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Modification of TiO2 electronic properties by means of chemical treatment (doping)
Zukalová, Markéta ; Lásková, Barbora ; Procházka, Jan ; Bastl, Zdeněk ; Havlíček, D. ; Kavan, Ladislav
The product of the reaction of nanofibrous anatase with ammonia in gas phase is nanofibrous cubic titanium oxynitride, c-TiO2N3. In contrary to the preparation of cubic titaniurn oxynitride from microcrystalline TiO2, requiring temperatures above 800°C, the conversion of nanofibrous TiO2 to TiO2N3 is completed at about 500°C due to its enhanced chemical reactivity. This conversion is fully reversible; the product of the back reaction is again nanofibrous Ti02. By the thermal treatment of nanofibrous anatase in H2 flow at 800°C for 2 hours the mixture of black disordered anatase, rutile and titanium suboxides was prepared. Evidently, particular phases can be synthesized simply by tuning the temperature of the treatment, which is a subject of the further research.
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GRAPHENE UNDER UNIAXIAL DEFORMATION: A RAMAN STUDY
Frank, Otakar ; Tsoukleri, G. ; Parthenios, J. ; Papagelis, K. ; Riaz, I. ; Jalil, R. ; Novoselov, K. S. ; Kalbáč, Martin ; Kavan, Ladislav ; Galiotis, C.
The presented work summarizes various aspects of uniaxial deformation in monolayer graphene studied by means of Raman spectroscopy. Graphene flakes were subjected to tension - compression uniaxial loading using the cantilever beam technique. The evolution of the Raman single-resonance (G) and double-resonance (2D) bands was monitored at strain levels < 1%. The position of all peaks redshifts under tension and blueshifts under compression. The G peak splitting into two sub-bands (G(-) and G(+)) which is caused by symmetry lowering, is observed in both strain directions. The sub-bands' intensities are used to calculate the crystal lattice orientation of the measured graphene flakes with respect to the strain axis. The nature and splitting of the 2D band even in the unstrained flakes, when excited by the 785 nm (1.58 eV) laser line, is interpreted as the interplay between two distinct double resonance scattering processes.
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16th International Symposium on Intercalation Compound - ISIC16. Abstracts Book
Zima, Vítězslav ; Kavan, Ladislav ; Čejka, Jiří ; Lang, Kamil ; Vlček, Milan ; Beneš, L. ; Svoboda, Jan ; Melánová, Klára ; Frumarová, Božena ; Knotek, P. ; Jůza, Josef ; Látalová, Petra
The topic of the papers published in this proceedings is chemistry, properties and applications of intercalation compounds and related materials.
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Catalytic and photocatalytic processes on 18O-labeled TiO2
Kavan, Ladislav ; Zukalová, Markéta ; Ferus, Martin ; Kürti, J. ; Koltai, J. ; Civiš, Svatopluk
18O-isotope labelled titania (anatase, rutile) was synthesized. The products were characterized by Raman spectra together with their quantum chemical modelling. The interaction with carbon dioxide was investigated using high-resolution FTIR spectroscopy, in dark and upon UV-excitation. The oxygen isotope exchange at the Ti18O2/C16O2 interface was elucidated. The C18O2 was formed as the dominating final product with a minor content of C16O18O. The rate of oxygen-isotope exchange is highly sensitive to the conditions of the titania pretreatment. The vacuum-annealed Ti18O2 at 450 C exhibited a very high spontaneous oxygen exchange activity with gaseous C16O2. A mechanism for the 18O/16O exchange process is discussed at the molecular level. The photocatalytic formation of methane, acetylene and C16O released from the Ti18O2 surface was triggered by an XeCl excimer laser irradiation.
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Fullerene C60 in Aqueous Medium
Kocábová, Jana ; Gál, Miroslav ; Hromadová, Magdaléna ; Kavan, Ladislav ; Pospíšil, Lubomír ; Sokolová, Romana
The aqueous solution of C60 was investigated by electrochemical and spectroscopis methods such as UV-Vis, Raman, FTIR and AFM techniques. The association constants of fullerene-gamma-cyclodextrin complex and ,ethanofullerene conjugates with beta-cyclodextrins in aqueous solution were evaluated from the shifts of the formal redox potential of complexed and uncomplexed fullerene. The most suitable techniques for electrochemical characterization of fullerene derivatives proved to be the low-frequency phase-sensitive AC polarography and the steady-state voltammetry.
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Fotokatalytické technologie a nové nanopovrchové materiály v roce 2005
Peterka, F. ; Jirkovský, Jaromír ; Šubrt, Jan ; Špatenka, P. ; Krýsa, J. ; Lukeš, Petr ; Kavan, Ladislav ; Štengl, Václav ; Kolouch, A. ; Klusoň, P.
Práce předkládá souhrnnou informaci o současném stavu výzkumu a vývoje fotokatalytických TiO2 nanomateriálů a jejich praktickém využití v průmyslu a ve společnosti. Dále jsou prezentovány hlavní cíle nového evropského projektu COST „PHONASUM“ (COST 540) a Výzkumného centra pro nanopovrchové inženýrství „NANOPIN“ založeného v roce 2005 v rámci Programu výzkumu a vývoje MŠMT ČR.
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Fotokatalytické technologie a nové nanomateriály 2005
Peterka, F. ; Jirkovský, J. ; Šubrt, Jan ; Špatenka, P. ; Krýsa, J. ; Lukeš, P. ; Kavan, L. ; Štengl, Václav ; Kolouch, A. ; Klusoň, P.
Vývoj nanokrystalických fotokatalytických materiálů je rychle se rozvíjející obor vědy a technologie.
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