Yu. A. Krutyakov

A versatile synthesis of highly bactericidal Myramistin® stabilized silver nanoparticles

Silver nanoparticles stabilized by a well-known antibacterial surfactant benzyldimethyl[3-(myristoylamino)propyl]ammonium chloride (Myramistin(®)) were produced for the first time by borohydride reduction of silver chloride sol in water. Stable aqueous dispersions of silver nanoparticles without evident precipitation for several months could be obtained. In vitro bactericidal tests showed that Myramistin(®) capped silver NPs exhibited notable activity against six different microorganisms-gram-positive and gram-negative bacteria, yeasts and fungi. The activity was up to 20 times higher (against E. coli) compared to Myramistin(®) at the same concentrations and on average 2 times higher if compared with citrate-stabilized NPs.

Formation of surface layers on silver nanoparticles in aqueous and water-organic media

Synthetic aspects of silver nanoparticle preparation in one-and two-phase aqueous and water-organic media and the influence of experimental factors on particle size and surface hydrophilicity/hydrophobicity are studied. It is shown that silver nanoparticles with controlled mean size and surface hydrophilic-hydrophobic properties can be obtained through direct synthesis or successive transformations.

Aggregative stability and polydispersity of silver nanoparticles prepared using two-phase aqueous organic systems

Synthetic aspects of obtaining silver organosols in two-phase aqueous organic systems and the influence of process conditions on the polydispersity and aggregative stability of obtained silver nanoparticles are considered.

Sensitized Fluorescence of Silver Nanoparticles in the Presence of Pyrene

The fluorescence of pyrene adsorbed onto the surface of the cetyltrimethylammonium-coated silver nanoparticles was studied. Pyrene molecules adsorbed on freshly prepared silver particles were found to be in close proximity to silver surface thus providing the possibility of energy transfer from excited pyrene to silver cores of the particles. In that case along with the expected fluorescence of pyrene we observed the fluorescence of the silver nanoparticles induced by the excited pyrene molecules. In due course the restructuring of the cetyltrimethylammonium layer resulted in moving of pyrene molecules away from silver surface and simultaneous disappearance of the silver nanoparticles fluorescence band. These data strongly support the recent hypothesis of fluorophore-plasmon coupled emission.

Adsorption preconcentration of pyrene by silver nanoparticles and its determination in aqueous solutions

The reduction of silver nitrate with sodium borohydrate in an aqueous medium in the presence of cetyl trimethylammonium bromide gives a stable sol of silver, which can adsorb nonpolar organic compounds, e.g., polycyclic aromatic hydrocarbons, on the surface of metal nanoparticles. The subsequent luminescent determination demonstrated the effect of sensitized luminescence of silver nanoparticles, which could provide a basis for the determination of traces of polycyclic aromatic compounds in water.

Photochemical synthesis of highly bactericidal silver nanoparticles

In this work we describe an experimental technique that makes it possible to obtain highly bactericidal silver nanoparticles (NPs). Synthesis was carried out using nontoxic reagents, and the technique consisted of reducing silver by glucose via UV irradiation in the presence of oleic or myristic acids as stabilizers. The size of the NPs fell in the range of 4–18 nm, and the average diameter was about 7 ± 1 nm (oleic acid) and 4 ± 1 nm (myristic acid). Unlike previous reports, where the Tollens reaction was used only with the assistance of thermal activation, we conducted the UV reduction of a silver nitrate solution, glucose, and the stabilizer at room temperature for the first time. The minimum inhibition concentration of nanosized silver against a gram-negative Escherichia coli was 1 μg/ml. Thus, the activity of the NPs appeared to be considerably higher than that of nanosilver samples that are currently known.

Synthesis and adsorption and luminescence properties of hydrophobic silver nanoparticles in the presence of pyrene

A procedure was developed for the synthesis of hydrophobic silver nanoparticles with an average size of 4 nm in two-phase water-organic emulsions. The physical properties of the obtained silver organosol were studied by molecular spectroscopy and electron microscopy. It was found that the synthesized silver nanoparticles had a specific surface of 60–110 m2/g. It was shown that chemically modified silver nanoparticles can be used as an adsorbent for preconcentrating polycyclic aromatic hydrocarbons (using pyrene as an example) from dilute n-hexane solutions followed by luminescence determination at room temperature.

Chemically modified silver nanoparticles as a new sorbent for preconcentration of polycyclic aromatic hydrocarbons from aqueous solutions

236 Currently, considerable attention is paid to determination of compounds contaminating the environment, in particular, polycyclic aromatic hydrocarbons (PAHs) due to their high carcinogenic activity [1]. Determination of PAH concentrations in aqueous media poses great difficulty. This stimulates the development of highly sensitive and highly selective methods of analysis. Usually, analysis of environmental objects for PAHs includes preconcentration followed by identification and quantitative determination. In recent years, alternative methods based on sorption preconcentration followed by luminescence determination of PAHs at room temperature have been developed [2, 3]. The sorption methods are more practicable than other preconcentration methods, for example, liquid and supercritical fluid extraction. In this study, PAHs were preconcentrated from aqueous solutions using chemically modified silver nanoparticles as sorbents. PAH are sorbed on them under static conditions, i.e., by mere stirring of the analyte with the sorbent, and then determined based on sensitized fluorescence intensity of silver nanoparticles at room temperature. A specific feature of this approach is the absence of the stage of desorption of the analytes, which is most often incomplete. Pyrene was chosen as the model PAH. This choice was due to the fact that this compound is often used as a fluorescence probe for the study of the state of sorbates and physicochemical properties of sorbents owing to the high sensitivity of its fluorescence spectra to change in the local environment [4, 5]. The fluorescence spectra of pyrene and the absorption spectra of silver nanoparticles lie in the same region, which is a necessary condition for the appearance of sensitized fluorescence of silver nanoparticles [6]. Chemically modified silver nanoparticles were prepared by reduction of silver nitrate in an aqueous solution with an excess of sodium borohydride in the presence of cetyltrimethylammonium bromide (CTAB). CTAB (0.44 g) was dissolved in doubly distilled water (20 mL), silver nitrate (0.17 g) was added, and an aqueous solution (5 mL) containing sodium borohydride (0.08 g) was added dropwise. The mixture was stirred at room temperature for 30 min. The aqueous sol of silver nanoparticles was used as the sorbent either directly (concentrated sol) or after 10-fold dilution with doubly

Formation mechanisms of anisotropic silver nanostructures in polyol synthesis

In this article, the reduction of silver nitrate in ethylene glycol media in the presence of polyvinylpyrrolidone was studied. Based on experimental data it was shown that polyvinylpyrrolidone crucially influences polyol synthesis of silver nanorods. Their mass molecular characteristics are the key parameters influencing both the yield and parameters of the final product.

Electric discharge in liquids as technique to obtain high-dispersed materials based on metals of IB group

Nowadays, there is an intensive development of the electric arc discharge method, first proposed in 1922 by T. Svedberg. That method is an effective tool for the synthesis of nanomaterials such as metals, oxides, binary compounds and, in some cases, has undoubted advantages compared to the other methods. In particular, the formation of silver and gold nanoparticles is possible in the absence of any reductants and surfactants. The copper nanostructures synthesis is based on the more cost effective and productive technology compared to the other physical methods. In this article, the main achievements and prospects for the application of the electric discharge method in liquid for the synthesis of the silver, gold and copper nanostructures are presented.