoms of the nitridoosmate groups. Within the first of the two crystallographically distinguishable anions one can clearly differentiate between oxygen and nitrogen atoms while the second one exhibits a N/O disorder over two positions. The infrared spectrum of [Ag(NH₃)₂]Ag(OsO₃N)₂ shows the typical absorptions which can be attributed to the complex anions and the NH₃ ligands.     

Electrochemical Precipitation of Dispersed Ni-Ag Powders in Ammonia Electrolytes

The electrochemical precipitation of a dispersed Ni-Ag powder from aqueous systems [Ni(NH₃)₆]²⁺-[Ag(NH₃)₂]⁺-(NH₄)₂SO₄−NH₃ ⋂ H₂O was studied.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 4, 2005, pp. 563–565.Original Russian Text Copyright © 2005 by Kuntyi, Olenych.     

Effect of alkali metals and metal-ammonia complexes on electroosmosis,effective field strength,and resolution in the separation of diuretics by CZE

The counter ion in CZE separation systems affects resolution, effective field strength and electroosmosis. Alkali metals (lithium, sodium, potassium, and cesium), the ammonium ion, and several complexes of metals with ammonia ([Ag(NH₃)₂]⁺, [Cu(NH₃)₄]²⁺, [Zn(NH₃)₄]²⁺, [Cd(NH₃)₄]²⁺, [Ni(NH₃)₆]²⁺, and [Co(NH₃)₆]²⁺) have been studied for their effect on the separation of diuretics. With the alkali metals the electroosmotic flow velocity decreased and the effective field strength and resolution increased as the hydrated radius of the alkali metal decreased. All the metal-ammonia complexes except that with silver greatly reduced the electroosmotic flow velocity (V_eo) and had only a slight effect on the effective field strength (E_eff). Because these complexes had a negligible effect on the ionic strength of the buffer, they enabled high separating power to be maintained during the separation, and hence the use of more energy in the separation system. This yielded better resolution of the compounds, but the analysis time was then compromised. A simultaneous reduction in capillary length and V_eo while maintaining the high voltage enabled increased resolution without an increase in analysis time. The ability to control V_eo by adding small concentrations (< 100 μM ) of metal complexes to the buffer solution makes it possible to adjust the analysis time and capillary length independently while employing high separation power.     

Preparation of raspberry-like polypyrrole composites with applications in catalysis

Raspberry-like composites were prepared by coating the silver/polypyrrole core/shell composites onto the surface of silica spheres via oxidation polymerization of pyrrole monomer with [Ag(NH₃)₂]⁺ ions as oxidants. The whole process allowed the absence of stabilizers, which greatly improved the quality of the conducting polymer composites. The morphology of the resulting composites was investigated, which can be described as raspberry-like; also, the structure and composition of the composites were characterized in detail. A possible formation mechanism was proposed. The present synthetic strategy substantially extended the scope of metal/conducting polymer composite synthesis. The raspberry-like composites exhibited excellent catalytic properties in the reduction of methylene blue dye with the reducing agent of sodium borohydride.     

Electrorheological properties of carbon nanotube/polyelectrolyte self‐assembled polystyrene particles by layer‐by‐layer assembly

Sulfonated polystyrene (PS) particles were prepared by the sulfonation of PS microspheres with H₂SO₄. Then, composite particles were synthesized by layer‐by‐layer (LbL) self‐assembly with funtionalized multiwall carbon nanotubes (fMCNTs) and polyelectrolytes on sulfonated PS particles. The amount of fMCNTs on PS particles was adjusted by controlling the number of fMCNT layers by LbL self‐assembly. Composite particles were characterized by ζ‐potential analysis, scanning electron microscopy, and thermal analysis. The electrorheological (ER) properties of composite particles in insulating oil was investigated with varying the number of fMCNT layers under controlled electric fields. It was observed that the number of fMCNT layers was a critical factor to determine the ER properties of composite particles. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1058–1065, 2008     

The catalytic effect of transition metal-ion ammine complexes on the decomposition of hydrogen peroxide in the presence of Dower-50W resin in aqueous medium

Summary The kinetics of the catalytic decomposition of hydrogen peroxide was studied in the presence of Dowex-50W resin in the form of some transition metal-ion ammine complexes in an aqueous medium. The transition metal-ions, Co²⁺, Ag⁺, Cd²⁺ and Zn²⁺ were chosen in this study and the rate constants (per gram of dry resin) were evaluated at various resin weights in the 25–40°C range. A coloured compound (peroxo-metal complex), which formed at the beginning of the reaction in each case, was found to contain the catalytic active species. Probable mechanisms for the reactions are proposed. The activation energy and the change in the entropy of activation increased in the following sequence: [Ag(NH₃]₂]⁺< [Cd(NH₃)₆]²⁺<[Co(NH₃)₆]²⁺<[Zn(NH₃)₆]²⁺, which is also the probability sequence for the formation of the activated complex.     

The Neutral Complex (NH3)Ag(NCO)

Dissolution of solid AgNCO (silver isocyanate) in aqueous ammonia (25 %) and subsequent crystal growth at T = –9 °C furnished the new ammoniate (NH₃)Ag(NCO) as colorless crystals [P2₁/c (no. 14); a = 4.1817(3) Å, b = 14.445(1) Å, c = 6.1988(5) Å, β = 102.0(4)°, V = 365,6(2) ų; Z = 4]. In the molecular monammine complex, which is only stable at temperatures below T = 0 °C, silver is in a twofold, however, asymmetrical coordination by the isocyanate anion and ammonia. At the reaction conditions applied, AgNCO does not form an ionic diammine species (e.g. [Ag(NH₃)₂]⁺) as known from related silver salts. In this sense, the solvation chemistry of AgNCO exhibits a rarely observed feature.     

Controlled Aggregation of Multiple Guanidinium Ions through a Hydrogen‐Bonded Network Assembly with Deprotonated Forms of Kemp’s Triacid

A series of five complexes that incorporate the guanidinium ion and various deprotonated forms of Kemp’s triacid (H₃KTA) have been synthesized and characterized by single‐crystal X‐ray analysis. The complex [C(NH₂)₃⁺] ? [H₂KTA^?] ( 1 ) exhibits a sinusoidal layer structure with a centrosymmetric pseudo‐rosette motif composed of two ion pairs. The fully deprotonated Kemp’s triacid moiety in 3 [C(NH₂)₃⁺] ? [KTA^3?] ( 2 ) forms a record number of eighteen acceptor hydrogen bonds, thus leading to a closely knit three‐dimensional network. The KTA^3? anion adopts an uncommon twist conformation in [(CH₃)₄N⁺] ? 2 [C(NH₂)₃⁺] ? [KTA^3?] ? 2 H₂O ( 3 ). The crystal structure of [(nC₃H₇)₄N⁺] ? 2 [C(NH₂)₃⁺] ? [KTA^3?] ( 4 ) features a tetrahedral aggregate of four guanidinium ions stabilized by an outer shell that comprises six equatorial carboxylate groups that belong to separate [KTA^3?] anions. In 3 [(C₂H₅)₄N⁺] ? 20 [C(NH₂)₃⁺] ? 11 [HKTA^2?] ? [H₂KTA^?] ? 17 H₂O ( 5 ), an even larger centrosymmetric inner core composed of eight guanidinium ions and six bridging water molecules is enclosed by a crust composed of eighteen axial carboxyl/carboxylate groups from six HKTA^2? anions.     

Studies on the thermal decomposition of the silver group of alkali metal nitritocobaltates(III)

The thermal decomposition of nitritocobaltate(III) of the silver group of general formula M₂Ag[Co(NO₂)₆] (where M = K⁺, NH⁺₄, Rb⁺ or Cs⁺) has been investigated. Based on the thermal curves of the investigated compounds and chemical and diffractometric analysis, the mechanism of thermal decomposition has been determined. The results obtained indicate that the decomposition proceeds in three stages. As a result of decomposition in the first stage (300°C), nitrates of alkali metals, metallic silver and Co₃O₄ are formed. In the second stage (500°C), a partial decomposition of nitrates to alkali metal oxides occurs, and in the third stage the products are alkali metal oxides, silver and Co₃O₄. This paper also presents the dependence of the decomposition temperature of nitritocobaltates(III) of the silver group on the ionic radius of the outer-sphere cation.