NIMP| Mihaela FLOREA, Author at NIMP

Education

1999–2003: PhD in Chemistry (PhD supervisor: Prof. Paul Grange); Thesis Title: „Relationship between structure and activity of vanadium aluminium oxynitrides in propane ammoxidation”- awarded with “La plus grande distinction”– published results: 9 ISI articles and one European patent

Université Catholique de Louvain (UCL)/Louvain-la-Neuve/Belgium

1997–1999: Master of Science in Catalysis; Thesis Title: „Ru-MCM-41 catalysts for stereocontrolled hydrogenation of prostaglandin intermediates” – published results: 2 ISI articles

Faculty of Chemistry/University of Bucharest (UB)/Romania

2005–2007: Master of Science – Project manager; Academy of the Economics Studies/Bucharest/Romania.

Positions

April 2018 – onwards : Scientific Researcher I degree – National Institute of Material Physics, Magurele, Romania

2007 – onwards : Senior researcher – Catalysis and Catalytic Processes Research Center, Faculty of Chemistry, University of Bucharest, Romania

February 2017 – March 2018 : Senior researcher III degree – National Institute of Material Physics, Magurele, Romania

February 2007 – January 2017: Lecturer – Faculty of Chemistry, University of Bucharest, Romania

February 2004 – January 2007: Assistant Professor – Faculty of Chemistry, University of Bucharest, Romania

Awards

Romanian Academy award "I.G. Murgulescu", 2020

Research interests

Catalytic applications for MAX phase and newly discovered 2D materials- MXene.
Design of materials for energy applications - electrocatalysts for OER, HOR, ORR reactions.
H2 production by water splitting
Synthesis of added values products by catalytic selective oxidation reaction and catalytic chemoselective hydrogenation reaction.
Catalytic selective oxidation of methane.

Expertize

Teaching experience - 12 years in catalysis, catalytic processes, solids surface characterization, analytical chemistry and green chemistry. Since 2004, as Teaching-Researcher at the Faculty of Chemistry, I was in charge of bachelor and master courses being also the promoter of bachelor and master students from our department (2/year). I created an effective learning environment through the use of a variety of instructional methods, I supervised practical courses and I developed educational laboratory experiments.

Practical experience - 18 years in preparation of inorganic nanomaterials; chemical synthesis, work under inert atmosphere; Heterogeneous catalysis; Green energy production; Biomass valorisation; oxidation reactions, isomerization reactions; analytical methods: HPLC, GC, GC-MS, TLC, TAP; Determination of surface and bulk properties: XPS, BET, RAMAN, XRD, FTIR, UV-Vis, SEM, etc.

Books

M. Florea, V.I. Parvulescu, Selective Oxidation of Biomass Constitutive Polymers to Valuable Platform Molecules and Chemicals, in Chemicals and Fuels from Bio-Based Building Blocks, First Edition, F. Cavani, S. Albonetti, F. Basile, A.A. Gandini, Wiley-VCH Verlag GmbH & Co. KGaA., 2016, chapter 15, 379-402; ISBN: 978-3-527-33897-9.

Patents

Ammoxidation of hydrocarbons and hydrogenated metallo oxynitride catalysts therefore, R. Prada Silvy, M. Florea, P. Grange, EP1476420 /2004.
Procedeu de oxidare selectivă a p-cimenului din surse regenerabile în prezență de catalizatori eterogeni oxizi micști pe bază de cobalt, NEATU Florentina; NEATU Stefan; FLOREA Mihaela, RO133419-A0 /28 Jun 2019
Procedeu de reducere fotocatalitica a apei in prezenta de fotocatalizatori eterogeni oxizi micsti de nichel, zinc si titan, Neatu Stefan; Neatu Florentina; Florea Mihaela; Trandafir Mihaela Mirela, A00716/08.11.2019

Projects

1. 2D metallic carbide as active and selective catalysts for direct oxidation of CH4

Project Type: ERC-LIKE, Start Date: 2021-11-01 End Date: 2023-10-31

2. Holistic design of fuel cell electrocatalysts for the least power applications

Project Type: M-ERANET, Start Date: 2019-06-01 End Date: 2022-06-02

3. New approaches for the synthesis of hybrid organic-inorganic perovskit (HOIP)-type materials with possible ferroelectric properties for photovoltaic applications

Project Type: IDEI, Start Date: 2017-07-17 End Date: 2019-12-31

Publications

1. A comparative overview of MXenes and metal oxides as cocatalysts in clean energy production through photocatalysis

Authors: Nair, MM; Iacoban, AC; Neatu, F; Florea, M; Neatu, S

Published: JUN 20 2023, JOURNAL OF MATERIALS CHEMISTRY A, 11, DOI: 10.1039/d2ta08983a

Photocatalytic conversion of H2O, CO2 and N-2 represents one promising approach to harvest and store solar energy, for which efficient visible light responsive semiconductors are inevitable. Often, the presence of a small amount of an additional component called a "cocatalyst", is required to synergistically enhance the performance of the photocatalyst. Tremendous efforts were made in the past to identify inexpensive materials to be used as cocatalysts, for which metal oxides (MOs) are one of the traditional choices. Among alternative categories of materials investigated, the recently discovered MXenes display enormous potential owing to their unique 2D layered structure, tuneable composition, abundant surface functionalities and superior electronic conductivity. Specifically, MOs and MXenes encompass a variety of distinct as well as analogous characteristics that allows them to be tailored to different extents. Unfortunately, a comprehensive overview covering the synthetic, structural and photocatalytic aspects of MOs and MXenes is not available as of now. Herein, we intend to summarize the progress achieved so far in these two families of materials to be used as cocatalysts for the photoconversion of H2O, CO2 and N-2. Followed by a general introduction, we briefly outline the fundamental principles and the role of cocatalysts in photocatalytic reactions. A discussion regarding the use of MOs and MXenes as cocatalysts for the conversion of H2O, CO2 and N-2 is then provided in separate sections. Critical assessment regarding structure and morphology control, surface properties and stability concerns can not only help to recognize the challenges that limit further advancement, but can also highlight the future research directions of these materials for the effective transformation of H2O, CO2 and N-2.

2. Partial replacement of Pb²⁺ in MAPbI_2.6Cl_0.4 perovskite films and their photovoltaic performance

Authors: Derbali, S; Nouneh, K; Leonat, LN; Stancu, V; Tomulescu, AG; Galca, AC; Touhami, ME; Pintilie, I; Florea, M

Published: APR 2023, JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS, 34, 903, DOI: 10.1007/s10854-023-10318-9

Replacing lead atoms in halide perovskite materials is of significant importance for the development of environmentally friendly perovskite solar cells. In this paper, we investigated the effect of doping the MAPbI(2.6)Cl(0.4) hybrid perovskite (MA-methyl ammonium) with non-toxic elements, such as alkaline earth metal ions (Mg2+) and transition metal ions (Zn2+). The structural, morphological, and optical properties of the prepared samples were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and UV-Vis. spectroscopy. Finally, the doped films were used as photoactive layers in solar devices in order to evaluate their photovoltaic performance. Zn proved to be more appropriate to replace partially Pb and films with higher quality were obtained. As a result, the MAPb1(-x)Zn(x)I(2.6)Cl(0.4) based solar cells have demonstrated a slight improvement of the photovoltaic performances, resulting in a uniform and narrower PCEs (power conversion efficiency) range, compared to pristine MAPbI(2.6)Cl(0.4) based devices.

3. Iron-doped Co₃O₄ catalysts prepared by a surfactant-assisted method as effective catalysts for malic acid oxidative decarboxylation

Authors: Mitran, G; Neatu, S; Pavel, OD; Urda, A; Mirea, AG; Florea, M; Neatu, F

Published: JUL 31 2023, CATALYSIS SCIENCE & TECHNOLOGY, 13, DOI: 10.1039/d3cy00121k

Iron-doped Co3O4 oxides prepared by a surfactant-assisted method exhibited good catalytic activity in malic acid conversion, and the oxygen defects associated with the presence of Co2+ played a key role in catalyst activation for pyruvic acid production. The most active catalyst, for which the malic acid conversion was 70% and the pyruvic acid yield was 24%, has an inverse spinel type structure (Fe3+ replaces Co2+ from tetrahedral sites, while Fe2+ replaces Co3+ from octahedral sites) as well as a small energy difference between the highest occupied orbital and the lowest unoccupied orbital (low band-gap, E-g). The catalyst with the highest Co2+ loading showed the highest yield of pyruvic acid.

4. Partial replacement of Pb2+ in MAPbI(2.6)Cl(0.4) perovskite films and their photovoltaic performance

Authors: Derbali, S; Nouneh, K; Leonat, LN; Stancu, V; Tomulescu, AG; Galca, AC; Touhami, ME; Pintilie, I; Florea, M

Published: APR 2023, JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS, 34, 903, DOI: 10.1007/s10854-023-10318-9

5. Photo-stable, 1D-nanofilaments TiO2-based lepidocrocite for photocatalytic hydrogen production in water-methanol mixtures

Authors: Badr, HO; Natu, V; Neatu, S; Neatu, F; Kuncser, A; Rostas, AM; Racey, M; Barsoum, MW; Florea, M

Published: SEP 6 2023, MATTER, 6, DOI: 10.1016/j.matt.2023.05.026

Water and sunlight are the cleanest, most renewable, and abundant resources on Earth. Developing inexpensive, scalable photocatalysts that are highly stable for hydrogen (H-2) production has long been a cherished dream of humanity. Herein, we report on one-dimensional lepidocrocite-based sub-nanofilaments (NFs), approximate to 5 x 7 & Aring;(2) in cross-section, that generate H-2 from 80:20 v/v water/methanol mixtures when illuminated by simulated sunlight. The NFs were stable in the mixtures for times >4,300 h, 300 h of which were under irradiation. Apparent quantum yields as high as 11.7% were obtained. Based on deuterated water results, we conclude that water is the H-2 source. Further, no carbon dioxide (CO2) due to photocatalytic degradation of methanol was detected. Therefore, the NFs have strong green credentials and lucrative economic prospects for large scale up. We expect these NFs will lead to new lines for developing cheap and ultra-stable materials to produce H-2 photochemically for a long time.

6. Mesoporous Composite Bioactive Compound Delivery System for Wound-Healing Processes

Authors: Purcareanu, B; Ene, MD; Morosan, A; Mihaiescu, DE; Florea, MA; Ghica, A; Nita, RA; Drumea, V; Grigoroscuta, MA; Kuncser, A; Badica, P; Olariu, L

Published: SEP 2023, PHARMACEUTICS, 15, 2258, DOI: 10.3390/pharmaceutics15092258

Currently, the treatment of wounds is still a challenge for healthcare professionals due to high complication incidences and social impacts, and the development of biocompatible and efficient medicines remains a goal. In this regard, mesoporous materials loaded with bioactive compounds from natural extracts have a high potential for wound treatment due to their nontoxicity, high loading capacity and slow drug release. MCM-41-type mesoporous material was synthesized by using sodium trisilicate as a silica source at room temperature and normal pressure. The synthesized mesoporous silica was characterized by using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), N2 absorption-desorption (BET), Dynamic Light Scattering (DLS) and Fourier transform infrared spectroscopy (FT-IR), revealing a high surface area (BET, 1244 m2/g); pore diameter of approx. 2 nm; and a homogenous, ordered and hexagonal geometry (TEM images). Qualitative monitoring of the desorption degree of the Salvia officinalis (SO) extract, rich in ursolic acid and oleanolic acid, and Calendula officinalis (CO) extract, rich in polyphenols and flavones, was performed via the continuous recording of the UV-VIS spectra at predetermined intervals. The active ingredients in the new composite MCM-41/sage and marigold (MCM-41/SO & CO) were quantified by using HPLC-DAD and LC-MS-MS techniques. The evaluation of the biological composites' activity on the wound site was performed on two cell lines, HS27 and HaCaT, naturally involved in tissue-regeneration processes. The experimental results revealed the ability to stimulate collagen biosynthesis, the enzymatic activity of the main metalloproteinases (MMP-2 and MMP-9) involved in tissue remodeling processes and the migration rate in the wound site, thus providing insights into the re-epithelializing properties of mesoporous composites.

7. Design of electrocatalysts with reduced Pt content supported on mesoporous NiWO4 and NiWO4-graphene nanoplatelets composite for oxygen reduction and hydrogen oxidation in acidic medium

Authors: Somacescu, S; Osiceanu, P; Moreno, JMC; Culita, DC; Neatu, F; Trandafir, MM; Neatu, S; Kuncser, A; Szijjártó, GP; Tálas, E; Tompos, A; Borbáth, I; Florea, M

Published: FEB 22 2023, INTERNATIONAL JOURNAL OF HYDROGEN ENERGY, 48, DOI: 10.1016/j.ijhydene.2022.04.270

Herein, a new direct synthesis route leading to a mesoporous NiWO4 with crystalline framework and NiWO4 -graphene nanoplatelets (GNP) composite is reported. Ni and W assembled into a mesoporous tungstate type of symmetry by co-precipitation synthesis route and its composite with GNP were used as supports for electrocatalysts, with reduced Pt content (8 wt.%), in oxygen reduction reaction (ORR) and hydrogen oxidation reaction (HOR) in acidic medium. A comprehensive assessment of the modifications related to the crystalline and porous structures, morphological aspects as well as the surface chemistry aiming to explain the electrochemical properties was performed. It was found that the presence of GNP during the synthesis process leads, mainly, to the enhanced growth of NiWO4 nanocrystallites, as well as induces changes in the surface chemistry. The elec-trochemical results show that the introduction of GNPs into the NiWO4 composite support leads to a significant improvement in the activity of the Pt electrocatalyst in ORR and HOR compared to both initial NiWO4 and Pt/NiWO4 samples, as well as mechanical mixtures of these catalysts with carbon. Mass activity for hydrogen oxidation, determined in a mixed kinetic-diffusion controlled region, obtained on the 8 wt.% Pt/NiWO4-GNP catalyst was significantly higher compared to the commercial 20 wt.% Pt/C Quintech catalyst. Our comprehensive structural and surface chemistry assessments indicate this composite material as a viable electrocatalyst for PEMFCs using a broader type of fuels.& COPY; 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

8. Influence of Ferroelectric Filler Size and Clustering on the Electrical Properties of (Ag-BaTiO3)-PVDF Sub-Percolative Hybrid Composites

Authors: Padurariu, L; Horchidan, N; Ciomaga, CE; Curecheriu, LP; Lukacs, VA; Stirbu, RS; Stoian, G; Botea, M; Florea, M; Maraloiu, VA; Pintilie, L; Rotaru, A; Mitoseriu, L

Published: 2023 JAN 18 2023, ACS APPLIED MATERIALS & INTERFACES, DOI: 10.1021/acsami.2c15641

The paper presents a study concerning the role of ferroelectric filler size and clustering in the dielectric properties of 20%BaTiO3-80%PVDF and of 20% (2%Ag-98%BaTiO3)-PVDF hybrid nanocomposites. By finite element calculations, it was shown that using fillers with epsilon > 103 does not provide a permittivity rise in the composites and the effective dielectric constant tends to saturate to specific values determined by the filler size and agglomeration degree. Irrespective of the ferroelectric filler sizes, the addition of metallic ultrafine nanoparticles (Ag) results in permittivity intensification and the effect is even stronger if the metallic nanoparticles are connected to a higher degree with the ferroelectric particles' surfaces. When using coarse ferroelectric fillers, the probability of clustering is higher, thus favoring the permittivity increase by field concentration in small regions close to the interfaces separating dissimilar materials. The modeling results were validated by an experimental dielectric analysis performed in a series of PVDF-based thick films with the same amount of BaTiO3 fillers or with Ag-BaTiO3 hybrid fillers. Similar trends as predicted by simulations were found experimentally but with slightly higher permittivity values which were assigned to the modifications of the polymer phase composition due to the presence of nanofillers and the local sample inhomogeneity (the presence of clustering, in particular for coarse BaTiO3 grains), which create regions with enhanced local fields.

9. Aminocoumarin derivatives grafted on graphene oxide - new antimicrobial agents to combat the resistance of Mycobacterium tuberculosis and ESKAPE pathogens

Authors: Müuk, GR; Popa, M; Chifiriuc, MC; Voicu, SN; Florea, M; Neatu, F; Mihalache, I; Stoian, M; Anghel, EM; Culita, DC; Mitran, RA; Petrescu, S; Tudose, M

Published: DEC 1 2023, APPLIED SURFACE SCIENCE, 639, 158224, DOI: 10.1016/j.apsusc.2023.158224

Two hybrid materials, based on 7-amino-4-(trifluoromethyl)coumarin and 7-amino-4-methyl-coumarin that attach covalently to graphene oxide (GO) have been synthesized in two steps: i) increasing the number of carboxyl groups required for functionalization with aminocoumarin derivatives by derivatization of the hydroxyls groups with chloroacetic acid, transforming GO into GO-COOH material; ii) activation of carboxylic groups using the carbodiimide-promoted reaction. The obtained composites were characterized by numerous methods that highlighted their successful obtaining. The antimicrobial activity was evaluated on resistant Mycobacterium tuberculosis strains, as well as on ESKAPE pathogens ((Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp.) in planktonic and biofilm growth states. The biocompatibility of the materials has been assayed using 3-(4, 5-dimethylthiazol-2-yl)2, 5-diphenyltetrazolium bromide assay as well as by measuring the level of nitric oxide/total reactive oxygen species and superoxide release in treated cells. The results have shown that materials exhibited improved inhibitory activity against resistant M. tuberculosis strains in comparison with GO, but also against planktonic and adherent strains. Also, the tested composites have been proved to be biocompatible on the MRC-5 fibroblast cells, demonstrating their promising potential to develop novel agents effective against multidrug resistant pathogens, including M. tuberculosis, as well as by the activation of a pro-inflammatory and of an oxidative response in the mammalian cells.

10. A comparative overview of MXenes and metal oxides as cocatalysts in clean energy production through photocatalysis

Authors: Nair, MM; Iacoban, AC; Neatu, F; Florea, M; Neatu, S

Published: JAN 2023, JOURNAL OF MATERIALS CHEMISTRY A, DOI: 10.1039/d2ta08983a

11. Influence of Ferroelectric Filler Size and Clustering on the Electrical Properties of (Ag-BaTiO3)-PVDF Sub-Percolative Hybrid Composites

Authors: Padurariu, L; Horchidan, N; Ciomaga, CE; Curecheriu, LP; Lukacs, VA; Stirbu, RS; Stoian, G; Botea, M; Florea, M; Maraloiu, VA; Pintilie, L; Rotaru, A; Mitoseriu, L

Published: JAN 2023, ACS APPLIED MATERIALS & INTERFACES, DOI: 10.1021/acsami.2c15641

12. A comparative overview of MXenes and metal oxides as cocatalysts in clean energy production through photocatalysis

Authors: Nair, MM; Iacoban, AC; Neatu, F; Florea, M; Neatu, S

Published: 2023 JAN 16 2023, JOURNAL OF MATERIALS CHEMISTRY A, DOI: 10.1039/d2ta08983a

13. Structural properties and near-infrared light from Ce3+/Nd3+-co-doped LaPO4 nanophosphors for solar cell applications

Authors: AitMellal, O; Oufni, L; Messous, MY; Tahri, M; Neatu, S; Florea, M; Neatu, F; Secu, M

Published: JAN 2022, JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS, DOI: 10.1007/s10854-021-07615-6

To enhance the spectral response of solar cells, an experimental study on LaPO4:0.01Ce(3+)/xNd(3+) (x = 0, 2, 4 mol%) was carried out, where structural and morphological properties of the prepared samples were well characterized by the means of X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electronic microscope. Additionally, the photoluminescence behavior of phosphors in ultraviolet-visible (UV-VIS) and Near-infrared (NIR) regions were investigated to confirm the energy transfer (ET) from Ce3+ to Nd3+. Moreover, the quantum efficiency of Ce3+/Nd3+-co-doped samples was estimated as high as similar to 172% and the possible ET process was described. Accordingly, the LaPO4:Ce3+/Nd3+ phosphors can convert the UV light (275 nm) into NIR photons (approx. 1059 nm) through the possible two-pathway energy transfer processes from Ce3+ sensitizer ions to Nd3+ activators. Obtained NIR down-conversion emissions are suitable for improving the conversion efficiency of c-Si solar cells.

14. Tuning the acidity by addition of transition metal to Mn modified hollow silica spheres and their catalytic activity in ethanol dehydration to ethylene

Authors: Florea, M; Bocirnea, A; Neatu, S; Kuncser, AM; Trandafir, MM; Neatu, F

Published: SEP 25 2022, APPLIED CATALYSIS A-GENERAL, 646, 118860, DOI: 10.1016/j.apcata.2022.118860

Due to the currently worldwide petrochemical feedstock shortage, the ethylene synthesis from renewable non-oil sources becomes of high interest. The catalysts were prepared in two steps: (i) formation of spheres containing the carbon-coated Mn core by hydrothermal method, (ii) formation of the Si-Zr oxide shell by sol-gel method. The prepared catalysts were characterized by N2 physisorption, SEM-EDX, XRD, XPS, and NH3-TPD. The catalytic results have shown that Fe, Zn or Ni modified Mn core exhibited superior activity compared to the catalysts containing only Mn in the core. With 75% yield and 98% ethanol conversion at 350 degrees C and WHSV of 1.4 h-1, MnNi@SiZr was the best catalyst. These results are due to an increased number of acid sites compared to the other materials and an optimal ratio of weak/medium acid sites. Our findings suggest new lines for developing active and stable catalysts for ethylene synthesis from ethanol.

15. A green way for pyruvic acid synthesis from biomass-derived L-malic acid on tetrahedral versus octahedral cobalt sites/hematite

Authors: Mitran, G; Urda, A; Pavel, OD; Neatu, S; Florea, M; Neatu, F

Published: MAR 2022, BIOMASS CONVERSION AND BIOREFINERY, DOI: 10.1007/s13399-022-02513-1

A series of cobalt-iron mixed oxides, CoxFe3-xO4 (x = 0; 0.05; 0.1; 0.15), were synthesized by coprecipitation and tested for oxidative decarboxylation of malic acid to pyruvic or malonic acid. The characterization of catalysts was performed by different techniques such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFT) and Ultraviolet-visible spectroscopy (UV-Vis). Among studied catalysts, Co0.15Fe2.85O4 sample (denoted Co3Fe) showed the highest malic acid conversion in oxidative decarboxylation reaction as well as the highest pyruvic acid yield. This behavior can be due to the fact that this sample has the highest content of tetrahedral Co2+ that replaces Fe3+ from octahedral position that determine an increased number of defects that play a crucial role for the malic acid conversion.

16. Structural properties and near-infrared light from Ce3+/Nd3+-co-doped LaPO4 nanophosphors for solar cell applications

Authors: AitMellal, O; Oufni, L; Messous, MY; Tahri, M; Neatu, S; Florea, M; Neatu, F; Secu, M

Published: MAR 2022, JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS, 33, DOI: 10.1007/s10854-021-07615-6

17. Green Epoxidation of Olefins with ZnxAl/MgxAl-LDH Compounds: Influence of the Chemical Composition

Authors: Zavoianu, R; Cruceanu, A; Pavel, OD; Bradu, C; Florea, M; Birjega, R

Published: FEB 2022, CATALYSTS, 12, 145, DOI: 10.3390/catal12020145

This contribution concerns the effect of the chemical composition of the brucite-type layer of bi-cationic LDH materials ZnxAl and MgxAl (x = 2-5) and tri-cationic LDH MgyZnzAl (y + z = 4, y = 1, 2, 3) on their catalytic activity for olefin epoxidation with H2O2 in the presence of acetonitrile. LDH materials were prepared by the standard method of co-precipitation at constant pH 10, using an aqueous solution of the corresponding metal nitrates and a basic solution containing NaOH and Na2CO3. The fresh LDHs were calcined to yield the corresponding mixed oxides and then the recovery of the LDH structure by hydration of the mixed oxides was performed. The resulting samples were characterized by AAS, XRD, DRIFT, DR-UV-Vis, BET and determination of basic sites. The results of the catalytic tests for olefin epoxidation were well correlated with the basicity of the samples, which was in turn related to the M2+/Al3+ ratio and the electronegativity of different bivalent metals in the brucite-type layer.

18. Electrocatalytic Properties of Mixed-Oxide-Containing Composite-Supported Platinum for Polymer Electrolyte Membrane (PEM) Fuel Cells

Authors: Ayyubov, I; Talas, E; Salmanzade, K; Kuncser, A; Paszti, Z; Neatu, S; Mirea, AG; Florea, M; Tompos, A; Borbath, I

Published: MAY 2022, MATERIALS, 15, 3671, DOI: 10.3390/ma15103671

TiO2-based mixed oxide-carbon composite supports have been suggested to provide enhanced stability for platinum (Pt) electrocatalysts in polymer electrolyte membrane (PEM) fuel cells. The addition of molybdenum (Mo) to the mixed oxide is known to increase the CO tolerance of the electrocatalyst. In this work Pt catalysts, supported on Ti1-xMoxO2-C composites with a 25/75 oxide/carbon mass ratio and prepared from different carbon materials (C: Vulcan XC-72, unmodified and functionalized Black Pearls 2000), were compared in the hydrogen oxidation reaction (HOR) and in the oxygen reduction reaction (ORR) with a commercial Pt/C reference catalyst in order to assess the influence of the support on the electrocatalytic behavior. Our aim was to perform electrochemical studies in preparation for fuel cell tests. The ORR kinetic parameters from the Koutecky-Levich plot suggested a four-electron transfer per oxygen molecule, resulting in H2O. The similarity between the Tafel slopes suggested the same reaction mechanism for electrocatalysts supported by these composites. The HOR activity of the composite-supported electrocatalysts was independent of the type of carbonaceous material. A noticeable difference in the stability of the catalysts appeared only after 5000 polarization cycles; the Black Pearl-containing sample showed the highest stability.

19. Increasing Permittivity and Mechanical Harvesting Response of PVDF-Based Flexible Composites by Using Ag Nanoparticles onto BaTiO3 Nanofillers

Authors: Horchidan, N; Ciomaga, CE; Curecheriu, LP; Stoian, G; Botea, M; Florea, M; Maraloiu, VA; Pintilie, L; Tufescu, FM; Tiron, V; Rotaru, A; Mitoseriu, L

Published: MAR 2022, NANOMATERIALS, 12, 934, DOI: 10.3390/nano12060934

The role of Ag addition on the structural, dielectric, and mechanical harvesting response of 20%(xAg - (1 - x)BaTiO3) - 80%PVDF (x = 0, 2, 5, 7 and 27 vol.%) flexible composites is investigated. The inorganic fillers were realized by precipitating fine (similar to 3 nm) silver nanoparticles onto BaTiO3 nanoparticles (similar to 60 nm average size). The hybrid admixtures with a total filling factor of 20 vol.% were embedded into the PVDF matrix. The presence of filler enhances the amount of beta-PVDF polar phase and the BaTiO3 filler induces an increase of the permittivity from 11 to 18 (1 kHz) in the flexible composites. The addition of increasing amounts of Ag is further beneficial for permittivity increase; with the maximum amount (x = 27 vol.%), permittivity is three times larger than in pure PVDF (epsilon(r) similar to 33 at 1 kHz) with a similar level of tangent losses. This result is due to the local field enhancement in the regions close to the filler-PVDF interfaces which are additionally intensified by the presence of silver nanoparticles. The metallic addition is also beneficial for the mechanical harvesting ability of such composites: the amplitude of the maximum piezoelectric-triboelectric combined output collected in open circuit conditions increases from 0.2 V/cm(2) (PVDF) to 30 V/cm(2) for x = 27 vol.% Ag in a capacitive configuration. The role of ferroelectric and metallic nanoparticles on the increasing mechanical-electric conversion response is also been explained.

20. Potassium-containing triple-cation mixed-halide perovskite materials: Toward efficient and stable solar cells

Authors: Derbali, S; Nouneh, K; Florea, M; Leonat, LN; Stancu, V; Tomulescu, AG; Galca, AC; Secu, M; Pintilie, L; Touhami, ME

Published: MAR 25 2021, JOURNAL OF ALLOYS AND COMPOUNDS, 858, DOI: 10.1016/j.jallcom.2020.158335

In this paper, potassium based triple cation mixed-halide perovskite films were explored in order to enhance the stability and photovoltaic performance of perovskite based solar cells. It was found that adding potassium (K+) to a double cation mixed halide perovskite (FA(0.80)MA(0.20)PbI(2.8)Cl(0.2)), structural, morphological and optoelectronic properties of perovskites are improved. The perovskite films were prepared by one-step spin coating method with and without K+ and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), UV-Vis spectroscopy, X-ray photoelectron spectroscopy (XPS), and photoluminescence spectroscopy (PL). The results indicate that potassium incorporation reduces significantly the yellow non-perovskite delta-phase formation and improves the perovskite film quality, thus contributing to the reduction of hysteresis, improves the stability and increases the PCE up to 12.51%. Furthermore, the doped devices exhibit reduced hysteresis and provide remarkable shelf stability by retaining more than 70% of the initial efficiency with low humidity over 850 h. (C) 2020 Elsevier B.V. All rights reserved.

21. Investigation of Opto-Electronic Properties and Stability of Mixed-Cation Mixed-Halide Perovskite Materials with Machine-Learning Implementation

Authors: Filipoiu, N; Mitran, TL; Anghel, DV; Florea, M; Pintilie, I; Manolescu, A; Nemnes, GA

Published: SEP 2021, ENERGIES, 14, DOI: 10.3390/en14175431

The feasibility of mixed-cation mixed-halogen perovskites of formula A(x)A'1-xPbXyXz'X3-y-z '' is analyzed from the perspective of structural stability, opto-electronic properties and possible degradation mechanisms. Using density functional theory (DFT) calculations aided by machine-learning (ML) methods, the structurally stable compositions are further evaluated for the highest absorption and optimal stability. Here, the role of the halogen mixtures is demonstrated in tuning the contrasting trends of optical absorption and stability. Similarly, binary organic cation mixtures are found to significantly influence the degradation, while they have a lesser, but still visible effect on the opto-electronic properties. The combined framework of high-throughput calculations and ML techniques such as the linear regression methods, random forests and artificial neural networks offers the necessary grounds for an efficient exploration of multi-dimensional compositional spaces.

22. Enhancing stability of hybrid perovskite solar cells by imidazolium incorporation

Authors: Tomulescu, AG; Leonat, LN; Neatu, F; Stancu, V; Toma, V; Derbali, S; Neatu, S; Rostas, AM; Besleaga, C; Patru, R; Pintilie, I; Florea, M

Published: AUG 1 2021, SOLAR ENERGY MATERIALS AND SOLAR CELLS, 227, DOI: 10.1016/j.solmat.2021.111096

Hybrid perovskites based solar cells have demonstrated high conversion efficiency but poor long-term stability. This study reports on the results obtained after doping the CH3NH3PbI2.6Cl0.4 mixed halide perovskite with imidazolium (C3N2H5+, denoted IM) on the "A site" position of a perovskite, to improve photovoltaic performances and stability of hybrid perovskite solar cells. The perovskite films were investigated exhaustively by different characterization techniques: X-ray diffraction, Atomic Force Microscopy, Scanning Electron Microscopy, UV-Vis, X-ray Photoelectron Electron Paramagnetic Resonance spectroscopies, Impedance Spectroscopy and Incident Photon-to-Electron Conversion Efficiency. The photovoltaic parameters were determined by measuring the IV curves of the corresponding solar cells. The amount of IM inserted in the perovskite play a key role on the film properties. The calculated new tolerance factors according to the "globularity factor" are experimentally proved and thus at doping concentrations greater than 20% for CH3NH3PbI2.6Cl0.4 perovskite the 3D structure is no longer obtained. However, below this value, the IM substituted perovskite film possesses an improved film quality and crystallinity as compared to the pristine film. Substituting MA+ with IM+ provides a favorable way to reduce recombination processes and shows great potential to achieve high stability, and an improved charge generation, resulting in increased PCE values. We find that the optimal percentage of imidazolium incorporation to achieve better stability of solar cells is 6%.

23. NiO/Sr doped Ce(0.85)Pr0.10 Er0.05O(2-delta) mesoarchitectured catalyst for partial oxidation of CH4 and anode fueled by H-2

Authors: Navarrete, L; Florea, M; Osiceanu, P; Calderon-Moreno, JM; Trandafir, MM; Somacescu, S; Serra, JM

Published: AUG 2021, MICROPOROUS AND MESOPOROUS MATERIALS, 323, DOI: 10.1016/j.micromeso.2021.111171

Our study focuses on an advanced exploratory research based on the development of the new IT-SOFCs anode compositions in conjunction with surfactants as template to obtain mesoarchitectured catalysts. We designed NiO/Sr doped Ce0.85Pr0.10 Er0.05O2-o (2.5 and 5 mol.% Sr) mesoarchitectures with robust crystalline framework following a hydrothermal synthesis route. NiO was deposited by wet impregnation and calcined in air at 900.C, in order to assure a good interaction between Ni and mesoporous matrix. The obtained materials exhibit a cubic CeO2 fluorite phase with Pr2O3 and SrCeO3 as secondary phase traces and these were assessed as catalyst for the partial oxidation of CH4 over time and IT-SOFCs anode under reducing atmosphere. The electrochemical behavior as anode fed by wet H2 (2.5% vol. H2O) was investigated in the NiO/CPS/YSZ/GDC/Pt electrochemical cells. The compositional effect on the structural properties, surface chemistry, catalytic and electrochemical performance were highlighted. Sr incorporated in the lattice, proved by X-ray Photoelectron Spectroscopy, guarantees an excellent stability of the catalysts over time for 20h, during partial oxidation of CH4 with high CH4 conversion and CO selectivity (90% in the range 700-800.C) as well as a better performance as IT-SOFCs anode.

24. Comparative investigation of structural, EPR, optical and photoluminescence properties of nanostructured LaPO4:Ce/RE/Me and LaPO4:Yb/Er phosphors prepared by co-precipitation method

Authors: AitMellal, O; Oufni, L; Messous, MY; Trandafir, MM; Chirica, IM; Florea, M; Neatu, S; Rostas, AM; Secu, M; Neatu, F

Published: SEP 2021, JOURNAL OF SOLID STATE CHEMISTRY, 301, DOI: 10.1016/j.jssc.2021.122310

In this work, the structural, thermal, vibrational, morphological, magnetic and optical properties of LaPO4:Ce/RE/Me (RE=Nd3+, Tb3+; Me-Cr3+, Mn2+) and LaPO4:Yb3+/Er3+ phosphors prepared by the co-precipitation method are presented. The obtained materials crystallized in monoclinic structure with the P2(1)/n space group and the particles were of nanorod shape with about 200 nm in length and the diameter approximately 19 nm. The presence of dopant ions was confirmed by both electron paramagnetic resonance (EPR) and UV-visible spectroscopies. In addition, the down-conversion (DC) and up-conversion (UC) of the LaPO4 nanophosphors via the 275 and 980 nm excitations, respectively, were considered, and a wide range of electronic transitions was observed. Based on the photoluminescence (PL) spectra, there is an efficient energy transfer (ET) process from Ce3+ donors to Nd3+ and Tb3+ acceptors, and the computed ET efficiency was 70% and 88%, respectively. The Ce3+/Cr3+ and Ce3+/Mn2+ doped LaPO4 showed weak far-red and green luminescence with much smaller ET efficiency of about 3.7 and 0.4%, respectively. LaPO4:Yb3+/Er3+ showed UC luminescence under the 980 nm laser radiation, and the resulted red and green light was attributed to the Er3+ transitions.

25. Structural Details of BaTiO3 Nano-Powders Deduced from the Anisotropic XRD Peak Broadening

Authors: Pasuk, I; Neatu, F; Neatu, S; Florea, M; Istrate, CM; Pintilie, I; Pintilie, L

Published: MAY 2021, NANOMATERIALS, 11, DOI: 10.3390/nano11051121

In this study, nano-BaTiO3 (BTO) powders were obtained via the solvothermal method at different reaction times and were investigated using transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectroscopy. The results were compared with those obtained for a larger crystallite size BTO powder (BTO-m). The sizes of the cuboid crystallites (as determined by XRD and TEM) ranged from about 18 to 24 nm, depending on the reaction time. The evolution with temperature of the structure parameters of nano-BTO was monitored by means of X-ray diffraction and Raman spectroscopy and no signs of phase transition were found up to 170 degrees C. Careful monitoring of the dependence of the XRD peak widths on the hkl indices showed that the effect of the cubic crystallite shape upon the XRD peak widths was buried by the effect of hidden tetragonal line splits and by anisotropic microstrain. The good correlation of the line widths with the tetragonal split amplitudes, observed especially for BTO-m above the transition temperature, indicates tetragonal deformations, as also revealed by Raman spectroscopy. The large anisotropic microstrain shown by the nano-powders, which had a maximum value in the directions, was considered evidence of the phenomenon of surface relaxation of cubic crystallites edged by {100} faces. The observed behavior of the nano-BTO structures with increasing temperature may suggest a correlation between the surface relaxation and tetragonal deformation in the nano-cubes. The experimental results for both nano-BTO and mezoscale-BTO are in agreement with the core-shell model.

26. Recent progress in electrocatalysts and electrodes for portable fuel cells

Authors: Neatu, S; Neatu, F; Chirica, IM; Borbath, I; Talas, E; Tompos, A; Somacescu, S; Osiceanu, P; Folgado, MA; Chaparro, AM; Florea, M

Published: AUG 28 2021, JOURNAL OF MATERIALS CHEMISTRY A, 9, 17128, DOI: 10.1039/d1ta03644k

Fuel cells are devices that transform efficiently the chemical energy of hydrogen or another fuel into clean electricity. The fuel cell technology is attractive for its high-energy efficiency and expanded fuel flexibility and it became very relevant in the last decade. Moreover, the utilization of fuel cells for portable electronic devices has seen remarkable increase in the last few years. Performances of fuel cells, among others, strongly depend on the types of electrocatalysts and membrane, anion exchange or cation exchange, used in the system. Therefore, a status report about the latest advances in electrocatalysts and electrodes for portable fuel cells is the objective of this review paper. Herein, the recent progress in designing electrocatalysts for producing high performance fuel cells with truly potential applicability to be used in portable devices is highlighted.

27. Structural and Optical Investigations of Ce3+/Mn2+-Doped LaPO4 Phosphors

Authors: Aitmellal, O; Oufni, L; Messous, MY; Neatu, F; Florea, M; Neatu, S; Rostas, AM; Secu, M

Published: APR 2021, JOURNAL OF ELECTRONIC MATERIALS, 50, 2147, DOI: 10.1007/s11664-020-08678-7

Lanthanum orthophosphate (LaPO4) and La0.95-xCe0.05MnxPO4 (x = 0.00, 0.03, 0.10) phosphors were synthesized by a simple and cost-efficient co-precipitation method and the formation of LaPO4 nanorods with a monoclinic P21/n crystal structure was observed. X-ray diffraction pattern analysis indicated a slight distortion of the LaPO4 crystalline structure and an increase of the lattice strain as a consequence of the Mn2+ and Ce3+ dopants incorporation in the host matrix. Scanning electron microscopy revealed that the microstructure of all powders consists of agglomerations of nanorods, which are around 17 +/- 3 nm in diameter and length ranging from 100 nm to 300 nm. Electron paramagnetic resonance measurements have indicated the presence of Mn2+ in isolated species, but also as agglomerates. Ce3+ and Mn2+ doping of LaPO4 resulted also in a decrease of the band gap up to 4.70 eV compared to the un-doped sample. Because of an energy transfer effect from Ce3+ to Mn2+ ions, green emission of Mn2+ ions at around 550 nm was observed upon 275 nm excitation.

28. Carbon-Coated SiO2 Composites as Promising Anode Material for Li-Ion Batteries

Authors: Buga, MR; Spinu-Zaulet, AA; Ungureanu, CG; Mitran, RA; Vasile, E; Florea, M; Neatu, F

Published: AUG 2021, MOLECULES, 26, DOI: 10.3390/molecules26154531

Porous silica-based materials are a promising alternative to graphite anodes for Li-ion batteries due to their high theoretical capacity, low discharge potential similar to pure silicon, superior cycling stability compared to silicon, abundance, and environmental friendliness. However, several challenges prevent the practical application of silica anodes, such as low coulombic efficiency and irreversible capacity losses during cycling. The main strategy to tackle the challenges of silica as an anode material has been developed to prepare carbon-coated SiO2 composites by carbonization in argon atmosphere. A facile and eco-friendly method of preparing carbon-coated SiO2 composites using sucrose is reported herein. The carbon-coated SiO2 composites were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, thermogravimetry, transmission and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy, cyclic voltammetry, and charge-discharge cycling. A C/SiO2-0.085 M calendered electrode displays the best cycling stability, capacity of 714.3 mAh center dot g(-1), and coulombic efficiency as well as the lowest charge transfer resistance over 200 cycles without electrode degradation. The electrochemical performance improvement could be attributed to the positive effect of the carbon thin layer that can effectively diminish interfacial impedance.

29. Applications of MAX phases and MXenes as catalysts

Authors: Chirica, IM; Mirea, AG; Neatu, S; Florea, M; Barsoum, MW; Neatu, F

Published: SEP 21 2021, JOURNAL OF MATERIALS CHEMISTRY A, 9, 19612, DOI: 10.1039/d1ta04097a

MAX phases and MXenes are important materials that have recently gained great popularity due to their special properties, which render them particularly useful in many applications, including catalytic ones. This can be seen in the large number of publications that appear annually on these materials and their applications. This review aims to evaluate MAX phases and MXenes as materials for heterogeneous, non-electrocatalytic, catalytic applications. The review begins with a brief introduction to the MAX phase and MXene properties that recommend them as potential materials for heterogeneous catalytic applications, followed by four sections grouped according to the processes in which they have already proven effective. These include supports to activate the C-H or C-O bonds in applications such as dehydrogenation of light or aromatic alkanes, methanol formation from CH4, dry reforming, and CO oxidation or the water gas shift reaction (Section 2), and their use in fine chemical reactions (Section 3) and in chemical degradation (Section 4). The last section deals with photocatalytic applications (Section 5). The review ends by highlighting the huge potential of these materials for a wide range of heterogeneous catalytic applications as well as the challenges ahead.

30. NiO / Sr doped Ce(0.85)Pr0.10 Er0.05O(2-delta) mesoarchitectured catalyst for partial oxidation of CH4 and anode fueled by H-2

Authors: Navarrete, L; Florea, M; Osiceanu, P; Calderon-Moreno, JM; Trandafir, MM; Somacescu, S; Serra, JM

Published: AUG 2021, MICROPOROUS AND MESOPOROUS MATERIALS, 323, 111171, DOI: 10.1016/j.micromeso.2021.111171

31. CuWO4 with CuO and Cu(OH)(2) Native Surface Layers for H2S Detection under in-Field Conditions

Authors: Somacescu, S; Stanoiu, A; Dinu, IV; Calderon-Moreno, JM; Florea, OG; Florea, M; Osiceanu, P; Simion, CE

Published: JAN 2021, MATERIALS, 14, DOI: 10.3390/ma14020465

The paper presents the possibility of detecting low H2S concentrations using CuWO4. The applicative challenge was to obtain sensitivity, selectivity, short response time, and full recovery at a low operating temperature under in-field atmosphere, which means variable relative humidity (%RH). Three different chemical synthesis routes were used for obtaining the samples labeled as: CuW1, CuW2, and CuW3. The materials have been fully characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). While CuWO4 is the common main phase with triclinic symmetry, different native layers of CuO and Cu(OH)(2) have been identified on top of the surfaces. The differences induced into their structural, morphological, and surface chemistry revealed different degrees of surface hydroxylation. Knowing the poisonous effect of H2S, the sensing properties evaluation allowed the CuW2 selection based on its specific surface recovery upon gas exposure. Simultaneous electrical resistance and work function measurements confirmed the weak influence of moisture over the sensing properties of CuW2, due to the pronounced Cu(OH)(2) native surface layer, as shown by XPS investigations. Moreover, the experimental results obtained at 150 degrees C highlight the linear sensor signal for CuW2 in the range of 1 to 10 ppm H2S concentrations and a pronounced selectivity towards CO, CH4, NH3, SO2, and NO2. Therefore, the applicative potential deserves to be noted. The study has been completed by a theoretical approach aiming to link the experimental findings with the CuW2 intrinsic properties.

32. Degenerated TiO(2)Semiconductor Modified with Ni and Zn as Efficient Photocatalysts for the Water Splitting Reaction

Authors: Neatu, F; Abramiuc, LE; Trandafir, MM; Negrea, RF; Florea, M; Teodorescu, CM; Neatu, S

Published: SEP 17 2020, CHEMCATCHEM, 12, DOI: 10.1002/cctc.202000691

The development of robust, safe, cost-effective and efficient photocatalytic systems for water splitting should take into account the presence of a proper and powerful photon absorber and an efficient, low-cost and earth-abundant electrocatalyst to perform the reaction at high conversions. In this study, Ni-Zn/TiO(2)ternary composites with high photocatalytic activity for water splitting under UV irradiation were successfully prepared via a simple and low-cost deposition-precipitation route. Thus, different Ni : Zn molar ratios (1 : 0, 1 : 1, 3 : 1, 6 : 1, 9 : 1, and 0 : 1) were deposited on TiO(2)in order to reach a total metal loading of 50 wt. %. The obtained composites were characterized using several techniques, such as: X-ray diffraction, UV-Vis spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. The most active synthesized composite, namely Ni-Zn/TiO2(9 : 1), exhibits H(2)generation rate above 17 mmols g(-1) h(-1), which is nearly one thousand times higher than that obtained with TiO(2)Evonik P25. Our study demonstrates that TiO(2)becomes a degenerated semiconductor in the presence of Ni and ZnO, with remarkable photocatalytic properties. Thus, the obtained results can open new opportunities in the preparation of very active materials for hydrogen production based on the optimization of three-component structures.

33. Degenerated TiO2 Semiconductor Modified with Ni and Zn as Efficient Photocatalysts for the Water Splitting Reaction

Authors: Neatu, F; Abramiuc, LE; Trandafir, MM; Negrea, RF; Florea, M; Teodorescu, CM; Neatu, S

Published: SEP 17 2020, CHEMCATCHEM, 12, 4651, DOI: 10.1002/cctc.202000691

34. Influence of doping the inorganic cation with Eu or Sb on the properties of perovskite films

Authors: Stancu, V; Leonat, LN; Tomulescu, AG; Derbali, S; Pintilie, L; Besleaga, C; Galca, AC; Neatu, F; Neatu, T; Florea, M; Pintilie, I

Published: JUL 2020, PHYSICA SCRIPTA, 95, DOI: 10.1088/1402-4896/ab90be

This study reports on the results obtained after doping the [CH3NH3](0.94)[C3N2H5](0.06)PbI2.6Cl0.4 mixt halide perovskite with europium or antimony (Eu3+/Sb3+) at the 'B site'. This way two new complex compounds were obtained, [CH3NH3](0.94)[C3N2H5](0.06)Pb1-yByI2.6Cl0.4 (B = Eu or Sb and y = 0-0.05) as perovskite precursor solutions and deposited as thin films. The properties of the perovskite films were investigated by various characterization techniques: x-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), UV-vis spectroscopy while the photovoltaic parameters were determined by measuring the IV curves of the corresponding solar cells. We find that doping the mixt halide perovskite with very small quantities of Sb improves the quality of the perovskite films and further improves the stability of perovskite solar cells.

35. CeO2:Mn3O4 Catalytic Micro-Converters Tuned for CH4 Detection Based on Catalytic Combustion under Real Operating Conditions

Authors: Simion, CE; Florea, OG; Florea, M; Neatu, F; Neatu, S; Trandafir, MM; Stanoiu, A

Published: MAY 2020, MATERIALS, 13, DOI: 10.3390/ma13092196

Mesoporous CeO2:Mn3O4 materials (3:7 and 7:3 molar ratio) were prepared by co-precipitation and deposited as porous thick films over alumina (Al2O3) planar substrate provided with Pt meander. The aim was oriented towards detecting low levels methane (CH4) at moderate operating temperatures. Herein we demonstrated that the sensitivity of catalytic micro-converters (CMCs) towards a given peak of CH4 concentration corresponds to specific gas-surface interaction phenomena. More precisely, a transition from thermal conductivity to combustion rate is likely to occur when CMCs are operated under real atmospheric conditions (normal pressure, presence of relative humidity, and constant operating temperature). The response to CH4 was analyzed over different gas flows and different gas concentrations under the same operating regime. The materials were fully characterized by adsorption-desorption isotherms, H-2-Temperature Programmed Reduction (H-2-TPR), X-ray Diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Scanning Electron Microscopy (SEM), and Raman spectroscopies. Thus, the applicative aspect of using CeO2:Mn3O4 as moderate temperature CMC for CH4 detection is brought to the fore.

36. Crown-ether functionalized graphene oxide for metal ions sequestration

Authors: Petrescu, S; Avramescu, S; Musuc, AM; Neatu, F; Florea, M; Ionita, P

Published: FEB 2020, MATERIALS RESEARCH BULLETIN, 122, DOI: 10.1016/j.materresbull.2019.110643

Graphene oxide has been synthesized, additionally derivatized with chloroacetic acid for increase the number of available carboxylic groups and further functionalized with crown-ether moieties. The thus obtained material was characterized by IR, thermal analysis, SEM, Raman, and XPS. Tests on adsorption of several metal cations showed that cooper and iron are more retained than potassium.

37. Undoped SnO2 as a Support for Ni Species to Boost Oxygen Generation through Alkaline Water Electrolysis

Authors: Neatu, S; Neatu, F; Diculescu, VC; Trandafir, MM; Petrea, N; Somacescu, S; Krumeich, F; Wennmacher, JTC; Knorpp, AJ; van Bokhoven, JA; Florea, M

Published: APR 22 2020, ACS APPLIED MATERIALS & INTERFACES, 12, 18420, DOI: 10.1021/acsami.9b19541

In this study, the synergistic behavior of Ni species and bimodal mesoporous undoped SnO2 is investigated in oxygen evolution reactions (OERs) under alkaline conditions without any other modification of the compositional phases or using noble metals. An efficient and environmentally friendly hydrothermal method to prepare bimodal mesoporous undoped SnO2 with a very high surface area (>130 m(2) g(-1)) and a general deposition-precipitation method for the synthesis of well-dispersed Ni species on undoped SnO2 are reported. The powders were characterized by adsorption-desorption isotherms, TG-DTA, XRD, SEM, TEM, Raman, TPRH2, and XPS. The best NiSn composite generates, under certain experimental conditions, a very high TOF value of 1.14 s(-1) and a mass activity higher than 370 A g(-1), which are remarkable results considering the low amount of Ni deposited on the electrode (3.78 ng). Moreover, in 1 M NaOH electrolyte, this material produces more than 24 mA cm(-2) at an overpotential value of approximately +0.33 V, with only 5 wt % Ni species. This performance stems from the dual role of undoped SnO2, on the one hand, as a support for active and well-dispersed Ni species and on the other hand as an active player through the oxygen vacancies generated upon Ni deposition.

38. Highly Active Transition Metal-Promoted CuCeMgAlO Mixed Oxide Catalysts Obtained from Multicationic LDH Precursors for the Total Oxidation of Methane

Authors: Al-Aani, HMS; Trandafir, MM; Fechete, I; Leonat, LN; Badea, M; Negrila, C; Popescu, I; Florea, M; Marcu, IC

Published: JUN 2020, CATALYSTS, 10, DOI: 10.3390/catal10060613

To improve the catalytic performance of an active layered double hydroxide (LDH)-derived CuCeMgAlO mixed oxide catalyst in the total oxidation of methane, it was promoted with different transition-metal cations. Thus, two series of multicationic mixed oxides were prepared by the thermal decomposition at 750 degrees C of their corresponding LDH precursors synthesized by coprecipitation at constant pH of 10 under ambient atmosphere. The first series of catalysts consisted of four M(3)CuCeMgAlO mixed oxides containing 3 at.% M (M = Mn, Fe, Co, Ni), 15 at.% Cu, 10 at.% Ce (at.% with respect to cations), and with Mg/Al atomic ratio fixed to 3. The second series consisted of four Co(x)CuCeMgAlO mixed oxides withx= 1, 3, 6, and 9 at.% Co, while keeping constant the Cu and Ce contents and the Mg/Al atomic ratio. All the mixed oxides were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) coupled with X-ray energy dispersion analysis (EDX), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption-desorption at -196 degrees C, temperature-programmed reduction under hydrogen (H-2-TPR), and diffuse reflectance UV-VIS spectroscopy (DR UV-VIS), while thermogravimetric and differential thermal analyses (TG-DTG-DTA) together with XRD were used for the LDH precursors. The catalysts were evaluated in the total oxidation of methane, a test reaction for volatile organic compounds (VOC) abatement. Their catalytic performance was explained in correlation with their physicochemical properties and was compared with that of a reference Pd/Al(2)O(3)catalyst. Among the mixed oxides studied, Co(3)CuCeMgAlO was found to be the most active catalyst, with a temperature corresponding to 50% methane conversion (T-50) of 438 degrees C, which was only 19 degrees C higher than that of a reference Pd/Al(2)O(3)catalyst. On the other hand, this T(50)value was ca. 25 degrees C lower than that observed for the unpromoted CuCeMgAlO system, accounting for the improved performance of the Co-promoted catalyst, which also showed a good stability on stream.

39. Exploring the effect of aliovalent substitution of Pb2+ by Eu3+ on structural, morphological and optical properties of CH3NH3PbI3 perovskite films

Authors: Derbali, S; Nouneh, K; Florea, M; Neatu, F; Neatu, S; Leonat, LN; Secu, M; Tomulescu, AG; Stancu, V; Pintilie, L; Touhami, ME; Galca, AC

Published: APR 2020, PHYSICA SCRIPTA, 95, DOI: 10.1088/1402-4896/ab5baa

In this work, the effect of aliovalent substitution of Pb2+ by Eu3+ on structural, morphological and optical properties of CH3NH3PbI3 (MAPbI(3)) was studied, aiming to improve the properties of perovskite films used in solar cells application. The surface morphology, the microstructure and the optical properties of the obtained films containing different Europium (Eu) concentrations were characterized by atomic force microscopy, x-ray photoelectron spectroscopy, x-ray diffraction, UV-vis spectroscopy and photoluminescence spectroscopy.

40. Highly Efficient Ultralow Pd Loading Supported on MAX Phases for Chemoselective Hydrogenation

Authors: Trandafir, MM; Neatu, F; Chirica, IM; Neatu, S; Kuncser, AC; Cucolea, EI; Natu, V; Barsoum, MW; Florea, M

Published: MAY 15 2020, ACS CATALYSIS, 10, 5908, DOI: 10.1021/acscatal.0c00082

Palladium is one of the most efficient metals for the hydrogenation of organic compounds. However, when molecules, such as nitroaromatics, with several reducible functionalities, are hydrogenated, Pd, like any other very active metal, such as nickel or platinum, often behaves unselectively. One strategy to render Pd more selective is to choose the proper support. Herein, we show that MAX phase powders of Ti3SiC2, Ti2AlC, or Ti3AlC2 can chemoselectively hydrogenate 4-nitrostyrene to 4-aminostyrene, with 100% selectivity, at around 3-4% conversion. To boost the latter, we loaded Ti3SiC2 with 0.0005 wt % Pd and increased the conversion to 100% while maintaining the 4-AS selectivity at >90%. By optimizing the Pd loading, we were also able to increase the turnover frequency 100-fold relative to previous literature results. The identification of this highly efficient and chemoselective system has broad implications for the design of cost-effective, earth-abundant, nontoxic, metal catalysts, with ultralow noble metal loadings.

41. Reticulated Mesoporous TiO2 Scaffold, Fabricated by Spray Coating, for Large-Area Perovskite Solar Cells

Authors: Tomulescu, AG; Stancu, V; Besleaga, C; Enculescu, M; Nemnes, GA; Florea, M; Dumitru, V; Pintilie, L; Pintilie, I; Leonat, L

Published: JAN 2020, ENERGY TECHNOLOGY, 8, DOI: 10.1002/ente.201900922

Development of reproducible, low-cost fabrication technologies that are readily adaptable to large-scale production, is one of the main challenges in the field of perovskite solar cells (PSCs). So far, for all the other layers in a solar cell, large-area deposition methods have been adapted, except for mesoporous fabrication. Herein, the fabrication of mesoporous TiO2 scaffolds using a large-area deposition technique, such as spray coating, is shown. Moreover, this technique induces the formation of a very specific reticulated structure with well-delimited, oval-shaped cavities. The cavities have irregular dimensions, with diameters in the range of 3-7 mu m, approximate to 350 nm height, resulting in an overall increase in roughness of one order of magnitude, compared with the spin-coated mesoporous scaffold. Using this rough structured mesoporous TiO2 in PSCs not only does not affect the efficiency of solar cells but actually improves it from an average of 10% to 12% in comparison with the devices containing a spin-coated mesoporous scaffold.

42. Methane Combustion Using Pd Deposited on CeOx-MnOx/La-Al2O3 Pellistors

Authors: Florea, OG; Stanoiu, A; Gheorghe, M; Cobianu, C; Neatu, F; Trandafir, MM; Neatu, S; Florea, M; Simion, CE

Published: NOV 2020, MATERIALS, 13, DOI: 10.3390/ma13214888

Pd deposited on CeOx-MnOx/La-Al2O3 has been prepared as a sensitive material for methane (CH4) detection. The effect of different amounts (1.25%, 2.5% and 5%) of Pd loading has been investigated. The as prepared materials were deposited on Pt microcoils using a drop-coating method, as a way of developing pellistors operated using a Wheatstone bridge configuration. By spanning the operating temperature range between 300 degrees C and 550 degrees C, we established the linearity region as well as the maximum sensitivity towards 4900 ppm of CH4. By making use of the sigmoid dependence of the output voltage signal from the Wheatstone bridge, the gas surface reaction and diffusion phenomena have been decoupled. The pellistor with 5% Pd deposited on CeOx-MnOx/La-Al2O3 exhibited the highest selective-sensitivity in the benefit of CH4 detection against threshold limits of carbon monoxide (CO), sulfur dioxide (SO2) and hydrogen sulfide (H2S). Accordingly, adjusting the percent of Pd makes the preparation strategies of pellistors good candidates towards CH4 detection.

43. VAlPOs as Efficient Catalysts for Glycerol Conversion to Methanol

Authors: Mitran, G; Neatu, F; Neatu, S; Trandafir, MM; Florea, M

Published: JUL 2020, CATALYSTS, 10, DOI: 10.3390/catal10070728

The catalytic activity of a series of vanadium aluminophosphates catalysts prepared by sol-gel method followed by combustion of the obtained gel was evaluated in glycerol conversion towards methanol. The materials were characterized by several techniques such as X-ray diffraction (XRD), UV-vis, Fourier-transform infrared (FTIR), Raman and X-ray photoelectron (XPS) spectroscopies. The amount of vanadium incorporated in aluminophosphates framework played an important role in the catalytic activity, while in the products distribution the key role is played by the vanadium oxidation state on the surface. The sample that contains a large amount of V(4+)has the highest selectivity towards methanol. On the sample with the lowest vanadium loading the oxidation path to dihydroxyacetone is predominant. The catalyst with higher content of tetrahedral isolated vanadium species, such V5APO, is less active in breaking the C-C bonds in the glycerol molecule than the one containing polymeric species.

44. Bulk Versus Surface Modification of Alumina with Mn and Ce Based Oxides for CH4 Catalytic Combustion

Authors: Neatu, S; Trandafir, MM; Stanoiu, A; Florea, OG; Simion, CE; Leonat, LN; Cobianu, C; Gheorghe, M; Florea, M; Neatu, F

Published: JUN 1 2019, MATERIALS, 12, DOI: 10.3390/ma12111771

This study presents the synthesis and characterization of lanthanum-modified alumina supported cerium-manganese mixed oxides, which were prepared by three different methods (coprecipitation, impregnation and citrate-based sol-gel method) followed by calcination at 500 degrees C. The physicochemical properties of the synthesized materials were investigated by various characterization techniques, namely: nitrogen adsorption-desorption isotherms, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and H-2-temperature programmed reduction (TPR). This experimental study demonstrated that the role of the catalytic surface is much more important than the bulk one. Indeed, the incipient impregnation of CeO2-MnOx catalyst, supported on an optimized amount of 4 wt.% La2O3-Al2O3, provided the best results of the catalytic combustion of methane on our catalytic micro-convertors. This is mainly due to: (i) the highest pore size dimensions according to the Brunauer-Emmett-Teller (BET) investigations, (ii) the highest amount of Mn4+ or/and Ce4+ on the surface as revealed by XPS, (iii) the presence of a mixed phase (Ce2MnO6) as shown by X-ray diffraction; and (iv) a higher reducibility of Mn4+ or/and Ce4+ species as displayed by H-2-TPR and therefore more reactive oxygen species.

45. Next frontiers in cleaner synthesis: 3D printed graphene-supported CeZrLa mixed -oxide nanocatalyst for CO2 utilisation and direct propylene carbonate production

Authors: Middelkoop, V; Slater, T; Florea, M; Neatu, F; Danaci, S; Onyenkeadi, V; Boonen, K; Saha, B; Baragau, LA; Kellici, S

Published: MAR 20 2019, JOURNAL OF CLEANER PRODUCTION, 214, 614, DOI: 10.1016/j.jclepro.2018.12.274

A rapidly-growing 3D printing technology is innovatively employed for the manufacture of a new class of heterogenous catalysts for the conversion of CO2 into industrially relevant chemicals such as cyclic carbonates. For the first time, directly printed graphene-based 3D structured nanocatalysts have been developed combining the exceptional properties of graphene and active CeZrLa mixed-oxide nano particles. It constitutes a significant advance on previous attempts at 3D printing graphene inks in that it does not merely explore the printability itself, but enhances the efficiency of industrially relevant reactions, such as CO2 utilisation for direct propylene carbonate (PC) production in the absence of organic solvents. In comparison to the starting powder, 3D printed GO-supported CeZeLa catalysts showed improved activity with higher conversion and no noticeable change in selectivity. This can be attributed to the spatially uniform distribution of nanoparticles over the 2D and 3D surfaces, and the larger surface area and pore volume of the printed structures. 3D printed GO-supported CeZeLa catalysts compared to unsupported 3D printed samples exhibited higher selectivity and yield owing to the great number of new weak acid sites appearing in the supported sample, as observed by NH3-TPD analysis. In addition, the catalyst's facile separation from the product has the capacity to massively reduce materials and operating costs resulting in increased sustainability. It convincingly shows the potential of these printing technologies in revolutionising the way catalysts and catalytic reactors are designed in the general quest for clean technologies and greener chemistry. 2019 Elsevier Ltd. All rights reserved.

46. Bimodal mesoporous NiO/CeO2-delta-YSZ with enhanced carbon tolerance in catalytic partial oxidation of methane-Potential IT-SOFCs anode

Authors: Somacescu, S; Cioatera, N; Osiceanu, P; Calderon-Moreno, JM; Ghica, C; Neatu, F; Florea, M

Published: FEB 2019, APPLIED CATALYSIS B-ENVIRONMENTAL, 241, 406, DOI: 10.1016/j.apcatb.2018.09.065

In the present study we report on the activity, selectivity and stability of the bimodal mesoporous NiO/CeO2-delta-YSZ anodes for IT-SOFCs applications. These materials present high concentration of C3+ ions stably retained in the lattice, which proved to be efficient for the catalytic partial oxidation of CH4 to syngas in the temperature range 600-800 degrees C. The excellent carbon tolerance was proved by a comprehensive XPS analysis, which monitored the amount of carbon before and after catalytic partial oxidation of methane (CPOM) tests. The mesoporous anodes templated by hexadecyltrimethylammonium bromide (CTAB) and tripropylamine (TPA) were obtained using a hydrothermal synthesis route. The effect of Ni and Ce incorporation on the yttria stabilized zirconia (YSZ) structure, texture, morphology and surface chemistry was discussed and correlated with catalytic and electrochemical behavior. The exhaustive characterization of the bulk and surface properties of the catalysts have been accomplished by means of complementary methods: XRD, SEM / EDX / HR TEM, TGA / TPR, XPS. The electrochemical and catalytic performance were improved when the surface contains more reduced ceria and NiO was formed as secondary phase. These features lead to a large number of vacancies and consequently a better oxygen migration, which facilitate the carbon removal.

47. Coordination polymers and a dinuclear complex constructed from zinc(II) ions and fluorescein: iodine adsorption and optical properties

Authors: Raduca, M; Ene, CD; Ionescu, S; Florea, M; Madalan, AM

Published: APR 18 2019, JOURNAL OF COORDINATION CHEMISTRY, 72, 1237, DOI: 10.1080/00958972.2019.1605442

1-D coordination polymers, (1)(infinity)[Zn(fl)(2)]center dot 2EtOH and (1)(infinity)[Zn(fl)(2)]center dot 2MeOH, and a dinuclear complex, [{Zn(fl)(2)}(2)(dienpip)]center dot 4H(2)O center dot 4EtOH (dienpip= N,N '-bis(2-aminoethyl)piperazine), were obtained using Zn(II) ions and fluorescein anions (fl). Thermal analysis shows stability of the polymers after solvent removal up to more than 400 degrees C. Crystallization solvent molecules were removed under reduced pressure with the preservation of the polymeric structure, (1)(infinity)[Zn(fl)(2)]. Desolvated crystals were exposed to I-2 vapors and the crystal structure determination by X-ray diffraction confirmed the presence of I-2 molecules in the channels generated in crystals by the metal-organic framework. The iodine content, evaluated by X-ray diffraction, corresponds to the overall formula (1)(infinity)[Zn(fl)(2)]center dot 0.3I(2). The optical properties of the coordination polymers and the dinuclear complex have been investigated. [GRAPHICS] .

48. Behavior of Molybdenum-Vanadium Mixed Oxides in Selective Oxidation and Disproportionation of Toluene

Authors: Mitran, G; Neatu, F; Pavel, OD; Trandafir, MM; Florea, M

Published: MAR 1 2019, MATERIALS, 12, DOI: 10.3390/ma12050748

This study deals with the behavior of molybdenum-vanadium (Mo/V) mixed oxides catalysts in both disproportionation and selective oxidation of toluene. Samples containing different Mo/V ratios were prepared by a modified method using tetradecyltrimethylammonium bromide and acetic acid. The catalysts were characterized using several techniques: nitrogen adsorption-desorption isotherms, X-Ray diffraction (XRD), ammonia temperature-programmed desorption (TPD-NH3), temperature-programmed reduction by hydrogen (H-2-TPR), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, Fourier-transform infrared-spectroscopy (FTIR) and ultraviolet-visible spectroscopies (UV-VIS). The XRD results evidenced the presence of orthorhombic -MoO3 and V2O5 phases, as well as monoclinic -MoO3 and V2MoO8 phases, their abundance depending on the Mo to V ratio, while the TPD-NH3 emphasized that, the total amount of the acid sites diminished with the increase of the Mo loading. The TPR investigations indicated that the samples with higher Mo/V ratio possess a higher reducibility. The main findings of this study led to the conclusion that the presence of strong acid sites afforded a high conversion in toluene disproportionation (Mo/V = 1), while a higher reducibility is a prerequisite to accomplishing high conversion in toluene oxidation (Mo/V = 2). The catalyst with Mo/V = 1 acquires the best yield to xylenes from the toluene disproportionation reaction, while the catalyst with Mo/V = 0.33 presents the highest yield to benzaldehyde.

49. La0.75Sr0.25XO3 (X = Fe, Mn or Cr) with coking tolerance for CH4/H2O reaction: effect of H2S on catalytic performance

Authors: Florea, M; Somacescu, S; Postole, G; Urda, A; Neatu, F; Neatu, S; Massin, L; Gelin, P

Published: MAY 7 2019, CATALYSIS SCIENCE & TECHNOLOGY, 9, 2366, DOI: 10.1039/c9cy00065h

The influence of the B type cation from the ABO(3) perovskite formulation La0.75Sr0.25XO3 (LSX, where X is Fe, Mn or Cr) on the C and H2S tolerance and its catalytic activity for the methane/water reaction has been studied. The samples were prepared by a simple and cost-efficient citrate method. The exhaustive characterization of the bulk and surface properties of the catalysts has been accomplished by means of complementary methods: nitrogen adsorption-desorption isotherm measurements, XRD, TPR and XPS. Their catalytic properties in CH4/H2O reactions (CH4/H2O molar ratios of 10 and 1) were studied in the presence and absence of H2S in order to evaluate their potential use as anode materials in solid oxide fuel cells operated on natural gas. Before addition and upon suppression of H2S, the activity varied in the following order: LSF > LSM >> LSC. This correlates with the oxygen mobility determined by TPR. A strong promoting effect of H2S on the catalytic activity is observed for LSC, which makes this sample the most active of the series, while H2S has a weak influence on the other perovskites. The oxygen vacancies and the presence of S2- were identified as being responsible for the enhanced catalytic activity upon H2S addition.

50. The hysteresis-free behavior of perovskite solar cells from the perspective of the measurement conditions

Authors: Nemnes, GA; Besleaga, C; Tomulescu, AG; Leonat, LN; Stancu, V; Florea, M; Manolescu, A; Pintilie, I

Published: MAY 14 2019, JOURNAL OF MATERIALS CHEMISTRY C, 7, 5274, DOI: 10.1039/c8tc05999c

We investigate how far the hysteresis-free behavior of perovskite solar cells can be reproduced using particular pre-conditioning and measurement conditions. As there are currently more and more reports of perovskite solar cells without J-V hysteresis it is crucial to distinguish between genuine performance improvements and measurement artifacts. We focus on two of the parameters that influence the dynamic J-V scans, namely the bias scan rate and the bias poling voltage, and point out measurement conditions for achieving a hysteresis-free behavior. In this context we discuss the suitability of defining a hysteresis index (HI) for the characterization of dynamic J-V scans. Using HI, aging effects are also investigated, establishing a potential connection between the sample degradation and the variation of the maximal hysteresis on one hand, and the relaxation time scale of the slow process on the other hand. Pre-poling induced recombination effects are identified. In addition, our analysis based on sample pre-biasing reveals potential indications regarding two types of slow processes, with two different relaxation time scales, which provides further insight regarding ionic migration.

51. Highly -sensitive near infrared luminescent nanothermometers based on binary mixture

Authors: Avram, D; Colbea, C; Florea, M; Tiseanu, C

Published: MAY 15 2019, JOURNAL OF ALLOYS AND COMPOUNDS, 785, 259, DOI: 10.1016/j.jallcom.2019.01.162

We propose a simple strategy to obtain a luminescence intensity ratio nanothermometer operating in the near infrared range (1000-1700 nm) by use of binary mixtures of lanthanide doped Y2O3 selected as 1% Ho - Y2O3 + 1%Er - Y2O3 and 1%Ho - Y2O3 + 1%Nd - Y2O3. All nanoparticles were synthetized by citrate complexation method and thermally annealed at 800 degrees C. The temperature evolution of the emission properties was monitored in the range of 297-472 K and analyzed in terms of emission shape, intensity, dynamics, excitation wavelength, acquisition mode and weight ratio of the binary mixture. A maximum relative sensitivity of 1%K-1 at 297 K was recorded for the 3/1 weight ratio Ho - Y2O3 + Er - Y2O3 binary mixture upon excitation at 536.8 nm. For the more appropriate excitation wavelength for bioimaging applications at 649.7 nm, a relative sensitivity of 0.55-0.6% K-1 was recorded in the relevant physiological temperature range (300-320 K) for the 3/1 weight ratio Ho - Y2O3 + Er - Y2O3 binary mixture. To the best of our knowledge, our study also represents a first report on the near -infrared luminescence (around 1200 nm) lifetime thermometry for a Ho doped nanoparticle. Comparison with the literature demonstrates that our system represents a promising near-infrared thermometer, with a non-sophisticated and reproducible configuration that is open to multiple optimization routes. (C) 2019 Elsevier B.V. All rights reserved.

52. Imaging dopant distribution across complete phase transformation by TEM and upconversion emission

Authors: Avram, D; Colbea, C; Florea, M; Lazar, S; Stroppa, D; Tiseanu, C

Published: SEP 28 2019, NANOSCALE, 11, 16754, DOI: 10.1039/c9nr04345d

Correlating dopant distribution to its optical response represents a complex challenge for nanomaterials science. Differentiating the "true" clustering nature from dopant pairs formed in statistical distribution complicates even more the elucidation of doping-functionality relationship. The present study associates lanthanide dopant distribution, including all significant events (enrichment, depletion and surface segregation), to its optical response in upconversion (UPC) at the ensemble and single-nanoparticle level. A small deviation from the Er nominal concentration of a few percent is able to induce clear differences in Er UPC emission color, intensity, excited-state dynamics and ultimately, UPC mechanisms, across tetragonal to monoclinic phase transformation in rationally designed Er doped ZrO2 nanoparticles. Rare evidence of a heterogeneous dopant distribution leading to the coexistence of two polymorphs in a single nanoparticle is revealed by Z- and phase contrast transmission electron microscopy (TEM). Despite their spatial proximity, Er in the two polymorphs are spectroscopically isolated, i.e. they do not communicate by energy transfer. Segregated Er, which is well imaged in TEM, is absent in UPC, while the minor phase content overlooked by X-ray diffraction and TEM is revealed by UPC. The outstanding sensitivity of combined TEM and UPC emission to subtle deviations from uniform doping in the diluted concentration regime renders such an approach relevant for various functional oxides supporting lanthanide dopants as emitters.

53. Selective catalytic oxidation reaction of p-xylene on manganese-iron mixed oxide materials

Authors: Nicolae, S; Neatu, F; Florea, M

Published: MAR-APR 2018, COMPTES RENDUS CHIMIE, 21, 361, DOI: 10.1016/j.crci.2017.06.005

Mixed manganese iron oxides (Mn/Fe/O) as heterogeneous catalysts were prepared by hydrothermal treatment and citrate methods to be tested in the oxidation of p-xylene (PX) using as oxidation agent molecular oxygen, hydrogen peroxide, and tert-butyl hydroperoxide. Preparation of mixed Mn-Fe oxide by the citrate method releases materials with smaller particle size and lower degree of crystallinity as compared with the hydrothermal one, which further leads to a higher activity toward the oxidation of PX. A conversion of PX of 98% and a yield in p-toluic acid of 93% were obtained in the presence of Mn/Fe/O prepared by the citrate method using tert-butyl hydroperoxide as an oxidizing agent. (C) 2017 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.

54. Near infrared emission properties of Er doped cubic sesquioxides in the second/third biological windows

Authors: Avram, D; Tiseanu, I; Vasile, BS; Florea, M; Tiseanu, C

Published: DEC 21 2018, SCIENTIFIC REPORTS, 8, DOI: 10.1038/s41598-018-36639-y

In the recent years, there is an extensive effort concentrated towards the development of nanoparticles with near-infrared emission within the so called second or third biological windows induced by excitation outside 800-1000 nm range corresponding to the traditional Nd (800 nm) and Yb (980 nm) sensitizers. Here, we present a first report on the near-infrared (900-1700 nm) emission of significant member of cubic sesquioxides, Er-Lu2O3 nanoparticles, measured under both near-infrared up-conversion and low energy X-ray excitations. The nanoparticle compositions are optimized by varying Er concentration and Li addition. It is found that, under ca. 1500 nm up-conversion excitation, the emission is almost monochromatic (>93%) and centered at 980 nm while over 80% of the X-ray induced emission is concentrated around 1500 nm. The mechanisms responsible for the up-conversion emission of Er - Lu2O3 are identified by help of the up-conversion emission and excitation spectra as well as emission decays considering multiple excitation/emission transitions across visible to near-infrared ranges. Comparison between the emission properties of Er-Lu2O3 and Er-Y2O3 induced by optical and X-ray excitation is also presented. Our results suggest that the further optimized Er-doped cubic sesquioxides represent promising candidates for bioimaging and photovoltaic applications.

55. Alternative valorization of red mud waste as functional materials with catalytic activity for sulfide oxidation in wastewater

Authors: Cruceanu, A; Zavoianu, R; Pavel, OD; Florea, M; Mara, L

Published: APR 2018, INTERNATIONAL JOURNAL OF ENVIRONMENTAL SCIENCE AND TECHNOLOGY, 15, 908, DOI: 10.1007/s13762-017-1449-1

This work investigates the catalytic properties toward sulfide oxidation in wastewater for three composites which are functional materials obtained from red mud waste following its neutralization, chemical activation and functionalization of the iron by treatment with disodium salt of ethylenediaminetetraacetic acid, trisodium citrate or a combination of these two organic ligands. X-ray diffraction and diffuse reflectance Fourier transformed infrared spectroscopy characterizations indicated the coexistence of the corresponding iron chelates phases along with hematite the main crystallographic phase from red mud. The most active catalyst was the red mud-derived material obtained by functionalization with the mixture of ethylenediaminetetraacetate and citrate ligands. The results obtained after its testing in multiple reaction cycles showed that the decrease in conversion after 10 reaction cycles was less than 5%. Considering the results of diffuse reflectance ultraviolet visible narrow infrared spectroscopical analysis which revealed that this solid contains species with lower bond strength, it has been inferred that both the higher catalytic activity, as well as the enhanced stability, is directly related to the versatility of the active species.

56. Doped ceria prepared by precipitation route for steam reforming of methane

Authors: Florea, M; Matei-Rutkovska, F; Postole, G; Urda, A; Neatu, F; Parvulescu, VI; Gelin, P

Published: MAY 15 2018, , DOI: 10.1016/j.cattod.2016.12.006

57. Thermal behaviour of sym-octahydroacridines and their corresponding N(10)-oxides

Authors: Marinescu, M; Potmischil, F; Florea, M; Constantinescu, C

Published: JAN 2018, , DOI: 10.1007/s10973-016-5862-3

58. The Cu- and Zn-complex-catalyzed methanolysis of the chemical warfare nerve agents soman, sarin, and VX

Authors: Petrea, N; Petre, R; Pretorian, A; Toader, C; Somoghi, V; Neatu, F; Florea, M; Neatu, S

Published: MAR-APR 2018, COMPTES RENDUS CHIMIE, 21, 345, DOI: 10.1016/j.crci.2017.08.006

The catalytic methanolysis of the chemical warfare nerve agents soman, sarin, and VX was investigated by using Cu or Zn complexes. Although VX withstood decontamination, the decomposition yield being around 96%, the soman and sarin deposited on different surfaces were almost fully destroyed under ambient conditions. The catalytic tests performed on a wide range of contaminated surfaces confirm the activity of the investigated catalytic systems, these complexes being suitable, from an economical point of view, for use in the formulation of a possible decomposition kit with military or civilian applicability. (C) 2017 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.

59. Influence of Gd and Pr doping on the properties of ceria: texture, structure, redox behaviour and reactivity in CH4/H2O reactions in the presence of H2S

Authors: Florea, M; Postole, G; Matei-Rutkovska, F; Urda, A; Neatu, F; Massin, L; Gelin, P

Published: MAR 7 2018, CATALYSIS SCIENCE & TECHNOLOGY, 8, 1348, DOI: 10.1039/c7cy02192e

Ceria materials doped by Gd and/or Pr were prepared by a precipitation route and calcined in air at 500 and 900 degrees C. The effects of doping and thermal treatment on the materials' surfaces were studied by X-ray photoelectron and Raman spectroscopies. The redox properties were investigated using temperature-programmed reduction experiments in H-2 and CH4 followed by temperature-programmed oxidation in O-2. The catalytic properties of these materials in CH4/H2O reaction in the absence/presence of H2S were evaluated at 750 degrees C in a large excess of CH4 with respect to H2O. The materials were classified by order of reactivity as follows: CPO > CGPO > CeO2 > CGO, which can be primarily related to the surface area variation. Comparing the activity per m(2) of various samples indicates that the catalytic activity is correlated with the Ce3+ concentration at the surface as measured by XPS. Gd-doped and undoped samples exhibit the highest surface Ce3+ concentration as well as the highest activity in SMR per m(2), while Pr-doped samples are the least active (activity per m(2)) with the lowest surface Ce3+ concentrations. H2S has a sharp promoting effect on the catalytic behavior of ceria-based materials, improving the production of H-2 by almost one order of magnitude.

60. Heavy doping of ceria by wet impregnation: a viable alternative to bulk doping approaches

Authors: Florea, M; Avram, D; Maraloiu, VA; Cojocaru, B; Tiseanu, C

Published: OCT 7 2018, NANOSCALE, 10, 18054, DOI: 10.1039/c8nr03695k

To avoid the deleterious effects of dopant segregation, synthesis methods that facilitate a homogenous dopant distribution in the ceria lattice were employed. Though doping ceria by wet impregnation was also credited to induce a homogeneous solid solution even in the heavy regime (concentration >= 20%, A. Corma, P. Atienzar, H. Garcia and J. Chane-Ching, Nat. Mater., 2004, 3, 394-397), no follow up investigation has been reported. Herein, we investigated ceria nanoparticles (1% Tm-CeO2 and 1% Eu-CeO2) wetimpregnated with trivalent rare-earth (Yb, 20%), bivalent (Ca, 20%) and isovalent (Zr, 30%) metals, followed by annealing in air. Homogeneity of the solid solutions of Yb-impregnated ceria was confirmed by a two-feature characterization toolbox that included X-ray diffraction, Raman spectroscopy, transmission electron microscopy, as well as up-conversion emission as a probe tool. Since the up-conversion emission of Tm was not detectable in the absence of Yb while its efficiency depends on the average distance between Yb and Tm ions, the Yb incorporation and its migration from the surface to the lattice bulk sites in wet-impregnated ceria can be "visualized" and compared with that of the Yb bulk-doped counterpart. The use of Eu luminescence as a local probe confirmed the homogeneity of solid solutions of Ca and Zr-impregnated ceria and also sustained the opposite roles of Ca and Zr as the repeller and the scavenger of oxygen vacancies, respectively. All these results suggested that heavy doping of ceria by wet impregnation with metals with +2, +3 and +4 valencies represent a facile alternative to conventional doping approaches. Therefore, the effects of the amount and the type of metal dopant on the structural properties of CeO2 could be investigated in a more systematic and probably a more reproducible manner, which would significantly increase the potential of ceria in catalysis and other applications.

61. Up-conversion luminescence of Er(Yb)-CeO2: Status and new results

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

Published: JUL 15 2017, JOURNAL OF ALLOYS AND COMPOUNDS, 711, 636, DOI: 10.1016/j.jallcom.2017.04.043

We investigate the down- and up-conversion properties of Er (0.3, 1 and 3%)-CeO2 and Er(1%)Yb(20%)-CeO2 nanoparticles by use of ns pulsed monochromatic excitation. The emission spectra were recorded in the visible to near-infrared range (500-1100 nm) under ultraviolet, visible (490 and 650 nm) and near infrared (790, 971/977 and 1470 nm) up-conversion excitations as well as X-ray excitation. The structural properties were characterized by X-ray diffraction, Raman, Diffuse Reflectance UV/Vis and Diffuse Reflectance Fourier Transform Infrared spectroscopies. The role of CeO2 charge transfer band as a level selective antenna sensitizer, the dopant induced oxygen vacancies and the effect of Er concentration on the overall emission properties are highlighted. The mechanisms involved in the up-conversion emission in Er-CeO2 and Er,Yb-CeO2 are analysed in terms of up-conversion excitation spectra, up-conversion emission decays and evolution of the red to green emission ratio with Er concentration and delay after the laser pulse. Our findings are also discussed in the context of a comprehensive literature survey regarding the actual stage of research on the luminescence of Er and Er,Yb doped CeO2 and their possible applications. (C) 2017 Elsevier B.V. All rights reserved.

62. New ways to use the red mud waste as raw material for inorganic-organic hybrid hydrogels

Authors: Sandu, T; Sarbu, A; Zavoianu, R; Spatarelu, CP; Florea, M; Bradu, C; Mara, EL; Dragut, DV; Alexandrescu, E; Zaharia, A; Radu, AL

Published: DEC 10 2017, , DOI: 10.1016/j.minpro.2017.11.005

63. Self-assembled (Ni/Cu, Ti)-YSZ with potential applications for IT-SOFCs: Catalytic and electrochemical assessment

Authors: Somacescu, S; Navarrete, L; Florea, M; Calderon-Moreno, JM; Serra, JM

Published: JAN 5 2017, , DOI: 10.1016/j.jallcom.2016.08.193

64. Functional layered double hydroxides and their catalytic activity for 1,4-addition of n-octanol to 2-propenonitrile

Authors: Zavoianu, R; Pavel, OD; Cruceanu, A; Florea, M; Birjega, R

Published: SEP 15 2017, APPLIED CLAY SCIENCE, 146, 422, DOI: 10.1016/j.clay.2017.06.030

This contribution concerns the catalytic activity of functional layered double hydroxides (LDHs) for 1,4-addition of n-octanol to 2-propenonitrile aiming to investigate the influence of the organic interlayer anion nature on their physico-chemical and catalytic performances. Two series of functional LDHs, e.g. Mg2.5Al, and Zn2.5Al respectively, were synthesized by co-precipitation at pH 9.5 using a metal nitrates M2+ (NO3)(2)center dot 6H(2)O (M2+ = Mg, Zn), Al(NO3)(3)center dot 9H(2)O solution, an organic acid sodium salt (e.g. sodium dodecyl sulfate (NaDS), sodium laurate (NaL), or sodium stearate (NaS)) and NaOH solution for pH adjustment. XRD, DRIFTS and DR-UV-Vis-NIR characterizations indicated a better intercalation of DS in the interlayer region compared to L or S. The catalytic activity of these solids was related to both their organophilic character and basicity, Mg2.5Al-DS samples, which were more basic, showed a higher activity than Zn2.5Al-DS.

65. Down-/Up-Conversion Emission Enhancement by Li Addition: Improved Crystallization or Local Structure Distortion?

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

Published: JUL 6 2017, JOURNAL OF PHYSICAL CHEMISTRY C, 121, 14284, DOI: 10.1021/acs.jpcc.7b02897

Local symmetry distortion by Li addition is acknowledged as an effective strategy for enhancing the luminescence of lanthanide (Ln) doped into a wide range of lattice hosts. Despite extensive literature, direct evidence that supports Li-induced modification of the local crystal-field at the Ln sites is still missing. Herein, we show that the emission enhancement by Li addition in Ln,Li-Y2O3 is due to improved crystallization and not to local structure distortion. Our approach is based on the premise that any distortion/lowering of the local symmetry would reflect into the alteration of the emission shapes and shortening of the emission decays. To this aim, we have extensively investigated the evolution with Li addition and calcination temperature of down (optical and X-ray induced) and up-conversion (UPC) emission of Ln-Y2O3 measured across the visible to near-infrared range. First, a center to center (corresponding to Ln in the C-2 and S-6/C-3i sites of the cubic Y2O3 lattice) as well as global comparison of the emission properties of Li free and Li codoped Y2O3 are presented by use of Eu, Sm, Tb and Dy as local probes in the visible range. Next, the effect of Li on the up-conversion emission of Er-Y2O3 is analyzed in terms of UPC pathways, emission shape and intensity, decays and excitation spectra. It is concluded that Li addition does not change either the local structure around C-2 or S-6 Ln centers or the relative contribution of these. Moreover, it is found that the effects of Li doping on the emission properties of Ln-Y2O3 are like extending the calcination temperature of Li-free Ln-Y2O3 from 800 degrees C to similar to 1000-1100 degrees C. Additionally, a relatively intense 1500 to 980 nm UPC emission is evidenced for the first time for Er-Y2O3, while a relatively intense "emission around 1500 nm was measured under X-ray excitation. Taken together, our findings highlight the need for revisiting the traditional optimization strategy based on Li modification but also the promise of Er-Y2O3 nanoparticles for optical/X-ray applications in the near-infrared range.

66. Sensors based on mesoporous SnO2-CuWO4 with high selective sensitivity to H2S at low operating temperature

Authors: Stanoiu, A; Simion, CE; Calderon-Moreno, JM; Osiceanu, P; Florea, M; Teodorescu, VS; Somacescu, S

Published: JUN 5 2017, JOURNAL OF HAZARDOUS MATERIALS, 331, 160, DOI: 10.1016/j.jhazmat.2017.02.038

Development of new sensitive materials by different synthesis routes in order to emphasize the sensing properties for hazardous H2S detection is one of a nowadays challenge in the field of gas sensors. In this study we obtained mesoporous SnO2-CuWO4 with selective sensitivity to H2S by an inexpensive synthesis route with low environmental pollution level, using tripropylamine (TPA) as template and polyvinylpyrrolidone (PVP) as dispersant/stabilizer. In order to bring insights about the intrinsic properties, the powders were characterized by means of a variety of complementary techniques such as: X-Ray Diffraction, XRD; Transmission Electron Microscopy, TEM; High Resolution TEM, HRTEM; Raman Spectroscopy, RS; Porosity Analysis by N-2 adsorption/desorption, BET; Scanning Electron Microscopy, SEM and X-ray Photoelectron Spectroscopy, XPS. The sensors were fabricated by powders deposition via screen printing technique onto planar commercial Al2O3 substrates. The sensor signals towards H2S exposure at low operating temperature (100 degrees C) reaches values from 10(5) (for SnWCu600) to 10(6) (for SnWCu800) over the full range of concentrations (5-30 ppm). The recovery processes were induced by a short temperature trigger of 500 degrees C. The selective sensitivity was underlined with respect to the H2S, relative to other potential pollutants and relative humidity (10-70% RH). (C) 2017 Elsevier B.V. All rights reserved.

67. Potential application of Ni and Co stabilized zirconia as oxygen reduction reaction catalyst

Authors: Neatu, F; Trandafir, MM; Marcu, M; Preda, L; Calderon-Moreno, JM; Neatu, S; Somacescu, S; Florea, M

Published: APR 2017, CATALYSIS COMMUNICATIONS, 93, 42, DOI: 10.1016/j.catcom.2016.12.026

A new facile template method for the preparation of Ni, Co doped ZrO2 self-assembled electrocatalysts for oxygen reduction reaction was employed. The effect of the Ni and Co incorporation into ZrO2 lattice on the structural, texturaL surface chemistry and its activity on ORR was emphasized. As X-ray diffraction reveals, the pseudo-cubic lattice of the tetragonal ZrO2 polymorph (t-ZrO2) is stabilized when Ni and Co are co-doping ZrO2. The results indicate that the synergetic effects arisen from the intimate electronic interaction of the mixed oxides present in the lattice of the zirconia phase, i.e. Nil-xCoxO (or NiO and CoO) in NCZ enhance the electrocatalytic activity of the catalyst. (C) 2017 Elsevier B.V. All rights reserved.

68. An adamantane-based COF: stability, adsorption capability, and behaviour as a catalyst and support for Pd and Au for the hydrogenation of nitrostyrene (vol 6, pg 8344, 2016)

Authors: Trandafir, MM; Pop, L; Hadade, ND; Florea, M; Neatu, F; Teodorescu, CM; Duraki, B; van Bokhoven, JA; Grosu, I; Parvulescu, VI; Garcia, H

Published: 2016, CATALYSIS SCIENCE & TECHNOLOGY, 6, 8573, DOI: 10.1039/c6cy90113a

69. Exploring porous nanosilica-TEMPO as heterogeneous aerobic oxidation catalyst: the influence of supported gold clusters

Authors: Shakir, AJ; Florea, M; Culita, DC; Ionita, G; Ghica, C; Stavarache, C; Hanganu, A; Ionita, P

Published: FEB 2016, JOURNAL OF POROUS MATERIALS, 23, 254, DOI: 10.1007/s10934-015-0076-9

TEMPO stable free radical has been supported on porous silica nanoparticles in different ways and the resulted materials have been tested as heterogeneous oxidation catalyst of three benzylic alcohols using air as final oxidant and nitrosonium tetrafluoroborate as cocatalyst. Good to excellent yields were obtained. The catalytic system consists in fact in two coupled cycles, NO/NO2 and TEMPO+/TEMPO, able to convert under mild conditions (room temperature, air, metal and halogen free condition) alcohols into aldehydes or ketones. Under these conditions, supported TEMPO on silica nanoparticles containing gold clusters lowers the efficiency of the catalyst.

70. An adamantane-based COF: stability, adsorption capability, and behaviour as a catalyst and support for Pd and Au for the hydrogenation of nitrostyrene

Authors: Trandafir, MM; Pop, L; Hadade, ND; Florea, M; Neatu, F; Teodorescu, CM; Duraki, B; van Bokhoven, JA; Grosu, I; Parvulescu, VI; Garcia, H

Published: 2016, Catalysis Science & Technology, 6, 8354, DOI: 10.1039/c6cy01631f

A bimodal (micro/mesoporous) COF was synthesized by coupling tetrakis-1,3,5,7-(4'-iodophenyl) adamantane with 4,4'-diethynylbiphenyl following a Sonogashira protocol. The COF preparation strategy led, however, to the incomplete recovery of the palladium catalyst and ICP-OES analysis indicated that around 0.1 wt% palladium remained inside the pores. Noteworthily, the remnant palladium catalyst is still accessible and can be valorised in additional catalytic reactions like the hydrogenation of nitrostyrene. Further deposition of 0.5 wt% active metals (like palladium or gold) enhanced the catalytic activity and tuned the catalyst selectivity with respect to analogous metal catalysts prepared using active carbon as a support. The resulting COF-supported metal NPs are stable and recyclable catalysts. Under normal conditions, this COF is also able to adsorb large amounts of weak electrophilic gases like carbon dioxide.

71. Oxidation of 5-hydroxymethyl furfural to 2,5-diformylfuran in aqueous media over heterogeneous manganese based catalysts

Authors: Neatu, F; Petrea, N; Petre, R; Somoghi, V; Florea, M; Parvulescu, VI

Published: DEC 1 2016, , DOI: 10.1016/j.cattod.2016.03.031

72. Synthesis of Terephthalic Acid by p-Cymene Oxidation using Oxygen: Toward a More Sustainable Production of Bio-Polyethylene Terephthalate

Authors: Neatu, F; Culica, G; Florea, M; Parvulescu, VI; Cavani, F

Published: NOV 9 2016, , DOI: 10.1002/cssc.201600718

73. Time-gated down-/up-conversion emission of Ho-CeO2 and Ho, Yb-CeO2 nanoparticles

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

Published: NOV 2016, , DOI: 10.1016/j.jlumin.2016.07.026

74. Defect induced tunable near infrared emission of Er-CeO2 by heterovalent co-dopants

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

Published: JUL 21 2016, , DOI: 10.1039/c6cp02754g

75. Graphene from Alginate Pyrolysis as a Metal-Free Catalyst for Hydrogenation of Nitro Compounds

Authors: Trandafir, MM; Florea, M; Neatu, F; Primo, A; Parvulescu, VI; Garcia, H

Published: JUL 7 2016, , DOI: 10.1002/cssc.201600197

76. Advances in luminescence of lanthanide doped Y2O3: case of S-6 sites

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

Published: MAY 1 2016, , DOI: 10.1364/OME.6.001635

77. Cross-coupling of p-xylene to 2,2 ',5,5 '-tetramethyl 1,1 '-biphenyl on supported vanadia catalysts

Authors: Mitran, G; Pavel, OD; Florea, M; Parvulescu, VI

Published: MAR 25 2016, , DOI: 10.1016/j.apcata.2016.01.010

78. Hydrogen production from glycerol steam reforming over molybdena-alumina catalysts

Authors: Mitran, G; Pavel, OD; Florea, M; Mieritz, DG; Seo, DK

Published: MAR 5 2016, , DOI: 10.1016/j.catcom.2016.01.029

79. Synthesis of ceria nanopowders by microwave-assisted hydrothermal method for dry reforming of methane

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

Published: JAN 30 2016, , DOI: 10.1016/j.ijhydene.2015.12.097

80. Effect of Mo/Ce ratio in Mo-Ce-Al catalysts on the hydrogen production by steam reforming of glycerol

Authors: Mitran, G; Pavel, OD; Mieritz, DG; Seo, DK; Florea, M

Published: 2016, , DOI: 10.1039/c6cy00999a

81. 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

82. Ni-doped (CeO2-delta)-YSZ mesoarchitectured with nanocrystalline framework: the effect of thermal treatment on structure, surface chemistry and catalytic properties in the partial oxidation of methane (CPOM)

Authors: Somacescu, S; Florea, M; Osiceanu, P; Calderon-Moreno, JM; Ghica, C; Serra, JM

Published: NOV 3 2015, JOURNAL OF NANOPARTICLE RESEARCH, 17, DOI: 10.1007/s11051-015-3206-z

Ni-doped (CeO2-delta)-YSZ (5 mol% Ni oxide, 10 mol% ceria) mesoarchitectures (MA) with nanocrystalline framework have been synthesized by an original, facile and cheap approach based on Triton X100 nonionic surfactant as template and water as solvent at a strong basic pH value. Following the hydrothermal treatment under autogenous pressure (similar to 18 bars), Ni, Ce, Y, and Zr were well ordered as MA with nanocrystalline framework, assuring thermal stability. A comprehensive investigation of structure, texture, morphology, and surface chemistry was performed by means of a variety of complementary techniques (X-Ray Diffraction, XRD; Raman Spectroscopy, RS; Brunauer-Emmett-Teller, BET; Temperature-Programmed Reduction, TPR; Transmission Electron Microscopy, TEM and DF-STEM; X-ray Photoelectron Spectroscopy, XPS; Catalytic activity and selectivity). N-2 sorption measurements highlighted that the mesoporous structure is formed at 600 degrees C and remains stable at 800 degrees C. At 900 degrees C, the MA collapses, favoring the formation of macropores. The XRD and Raman Spectroscopy of all samples showed the presence of a pure, single phase with fluorite-type structure. At 900 degrees C, an increased tetragonal distortion of the cubic lattice was observed. The surface chemistry probed by XPS exhibits a mixture of oxidation states (Ce3+ + Ce4+) with high percentage of Ce3+ valence state similar to 35 % and (Ni3+ and Ni2+) oxidation states induced by the thermal treatment. These nanoparticles assembled into MA show high stability and selectivity over time in catalytic partial oxidation of methane (CPOM). These promising performances suggest an interesting prospect for introduction as anode within IT-SOFC assemblies.

83. Mesostructured vanadia-alumina catalysts for the synthesis of vitamin K-3

Authors: Florea, M; Marin, RS; Palasanu, FM; Neatu, F; Parvulescu, VI

Published: OCT 1 2015, , DOI: 10.1016/j.cattod.2014.12.026

84. Time delay and excitation mode induced tunable red/near-infrared to green emission ratio of Er doped BiOCl

Authors: Avram, D; Florea, M; Tiseanu, I; Tiseanu, C

Published: SEP 9 2015, , DOI: 10.1088/0022-3727/48/35/355501

85. Deoxygenation of oleic acid: Influence of the synthesis route of Pd/mesoporous carbon nanocatalysts onto their activity and selectivity

Authors: Dragu, A; Kinayyigit, S; Garcia-Suarez, EJ; Florea, M; Stepan, E; Velea, S; Tanase, L; Colliere, V; Philippot, K; Granger, P; Parvulescu, VI

Published: SEP 5 2015, , DOI: 10.1016/j.apcata.2015.01.008

86. 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

87. 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

88. 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

89. Evidence of A-B site cooperation in the EuFeO3 perovskite from Eu-151 and Fe-57 Mossbauer spectroscopy, EXAFS, and toluene catalytic oxidation

Authors: Florea, M; Alifanti, M; Kuncser, V; Macovei, D; Apostol, N; Granger, P; Parvulescu, VI

Published: JUL 2014, JOURNAL OF CATALYSIS, 316, 140, DOI: 10.1016/j.jcat.2014.04.016

EuFeO3 perovskite was considered as a case study of the cooperative effects of the rare earth and transition metal elements in the total catalytic oxidation of aromatic hydrocarbons. For this purpose, a EuFeO3 perovskite was prepared using the citrate route. Extensive characterization was performed via ex situ and in situ methods. EXAFS revealed that oxygen vacancies are formed in the nearest neighborhood of Fe and next-nearest neighborhood of Eu. Combining Eu-151 and Fe-57 Mossbauer experiments also suggested local oxygen defects in the proximity of the Eu cations during the reaction, as well as cooperative electron delocalization effects between Eu and Fe. XPS has shown the +3 oxidation state of both Eu and Fe cations and the relatively strong ionicity of the Fe-O chemical bonds, as suggested by the weakened 2p(3/2) satellite in the Fe2p spectrum. A systematic change of this satellite with the A cation in AFeO(3) perovskites was also discussed. The thermal treatment of the catalyst at 623 K, in air or toluene, was accompanied by a partial reduction of Fe and a partial oxidation of Eu, respectively. The interaction between the two elements appeared to be influenced mainly by the temperature and only slightly by the sample environment during further treatments. Catalytic oxidation of toluene on this perovskite led only to the production of carbon dioxide and water with no side-product formation from partial oxidation reactions. All the characterization and catalytic results preferably agree with a Volkenstein mechanism. (C) 2014 Elsevier Inc. All rights reserved.

90. 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

91. 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

92. Comment on "High multi-photon visible upconversion emissions of Er3+ singly doped BiOCl microcrystals: A photon avalanche of Er3+ induced by 980 nm excitation" [Appl. Phys. Lett. 103, 231104 (2013)]

Authors: Tiseanu, C; Florea, M; Cojocaru, B

Published: JUN 9 2014, , DOI: 10.1063/1.4882167

93. Thermal behavior of several stable hydrazyl free radicals and of their parent hydrazines

Authors: Marinescu, M; Zalaru, C; Florea, M; Ionita, P

Published: APR 2014, , DOI: 10.1007/s10973-013-3448-x

94. Heavily impregnated ceria nanoparticles with europium oxide: spectroscopic evidences for homogenous solid solutions and intrinsic structure of Eu3+-oxygen environments

Authors: Avram, D; Rotaru, C; Cojocaru, B; Sanchez-Dominiguez, M; Florea, M; Tiseanu, C

Published: MAR 2014, , DOI: 10.1007/s10853-013-7904-6

95. Structural changes during toluene complete oxidation on supported EuFeO3 monitored by in situ Eu-151 and Fe-57 Mossbauer spectroscopy

Authors: Florea, M; Alifanti, M; Kuncser, V; Parvulescu, VI

Published: JUN 1 2013, CATALYSIS TODAY, 208, 59, DOI: 10.1016/j.cattod.2012.09.035

Pure EuFeO3 and ceria were prepared via a sol-gel citrate route and were calcined at 700 degrees C. Separately, a 20 wt% EuFeO3/CeO2 was prepared via incipient wetness impregnation of calcined ceria with citrate precursors and calcined in the same conditions. SBET, XRD, toluene chemisorption, toluene-TPD and in situ Eu-151 and Fe-57 Mossbauer investigations were performed. All characterization data indicate the formation of a well-dispersed EuFeO3 at the surface of CeO2. During the oxidation of toluene Eu-151 and Fe-57 Mossbauer spectroscopy suggested a cooperative effect of the cations. The catalysts were tested in total oxidation of toluene. In terms of intrinsic activity for toluene combustion, supported catalysts were more active than bulk EuFeO3. All structural changes during operation time were reversible. (C) 2012 Elsevier B.V. All rights reserved.

96. Postsynthetic Modification of a Metal-Organic Framework (MOF) Structure for Enantioselective Catalytic Epoxidation

Authors: Candu, N; Tudorache, M; Florea, M; Ilyes, E; Vasiliu, F; Mercioniu, I; Coman, SM; Haiduc, I; Andruh, M; Parvulescu, VI

Published: MAY 2013, CHEMPLUSCHEM, 78, 450, DOI: 10.1002/cplu.201300076

Postsynthetic modification of [Cu2(mand)2(hmt)] (mand=mandelic acid, hmt=hexamethylenetetramine) with a chiral, dimeric chromium(III)salen complex led to a robust structure. Characterization of this new material showed that it perfectly preserved the textural and structural properties of the parent metalorganic framework (MOF). Although epoxidation of trans-methyl cinnamate with hydrogen peroxide led to copper leaching of 23%, experiments performed with N-methylmorpholine-N-oxide indicated no leaching, even after 72h of exposure. The obtained chiral MOF is an effective catalyst for the enantioselective epoxidation of trans-methyl cinnamate and leads to (2R,3S)-phenylglycidate with a high enantiomeric excess at room temperature.

97. A Robust Metal-Organic Framework Constructed from Alkoxo-Bridged Binuclear Nodes and Hexamethylenetetramine Spacers: Crystal Structure and Sorption Studies

Authors: Ilyes, E; Florea, M; Madalan, AM; Haiduc, I; Parvulescu, VI; Andruh, M

Published: AUG 6 2012, , DOI: 10.1021/ic301139j

98. Benzylation of benzene with benzyl alcohol on zeolite catalysts

Authors: Candu, N; Florea, M; Coman, SM; Parvulescu, VI

Published: FEB 15 2011, , DOI: 10.1016/j.apcata.2010.11.044

99. 1-BUTANOL DEHYDRATION AND DEHYDROGENATION OVER VANADIUM ALUMINIUM OXYNITRIDE CATALYSTS

Authors: Florea, M; Delsarte, S; van Keulen, E; Grange, P

Published: FEB 2011, , DOI:

100. Novel Pd heterogeneous catalysts for cycloisomerisation of acetylenic carboxylic acids

Authors: Neatu, F; Protesescu, L; Florea, M; Parvulescu, VI; Teodorescu, CM; Apostol, N; Toullec, PY; Michelet, V

Published: DEC 2010, GREEN CHEMISTRY, 12, 2149, DOI: 10.1039/c0gc00258e

The Pd-TPPTS complex (TPPTS - trisodium salt of 3,3',3 ''-phosphanetriyl benzenesulfonic acid) and PdCl42- salt heterogenised onto Zn2AlNO3 layered double hydroxide (LDH) using an ion-exchange procedure, have been shown to be efficient green catalysts in the cycloisomerisation reaction of acetylenic carboxylic acids to the corresponding 5-membered heterocycles.

101. Modifications of the Catalytic Activity for Cyanoethylation Induced by the Memory Effect of Mg/Al-Type Modified Hydrotalcites

Authors: Pavel, OD; Birjega, R; Angelescu, E; Zavoianu, R; Florea, M; Mitran, G

Published: APR 2010, , DOI:

102. Epoxidation of cyclohexene with O-2 and isobutyraldehyde catalysed by cobalt modified hydrotalcites

Authors: Angelescu, E; Ionescu, R; Pavel, OD; Zavoianu, R; Birjega, R; Luculescu, CR; Florea, M; Olar, R

Published: JAN 15 2010, , DOI: 10.1016/j.molcata.2009.09.009

103. Total oxidation of toluene on ferrite-type catalysts

Authors: Florea, M; Alifanti, M; Parvulescu, VI; Mihaila-Tarabasanu, D; Diamandescu, L; Feder, M; Negrila, C; Frunza, L

Published: MAR 30 2009, CATALYSIS TODAY, 141, 366, DOI: 10.1016/j.cattod.2008.05.005

Ferrite catalysts were prepared following two routes, i.e. the hydrothermal one and the calcination of an oxide mixture. In the first route sodium hydroxide, ferrous sulfate and the sulfate of the substituting ion (Mn, Ni) were used. The ferrites obtained using this route was NixFe3-xO4 (x = 0.5) and MnxFe3-xO4 (x similar to 0.65). Following the second route were prepared three samples: NiFe2O4, Ni0.5Zn0.5Fe2O4 and MnFe2O4. Two of them contain the corresponding ferrites while the latter is a presintered oxide mixture (Fe2O3-Mn2O3). All the samples were fully characterized using chemical analysis, X-ray fluorescence spectroscopy and EDX, nitrogen adsorption-desorption isotherms at -196 degrees C, X-ray diffraction (XRD), FTIR, scanning electron microscopy and XPS. The catalytic activity evaluation was made using a mixture of 1700 ppm vol. of toluene and air flowing at 100 ml min(-1) raising the temperature up to 600 degrees C in steps of 25 degrees C. Among these systems the sample representing the presintered Fe2O3-Mn2O3 mixture showed the highest activity. (C) 2008 Elsevier B.V. All rights reserved.

104. Local environment of vanadium in V/Al/O-mixed oxide catalyst for propane ammoxidation: Characterization by in situ valence-to-core X-ray emission spectroscopy and X-ray absorption spectroscopy

Authors: Safonova, OV; Florea, M; Bilde, J; Delichere, P; Millet, JMM

Published: NOV 15 2009, , DOI: 10.1016/j.jcat.2009.09.014

105. Transesterification of vegetable oils on basic large mesoporous alumina supported alkaline fluorides-Evidences of the nature of the active site and catalytic performances

Authors: Verziu, M; Florea, M; Simon, S; Simon, V; Filip, P; Parvulescu, VI; Hardacre, C

Published: APR 1 2009, , DOI: 10.1016/j.jcat.2009.01.012

106. The impact of the "memory effect" on the catalytic activity of Mg/Al; Mg,Zn/Al; Mg/Al,Ga hydrotalcite-like compounds used as catalysts for cycloxene epoxidation

Authors: Angelescu, E; Pavel, OD; Birjega, R; Florea, M; Zavoianu, R

Published: JUN 15 2008, , DOI: 10.1016/j.apcata.2007.12.022

107. WO(x)-CeO(2) and WO(x)-Nb(2)O(5) catalysts deactivation during hexane isomerization

Authors: Mamede, AS; Payen, E; Granger, P; Florea, M; Parvulescu, VI

Published: MAY 2008, , DOI: 10.1002/aic.11468

108. Mo-V-M-O (M = Ni, Cu, Zn, Sb, Ta) MIXED METAL OXIDES PREPARED BY SOLID-SOLID REACTIONS FOR OXIDATIVE DEHYDROGENATION OF ISOBUTANE

Authors: Mitran, G; Marcu, IC; Florea, M; Sandulescu, I

Published: MAY 2008, , DOI:

109. Plasma-assisted catalysis total oxidation of trichloroethylene over gold nano-particles embedded in SBA-15 catalysts

Authors: Magureanu, M; Mandache, NB; Hu, JC; Richards, R; Florea, M; Parvulescu, VI

Published: NOV 15 2007, , DOI: 10.1016/j.apcatb.2007.05.030

110. Acylation of different amino derivatives with fatty acids on UL-MFI-type catalysts

Authors: Musteata, M; Musteata, V; Dinu, A; Florea, M; Hoang, VT; Trong-On, D; Kaliaguine, S; Parvulescu, VI

Published: NOV 2007, , DOI: 10.1351/pac200779112059

111. Metal-triflate ionic liquid systems immobilized onto mesoporous MS41 materials as new and efficient catalysts for N-acylation

Authors: Coman, SM; Florea, M; Parvulescu, VI; David, V; Medvedovici, A; De Vos, D; Jacobs, PA; Poncelet, G; Grange, P

Published: JUL 25 2007, , DOI: 10.1016/j.jcat.2007.04.022

112. Ceria-based oxides as supports for LaCoO3 perovskite; catalysts for total oxidation of VOC

Authors: Alifanti, M; Florea, M; Parvulescu, VI

Published: JAN 31 2007, , DOI: 10.1016/j.apcatb.2005.10.037

113. Effect of nitridation on the electronic environment of vanadium in VAlO(N) powder catalysts, used for the ammoxidation of propane

Authors: Silversmit, G; Poelman, H; De Gryse, R; Bras, W; Nikitenko, S; Florea, M; Grange, P; Delsarte, S

Published: DEC 15 2006, , DOI: 10.1016/j.cattod.2006.07.013

114. Understanding the role of nitridation in butan-1-ol and butan-2-ol dehydration mechanisms over oxynitrides

Authors: Delsarte, S; Florea, M; Mauge, F; Grange, P

Published: AUG 1 2006, , DOI: 10.1016/j.cattod.2006.01.033

115. High surface area Mo-V-Te-Nb-O catalysts: Preparation, characterization and catalytic behaviour in ammoxidation of propane

Authors: Florea, M; Mamede, AS; Eloy, P; Parvulescu, VI; Gaigneaux, EM

Published: MAR 15 2006, , DOI: 10.1016/j.cattod.2005.11.080

116. Effect of LaCoO3 perovskite deposition on ceria-based supports on total oxidation of VOC

Authors: Alifanti, M; Florea, M; Cortes-Corberan, V; Endruschat, U; Delmon, B; Parvulescu, VI

Published: MAR 15 2006, , DOI: 10.1016/j.cattod.2005.11.017

117. Preparation of Mo-V-Te-Nb mixed oxides using the template route

Authors: Florea, M; Gaigneaux, EM; Parvulescu, VI

Published: 2006, , DOI: 10.1016/S0167-2991(06)80979-1

118. In situ structural changes during toluene complete oxidation on supported EuCoO3 monitored with Eu-151 Mossbauer spectroscopy

Authors: Alifanti, M; Florea, M; Filotti, G; Kuncser, V; Cortes-Corberan, V; Parvulescu, VI

Published: SEP 30 2006, CATALYSIS TODAY, 117, 336, DOI: 10.1016/j.cattod.2006.05.036

Ceria-zirconia supported (10 and 20 wt.% EuCoO3) versus bulk EuCoO3 perovskite were prepared via citrate decomposition at 700 degrees C and tested for toluene complete oxidation. S-BET, XRD, XPS, H-2-TPD and in situ Eu-151 Mossbauer investigations were performed. Electron delocalization processes around the Eu cations are induced by the reaction, as proved via the evolution of the Mossbauer parameters. All characterization data indicate the formation of a well-dispersed EuCoO3 at the surface of Ce0.9Zr0.1O2 for the 10 wt.% loading and larger crystallite formation for 20 wt.% loading. In terms of intrinsic activity for toluene combustion, supported catalysts were more active than bulk EuCoO3. All structural changes during operation time are reversible. (C) 2006 Elsevier B.V. All rights reserved.

119. Supported perovskites for total oxidation of toluene

Authors: Alifanti, M; Florea, M; Somacescu, S; Parvulescu, VI

Published: SEP 1 2005, , DOI: 10.1016/j.apcatb.2005.02.018

120. Vanadium aluminium oxynitride catalysts for propane ammoxidation reaction - Effect of the V/Al ratio on the structure and catalytic behviour

Authors: Florea, M; Silvy, RP; Grange, P

Published: MAY 26 2005, , DOI: 10.1016/j.apcata.2005.02.032

121. Evidence for the participation of lattice nitrogen from vanadium aluminum oxynitrides in propane ammoxidation

Authors: Olea, M; Florea, M; Sack, I; Silvy, RP; Gaigneaux, EM; Marin, GB; Grange, P

Published: MAY 15 2005, , DOI: 10.1016/j.jcat.2005.02.020

122. Supported Co-based perovskites as catalysts for total oxidation of methane

Authors: Alifanti, M; Blangenois, N; Florea, M; Delmon, B

Published: MAR 8 2005, , DOI: 10.1016/j.apcata.2004.11.005

123. Epoxidation of cyclohexene on silicalite embedded BiOx clusters

Authors: Parvulescu, VI; Florea, M; Gelbard, G; Centeno, MA; Macovei, D; Lemay, G; Kaliaguine, S

Published: 2004, RECENT ADVANCES IN THE SCIENCE AND TECHNOLOGY OF ZEOLITES AND RELATED MATERIALS, PTS A - C, 154, 2654, DOI:

Silicalite embedded BiOx Clusters were prepared both with and without Na using sodium silicate and tetraethylorthosilicate as silicium precursors. Catalysts with 3 and 5 wt% Bi were obtained. The MFl structure was established from XRD, TEM, and N-2 adsorption measurements. No deterioration of the silicalite framework by bismuth was observed. Bi exists as BiOx clusters as evidenced from XPS and EXAFS characterization. These clusters are localized inside the silicalite channels. Py-FTIR measurements indicated that 5wt% Bi led to the formation of strong Lewis acid sites. Epoxidation of cyclohexene was found to depend oil both Bi and Na content. On 3%Bi-ZSM-5 it occurred with rather good conversion and selectivity to epoxide. No visible leaching was evidenced. The catalysts were reused for several runs.

124. Influence of the co-precipitation pH on the physico-chemical and catalytic properties of vanadium aluminum oxide catalyst

Authors: Blangenois, N; Florea, M; Grange, P; Silvy, RP; Chenakin, SP; Bastin, JM; Kruse, N; Barbero, BP; Cadus, L

Published: JUN 10 2004, , DOI: 10.1016/j.apcata.2003.12.008

125. Vanadium aluminium oxynitride catalyst for propane ammoxidation

Authors: Florea, M; Silvy, RP; Grange, P

Published: MAY-JUN 2004, , DOI:

126. Influence of the nitrogen content on butan-1-ol and butan-2-ol dehydration properties of nitrided phosphates

Authors: Delsarte, S; Florea, M; Grange, P

Published: MAY-JUN 2004, , DOI:

127. Influence of the preparation conditions on the physico-chemical and catalytic properties of a vanadium-aluminum oxynitride propane ammoxidation catalyst

Authors: Silvy, RP; Blangenois, N; Florea, M; Grange, P; Cadus, L; Barbero, B

Published: MAY-JUN 2004, , DOI:

128. Influence of the reaction conditions on the activity properties of vanadium-aluminium oxynitride propane ammoxidation catalyst

Authors: Florea, M; Silvy, RP; Grange, P

Published: DEC 8 2003, , DOI: 10.1016/S0926-860X(03)00591-X

129. Propane ammoxidation catalyst based on vanadium-aluminum oxynitride

Authors: Silvy, RP; Florea, M; Blangenois, N; Grange, P

Published: AUG 2003, , DOI: 10.1002/aic.690490830

130. New class of catalysts for the propane ammoxidation process based on vanadium aluminum oxynitrides

Authors: Florea, M; Prady-Silvy, R; Grange, P

Published: APR 2003, , DOI: 10.1023/A:1022857211248

131. Ru-MCM-41 catalysts for diastereoselective hydrogenation

Authors: Florea, M; Sevinci, M; Parvulescu, VI; Lemay, G; Kaliaguine, S

Published: JUN 2001, , DOI: 10.1016/S1387-1811(01)00224-4

132. Low metal loading Ru-MCM-41 stereocontrolled hydrogenation of prostaglandin intermediates

Authors: Coman, S; Florea, M; Cocu, F; Parvulescu, VI; Jacobs, PA; Danumah, C; Kaliaguine, S

Published: NOV 7 1999, , DOI: 10.1039/a907119i

133. Synthesis and Characterization of Graphite Oxide Derived TiO2-Carbon Composites as Potential Electrocatalyst Supports

Authors: Ayyubov, I; Borbath, I; Paszti, Z; Sebestyen, Z; Mihaly, J; Szabo, T; Illes, E; Domjan, A; Florea, M; Radu, D; Kuncser, A; Tompos, A; Talas, E

Published: OCT 2021 , TOPICS IN CATALYSIS, DOI: 10.1007/s11244-021-01513-1

TiO2-C (carbon) hybrid materials are promising electrocatalyst supports because the presence of TiO2 results in enhanced stability. Use of new types of carbonaceous materials such as reduced graphene oxide instead of traditional active carbon provides certain benefits. Although the rutile polymorph of TiO2 seems to have the most beneficial properties in these hybrid materials, the anatase type is more frequent in TiO2-rGO composites, especially in graphite oxide (GO) derived ones, as GO has several properties which may interfere with rutile formation. To explore and evaluate these peculiarities and their influence on the composite formation, we compared TiO2-C systems formulated with GO and Black Pearls (BP) carbon. Various physicochemical methods, such as attenuated total reflection infrared (ATR-IR)-, solid state NMR-, Raman- and X-ray photoelectron spectroscopy, X-ray powder diffraction (XRD), electron microscopy, etc. were used to characterize the samples from the different stages of our multistep sol-gel synthesis. Our experiments demonstrated that utilization of GO is indeed feasible for composite preparation, although its sodium contamination has to be removed during the synthesis. On the other hand, high temperature treatment and/or solvothermal treatment during composite synthesis resulted in decomposition of the functional groups of the GO and the functional properties of the final product were similar in case of both composites. However, Pt/TiO2-GO derived sample showed higher oxygen reduction reaction activity than Pt/TiO2-BP derived one. Based on the decrease of electrochemical surface area, the stability order was the following: Pt/C (commercial) < Pt/TiO2-BP derived C < Pt/TiO2-GO derived C.

134. Structural and Optical Investigations of Ce3+/Mn2+-Doped LaPO4 Phosphors

Authors: Aitmellal, O; Oufni, L; Messous, MY; Neatu, F; Florea, M; Neatu, S; Rostas, AM; Secu, M

Published: , JOURNAL OF ELECTRONIC MATERIALS, DOI: 10.1007/s11664-020-08678-7

135. A green way for pyruvic acid synthesis from biomass-derived L-malic acid on tetrahedral versus octahedral cobalt sites/hematite

Authors: Mitran, G; Urda, A; Pavel, OD; Neatu, S; Florea, M; Neatu, F

Published: , BIOMASS CONVERSION AND BIOREFINERY, DOI:

136. Synthesis and Characterization of Graphite Oxide Derived TiO2-Carbon Composites as Potential Electrocatalyst Supports

Authors: Ayyubov, I; Borbath, I; Paszti, Z; Sebestyen, Z; Mihaly, J; Szabo, T; Illes, E; Domjan, A; Florea, M; Radu, D; Kuncser, A; Tompos, A; Talas, E

Published: , TOPICS IN CATALYSIS, DOI:

137. Applications of MAX phases and MXenes as catalysts

Authors: Chirica, IM; Mirea, AG; Neatu, S; Florea, M; Barsoum, MW; Neatu, F

Published: , JOURNAL OF MATERIALS CHEMISTRY A, DOI: 10.1039/d1ta04097a

138. Structural properties and near-infrared light from Ce3+/Nd3+-co-doped LaPO4 nanophosphors for solar cell applications

Authors: AitMellal, O; Oufni, L; Messous, MY; Tahri, M; Neatu, S; Florea, M; Neatu, F; Secu, M

Published: , JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS, DOI:

Dr. Mihaela FLOREA

Scientific Researcher I

Education

Positions

Awards

Research interests

Expertize

Books

Patents

Projects

1. 2D metallic carbide as active and selective catalysts for direct oxidation of CH4

2. Holistic design of fuel cell electrocatalysts for the least power applications

3. New approaches for the synthesis of hybrid organic-inorganic perovskit (HOIP)-type materials with possible ferroelectric properties for photovoltaic applications

Publications

1. A comparative overview of MXenes and metal oxides as cocatalysts in clean energy production through photocatalysis

2. Partial replacement of Pb2+ in MAPbI2.6Cl0.4 perovskite films and their photovoltaic performance

3. Iron-doped Co3O4 catalysts prepared by a surfactant-assisted method as effective catalysts for malic acid oxidative decarboxylation

4. Partial replacement of Pb2+ in MAPbI(2.6)Cl(0.4) perovskite films and their photovoltaic performance

5. Photo-stable, 1D-nanofilaments TiO2-based lepidocrocite for photocatalytic hydrogen production in water-methanol mixtures

6. Mesoporous Composite Bioactive Compound Delivery System for Wound-Healing Processes

7. Design of electrocatalysts with reduced Pt content supported on mesoporous NiWO4 and NiWO4-graphene nanoplatelets composite for oxygen reduction and hydrogen oxidation in acidic medium

8. Influence of Ferroelectric Filler Size and Clustering on the Electrical Properties of (Ag-BaTiO3)-PVDF Sub-Percolative Hybrid Composites

9. Aminocoumarin derivatives grafted on graphene oxide - new antimicrobial agents to combat the resistance of Mycobacterium tuberculosis and ESKAPE pathogens

10. A comparative overview of MXenes and metal oxides as cocatalysts in clean energy production through photocatalysis

11. Influence of Ferroelectric Filler Size and Clustering on the Electrical Properties of (Ag-BaTiO3)-PVDF Sub-Percolative Hybrid Composites

12. A comparative overview of MXenes and metal oxides as cocatalysts in clean energy production through photocatalysis

13. Structural properties and near-infrared light from Ce3+/Nd3+-co-doped LaPO4 nanophosphors for solar cell applications

14. Tuning the acidity by addition of transition metal to Mn modified hollow silica spheres and their catalytic activity in ethanol dehydration to ethylene

15. A green way for pyruvic acid synthesis from biomass-derived L-malic acid on tetrahedral versus octahedral cobalt sites/hematite

16. Structural properties and near-infrared light from Ce3+/Nd3+-co-doped LaPO4 nanophosphors for solar cell applications

17. Green Epoxidation of Olefins with ZnxAl/MgxAl-LDH Compounds: Influence of the Chemical Composition

18. Electrocatalytic Properties of Mixed-Oxide-Containing Composite-Supported Platinum for Polymer Electrolyte Membrane (PEM) Fuel Cells

19. Increasing Permittivity and Mechanical Harvesting Response of PVDF-Based Flexible Composites by Using Ag Nanoparticles onto BaTiO3 Nanofillers

20. Potassium-containing triple-cation mixed-halide perovskite materials: Toward efficient and stable solar cells

21. Investigation of Opto-Electronic Properties and Stability of Mixed-Cation Mixed-Halide Perovskite Materials with Machine-Learning Implementation

22. Enhancing stability of hybrid perovskite solar cells by imidazolium incorporation

23. NiO/Sr doped Ce(0.85)Pr0.10 Er0.05O(2-delta) mesoarchitectured catalyst for partial oxidation of CH4 and anode fueled by H-2

24. Comparative investigation of structural, EPR, optical and photoluminescence properties of nanostructured LaPO4:Ce/RE/Me and LaPO4:Yb/Er phosphors prepared by co-precipitation method

25. Structural Details of BaTiO3 Nano-Powders Deduced from the Anisotropic XRD Peak Broadening

26. Recent progress in electrocatalysts and electrodes for portable fuel cells

27. Structural and Optical Investigations of Ce3+/Mn2+-Doped LaPO4 Phosphors

28. Carbon-Coated SiO2 Composites as Promising Anode Material for Li-Ion Batteries

29. Applications of MAX phases and MXenes as catalysts

30. NiO / Sr doped Ce(0.85)Pr0.10 Er0.05O(2-delta) mesoarchitectured catalyst for partial oxidation of CH4 and anode fueled by H-2

31. CuWO4 with CuO and Cu(OH)(2) Native Surface Layers for H2S Detection under in-Field Conditions

32. Degenerated TiO(2)Semiconductor Modified with Ni and Zn as Efficient Photocatalysts for the Water Splitting Reaction

33. Degenerated TiO2 Semiconductor Modified with Ni and Zn as Efficient Photocatalysts for the Water Splitting Reaction

34. Influence of doping the inorganic cation with Eu or Sb on the properties of perovskite films

35. CeO2:Mn3O4 Catalytic Micro-Converters Tuned for CH4 Detection Based on Catalytic Combustion under Real Operating Conditions

36. Crown-ether functionalized graphene oxide for metal ions sequestration

37. Undoped SnO2 as a Support for Ni Species to Boost Oxygen Generation through Alkaline Water Electrolysis

38. Highly Active Transition Metal-Promoted CuCeMgAlO Mixed Oxide Catalysts Obtained from Multicationic LDH Precursors for the Total Oxidation of Methane

39. Exploring the effect of aliovalent substitution of Pb2+ by Eu3+ on structural, morphological and optical properties of CH3NH3PbI3 perovskite films

40. Highly Efficient Ultralow Pd Loading Supported on MAX Phases for Chemoselective Hydrogenation

41. Reticulated Mesoporous TiO2 Scaffold, Fabricated by Spray Coating, for Large-Area Perovskite Solar Cells

42. Methane Combustion Using Pd Deposited on CeOx-MnOx/La-Al2O3 Pellistors

43. VAlPOs as Efficient Catalysts for Glycerol Conversion to Methanol

44. Bulk Versus Surface Modification of Alumina with Mn and Ce Based Oxides for CH4 Catalytic Combustion

45. Next frontiers in cleaner synthesis: 3D printed graphene-supported CeZrLa mixed -oxide nanocatalyst for CO2 utilisation and direct propylene carbonate production

46. Bimodal mesoporous NiO/CeO2-delta-YSZ with enhanced carbon tolerance in catalytic partial oxidation of methane-Potential IT-SOFCs anode

47. Coordination polymers and a dinuclear complex constructed from zinc(II) ions and fluorescein: iodine adsorption and optical properties

48. Behavior of Molybdenum-Vanadium Mixed Oxides in Selective Oxidation and Disproportionation of Toluene

49. La0.75Sr0.25XO3 (X = Fe, Mn or Cr) with coking tolerance for CH4/H2O reaction: effect of H2S on catalytic performance

50. The hysteresis-free behavior of perovskite solar cells from the perspective of the measurement conditions

51. Highly -sensitive near infrared luminescent nanothermometers based on binary mixture

52. Imaging dopant distribution across complete phase transformation by TEM and upconversion emission

53. Selective catalytic oxidation reaction of p-xylene on manganese-iron mixed oxide materials

54. Near infrared emission properties of Er doped cubic sesquioxides in the second/third biological windows

55. Alternative valorization of red mud waste as functional materials with catalytic activity for sulfide oxidation in wastewater

56. Doped ceria prepared by precipitation route for steam reforming of methane

57. Thermal behaviour of sym-octahydroacridines and their corresponding N(10)-oxides

58. The Cu- and Zn-complex-catalyzed methanolysis of the chemical warfare nerve agents soman, sarin, and VX

59. Influence of Gd and Pr doping on the properties of ceria: texture, structure, redox behaviour and reactivity in CH4/H2O reactions in the presence of H2S

60. Heavy doping of ceria by wet impregnation: a viable alternative to bulk doping approaches

61. Up-conversion luminescence of Er(Yb)-CeO2: Status and new results

62. New ways to use the red mud waste as raw material for inorganic-organic hybrid hydrogels

63. Self-assembled (Ni/Cu, Ti)-YSZ with potential applications for IT-SOFCs: Catalytic and electrochemical assessment

64. Functional layered double hydroxides and their catalytic activity for 1,4-addition of n-octanol to 2-propenonitrile

65. Down-/Up-Conversion Emission Enhancement by Li Addition: Improved Crystallization or Local Structure Distortion?

66. Sensors based on mesoporous SnO2-CuWO4 with high selective sensitivity to H2S at low operating temperature

2. Partial replacement of Pb²⁺ in MAPbI_2.6Cl_0.4 perovskite films and their photovoltaic performance

3. Iron-doped Co₃O₄ catalysts prepared by a surfactant-assisted method as effective catalysts for malic acid oxidative decarboxylation