Bortel, Gábor

Durkó, Gábor

Jakab, Emma

Jalsovszky, István

Kováts, Éva

Pekker, Sándor

Repository of the Academy's Library

P - 0 7 7 3ROTOR-STATOR COCRYSTALS OF FULLERENESWITH CUBIC AND OCTAHEDRAL MOLECULESS. PEKKER 1, E. KOVATS 1, G. BORTEL 1, E. JAKAB 2,G. DURKO 3, I. JALSOVSZKY 31 Wigner Research Centre for Physics, Institute for Solid StatePhysics and Optics, Budapest, Hungary2 Research Centre for Natural Sciences, Institute of Materialsand Environmental Chemistry, Budapest, Hungary3 Eötvös Loránd University, Institute of Chemistry, Budapest,HungaryFullerenes form cocrystals with a great variety of organicmolecules. The majority of these materials belongs to varioushost-guest systems, depending on the shape and size of the countermolecules. Fullerene-cubane cocrystals represent a special family:none of the components form a host framework, they rather formseparated sublattices[1]. The major stabilizing factor of suchstructures is the almost perfect mach of the molecular surfaces ofconvex fullerenes and concave cubanes. The expanded fullerenesublattice confines cubanes in static positions. On the other hand,the atomic arrangement of the fullerene surface isincommensurate with that of cubane, therefore, the rotation offullerenes has no influence on the match. Thus, cubanes behaveas a molecular bearing for the freely rotating fullerene, resultingin unusual dynamics. The alternating array of static and rotatingcomponents distincts this family of rotor-stator phases from boththe orientationally ordered and plastic crystals. Rotor-statorproperties slightly depend on the size and symmetry of thefullerenes and the substituents of cubane, but the major propertiesare characteristic of the whole family. We present here a newmember of this family, the rotor-stator cocrystal of the endohedralSc3N@C80 with cubane. In this material the rotor-stator propertiesof the molecules are extended to the rotation of the endohedralSc3N units. Besides the cubic shaped cubane, octahedral and otherhigh-symmetry molecules may form similar cocrystals withfullerenes. In the absence of octahedral molecules of suitable size,we studied the fullerene cocrystals with the distorted octahedralpairs of mesitylene. We compare the influences of the cubic andoctahedral shapes on the structures and properties.References:1. Pekker, S., Kováts, É., Oszlányi, G., Bényei, Gy., Klupp,G., Bortel, G., Jalsovszky, I. Jakab, E., Borondics F.,Kamarás, K., Bokor, M., Kriza, G., Tompa, K., Faigel, G.,Nature Materials, 2005, 4, 764.Keywords: fullerenes; cocrystals; supramolecular chemistry; P - 0 7 7 4INVESTIGATION OF THE SOL-GEL CHEMISTRY FORTHE PREPARATION OF TIO2-ZRO2 AND PURE TIO2NANOSTRUCTURED POWDERSS. PFLEIDERER 1, D. LÜTZENKIRCHEN-HECHT 1,R. FRAHM 11 University of Wuppertal, Fachbereich C-Physik, Wuppertal,GermanyNanostructured titania materials can be used in a wide fieldof applications. The most popular application is maybe the use ofTiO2 nanoparticles as photocatalyst. For this application, it isimportant to have a look on the materials characteristics, whichwere found to influence the catalytic activity in a sensitive way.Desired characteristics for good catalysts are a small particle sizeand a large specific surface area, a high crystallinity and theanatase TiO2 polymorph. To prepare nanostructured materials withtailored characteristics, the sol-gel process is very popular. It hasbeen found by different research groups that the preparation ofTiO2-ZrO2 composite nanopowders is very interesting due to thestabilization of the crystallite size and phase and an enhancedphotocatalytic activity.Different possibilities are known to influence the sol-gelchemistry and by doing so the structure of the reaction products.Nevertheless, there are to our best knowledge no systematicalinvestigations of the influence of sol-gel chemistry on the reactionproducts of TiO2-ZrO2 composite samples, in contrast to the caseof pure TiO2 samples.We studied the influence of the zirconia concentration onthe composite powder structure and conducted furtherexperiments concerning the influence of the chemical reactionpath. The powders were prepared from titanium isopropoxide andzirconium n-propoxide precursors. Powder characterization wasmade with x-ray diffraction to determine the crystallite structureand size and x-ray absorption spectroscopy, which providesinformation about the crystallinity and the atomic environment ofthe absorbing species.We found that the possibility of crystallization of the titaniato anatase particles is only given for small zirconia concentrations.The crystallite size stayed nearly constant in the compositesamples with increasing annealing temperature and phasetransformations can substantially/successfully be suppressed,which could be derived from comparison with pure titaniapowders.Keywords: Sol-gel processes; Nanoparticles; X-ray absorptionspectroscopy; X-ray diffraction; 4th EuCheMS Chemistry CongressChem. Listy 106, s257–s1425 (2012)AUGUST 26–30, 2012, PRAGUE, CZECH REPUBLICs1249Poster Session 2Poster session 2 - Nanochemistry, Nanotechnology

ROTOR-STATOR COCRYSTALS OF FULLERENES WITH CUBIC AND OCTAHEDRAL MOLECULES

Abstract

Similar works

Full text

Available Versions

Repository of the Academy's Library