A. S. Lobach

A comparative study of graphene materials formed by thermal exfoliation of graphite oxide and chlorine trifluoride-intercalated graphite

Graphene 3D materials GM1 and GM2 obtained by explosive exfoliation of graphite oxide and graphite intercalated with chlorine trifluoride, respectively, have been studied by elemental analysis, X-ray photoelectron spectroscopy, mass spectrometry, infrared and Raman spectroscopy, and scanning electron microscopy. The specific surface area, the pore size, and electrical conductivity of the materials have been measured. A comparative study has shown that the gas mixture produced during the preparation of GM1 is less hazardous than that in the case of GM2. However, GM2 exhibits a higher conductivity and a larger size of graphene crystallites. The feasibility of isolation of a suspension of graphene nanosheets from the test 3D materials has been demonstrated. Possible applications of these materials are discussed.

Photoconducive and photodielectric properties of heterostructures composed of poly-N-epoxypropylcarbazole and MEH-PPV films with a zinc octabutylphthalocyanine additive

The subject of investigation is poly-N-epoxypropylcarbazole and poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylene-vinylene] films with zinc 2,3,9,10,16,17,23,24-octabutylphthalocyanine additives. The photoconducive and photodielectric properties of these heterostructures are studied in the absorption range of the metal complex. The photosensitivity of the structures depends on the triplet state of photogenerated electron-hole pairs, their dissociation in an external electric field, and charge carrier trapping. The increased photosensitivity of the heterostructures compared with that of constituent films is explained by a higher efficiency of dissociation of the photogenerated electron-hole pairs and a reduced influence of non-equilibrium carrier traps at the interfaces.

Sensitization of photosensitivity of photothermoplastic holographic recording media by metal (Zinc, Dysprosium) mono-and diphthalocyanines in the presence of praseodymium sesquioxide

Holographic properties, dark conductivity, and photoconductivity of films based on carbazolyl-containing cooligomer doped with zinc 2,3,9,10,16,17,23,24-octabutylphthalocyanine (PcBuZn), double-decker dysprosium phthalocyanine (Dy(Pc)2), and Pr2O3 particles were studied. The films with PcBuZn are characterized by higher photoconductivity, which is due to photogeneration of long-lived triplet charge pairs. The presence of Dy in the sensitizer molecules or Pr2O3 in the films enhances their photoconductivity, a change that is attributed to an increase in the rate of the singlet-triplet intersystem crossing of the charge pairs.

Near-infrared photosensitive composites with electron conductivity

Polymer composite films were prepared on the basis of poly(vinyl ethylal) doped with a low concentration of an anionic polymethine dye that absorbs light in the near IR region and a higher concentration of 2,4,5,7-tetranitro-9-fluorenone or tetrakis(benzylamino)octahydrofullerene organic acceptor. The photoconductivity of the polymer composite films increases on passing to fullerene derivatives. The main reason for this effect is a decrease in the influence of steric factors on intermolecular electronic transitions in the case of the near-spherical structure of acceptor molecules as compared with the planar structure.

Magnesium octa[(4′-benzo-15-crown-5)oxy]phthalocyaninate in water micellar solutions of sodium deoxycholate

Aggregation of magnesium octa-[(4′-benzo-15-crown-5)oxy]phthalocyaninate (Mgcr8Pc) in solutions of biocompatible anionic surfactant, sodium deoxycholate (SDC), was studied. It was shown using the electron absorption spectra that formation of Mgcr8Pc monomers in micellar solutions of SDC is affected by both increased surfactant concentration and by changes in the ionic strength of solution after sodium chloride is added. The effect of the chemical structure of biocompatible anionic surfactant on monomerization of crown-containing phthalocyanines was identified; this fact opens new possibilities for using this family of compounds for fluorescent diagnosis and photodynamic therapy.

Electric and Photoconductivity of Polymer Composites Containing Heteropolynuclear M(II)/Cr(III) Complexes in the Presence of Additives with Different Electron Donor-Acceptor Properties

Electro-and photoconductive properties of polymer composites doped with heteropolynuclear M(II)/Cr(III) (M = Zn, Co, Mn) complexes were studied in the presence of organic additives with different electron donor-acceptor properties: anthracene, fullerene C60, terephthaloyldianthracene, and bis(biphenyl)chromium(I) fulleride (Ph-Ph)2CrC60. Upon excitation of the d-d transition in Cr(III), the magnitude of inner photoelectric effect in composite films examined is the highest for the Zn(II)/Cr(III) complex and increases in the series of additives anthracene, fullerene C60, terephthaloyldianthracene, (Ph-Ph)2CrC60. The use of the dopant (Ph-Ph)2CrC60 increases photocurrent by about two orders of magnitude.

Dehydrogenation of compounds with weakened C-H bonds in the presence of platinum and palladium fullerides

Coordinated fullerene acts as a hydrogen acceptor in reactions with compounds having weakened C-H bonds (1,4-dihydropyridine and 9,10-dihydroanthracene). Metal fullerides are the dehydrogenation catalysts. They activate the C-H bonds of dihydroanthracene and diethyl 2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate in positions 9,10 and 1,4, respectively. No activation of norbornane carbon-hydrogen bonds with metal fullerides was observed under mild conditions.

Monomerization of crown-containing phthalocyanines in microheterogeneous organized systems

Optical spectroscopy in the UV and visible ranges, dynamic light scattering, and 1H NMR spectroscopy are used to study monomerization of magnesium octa[(4′-benzo-15-crown-5)oxy]phthalocyaninate (Mgcr8Pc) in aqueous solutions of anionic surfactants: sodium dodecyl benzenesulfonate, sodium bis-(2-ethylhexyl)sulfosuccinate, and sodium deoxycholate (SDBS, AOT, and SDC, accordingly). Structural differences in surfactant molecules determine organization of Mgcr8Pc molecules in microheterogeneous media. It is found that Mgcr8Pc is in a monomeric form in aqueous SDBS solutions at concentrations in the range of CMC1 to CMC2 (critical micelle concentration) and it is in a dimeric and/or aggregate form at concentrations below CMC1. In AOT/water solutions (direct micelles) or hexane/AOT (0.1 M)/water (inverted micelles), Mgcr8Pc is solubilized forming dimeric and/or aggregate forms. In micellar solutions of SDC, the Mgcr8Pc monomer is predominantly formed in the presence of NaCl. The results obtained using the NMR spectroscopy technique agree with the binding of Mgcr8Pc by SDBS micelles similar to solubilization of phthalocyanine by micellar solutions of sodium dodecyl sulfate.

Investigation of the electrical resistance of single-walled carbon nanotube films in the temperature range 4.2–290 K

Electrical resistance of films made of the source material and purified HiPCO and Arc single-walled carbon nanotubes (SWCNTs) with a thickness of 20−40 μm is 2.4 to 45 Ω (electrical conductivity of 0.42 × 103 to 5.03 × 103 S/m) at room temperature. The films have been formed by vacuum microfiltration of SWCNT suspensions in toluene and characterized by Raman and X-ray photoelectron spectroscopy and scanning electron microscopy. The conductivity of the films at room temperature depends on the type and degree of purity of the material of nanotubes. The resistance of the films decreases with the increasing temperature over the range of 4.2–290 K, and the rate of the step-down decreases with increasing purity of the material of the nanotubes. The conductivity of the films is semiconducting in character, and the electron transport is consistent with three-dimensional hopping conductivity.

Sensitizing the luminescence and photoconductivity of MEH−PPV films with organic dyes

This paper discusses the spectroluminescence, electro-, and photoconductive properties of films of poly [2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene-vinylene] with additives of neutral and intraionic organic dyes, which absorb and reradiate the light in the near-IR region. The sensitization of the inner photoelectric effect is explained by the photogeneration of charge carriers from the dye molecules. Luminescence quenching and an increase of the photoconductivity of the films are detected when fullerene C60 is added to them. The photoconductivity increase is associated with the capture of electrons and their transport over the C60 molecules.