National Institute Of Materials Physics - Romania

Publications

163 articles found

101. Heterogeneous Gold Catalyst: Synthesis, Characterization, and Application in 1,4-Addition of Boronic Acids to Enones

Authors: Moragues, A; Neatu, F; Parvulescu, VI; Marcos, MD; Amoros, P; Michelet, V

Published: SEP 2015, ACS CATALYSIS, 5, 5067, DOI: 10.1021/acscatal.5b01207

The new 1 wt % Au/TiO2-UVM-7 catalyst was prepared and fully characterized. This heterogeneous catalyst proved to be active, selective and recyclable for the unprecedented gold-catalyzed 1,4-addition of various functionalized arylboronic acids to 2-cyclohexen-1-one and other selected enones using toluene as a solvent. The gold-based catalyst was recycled two times and played an active role in this reaction, and the nature of the solvent determined a remarkable change in the products' selectivities.

102. Toward a Unified Description of Luminescence-Local Structure Correlation in Ln Doped CeO2 Nanoparticles: Roles of Ln Ionic Radius, Ln Concentration, and Oxygen Vacancies

Authors: Avram, D; Sanchez-Dominguez, M; Cojocaru, B; Florea, M; Parvulescu, V; Tiseanu, C

Published: JUL 16 2015, , DOI: 10.1021/acs.jpcc.5b02240

103. Arylation of alkynes over hydrotalcite docked Rh-m-TPPTC complex

Authors: Neatu, F; Ciobanu, M; Stoflea, LE; Frunza, L; Parvulescu, VI; Michelet, V

Published: JUN 1 2015, CATALYSIS TODAY, 247, 162, DOI: 10.1016/j.cattod.2014.07.004

Rh-m-TPPTC complex was successful immobilized onto a hydrotalcite Zn-Al to convert selectively in aqueous media both the symmetric and nonsymmetric alkynes into functionalized alkenes, with boronic acids. The complex preserved its activity after the ionic exchange, leading to excellent results (similar to 87%) for the symmetric alkynes and also for the non-symmetrical alkynes (up to 99%). (C) 2014 Elsevier B.V. All rights reserved.

104. NIR to Vis - NIR up - conversion and X-ray excited emission of Er doped high Z BiOCl

Authors: Avram, D; Cojocaru, B; Florea, M; Teodorescu, V; Tiseanu, I; Tiseanu, C

Published: MAY 1 2015, OPTICAL MATERIALS EXPRESS, 5, 962, DOI: 10.1364/OME.5.000951

Herein, we investigate the emission properties of Er - BiOCl in the range of similar to 500 to 1700 nm under down - (488 and 973 nm) and NIR (telecom - wavelength at similar to 1500 nm) up - conversion excitation as well high energy X-ray excitation. The dependencies of red (similar to 670 nm) and NIR (similar to 800 nm) to green emission (similar to 543 nm) ratio with Er concentration, excitation mode and delay after laser pulse as well as the up - conversion excitation spectra and decays are analyzed in terms of competitive ground state absorption/excited state absorption and energy transfer up - conversion mechanisms. The CIE chromaticity diagram show single excitation (similar to 1500 nm), delay induced emission color change from yellowish green (delay of 0.001 ms) to reddish orange (delay of 1 ms). The X-ray induced emission of Er - BiOCl presents an atypical red to green emission ratio that exceeds that measured under optical down - conversion excitation by a factor of 13. The potential of Er - BiOCl for optical/X-ray imaging applications is discussed. (C)2015 Optical Society of America

105. Dry reforming of methane on ceria prepared by modified precipitation route

Authors: Rotaru, CG; Postole, G; Florea, M; Matei-Rutkovska, F; Parvulescu, VI; Gelin, P

Published: MAR 25 2015, , DOI: 10.1016/j.apcata.2015.01.024

106. Dielectric Properties of LDH-Type Layered Materials Containing Zn or Mg Ions : On the Non Monotonous Temperature Dependence of Relaxation Times

Authors: Frunza, L; Frunza, S; Ganea, CP; Zgura, I; Neatu, F; Parvulescu, VI

Published: 2015, ROMANIAN JOURNAL OF INFORMATION SCIENCE AND TECHNOLOGY, 18, 328, DOI:

The electrical behavior of layered double hydroxides containing Al or Ga as the trivalent ions and Mg or Zn as bivalent ions was evaluated using broadband dielectric spectroscopy in a wide temperature range. Besides conduction effects a relaxation peak is observable at high frequencies which is assigned to the reorientational fluctuations of water molecules adsorbed on the oxide surface or in the interlayer voids. The Maxwell-Wagner-Sillars peak, superimposed to the conductivity phenomenon is observable at low frequencies. A non-monotonous temperature dependence of the relaxation rates of the relaxation process has been found. A quantitative description of this dependence was possible based on a model assuming two competing processes: rotational fluctuation of water molecules and formation of additional defects. Reasonable values for the characteristic parameters were obtained. Thus the water behavior in the studied layered oxides is similar to that observed for water in other porous materials. However, the activation energy of the rotational fluctuation, the pre exponential factor and the number of defects are higher whereas the value of the energy of defect formation is lower in the layered oxide materials than for water confined to nanoporous molecular sieves, porous glasses or in bulk ice.

107. Layered materials of LDH-type containing Zn ions: dielectric measurements show rotational fluctuations of water molecules

Authors: Frunza, L; Ganea, P; Zgura, I; Frunza, S; Neatu, F; Parvulescu, VI

Published: 2015, 2015 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS), 70, DOI:

Layered double hydroxide (LDH) materials containing Zn ions were studied by broadband dielectric spectroscopy to follow up rotational molecular dynamics of confined water. One main relaxation process was observed in the experimental window; it was assigned to fluctuations of water molecules forming a strongly adsorbed thin layer upon the oxide surface. The temperature dependence of the relaxation rates has an unusual shape characterized by the presence of a maximum. Despite the characteristic parameters, this non-monotonous dependence is shown to be a rather general feature for water confined to LDHs.

108. Pure and almost pure NIR emission of Tm and Tm,Yb-CeO2 under UV, X-ray and NIR up-conversion excitation: key roles of level selective antenna sensitization and charge-compensation

Authors: Avram, D; Cojocaru, B; Urda, A; Tiseanu, I; Florea, M; Tiseanu, C

Published: 2015, , DOI: 10.1039/c5cp03458b

109. Lanthanide-lanthanide and lanthanide-defect interactions in co-doped ceria revealed by luminescence spectroscopy

Authors: Avram, D; Gheorghe, C; Rotaru, C; Cojocaru, B; Florea, M; Parvulescu, V; Tiseanu, C

Published: DEC 15 2014, , DOI: 10.1016/j.jallcom.2014.07.059

110. Graphenes in the absence of metals as carbocatalysts for selective acetylene hydrogenation and alkene hydrogenation

Authors: Primo, A; Neatu, F; Florea, M; Parvulescu, V; Garcia, H

Published: OCT 2014, , DOI: 10.1038/ncomms6291