OOO NanoMedTekh

Kiev, Ukraine

OOO NanoMedTekh

Kiev, Ukraine
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Stroyuk A.L.,Ukrainian Academy of Sciences | Andryushina N.S.,Ukrainian Academy of Sciences | Shcherban' N.D.,Ukrainian Academy of Sciences | Il'in V.G.,Ukrainian Academy of Sciences | And 4 more authors.
Theoretical and Experimental Chemistry | Year: 2012

Stable aqueous colloidal solutions of graphene oxide stabilized with sodium polyphosphate were obtained. During irradiation of the colloids the oxygen-containing groups of the graphene oxide are eliminated, and the aromatic graphite-like regions in its composition are expanded. This is accompanied by decrease in the energy of the electronic transitions E bg in such sp2-hybridized fragments. Photoreduction of the colloidal particles of graphene oxide leads to changes in their hydrodynamic size, resulting from ππ interactions between the aromatic fragments in the particles. It was shown that the E bg value can be varied purposefully in the range of 0.5-1.9 eV by varying the experimental conditions. © 2012 Springer Science+Business Media, Inc.

Andryushina N.S.,Ukrainian Academy of Sciences | Stroyuk A.L.,Ukrainian Academy of Sciences | Kuchmy S.Y.,Ukrainian Academy of Sciences | Lemesh N.V.,Ukrainian Academy of Sciences | And 2 more authors.
Theoretical and Experimental Chemistry | Year: 2014

The effect of the degree of photochemical reduction of colloidal graphene oxide (GO) on its ability to stabilize graphite microparticles and carbon nanotubes in aqueous solutions was determined. If photoreduced GO is used as stabilizer dispersions of graphite particles with an average size of 2-3 μm and nanotubes with lengths of up to 1 μm are formed. The amount of dispersed graphite particles increases many times with increase in the degree of reduction of the GO. The relationship between the amount of dispersed nanotubes and the degree of photoreduction of the GO passes through a minimum as a consequence of photoinduced removal of the functional groups of the GO and of decrease in its ability to interact with the partially hydroxylated surface of the nanotubes. © 2014, Springer Science+Business Media New York.

Yukhymchuk V.O.,Ukrainian Academy of Sciences | Dzhagan V.M.,Ukrainian Academy of Sciences | Dzhagan V.M.,TU Chemnitz | Valakh M.Y.,Ukrainian Academy of Sciences | And 4 more authors.
Materials Research Express | Year: 2015

A cubic-to-hexagonal phase transition in Si nanocrystals (NCs) is observed in situ by recording their Raman and photoluminescence (PL) spectra simultaneously. The formation of the hexagonal structure is concluded from the appearance of characteristic Raman peaks and intense PL with spectral positions reported previously for hexagonal Si. The phase transition occurs due to heating of the NCs by the laser beam, but it is supposed to be a photo-induced effect, as it does not occur as a consequence of solely thermal heating. Both the structural transition and concomitant switching of the bright PL emission are reversible and are supposed to be of interest from the viewpoint of application. © 2014 IOP Publishing Ltd.

Kurmach M.M.,Ukrainian Academy of Sciences | Yaremov P.S.,Ukrainian Academy of Sciences | Skoryk M.O.,OOO NanoMedTekh | Skoryk M.O.,NASU G.V. Kurdyumov Institute For Metal Physics | Shvets O.V.,Ukrainian Academy of Sciences
Theoretical and Experimental Chemistry | Year: 2016

It was established that Ti-, Sn-, and Zr-containing hierarchical zeolites of the BEA and MTW structural types contain two types of Lewis acid centers, the strength of which increases in the order Ti-MTW < Zr-MTW ≤ Sn-MTW, and also weak Brønsted acid centers formed by defect Sn—OH and Zr—OH terminal groups. The introduction of boron or aluminum ions into the structure of Ti-, Sn-, and Zr-silicate BEA and MTW zeolites leads to the appearance of additional Lewis and Brønsted acid centers. © 2016, Springer Science+Business Media New York.

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