Simultaneous Synthesis and Nitrogen Doping of Free-Standing Graphene Applying Microwave Plasma.

An experimental and theoretical investigation on microwave plasma-based synthesis of free-standing N-graphene, i.e., nitrogen-doped graphene, was further extended using ethanol and nitrogen gas as precursors. The in situ assembly of N-graphene is a single-step method, based on the introduction of N-containing precursor together with carbon precursor in the reactive microwave plasma environment at atmospheric pressure conditions. A previously developed theoretical model was updated to account for the new reactor geometry and the nitrogen precursor employed. The theoretical predictions of the model are in good agreement with all experimental data and assist in deeper understanding of the complicated physical and chemical process in microwave plasma. Optical Emission Spectroscopy was used to detect the emission of plasma-generated ''building units'' and to determine the gas temperature. The outlet gas was analyzed by Fourier-Transform Infrared Spectroscopy to detect the generated gaseous by-products. The synthesized N-graphene was characterized by Scanning Electron Microscopy, Raman, and X-ray photoelectron spectroscopies.

Prospects for microwave plasma synthesized N-graphene in secondary electron emission mitigation applications.

The ability to change the secondary electron emission properties of nitrogen-doped graphene (N-graphene) has been demonstrated. To this end, a novel microwave plasma-enabled scalable route for continuous and controllable fabrication of free-standing N-graphene sheets was developed. High-quality N-graphene with prescribed structural qualities was produced at a rate of 0.5 mg/min by tailoring the high energy density plasma environment. Up to 8% of nitrogen doping levels were achieved while keeping the oxygen content at residual amounts (~ 1%). The synthesis is accomplished via a single step, at atmospheric conditions, using ethanol/methane and ammonia/methylamine as carbon and nitrogen precursors. The type and level of doping is affected by the position where the N-precursor is injected in the plasma environment and by the type of precursors used. Importantly, N atoms incorporated predominantly in pyridinic/pyrrolic functional groups alter the performance of the collective electronic oscillations, i.e. plasmons, of graphene. For the first time it has been demonstrated that the synergistic effect between the electronic structure changes and the reduction of graphene π-plasmons caused by N doping, along with the peculiar "crumpled" morphology, leads to sub-unitary (< 1) secondary electron yields. N-graphene can be considered as a prospective low secondary electron emission and plasmonic material.

Microwave plasma-based direct synthesis of free-standing N-graphene.

Free-standing N-graphene was synthesized using a microwave plasma-based method at atmospheric pressure conditions through a single step and in a controllable manner. Using ethanol and ammonia as precursors, N-graphene with low relative amount of bonded oxygen and low level of saturated sp3 carbon bonds was produced. Adjusting the injection position of the nitrogen precursor in the plasma medium leads to selectivity in terms of doping level, nitrogen configuration and production yield. A previously developed theoretical model, based on plasma thermodynamics and chemical kinetics, was further updated to account for the presence of nitrogen precursor. The important role of HCN attachment to the graphene sheets as the main process of N-graphene formation is elucidated. The model predictions were validated by experimental results. Optical Emission Spectroscopy was used to detect the emission of plasma generated "building units" and to determine the gas temperature. The plasma outlet gas was analyzed by Fourier-Transform Infrared Spectroscopy to detect the generated gaseous by-products. The synthesized N-graphene was characterized by Scanning Electron Microscopy, Raman and X-ray photoelectron spectroscopies.

Microwave plasma enabled synthesis of free standing carbon nanostructures at atmospheric pressure conditions.

An experimental and theoretical study on microwave (2.45 GHz) plasma enabled assembly of carbon nanostructures, such as multilayer graphene sheets and nanoparticles, was performed. The carbon nanostructures were fabricated at different Ar-CH4 gas mixture composition and flows at atmospheric pressure conditions. The synthesis method is based on decomposition of the carbon-containing precursor (CH4) in the "hot" microwave plasma environment into carbon atoms and molecules, which are further converted into solid carbon nuclei in the "colder" plasma zones. By tailoring of the plasma environment, a controlled synthesis of graphene sheets and diamond-like nanoparticles was achieved. Selective synthesis of graphene flakes was achieved at a microwave power of 1 kW, Ar and methane flow rates of 600 sccm and 2 sccm respectively, while the predominant synthesis of diamond-like nanoparticles was obtained at the same power, but with higher flow rates, i.e. 1000 and 7.5 sccm, respectively. Optical emission spectroscopy was applied to detect the plasma emission related to carbon species from the 'hot' plasma zone and to determine the main plasma parameters. Raman spectroscopy and scanning electron microscopy have been applied to characterize the synthesized nanostructures. A previously developed theoretical model was further updated and employed to understand the mechanism of CH4 decomposition and formation of the main building units, i.e. C and C2, of the carbon nanostructures. An insight into the physical chemistry of carbon nanostructure formation in a high energy density microwave plasma environment is presented.

[Phosphogliv: mechanism of therapeutic action and clinical efficacy]. / Fosfogliv: mekhanizm deistviia i éffektivnost' primeneniia v klinike.

The review summarizes the results of long term study (from design to clinical trial) of a new hepatoprotective drug Phosphogliv. Some theoretical ground for its creation has been considered with special emphasis on its ingredient properties: soy bean phosphatidylcholine and glycyrrhizinic acid from licorice roots. Experimental and clinical data concerning polyene phosphatidylcholine repairing action on cell membranes as well as antiviral and immunomodulating effects of glycyrrhizinic acid are presented. Their selected combination in Phosphogliv provided its high efficiency in rat hepatitis models. After standard toxicology tests it was allowed to carry out the clinical trials of this preparation in the treatment of liver diseases patients--mainly with acute and chronic viral hepatitis B, C, A and mixed hepatitis B + C (total 203 patients). The inclusion of Phosphogliv into therapy coarse accelerated disappearance of intoxication symptoms and decrease of serum aminotransferase and other hepatic markers. The effect was more pronounced for intravenous drug form.