Modelling of the Phase Separation Behaviour of Semiflexible Diblock Copolymers

Silver salts are dissolved in poly(butyl methacrylate) to derive polymer electrolytes via coordinative interaction between the silver ion and the carbonyl oxygen atom. The dissolved silver ions react subsequently with propylene to form reversible silver/olefin complexes that can be utilized as olefin carriers for facilitated olefin transport. The complexation behavior and its effects on propylene transport were investigated by means of Raman and FT‐IR spectroscopy, as well as dielectric thermal analysis.     

Complexation of Silver Ions with Poly(butyl methacrylate) and Propylene Toward Facilitated Propylene Transport

Silver salts are dissolved in poly(butyl methacrylate) to derive polymer electrolytes via coordinative interaction between the silver ion and the carbonyl oxygen atom. The dissolved silver ions react subsequently with propylene to form reversible silver/olefin complexes that can be utilized as olefin carriers for facilitated olefin transport. The complexation behavior and its effects on propylene transport were investigated by means of Raman and FT‐IR spectroscopy, as well as dielectric thermal analysis.     

18-Crown-6-potassium Ferricyanide Complex as a Potentiometric Titrant

Abstract

An oxidimetric titrant, 18-Crown-6-potassium ferricyanide complex, has been prepared in acetonitrile. This reagent is proposed for redox titrations in aqueous - acetonitrile media of some reductant compounds. The general analytical conditions for using this complex and the procedures for potentiometric determinations of oxalate, arsenic (III), thiocyanate, nitrite, sulfite, thiosulphate and iodide ions, as well as hydrazine sulphate and hydrogen peroxide are presented.     

Simultaneous determination of halide and thiocyanate ions by potentiometric precipitation titration and multivariate calibration

Halide and thiocyanate ions can be determined by a precipitation titration with silver nitrate as the titrant, and the end-point can be evaluated by a potentiometric method, in which generally a silver indicator electrode is used as the indicator electrode and a double-junction Ag–AgCl electrode as the reference electrode. However, when mixtures of halide and thiocyanate are titrated, it is difficult to determine these components individually for there are overlapping steps in the potentiometric titration curves, especially in the case that there are obvious differences between concentrations of the components. In this paper, the linear equation for the potentiometric precipitation titration of a mixture of halide and thiocyanate ions was developed and it was then used for determining the components in the mixtures simultaneously with the aid of multivariate calibration methods. By application of this model, 27 synthetic mixtures with three- and four-component combinations of chloride, bromide, iodide and thiocyanate with low concentration levels from 1.8×10⁻⁴ to 6.2×10⁻⁴ mol l⁻¹ were analyzed and acceptable results were obtained.     

pH‐Dependent Coordination of AgI Ions by Histidine: Experiment,Theory, and a Model for SilE

Artificial implants and biomaterials lack the natural defense system of our body and, thus, have to be protected from bacterial adhesion and biofilm formation. In addition to the increasing number of implanted objects, the resistance of bacteria is also an important problem. Silver ions are well‐known for their antimicrobial properties, yet not a lot is known about their mode of action. Silver is expected to interact on many levels, thus the development of silver resistance is very difficult. Nevertheless, some bacteria are able to resist silver, even at higher concentrations. One such defense mechanism of bacteria against heavy‐metal intoxication includes an efflux system. SilE, a periplasmic silver‐binding protein that is involved in this defense mechanism, has been shown to possess numerous histidine functions, which strongly bind to silver atoms, as demonstrated by ourselves previously. Herein, we address the question of how histidine binds to silver ions as a function of pH value. This property is important because the local proton concentration in cells varies. Thus, we solved the crystal structures of histidine–silver complexes at different pH values and also investigated the influence of the amino‐acid configuration. These results were completed by DFT calculations on the binding strength and packing effects and led to the development of a model for the mode of action of SilE.     

A new method for the titrimetric determination of the ferricyanide ion

The direct titration of ferricyanide ions with the mercurous-thiocyanate system is studied, the influence of pH, thiocyanate concentration, time and temperature being considered. The standard deviation of the proposed method is 0.26 per cent.     

Stabilization of silver nanoparticles with copolymers of maleic acid

Silver nanoparticles are obtained by reducing AgNO₃ with sodium borohydride in an aqueous solution in the presence of maleic acid copolymers with ethylene, N-vinylpyrrolidone, or styrene, as well as their octadecylamide group-containing hydrophobized derivatives, as dispersants. The influence of the structural features of the dicarboxylic acid copolymers on the silver nanoparticle formation process and the conditions for producing sols containing spherical nanoparticles with sizes of 1.5–3.5 nm (according to the data of transmission electron microscopy) are determined. It is shown that, at the equimolar copolymer/silver cation ratio, the morphology of resulting silver nanoparticles weakly depends on the nature of comonomers of maleic acid and the presence of hydrophobic fragments, which play an auxiliary role in the stabilization of dispersions of nanoparticles by increasing their stability with respect to ionic strength and oxidation. Evolution of the particle sizes in the system is monitored beginning with copolymer solutions to silver sols by the methods of light scattering, transmission electron microscopy, and atomic force microscopy. According to the light scattering data, copolymers and their complexes with silver ions in solutions are partly aggregated at concentrations corresponding to the conditions of nanosilver synthesis. Silver sols are shown to contain stabilized nanoparticles, which represent core-polyelectrolyte corona-type micelles and micellar clusters with polyelectrolyte coronas.     

Enhancement of facilitated olefin transport by amino acid in silver-polymer complex membranes

Silver ions dissolved in a polymer matrix are additionally coordinated by carbonyl oxygens of asparagines and their counter anions interact with cationic sites, resulting in the enhanced activity of the silver ion as an olefin carrier for facilitated olefin transport.     

One-step synthesis of silver nanoparticles, nanorods, and nanowires on the surface of DNA network

Here, we describe a one-step synthesis of silver nanoparticles, nanorods, and nanowires on DNA network surface in the absence of surfactant. Silver ions were first adsorbed onto the DNA network and then reduced in sodium borohydride solution. Silver nanoparticles, nanorods, and nanowires were formed by controlling the size of pores of the DNA network. The diameter of the silver nanoparticles and the aspect ratio of the silver nanorods and nanowires can be controlled by adjusting the DNA concentration and reduction time.     

Synthesis of copolymer-stabilized silver nanoparticles for coating materials

Silver ions being less toxic than silver nanoparticles, a more safe material can be obtained to be used as antimicrobial coating. This can be achieved by using thiol chemistry and covalently attach the silver nanoparticles in the coating. Our aim is to produce a coating having antimicrobial properties of silver ions but with the silver nanoparticles firmly attached in the coating. Here, we present a way to produce silver nanoparticles that can be used as a component in a coating or as such to produce an antimicrobial coating. The silver nanoparticles presented here are stabilized by a copolymer (poly(butyl acrylate–methyl methacrylate)) that is soft and has well-known good film-producing properties. The reversible addition-fragmentation chain transfer radical polymerization technique used to prepare the polymers provides conveniently a thiol group for effective binding of the silver nanoparticles to the polymers and thus to the coating.     

Synthesis of positively charged silver nanoparticles via photoreduction of AgNO3 in branched polyethyleneimine/HEPES solutions

Branched polyethyleneimine (BPEI) and 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) were used collaboratively to reduce silver nitrate under UV irradiation for the synthesis of positively charged silver nanoparticles. The effects of molar ratio of the ingredients and the molecular weight of BPEI on the particle size and distribution were investigated. The mechanism for the reduction of Ag+ ions in the BPEI/HEPES mixtures entails oxidative cleavage of BPEI chains that results in the formation of positively charged BPEI fragments enriched with amide groups as well as in the production of formaldehyde, which serves as a reducing agent for Ag+ ions. The resultant silver nanoparticles are positively charged due to protonation of surface amino groups. Importantly, these positively charged Ag nanoparticles demonstrate superior SERS activity over negatively charged citrate reduced Ag nanoparticles for the detection of thiocyanate and perchlorate ions; therefore, they are promising candidates for sensing and detection of a variety of negatively charged analytes in aqueous solutions using surface-enhanced Raman spectroscopy (SERS).     

Liquid-liquid extraction of silver ion with benzothiacrown ether derivatives

The extraction behavior of mono-, poly-, anal bis-(benzothiacrown ether)s is studied for alkali, alkaline-earth, heavy, and transition metal ions in the presence of picrate. These ethers show high selectivity for silver ion. Silver extractions from binary and quaternary mixtures of silver with heavy or transition metal ions were successful, except for mixtures with mercury(II) ion. Silver was extracted from a copper ore with ca. 80% recovery.     

The effect of silver ions electrolytically introduced into colloidal nanodiamond solution on its viscosity and thermal conductivity

Experimental data have been presented on the influence of silver on the viscosity and thermal conductivity of a dispersion of diamond nanoparticles. A stable dispersion (5 wt %) of detonation nanodiamond particles has been used in the experiments. Silver ions have been introduced electrolytically into the dispersion of diamond nanoparticles. Silver concentration was not higher than 0.05 wt %. It has been shown that the introduction of silver ions significantly affects the thermal conductivity and viscosity of the dispersion.     

Reduction of silver ions to silver with polyaniline/poly(vinyl alcohol) cryogels and aerogels

The macroporous conducting polymer cryogels were prepared by the oxidation of aniline hydrochloride in the frozen aqueous solutions of poly(vinyl alcohol) at ? 24 °C. Corresponding polyaniline aerogels supported with poly(vinyl alcohol) have been obtained after thawing of cryogels followed by freeze-drying. Silver was deposited on the composites using the ability of polyaniline to reduce silver ions after the immersion in silver nitrate solutions. Swollen cryogels were coated only on the surface with macroscopic silver particles due to the closed-pore structure in cryogels and limited penetration of silver ions into macropores. The diffusion of silver ions to freeze-dried aerogels was better and further improved by vacuum treatment. Silver microcubes were produced in the pores, the weight fraction of silver in dry composites being typically several per cent, a maximum 13 wt%. The conductivity of the aerogels compressed to pellets depended on the processing and the highest value was 0.27 S cm^?1. The aerogels containing silver were characterized in detail with Raman spectroscopy.     

Complexes of silver(I) with peptides and proteins as produced in electrospray mass spectrometry

Silver(I) forms aqueous phase complexes with both sulfur and nonsulfur containing peptides and proteins. These complexes were introduced into the gas phase via electrospray, and their structures probed by means of tandem mass spectrometry. Experiments with di-, tri-, and oligopeptides show that the abundance of silver(I)-containing ions increases relative to that of proton-containing ions as peptide length increases. This increase is much more dramatic for methionine-containing peptides. Collision-induced dissociation of silver-peptide complexes yields a multitude of product ions that are silver containing. However, even for methioninecontaining peptides, very few of these product ions contain the methionine residue. The solution-phase structure and the gas-phase structure of the silver/peptide complex are not identical. The methionine sulfur acts as the silver anchoring point in solution. Desolvation in the gas phase leads to a rearrangement of the silver/peptide complex such that the silver ion becomes chelated to the nitrogen and oxygen atom on the peptide backbone in addition to the methionine sulfur. This rearrangement decreases the importance of the silver/sulfur bond to the extent that it is frequently broken upon collision activation and leads to the formation of silver/peptide product ions that are nonsulfur bearing.     

Synthesis of silver dendritic nanostructures protected by tetrathiafulvalene

Silver dendritic nanostructures protected by tetrathiafulvalene (TTF) were synthesized via reduction of silver ions with TTF in acetonitrile.     

Biosynthesis of silver nanoparticle using flowers of Calotropis gigantea (L.) W.T. Aiton and activity against pathogenic bacteria

Silver nanoparticles (AgNPs) from silver nitrate solution are carried out using the flower extract of Calotropis gigantea. Silver nanoparticles were characterized by UV–vis spectrophotometer, X-Ray diffractometer (XRD). Reduction of silver ions in the aqueous solution of silver during the reaction was observed by UV–vis spectroscopy. Crystalline nature of synthesized silver nanoparticles was studied by XRD pattern, refraction peak using the Scherrer’s equation. Antibacterial activity of the silver nanoparticles was performed by disc diffusion method against Bacillus subtilis, Pseudomonas putida and Escherichia coli. The antibacterial activity of synthesized silver nanoparticles by flower extract of C. gigantea was found against B. subtilis (10 mm). Synthesised AgNPs has the efficient antibacterial activity against Gram positive bacteria.     

Hierarchically porous silver monoliths from colloidal bicontinuous interfacially jammed emulsion gels

Silver monoliths with interconnected hierarchical pore networks and three-dimensional (3D) bicontinuous morphology are synthesized from a colloidal bicontinuous interfacially jammed emulsion gel (bijel) via reduction of silver ions within a nanoporous cross-linked polymer template. The pore sizes may be tuned independently and range from tens of nanometers to over a hundred micrometers. The method is straightforward as well as flexible and can pave the way to a host of hierarchical materials for current technologies.     

Photochemical Synthesis of Anisotropic Silver Nanoparticles in Aqueous Solutions in the Presence of Sodium Citrate

The rapid one-step photochemical synthesis of anisotropic silver nanoparticles (ANPs) is reported. Silver ANPs were prepared from silver nitrate by a citrate route in aqueous solutions at room temperature under exposure to unfiltered light of a DRK 120 high-pressure mercury lamp. The silver ANPs form through one-electron reduction of the silver cation in its chelate complex with the production of sodium citrate photolysis. In the course of synthesis, small charged silver clusters and nanoparticles are formed first, which are then stabilized by citrate ions. Key factors that influence the synthesis of silver ANPs and their further transformation have been determined.     

Complex citrates of metals in Inorganic Analysis : Some preliminary observations and the application of citrate complex formation in the qualitative analysis of the metallic ions of the Silver group

The use of sodium citrate as a reagent for the separation of silver group metals has been described. Silver, lead and mercurous ions are all capable of forming soluble citrate complexes, but they differ in their stability. The lead complex is not decomposed by soluble chlorides, whereas silver and mercurous complexes yield the insoluble chlorides. The fact that lead sulphate is soluble in a hot solution of sodium citrate has been utilized for the detection of lead, when present as insoluble sulphate, in a mixture.