Efficient mediated electrosynthesis of catalytically active ultrasmall mono- and bimetallic nanoparticles of Rh, Pd stabilized with CTAC was carried out in water.

Using C-60 and C-70 fullerenes as mediators, efficient mediated electrosynthesis of silver nanoparticles (AgNP) in toluene-DMF/0.1 M Bu4NBF4 medium was carried out by reduction of Ag+ at the potentials of the fullerene radical anions generation. Synthesis was performed in the absence and in the presence of poly(N-vinylpyrrolidone) (PVP) in the cathodic compartment of a diaphragm-separated cell by addition of Ag+ as AgNO3 into solution and in a single compartment cell by in situ generation of Ag+ by dissolution of an Ag-anode during electrolysis. In all cases, Ag+ ions are quantitatively reduced upon consumption of the theoretical amount of electricity; the generated metal is quantitatively obtained in solution bulk in the form of spherical NP with sizes in the range from 11 +/- 2 to 24 +/- 9 nm. In electrolysis in a single compartment cell, dispersion of the Ag-anode occurs along with its dissolution and the total current efficiency of AgNP is 131 divided by 163%. In the presence of PVP, individual AgNP are stabilized in the PVP shell. The isolated Ag/PVP nanocomposite is deposited on a solid support both in individual form and as three-component Ag/PVP/fullerene nanocomposite. In the absence of PVP, the Ag/fullerene nanocomposite is obtained. (C) 2018 The Electrochemical Society.

Ultra-fine gold (<2 nm), silver (5 ± 2 nm), and palladium (<1–2 nm) nanoparticles stabilized in polyvinylpyrrolidone shell were synthesized in N,N-dimethylformamide, using molecular oxygen dissolved in the electrolyte as mediator, by the reduction of the metals’ ions and complexes at the controlled potential of the oxygen reduction to its radical-anion. Pd-nanoparticles showed high catalytic activity in the reactions of p-nitrophenol reduction and Suzuki cross-coupling. Long-term ageing of spherical Ag-nanoparticles for 60 days in the post- electrolysis solution resulted in their consolidation (up to 17 ± 5 nm; the average size of crystallites 7.5 (3) nm). Upon similar exposure of Au-nanoparticles for 15 days, V-shaped nanoparticles were formed (length 112 ± 53 nm, width 58 ± 22 nm, crystallites 20(2)–31(1) nm); upon the isolation, dispersing into ethanol, and exposure for 48 h, hexagonal nanoparticles (105 ± 29 nm) and polygons (56 ± 25 nm, crystallites 24(2)–51(1) nm; upon dispersing into water and exposure for 8 h, spherical nanoparticles (13 ± 8 nm, crystallites 7(1)–13.4(5) nm). Thus obtained nanoparticles are characterized by methods of cyclic voltammetry, dynamic light scattering, scanning and high resolution transmission electron microscopy, and X-ray powder diffraction.

Metal complexes [Cr(bipy) 3 ] 3+ , [Co(bipy) 3 ] 3+ , and [Co(sep)] 3+ in aqueous media at the potentials of M(III)/M(II) redox couple are shown playing a role of mediators in the electrosynthesis of silver nanoparticles, stabilized in a polyvinylpyrrolidone shell, by means of Ag(I) reduction. [Cr(bipy) 3 ] 3+ is consumed under the conditions of long-term preparative electrolysis, the reduction process is accompanied by cathode passivation, therefore, the Ag+ ions complete conversion to the Ag-nanoparticles is unattainable. The two other metal complexes are fully remained unimpaired; the mediated electrosynthesis of the Ag-nanoparticles is carried out well effectively: the Ag-nanoparticles are produced in the solution bulk with a nearly quantitative yield, a theoretical charge being consumed. the [Co(bipy) 3 ] 3+ -mediated reduction of the Ag + ions, generated by a silver anode in situ dissolution in the course of single compartment cell electrolysis, is accompanied by the anode metal dispersion and results in the formation of polydisperse Ag-nanoparticles. The summary Ag-nanoparticle current efficiency in the solution bulk comes to 128%. Thus formed Ag-nanoparticles are characterized by using dynamic light scattering, scanning and transmission electron microscopy, and X-ray powder diffraction. The Ag-nanoparticles are spherical, with a mean size of 83 ± 53 nm, or have a form of nanowires, with a length of l = 1216 ± 664 nm and diameter of d = 94 ± 17 nm. The [Co(sep)] 3+ -mediated AgCl reduction gives ellipsoidal Ag-nanoparticles sized l = 46 ± 19 nm, d = 27 ± 7 nm; the silver crystallite mean size is 20(1)–34.4(9) nm.

Efficient electrosynthesis of spherical silver nanoparticles (AgNP) stabilized by poly(Nvinylpyrrolidone) (PVP40 and PVP1300) in the solution bulk in single compartment cell has been performed using a soluble silver anode as in situ supplier of Ag ions in water/ 0.1 M KNO3 medium. AgNP are obtained as a result of the methylviologen mediated electroreduction of Ag ions at the potentials of the MV/MV redox couple and the dispersion of the Ag-anode. The total current yield of AgNP (106 ÷ 163%) increases and the particle size decreases with increasing the PVP concentration. In the presence of PVP1300, the particle size is noticeably higher than in the presence of PVP40. The possibility of controlling the AgNP size in a sufficiently wide range from 26 ± 6 to 61 ± 12 nm is shown by varying the nature and concentration of PVP.

Efficient mediated electrosynthesis of nanocomposite Au@р(MVCA8+-co-St) (~6 nm), in which ultrasmall Au nanoparticles (Au-NP) were bound in nanocapsules of water-soluble nanoparticles of соpolymer р(MVCA8+-co-St) of tetraviologen calix[4]resorcinol (MVCA8+) with styrene (St), was accomplished by the reduction of AuI in aqueous medium. The quanti- tative reduction of AuI was carried out using the theoretically necessary amount of electricity and was not accompanied by the deposition of metal on the electrode. Radical cations of viologen units MV•+ of the molecule р(MVCA4•+-co-St) adsorbed on the electrode and π-dimers MV•+···MV•+ of π-polymers [р(MVCA4•+-co-St)] n deposited on the electrode act- ed as the reducing agents with respect to AuI. During electrolysis, the nanoparticles agglo- merated to 37—50 nm. The nanocomposite particles dispersed in ethanol had sizes of 72±16 nm and also contained Au-NP with sizes of 51±8 and 19±3 nm. The catalytic activity of the nanocomposite in the reduction of p-nitrophenol with sodium borohydride was demon- strated. A similar reduction of AgCl nanoparticles (~250 nm) led to the formation of silver nanoparticles with crystallite sizes in the range of 7—11 nm, the process was inefficient, however, even when using 250% of electricity, an incomplete reduction of AgCl was still observed.

In this article, we report the synthesis of mono- and bimetallic Pd–Ni nanocomposites supported on a multicharged polymeric matrix for catalytic applications.

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.

Methylviologen mediated reduction of Aui ions generated in situ by dissolution of a gold anode in single compartment cell has been used for the electrosynthesis of spherical gold nanoparticles (Au-NPs) stabilized by poly(N-vinylpyrrolidone). The size of Au-NPs was from 15±6 to 27±9 nm, depending on the electrosynthesis conditions. Au-NPs were characterized by cyclic voltammetry, UV-VIS spectroscopy, dynamic light scattering, scanning and transmission electron microscopy.

C-60 fullerene mediated electroreduction of Au(I) at potentials of the C-60/C-60(center dot-) redox couple was used to perform the electrosynthesis of an AuNP/C-60 nanocomposite in DCB-DMF (2:1)/0.1 M Bu4NCl medium. The nanocomposite consists of separate gold nanoparticles with various shapes and a mean size of similar to 27 +/- 14 nm, as well as larger nanoaggregates of such particles, isolated in a fullerene matrix. The mean size of metal crystallites is 9-14 nm. The electrolysis occurs efficiently, and Au(I) is quantitatively reduced to Au(0) upon consumption of the theoretical amount of electricity. The resulting metal nanoparticles and the nanocomposite are not deposited on the electrode and are completely stabilized in the solution bulk. All the particles were characterized by electron microscopy methods (SEM, HR TEM) and X-ray powder diffraction (XRPD). (C) 2017 The Electrochemical Society. All rights reserved.

Mediated electroreduction of Au(I) using C-70 fullerene, methano[60]fullerene and [60]fulleropyrrolidine as a mediator at the potentials of mediator reduction to the radical anion was used to obtain nanocomposites of gold nanoparticles (AuNP) with mediator in toluene-DMF (2:1, by volume)/0.1 M Bu4NCl medium. The nanocomposite consists of AuNP bound by fullerene to aggregates that are dispersed in a fullerene matrix. The aggregates have the form of a "flower". Size of aggregates (from 55 +/- 17 to 95 +/- 22 nm), AuNP (from 10 +/- 1 to 19 +/- 5 nm), metal crystallites (from 6 to 16 nm) depends on the nature of a mediator, and this dependence for aggregates and AuNP is antibate. The electrolysis occurs efficiently in all cases, and Au(I) is mediately quantitatively reduced to Au(0) with the formation of nanoparticles, and ultimately their aggregates, upon consumption of the theoretical amount of electricity. Metal and nanocomposite are not deposited in appreciable quantities on the electrode and are almost completely stabilized in the solution bulk. All the particles were characterized by electron microscopy methods (SEM, HR TEM) and X-ray powder diffraction (XRPD). (c) 2017 The Electrochemical Society. All rights reserved.

By example of fullerene-mediated electrosynthesis of Ag–C60 nanocomposite in water–o-dichlorobenzene, the possibility of using a liquid–liquid two-phase system for the electro- synthesis of metal nanoparticles has been demonstrated for the first time.

The possibility of using of molecular oxygen as a mediator in electrosynthesis of metal nanoparticles by reduction of their ions and complexes in aprotic media was demonstrated by the example of electrosynthesis of gold nanoparticles by reduction of Au(I) in DMF.

Electrosynthesis of gold nanoparticles (AuNp) was carried out by methylviologen mediated reduction of Au(i) at potentials of the MV2+/MV˙+redox couple in water/0.1 M NaCl medium, in the absence and in the presence of stabilizers.

An efficient mediated electrosynthesis of the spherical (85 nm) nanocomposite material Pd@p(MVCA8+-co-St) was carried out in an aqueous medium. Ultrasmall palladium nanoparticles (3—8 nm) are stabilized in nanocapsules of water-soluble nanoparticles of the copolymer p(MVCA8+-co-St) consisting of tetraviologen calix[4]resorcinol (MVCA8+) with styrene (St). The role of the mediator is played by viologen units of a polymer nanoparticle at potentials of the MV2+/MV∙+ redox couple. The high catalytic activity of the nanocomposite material in the reduction of nitrophenol with sodium borohydride is shown.

На основе ферроцен-1,1-диил-бисфосфиновых кислот Fc[P(R)(O)OH]2 (R = H, Me, Et, Ph) в метаноле создано два типа молекулярных роторов с электрохимическим двигателем. Моноанионы кислот за счет внутримолекулярной водородной связи фиксируются в цис-конформации, а дианионы за счет сил электростатического отталкивания – в транс-конформации. При переводе моноанионов в дианионы происходит управляемое вращение циклопентадиенильных колец из цис-конформации в транс-, а при обратном переключении происходит обратное вращение. В одном типе роторов вращение управляется обратимым изменением рН и состава раствора электрохимическим циклом окисления–ревосстановления N-фенил-N-изопропил-1,4-фенилендиамина, в другом типе – одноэлектронным окислением–ревосстановлением ферроценового ядра моноанионов. Последний тип ротора при комнатной температуре устойчиво функционирует только при малых временах ( < 1 c), при больших временах необратимо разрушается на стадии окисления.

Efficient electrosynthesis of palladium(0) nanoparticles is carried out in solution by mediated electrochemical reduction of a complex dianion [PdCl4]2– in the DMSO/0.1 M Bu4NCl medium. The mediator function was performed by methylviologen and tetraviologen calix[4]resorcines MVCA-C n 8+ with methyl (n = 1), n-pentyl (n = 5), and n-decyl (n = 10) substituents in resorcinol rings at the potentials of redox pairs MV2+/MV•+, MVCA-C n 8+ /MVCA-C n 4•+ . The resulting metal nanoparticles gradually aggregate to yield coarser particles. The smallest size (255 nm) have metal particles obtained in the presence of MVCA-C 5 8+ for the rest mediators, metal particles of the micron size are formed. Sonication results in disintegration of aggregates to nanoparticles.