Lendulet Porous Nanocomposites Research Group

Szeged, Hungary

Lendulet Porous Nanocomposites Research Group

Szeged, Hungary
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Ronavari A.,University of Szeged | Buchholcz B.,University of Szeged | Kukovecz A.,University of Szeged | Kukovecz A.,Lendulet Porous Nanocomposites Research Group | And 2 more authors.
Journal of Molecular Structure | Year: 2013

90-100 nm long protonated titanate nanotubes were synthesized by hydrothermal method from anatase at 155 °C. The bismuth and antimony affected crystallization of the tubular titanate structures during calcination was studied by transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectroscopy. It was shown that bismuth and antimony have different effects on the transformation; while in the presence of antimony oxide the trititanate-anatase-rutile phase transformation is hindered, the bismuth oxide promotes the crystallization process to rutile. © 2012 Elsevier B.V. All rights reserved.


Gyri Z.,University of Szeged | Havasi V.,University of Szeged | Madarasz D.,University of Szeged | Tatrai D.,University of Szeged | And 6 more authors.
Journal of Molecular Structure | Year: 2013

In this study our aim was partially substituting or replacing Dy 3+ co-dopant ions in SrAl2O4:Eu2+, Dy3+ phosphors with less expensive Ho3+ co-dopant ions in order to open a more economical way towards the industrial scale synthesis of long-persistent strontium-aluminate phosphors while maintaining the good optical properties of Dy3+ co-doped phosphors. This was achieved by finding the optimum ratio between the Dy3+ and Ho3+ co-dopants to get the highest initial intensity and by compensating the fast decay speed caused by Ho3+ co-doping via defect site generation in the host through non-stochiometric Sr/Al ratios. The initial emission intensity was the highest when the co-activator was substituted entirely with Ho3+ ions, and even the phosphors containing mixed co-activators featured higher initial emission intensities than the reference Dy3+ co-doped samples. However, the samples co-activated with Ho3+ or mixed co-activators exhibited faster decay speeds relative to the Dy3+ co-activated samples. This negative effect could be compensated by increasing the relative amount of aluminum in the phosphor. © 2012 Elsevier B.V. All rights reserved.


Sranko D.F.,University of Szeged | Canton S.,Lund University | Enghdahl A.,Lund University | Murath S.,University of Szeged | And 7 more authors.
Journal of Molecular Structure | Year: 2013

Various acrylates [E-phenylpropenoate, E-3(4′-nitrophenyl)propenoate, E-3(2′,5′-difluorphenyl)propenoate, E-3(2′-thienyl) propenoate, E-3(4′-imidazolyl)propenoate or E-2,3-dimethylpropenoate] were successfully intercalated into Ca(II)Fe(III) layered double hydroxide (CaFe-LDH) verified by a range of instrumental methods. The possible arrangements for the organic anions were suggested on the basis of basal spacing data, layer thickness and the dimensions of the quantum chemically optimised structures of the acrylate ions. Using the acrylate-CaFe-LDHs as reactant-filled nanoreactors, photoinitiated topotactic [2 + 2] cyclisation reactions followed by IR spectroscopy could be performed with many representatives [E-phenylpropenoate-, E-3(4′-nitrophenyl)propenoate-, E-3(2′, 5′-difluorphenyl)propenoate- or E-3(2′-thienyl)propenoate-CaFe-LDHs] resulting in cyclobutane derivatives within the layers of the host material indicating that there were domains where the intercalated anions were in close proximity to each other and in proper arrangement for the reaction to occur. © 2012 Elsevier B.V. All rights reserved.


Bugris V.,University of Szeged | Haspel H.,University of Szeged | Kukovecz A.,University of Szeged | Kukovecz A.,Lendulet Porous Nanocomposites Research Group | And 5 more authors.
Journal of Molecular Structure | Year: 2013

In this contribution the rehydration process of a dehydrated CaFe-LDH is described with the combination of thermogravimetric (TG), X-ray diffraction (XRD) and dielectric relaxation spectroscopic (DRS) measurements. Dehydration was followed by TG and the major steps were identified. For studying the rehydration procedure the dehydrated samples were treated in the 6-97% relative humidity range at several preset vapour contents at 298 K. For equilibration 72 h were allowed. Then, the XRD diffractograms and the DRS spectra were registered and the thermal behaviour of the partially rehydrated samples was also studied. From these measurements the various forms of water molecules interacting with the LDH were deduced and their relaxation behaviour in the rehydration procedure is described. © 2012 Elsevier B.V. All rights reserved.


Szabo M.,University of Szeged | Pusztai P.,University of Szeged | Leino A.-R.,University of Oulu | Kordas K.,University of Oulu | And 4 more authors.
Journal of Molecular Structure | Year: 2013

Tungsten-trioxide nanowire bundles were prepared using a simple hydrothermal method. Sodium-tungstate was used as precursor and sodium-sulfate as structure directing agent. All the reflections of the X-ray diffractogram of the synthesized wires belong to the hexagonal phase of the tungsten trioxide. The nanowires were successfully decorated with metal nanoparticles by wet impregnation. The TEM investigation showed that using different metal precursors resulted in different particle sizes and coverage on the surface. © 2012 Elsevier B.V. All rights reserved.


Buchholcz B.,University of Szeged | Haspel H.,University of Szeged | Kukovecz A.,University of Szeged | Kukovecz A.,Lendulet Porous Nanocomposites Research Group | And 2 more authors.
CrystEngComm | Year: 2014

Hydrothermally synthesized protonated titanate nanotubes were doped with nitrogen using ammonia gas as the dopant. Thermal decomposition of urea, which served as the ammonia source, offered a low-temperature synthesis route for obtaining a potential visible-light photocatalyst. Nitrogen doping could be achieved at as low as 200 °C. The doped samples were calcined at different temperatures and changes in the morphology and crystalline phase were studied by transmission and scanning electron microscopy, selected area electron diffraction, energy-dispersive X-ray spectroscopy and X-ray diffraction. The nitrogen content and calcination temperature were found to affect the size and shape of the particles as well as their crystalline phase to a great extent. H-form trititanate was shown to transform into rutile TiO2 through the anatase phase in parallel with the collapse of the nanotube morphology and the production of rod-like nanoparticles first and then finally round nitrogen-doped nanoparticles. A phase map was constructed from the data to facilitate the rational design of N-doped trititanate nanotube-based nanostructures. This journal is © the Partner Organisations 2014.

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