National Institute Of Materials Physics - Romania

Publications

5088 articles found

31. Mesoporous TiO2 from Metal-Organic Frameworks for Photoluminescence-Based Optical Sensing of Oxygen

Authors: Alfe, M; Gargiulo, V; Amati, M; Maraloiu, VA; Maddalena, P; Lettieri, S

Published: JUL 2021, CATALYSTS, 11, 795, DOI: 10.3390/catal11070795

32. The Physico-Chemical Properties and Exploratory Real-Time Cell Analysis of Hydroxyapatite Nanopowders Substituted with Ce, Mg, Sr, and Zn (0.5-5 at.%)

Authors: Chirica, IM; Enciu, AM; Tite, T; Dudau, M; Albulescu, L; Iconaru, SL; Predoi, D; Pasuk, I; Enculescu, M; Radu, C; Mihalcea, CG; Popa, AC; Rusu, N; Nita, S; Tanase, C; Stan, GE

Published: JUL 2021, MATERIALS, 14, 3808, DOI: 10.3390/ma14143808

33. Bandgap atomistic calculations on hydrogen-passivated GeSi nanocrystals

Authors: Cojocaru, O; Lepadatu, AM; Nemnes, GA; Stoica, T; Ciurea, ML

Published: JUN 30 2021, SCIENTIFIC REPORTS, 11, 13582, DOI: 10.1038/s41598-021-92936-z

34. Cyclophane with eclipsed pyrene units enables construction of spin interfaces with chemical accuracy

Authors: Metzelaars, M; Schleicher, S; Hattori, T; Borca, B; Matthes, F; Sanz, S; Burgler, DE; Rawson, J; Schneider, CM; Kogerler, P

Published: JUN 28 2021, CHEMICAL SCIENCE, 12, DOI: 10.1039/d1sc01036k

Advanced functionality in molecular electronics and spintronics is orchestrated by exact molecular arrangements at metal surfaces, but the strategies for constructing such arrangements remain limited. Here, we report the synthesis and surface hybridization of a cyclophane that comprises two pyrene groups fastened together by two ferrocene pillars. Crystallographic structure analysis revealed pyrene planes separated by similar to 352 pm and stacked in an eclipsed geometry that approximates the rare configuration of AA-stacked bilayer graphene. We deposited this cyclophane onto surfaces of Cu(111) and Co(111) at submonolayer coverage and studied the resulting hybrid entities with scanning tunnelling microscopy (STM). We found distinct characteristics of this cyclophane on each metal surface: on non-magnetic Cu(111), physisorption occurred and the two pyrene groups remained electronically coupled to each other; on ferromagnetic Co(111) nanoislands, chemisorption occurred and the two pyrene groups became electronically decoupled. Spin-polarized STM measurements revealed that the ferrocene groups had spin polarization opposite to that of the surrounding Co metal, while the pyrene stack had no spin polarization. Comparisons to the non-stacked analogue comprising only one pyrene group bolster our interpretation of the cyclophane's STM features. The design strategy presented herein can be extended to realize versatile, three-dimensional platforms in single-molecule electronics and spintronics.

35. Engineering hydrogenation active sites on graphene oxide and N-doped graphene by plasma treatment

Authors: Magureanu, M; Mandache, NB; Rizescu, C; Bucur, C; Cojocaru, B; Man, IC; Primo, A; Parvulescu, VI; Garcia, H

Published: JUN 15 2021, APPLIED CATALYSIS B-ENVIRONMENTAL, 287, 119962, DOI: 10.1016/j.apcatb.2021.119962

Graphene oxide (GO) and N-doped graphene [(N)G] graphenes were submitted to H-2 glow discharge under different discharge regimes, in both the negative glow and positive column plasma regions. The resulted catalysts were fully characterized using several techniques such as Raman, DRIFT and XPS spectroscopy, powder X-ray diffraction, H-2 pulse chemisorption and H-2-, CO2- and NH3-TPD experiments. Density functional theory calculations were performed taking a slab model of graphene sheet with an optimized C-C bond length (1.426 angstrom) and a 16 angstrom vacuum layer between sheets. An overview of these characterizations showed that the O/C atomic ratio of GO is influenced by the plasma regime, indicating the occurrence of O removal, as also predicted by DFT calculations. In the case of (N)G, the plasma treatment also removes pyridinic N with an increase of the C/N ratio. The efficiency of the plasma modification has been checked through catalytic tests in hydroisomerization of 1-octene and hydrogenation of alpha-methyl-styrene. Contrarily to classical thermal activation requiring high temperatures, the generation of the defects by treating with plasma occurs at voltages in the range of 2 5 kV. In consequence, the hydrogenation and isomerization of alkenes resulted with high yields and good selectivities. Graphene prepared from sodium alginate from brown algae was considered as reference in these investigations.

36. Electronic and transport properties of the dual-emitter organometallic compound IrQ(ppy)(2)

Authors: Polosan, S

Published: JUN 14 2021, JOURNAL OF ORGANOMETALLIC CHEMISTRY, 942, 121814, DOI: 10.1016/j.jorganchem.2021.121814

The structure of the IrQ(ppy)(2) organometallic dual phosphorescent compound was experimentally and theoretically investigated. The Metal-to-Ligand Charge Transfer toward the phenylpiridine and quinoline ligands explains its dual phosphorescence property. The IrQ(ppy)(2) organometallic's electronic properties extend the absorption spectra toward the lower energies than Ir(ppy)(3) due to the bandgap reduction induced by the quinoline ligand. The magneto-optical measurements reveal A-terms, which are produced by splitting the triplet states and B-terms, which arise when the electronic levels are mixed in the magnetic field. The IrQ(ppy)(2) molecule's transport properties confirm an ambipolar character, consisting of a higher hole transport character induced by the phenyilpiridine ligands and a lower electron transport character induced by the quinoline ligand. (C) 2021 Elsevier B.V. All rights reserved.

37. One-pot strategy for obtaining magnetic PMMA particles through ATRP using Fe(CO)(5) as co-initiator

Authors: Diacon, A; Rusen, E; Rizea, F; Ghebaur, A; Berger, D; Somoghi, R; Matei, A; Palade, P; Tutunaru, O

Published: JUN 5 2021, EUROPEAN POLYMER JOURNAL, 152, 110446, DOI: 10.1016/j.eurpolymj.2021.110446

The first aim of this study was to develop an ATRP process for methyl methacrylate (MMA) polymerization using Fe(CO)(5) as co-initiator. The kinetics analysis of the reaction in solution confirmed the controlled characteristic of the polymerization process. The process displays a slow initiation step and presents bimolecular termination reactions at higher molecular weights, confirmed by NMR analysis. Also, these observations are sustained by GPC, FT-IR, and XPS analyses, explaining the rather unusual dispersity values (1.4) for an ATRP reaction. The use of formic acid, which shifts the equilibrium towards Fe2+ species affording a quasi-controlled controlled polymerization process, is a key element in achieving control over the reaction. The Fe2+/Fe3+ ratio at the end of the reaction, determined by XPS analysis, suggests the possibility to generate magnetic iron oxide particles. Therefore, the synthesis strategy was adapted for use in the suspension polymerization process of MMA which permitted the production of magnetic PMMA particles through a facile one-pot approach, using only an ammonia treatment stage. The obtained PMMA particles, characterized by SEM, XPS, TEM, TGA, and XRD analyses, have porous characteristics and magnetic properties which makes them good candidates as catalyst supports, separation processes, or biomedical applications.

38. Influence of Ce addition and Pt loading upon the catalytic properties of modified mesoporous PtTi-SBA-15 in total oxidation reactions

Authors: Ciobanu, M; Petcu, G; Anghel, EM; Papa, F; Apostol, NG; Culita, DC; Atkinson, I; Todorova, S; Shopska, M; Naydenov, A; Velinova, R; Parvulescu, V

Published: JUN 5 2021, APPLIED CATALYSIS A-GENERAL, 619, 118123, DOI: 10.1016/j.apcata.2021.118123

A series of PtCeTi-SBA-15 catalysts, with different concentrations of Pt (0.25 %, 0.5 %, 1.0 %), were synthesized. New Ti-SBA-15 material was obtained by direct synthesis and used as support in successive immobilization of Pt and Ce precursors, changing their order of addition. The characterization of the catalysts has been achieved taking an ensemble of techniques which showed preservation of the support porous structure, high dispersion of the amorphous metal oxides and Pt?, the formation of metal crystals for samples with 1wt% Pt and variation of Pt? content on surface in condition of ceria addition. The best conversion (100 %) was obtained in oxidation of hydrocarbons (CH4, C3H8 and C6H14) for the samples with 1% Pt and a significant diminish of activity was obtained for catalyst in which Ce was added on PtTi-SBA-15 sample. Differently of these, CO oxidation was totally irrespective of the catalyst composition.

39. Structural and optical properties of amorphous Si-Ge-Te thin films prepared by combinatorial sputtering

Authors: Mihai, C; Sava, F; Simandan, ID; Galca, AC; Burducea, I; Becherescu, N; Velea, A

Published: JUN 3 2021, SCIENTIFIC REPORTS, 11, 11755, DOI: 10.1038/s41598-021-91138-x

40. Antioxidant activity of thirty-six peppers varieties and vasorelaxant of selected varieties

Authors: Machado, FB; de Mace, IYL; Campos, HM; Moreno, EKG; Silva, MFB; de Oliveira, JR; Ramalho, RRF; Nascimento, AD; Vaz, BG; da Cunha, LC; Ghedini, PC; Diculescu, VC; Gil, ED

Published: JUN 2021, FOOD BIOSCIENCE, 41, 100989, DOI: 10.1016/j.fbio.2021.100989

Peppers are consumed all over the world, have several benefits to human health, such as antioxidant properties that can prevent diseases related to free radicals such as cardiovascular, inflammatory diseases, cancer, among others. This work aimed to evaluate the antioxidant capacity (AOC) of 36 varieties of peppers through ABTS and DPPH radical scavenging, electroanalytical assays, and to verify the vasorelaxant properties of selected samples. The greater the amount of capsaicin found in the extracts, the higher the AOC the greater the vasorelaxation. Naga had the highest scoring for antioxidant capacity, pout showed the lowest antioxidant capacity, vase pyramid intermediate level, whereas the capsaicin content followed the same trend. Extracts from all pepper varieties studied presented vasorelaxant properties in independent and dependent endothelial pathways.