Electrosynthesis of nanocomposites of Ag,Au, Pd nanoparticles with aluminum(III), zinc(II), and titanium(IV) oxide-hydroxides

Journal of Solid State Electrochemistry - The two-step electrosyntheses of metal nanoparticles (MNP) (M = Pd, Ag, Au) nanocomposites with aluminum(III), zinc(II), titanium(IV)...     

Mediated electrosynthesis of silver nanoparticles in a two-phase water—isooctane system

Russian Chemical Bulletin - Efficient electrosynthesis of silver nanoparticles (AgNPs) in bulk solution of a two-phase water—isooctane system is carried out by electrolysis in an undivided...     

Methylviologen-mediated electrochemical synthesis of silver nanoparticles via the reduction of AgCl nanospheres stabilized by cetyltrimethylammonium chloride

Efficient synthesis of silver nanoparticles stabilized by cetyltrimethylammonium cations (Ag@CTA⁺) is carried out in aqueous medium by methylviologen-mediated electroreduction of silver chloride nanospheres stabilized by surface-active CTA⁺ cations (AgCl@CTA⁺, diameter ~330 nm), on a glassy carbon electrode at potentials of the MV²⁺/MV^?+ redox couple. The nanospheres AgCl@CTA⁺ can be reduced immediately on the electrode at a low rate and the resulting metal is deposited on the electrode. In the mediated reduction, the metal is not deposited on the cathode but the quantitative reduction of AgCl to Ag@CTA⁺ nanoparticles proceeds completely in solution volume at the theoretical charge. In aqueous solution, the nanoparticles are positively charged (electrokinetic (zeta) potential is +74.6 mV), their characteristic absorption maximum is at 423 nm and the average hydrodynamic diameter is 77 nm. Isolated Ag@CTACl nanoparticles have the size of 39 ± 15 nm. The preferential form of metal nanoparticles is sphere with the diameter of 34 ± 24 nm; nanorods are also obtained in small amounts (4%); the average size of metal grains is 8–16 nm.     

Mediated Electrosynthesis and Catalytic Activity of Nanocomposites Formed by Metal Nanoparticles with Poly(N-vinylpyrrolidone) and Nanocellulose

Russian Journal of Electrochemistry - Nanoparticles (NP) of Au, Ir, Pd, Pt, and Rh are synthesized by benzimidazo[1',2':1,2]quinolino-[4,3-b][1,2,5]oxodiazolo[3,4-f]quinoxaline...     

Catalog of dessins d’enfants with no more than 4 edges

In this work, all the dessins d’enfants with no more than 4 edges are listed and their Belyi pairs are computed. In order to enumerate all dessins, the technique of matrix model computations was used. The total number of dessins is 134; among them 77 are spherical, 53 of genus 1, and 4 of genus 2. The automorphism groups of all the dessins are also found. Dessins are listed by the number of edges. Dessins with the same number of edges are ordered lexicographically by their lists of 0-valencies. The corresponding matrix model for any list of 0-valencies is given and computed. Complex matrix models for dessins with 1–3 edges are used. For the dessins with 4 edges, we use Hermitian matrix model. Translated from Fundamentalnaya i Prikladnaya Matematika, Vol. 13, No. 6, pp. 35–112, 2007.     

Photoconduction in CDW conductors

Photoconduction study of quasi-1D conductors allows to distinguish between the single-particle and collective linear conduction, investigate the effect of screening on collective transport and obtain interesting new details of the electronic energy structure of pure and doped CDW conductors. Here we present results of photoconduction study in quasi-1D conductors o-TaS₃, K_0.3MoO₃, and NbS₃(I).     

Electrochemical method for producing globules of ultrasmall rhodium nanoparticles with poly(N-vinylpyrrolidone) bound to the surface of nanocellulose fibers

The study concerns the preparation of Rh nanoparticles (NPs) by room-temperature, methyl viologen (MV²⁺) mediated electrochemical reduction of RhCl₃ in the presence of poly(N-vinylpyrrolidone) (PVP, 40000 Da) and nanocellulose (NC, d = 57±36 nm) at a controlled potential of generation of MV^·+ radical cations in aqueous medium. When a theoretical amount of electricity is passed, the mediator is not consumed, while Rh^(III) is quantitatively reduced to Rh⁽⁰⁾. The reduction results in the Rh@PVP (141–191 nm in size) and Rh@PVP/NC nanocomposites dispersed in the solution bulk. The Rh@PVP/NC nanocomposite represents PVP globules (42±13 nm in size) with encapsulated ultrasmall spherical Rh NPs (1.3±0.4 nm in size) bound to the surface of NC fibers. The Rh nanocomposites exhibited high catalytic activity in the model reaction, viz., reduction of p-nitrophenol with sodium borohydride in aqueous medium. The catalytic activity increased in the presence of cetyltrimethylammonium chloride (CTAC).

     

Methylviologen-mediated electrochemical synthesis of platinum nanoparticles in solution bulk

Platinum nanoparticles (PtNPs) are synthesized by methylviologen-mediated reduction of PtCl₂ at the potentials of the MV²⁺/MV^?+ redox couple in 40% aqueous DMF solution. In the absence of stabilizing agents and in the presence of a stabilizer in the form of spherical silica NPs or alkylamine-modified silica NPs (SiO₂-NHR), a part of PtNPs (14–18%) are deposited on the electrode while the rest of particles remain in solution to form coarse aggregates which precipitate. In the latter case, PtNPs are also partly bound to form individual ultrafine NPs (3 ± 2 nm) on the SiO₂-NHR surface. In the presence of polyvinylpyrrolidone (PVP), the generated PtNPs (18 ± 9 nm) neither aggregate nor deposit on the cathode but are completely stabilized in solution being encapsulated within the PVP matrix. The obtained PtNPs are characterized by the methods of dynamic light-scattering and electron microscopy.     

Surface-active properties of a series of 1,1-dimethyl-1-alkylhydrazinium chlorides

The surface-active properties of a series of 1,1-dimethyl-1-alkylhydrazinium chlorides with C₁₀–C₁₈ in length were studied in comparison with Neonol AF 9–12 and Oksifos B surfactants. The limiting wetting angle, detergent and solubilization power, and foaming kinetics of these surfactants were studied in relation to the concentration of formation of monomolecular layer and type of the resulting micellar structures.