The Growth of Phosphonium Gold Nanoparticles in Alkaline Media: Kinetics and Mechanism of the Process

Colloid Journal - It has been found that the addition of ammonia water to a gold sol obtained by the Duff method induces the growth of the gold particles. The growth kinetics of such particles in...     

Metal nanoparticles on polymer surfaces: 6. Probing of non-glassy polystyrene surface layer

Peculiarities of the state of the surface layer of the amorphous glassy polymer polystyrene are studied with a specially developed experimental approach. The essence of the method consists in the observation via atomic force microscope for the depth and rate of embedding of gold nanoparticles in a polymer after their preliminary adsorption on the polymer surface from hydrosol. It is shown that the polymer glass-transition temperature near the boundary with air is substantially lowered relative to its bulk value. “Equilibrium” thickness of the non-glassy (“melted”) surface layer is determined through analysis of the data on the kinetics of nanoparticle embedding, and it is revealed that the layer thickness increases with temperature, reaching, near the “bulk” glass-transition temperature, the magnitude that is close to the diameter of the macromolecular coil. The results obtained are analyzed with allowance for published data, and the semi-empirical formula describing variations in the thickness of the non-glassy surface layer as a function of temperature in the interval between the “surface” and “bulk” glass-transition temperatures of a polymer is proposed.     

5-Substituted 3-Nitro-1-vinyl-1,2,4-triazoles

A series of 5-substituted 3-nitro-1-vinyl-1,2,4-triazoles were synthesized by alkaline treatment of the corresponding 1-(2-haloethyl- or 2-nitroxyethyl)-3-nitro-1,2,4-triazoles and by transvinylation of NH acids of the same series with vinyl acetate. The scope of applicability of the transvinylation procedure was established with respect to the azole pK _a value. The vinylic double bond on the nitrogen was shown to be inactive toward both nucleophilic and electrophilic reagents, whereas the halogen atom in position 5 exhibits enhanced reactivity. The latter factor provides the possibility for versatile structural modification via nucleophilic replacement of the 5-halogen atom by various groups, including triazolate ion.     

5-Methyl-7-chloro-l,2,4-triazolo[1,5-a]pyrimidine in reaction with azole salts

Reaction of 7-chloro-l,2,4-triazolo[l,5-a]pyrimidine with salts of five-membered nitrogen-containing NH-heterocycles carried out at heating in aprotic solvents yielded the corresponding 7-azolyl derivatives.     

Synthesis of polyhaloalkyl-substituted azoles

A number of haloalkyltetrazoles were obtained by the addition of polyhalo derivatives to vinyltetrazoles. A number of haloalkyl-substituted benzazoles were obtained by the reaction of imino ester hydrochlorides that have haloalkyl radicals with o-phenylenediamine and o-aminophenol.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 369–372, March, 1991.     

Nitration of Triazolyl-substituted Ketones

By nitration of 3-R-1,2,4-triazol-1-ylalkanones with a mixture of concentrated sulfuric and nitric acids a series of compounds was obtained containing a trinitromethyl fragment at the nitrogen of the ring.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 5, 2005, pp. 767–771.Original Russian Text Copyright © 2005 by Kofman, Kartseva, Glazkova, Krasnov.     

5-substituted 3-nitro-1-trinitromethyl-1,2,4-triazoles

A number of 5-R-substituted 3-nitro-1-trinitromethyl-1H-1,2,4-triazoles (R = Me, Cl, Br, N₃, NH₂, NO₂) were synthesized by nitration of the corresponding ω-(5-R-3-nitro-1H-1,2,4-triazol-1-yl)alkan-2-ones with mixtures of concentrated sulfuric and nitric acids.     

Metal nanoparticles on polymer surfaces. 7. The growth kinetics of gold nanoparticles embedded into surface layers of glassy polymers

It has been shown that citrate gold nanoparticles can be embedded (partly immersed) into the surface layers of different glassy polymers with subsequent seeded growth of the particles in an aqueous chloroauric acid–hydroxylamine mixed solution. Quantitative data have been obtained on the seeded growth kinetics, and it has been shown that its rate-limiting stage is the diffusion of metal ions from the bulk solution to the surface of gold nanoparticles.     

Metal Nanoparticles on Polymer Surfaces: 5. Catalytic Activity of Colloidal Platinum Films Incorporated in Polystyrene Surface Layer

The fundamental possibility to enlarge Pt nanoparticles in monolayer ensembles formed on polystyrene surfaces by the adsorption from hydrosol in solution of isopropanol and K₂PtCl₄ is demonstrated for the first time. The enlargement of “seeding” nanoparticles is performed after their preliminary incorporation (partial embedding) into the polymer surface layer by the annealing of a system within the range between “surface” and “bulk” glass transition temperatures of polystyrene. It is shown that a colloidal film of metallic platinum with a thickness up to 200 nm is formed in the course of enlargement and it is mechanically fixed in the polymer surface layer. Such a system exhibits, over a long time, high catalytic activity in the model reaction of methyl viologen reduction with hydrogen.__________Translated from Kolloidnyi Zhurnal, Vol. 67, No. 3, 2005, pp. 398–403.Original Russian Text Copyright © 2005 by Rudoy, Sukhov, Dement’eva, Abkhalimov, Vereshchagina, Kartseva, Ershov.     

Metal Nanoparticles on Polymer Surfaces: 3. Adsorption Kinetics of Gold Hydrosol Particles on Polystyrene and Poly(2-vinylpyridine)

The adsorption of gold hydrosol nanoparticles on the surfaces of polystyrene and poly(2-vinylpyridine) was studied using two techniques, quartz crystal microgravimetry and atomic force microscopy. The resultant experimental data indicated that the kinetics of this process is controlled by the diffusion. The nanoparticle adsorption, up to rather high polymer surface coverages (35%), is irreversible.