Oleg Yu. Posudievsky

New polyaniline–MoO3 nanocomposite as a result of direct polymer intercalation

A new nanocomposite based on polyaniline and MoO3 is prepared via direct intercalation of conducting polymer macromolecules. The method of preparation allows material to be obtained with peculiar electric and electronic properties.

Preparation of graphene oxide by solvent-free mechanochemical oxidation of graphite

Graphenes with different oxidation degrees are prepared by ultrasound assisted aqueous exfoliation of solvent-free mechanochemically treated graphite in the presence of solid oxidants, under comparatively mild conditions without using aggressive concentrated acids.

Improved dispersant-free liquid exfoliation down to the graphene-like state of solvent-free mechanochemically delaminated bulk MoS2

Molybdenum disulfide (MoS2) was recently found to exhibit an indirect-to-direct gap transition when its thickness is reduced to a single S–Mo–S trilayer sheet, which opens up opportunities for a range of novel optoelectronic applications. Here we first report the possibility of dispersant-free efficient liquid exfoliation down to the graphene-like state of solvent-free mechanochemically delaminated bulk MoS2. The graphene-like, single-sheet structure of MoS2 nanoparticles in the dispersions is confirmed by mutually complementary experimental methods. The proposed approach essentially improves the known liquid exfoliation method based on the ultrasound disintegration of bulk MoS2, because the proposed mechanochemical treatment of the initial bulk MoS2 could provide 100% yield of the single-sheet nanoparticles without the use of dispersants.

Effect of solvent nature on liquid-phase self-assembly of MEH-PPV/MCM-41 guest–host composites

Guest–host MEH-PPV/MCM-41 composites were prepared by liquid-phase self-assembly via insertion of poly[2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) macromolecules inside mesoporous silica. The effect of the solvent nature on the polymer loading and luminescence properties of the composites was explained by retained memory of the chain conformation in the parent solution. The intensity of photoluminescence of the obtained composites was found to be two orders of magnitude greater than that of the neat polymer.

Ultrasound-free preparation of graphene oxide from mechanochemically oxidized graphite

We propose an ultrasound-free preparation of graphene oxide using spontaneous exfoliation of specifically synthesized graphite oxide in water for the first time. Graphite was mechanochemically oxidized by KMnO4 in the presence of a stoichiometric amount of sulfuric acid. The shear stresses generated during the oxidation lead to primary delamination of the graphite oxide particles and in combination with the presence of the surface oxygen-containing functional groups facilitate their further exfoliation in water without the use of ultrasound disintegration. The synthesized graphene oxide luminesces in the blue region of the spectrum.

Nanosized effects in composites based on polyaniline and vanadium or iron oxides

It has been established by means of elemental analysis, X-ray diffraction, IR and optical spectroscopies, cyclic voltammetry and EPR that, due to the nanostructure, the composites based on polyaniline (PAn) and on vanadium or iron oxides display consistent specific spectral, electrochemical, magnetic properties which are associated with intermolecular interaction with charge transfer between conducting polymer and inorganic component of the composites and with formation of the united electronic system. The nanosized effects in both composites explored possess similarity as well as distinctions. While in the PAn–V2O5 nanocomposite direct interaction of the polyaniline macromolecules, intercalated in the V2O5 galleries, with V5+ ions takes place, resulting in charge transfer, the charge transfer between polyaniline and Fe3O4 particles of the PAn–Fe3O4 nanocomposite is motivated by the fact that during the synthesis of the composite the Fe3O4 particles in the starting sol and in the reaction medium carry a certain surface charge which they retain in the composite, thus acting as peculiar extra dopants for macromolecules of the conducting polymer.

Effect of monomer/oxidant mole ratio on polymerization mechanism, conductivity and spectral characteristics of mechanochemically prepared polypyrrole

The effect of the composition of the initial reaction mixture – pyrrole/oxidant mole ratio – on the mechanism of mechanochemical polymerization of pyrrole was studied. Experimental evidence in favor of the chain mechanism for mechanochemical formation of the highly conducting PPy at high monomer/oxidant mole ratio was first obtained. Interrelation between polymerization mechanism and structure, conductivity and spectral characteristics of the prepared polypyrrole samples was considered.

Efficient dispersant-free liquid exfoliation down to the graphene-like state of solvent-free mechanochemically delaminated bulk hexagonal boron nitride

It is shown that during mechanochemical treatment of the bulk hexagonal boron nitride (hBN) in the presence of an inert delamination agent the nanostructuring of hBN occurs: its partial delamination, shift of the layers relative to one another, reduction of the particle size. It is established that the reactive paramagnetic defects are formed in the structure of the nanostructured hBN, and their number is significantly reduced under the effect of water. The formation of oxygen-containing functional groups at the outer edge of the nanoparticles, and ability of such nanoparticles to effectively exfoliate in various organic solvents and in water under the effect of ultrasound are shown. The data of electron diffraction, XPS and UV-vis indicated the preservation of the hBN structure in the plane of the nanoparticles. The predominately monolayer morphology of the particles in the dispersions is confirmed by AFM microscopy and Raman spectroscopy.

Advanced electrochemical performance of hybrid nanocomposites based on LiFePO4 and lithium salt doped polyaniline

LiFePO4 (LFP) is one of the commercially usable cathode materials for lithium batteries. To overcome its main drawback—low conductivity—LFP particles are usually covered by carbon shell. But this approach lowers the capacity of the whole cathode due to electrochemical inactivity of the carbon shell at the required potentials. In the present work, we propose a novel approach which is based on mechanochemical insertion of LFP particles inside polyaniline doped with lithium salt. It is established that during charge–discharge of these nanocomposites, both LFP and polyaniline are redox active. It is shown that the prepared nanocomposites exhibit improved electrochemical performance as a cathode in lithium batteries compared with the individual LFP. It is shown that the presence of the polyaniline in the nanocomposite could facilitate the transport of lithium ions inside (outside) the inorganic component during discharge (charge).

Enhanced and tunable photoluminescence of polyphenylenevinylenes confined in nanocomposite films

Conformation of macromolecules and interchain interactions determine spectral properties of conjugated polymers (CP). An achievement of spatial confinement of isolated chains is one of the routes to use this feature of CP for their purposeful usage. In the present work, CP/O300 nanocomposites based on CP - poly(p-phenylenevinylene) and poly(2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene) - and silica nanoparticles (O300) are prepared. In comparison with many previously known hybrid nanomaterials synthesized with the similar purpose, CP/O300 nanocomposites are characterized by the essentially enhanced and tunable photoluminescence. The greatest change of color coordinates is observed for poly(p-phenylenevinylene)-based nanocomposites due to specific preparation method and interaction with the inorganic component. The main emission from CP in the CP/O300 nanocomposites is owing to 0–0 transitions, while 0–1 transitions, associated with aggregate states of the CP chains, are suppressed.