National Institute Of Materials Physics - Romania

Publications

5714 articles found

2051. Covalent Functionalization of Graphene Oxide with Cisplatin

Authors: Ciobotaru, CC; Damian, CM; Matei, E; Iovu, H

Published: MAR 2014, MATERIALE PLASTICE, 51, 80, DOI:

The objective of this study was to obtain graphene oxide starting from graphite and to covalently functionalize this nanomaterial with Cisplatin. The presence of the drug was pointed out using different methods like FTIR Spectroscopy, X-Ray Photoelectron Spectroscopy (XPS), Thermogravimetric analysis (TGA), RAMAN Spectroscopy, X-Ray Diffraction and Scanning electron microscopy (SEM).

2052. Cell Adhesion Response on Femtosecond Laser Initiated Liquid Assisted Silicon Surface

Authors: Ulmeanu, M; Sima, LE; Ursescu, D; Enculescu, M; Bazan, X; Quintana, I

Published: MAR 2014, CURRENT TOPICS IN MEDICINAL CHEMISTRY, 14, 629, DOI: 10.2174/1568026614666140118204946

Silicon substrates were irradiated at normal incidence with a femtosecond Ti:sapphire laser (Quatronix, 90 fs pulse duration, 1 kHz repetition rate, M-2 similar to 1.2, maximum energy peak 350 mJ) operating at a wavelength of 400 nm and focused via a microscope objective (Newport; UV Objective Model, 37x 0.11 N.A.). The laser scanning was assisted by liquids precursors media such as methanol and 1,1,2-trichlorotrifluoroethane. By altering the processing parameters, such as incident laser energy, scanning speed, and different irradiation media, various surface structures were produced on areas with 1 mm 2 dimensions. We analyzed the dependence of the surface morphology on laser pulse energy, scanning speed and irradiation media. Well ordered areas are developed without imposing any boundary conditions for the capillary waves that coarsens the ripple pattern. To assess biomaterial-driven cell adhesion response we investigated actin filaments organization and cell morphological changes following growth onto processed silicon substrates. Our study of bone cell progenitor interaction with laser nanoprocessed silicon lines has shown that cells anchor mainly to contact points along the nanostructured surface. Consequently, actin filaments are stretched towards the 15 mu m wide parallel lines increasing lateral cell spreading and changing the bipolar shape of mesenchymal stem cells.

2053. Synthesis and characterisation of Ni(II), Cu(II), and Zn(II) complexes with an acyclic Mannich base functionalised with thioglycolate moiety

Authors: Dumbrava, A; Olar, R; Badea, M; Grecu, MN; Patrascu, F; Marutescu, L; Stanica, N

Published: MAR 2014, JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY, 115, 2455, DOI: 10.1007/s10973-013-3437-0

New complexes ML(CNS)center dot nH(2)O [M = Ni, n = 0.5; M = Cu, n = 4.5; M = Zn, n = 0.5, HL: 6-mercapto-(1,4,8,11-tetraazaundecanyl)-6-carboxylic acid)] have been synthesised, chemical analysed, and characterised by different spectroscopic techniques (IR, UV-Vis-NIR, H-1 NMR, EPR, ESI-MS), and magnetic measurements. Based on the IR spectra a dinuclear structure with the 1,3-CSN coordination was proposed for Ni(II) and Cu(II) complexes. The dinuclear structure of Cu(II) complex is also consistent with both magnetic behaviour and EPR spectrum. According to TG, DTG and DTA curves the thermal transformations are complex processes, including dehydration, Mannich base oxidative degradation and thiocyanate decomposition. The final product of decomposition is the most stable metallic oxide, as XRD data indicates. The new complexes were also screened for their microbicidal and antibiofilm properties.

2054. 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

2055. Nonlinear features of surface-enhanced Raman scattering revealed under non-resonant and resonant optical excitation

Authors: Baibarac, M; Baltog, I; Mihut, L; Matea, A; Lefrant, S

Published: MAR 2014, JOURNAL OF OPTICS, 16, DOI: 10.1088/2040-8978/16/3/035003

By performing comparative Raman studies on nanometric thin films (9.5, 39, 88 and 185 nm) of copper phthalocyanine (CuPc) deposited on glass, Au and Ag supports, we demonstrate that the mechanism of the surface-enhanced Raman scattering (SERS) generated on Au and Ag substrates differs in the Stokes and anti-Stokes Raman branches depending on whether non-resonant (515.5 nm) or resonant (647.1 nm) optical excitation is applied. The evaluation of the SERS effect via the I-aS/I-S ratio reveals that this ratio is smaller or larger than that predicted by the Boltzmann law for non-resonant or resonant optical excitation, respectively. In the former case, the enhancement of the Stokes Raman emission is similar to a stimulated Raman process resulting from the plasmon coupling associated with the incident excitation light and spontaneous Stokes Raman emission. For the latter case, the amplification of the anti-Stokes Raman emission results from a wave-mixing process reminiscent of a single-beam CARS effect.

2056. A Simple Approach for the Magnetic Relaxation in Systems of Weakly-Interacting, Dispersive Nanoparticles in Applied Magnetic Field

Authors: Miu, DN; Sima, C; Jinga, SI; Vasile, BS; Miu, L

Published: MAR 2014, JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM, 27, 785, DOI: 10.1007/s10948-013-2345-7

We investigated the magnetic relaxation of weakly interacting, dispersive, single domain Fe nanoparticles in Fe/Al2O3 composites prepared by sequential pulsed laser deposition on (100) Si substrates. The external magnetic field was oriented parallel to the substrate and applied in zero-field cooling conditions. It was found that the relaxation of the irreversible magnetic moment m (irr) is similar to the well-known vortex-creep process in disordered superconductors with poor supercurrent redistribution across the sample, leading to a power-law dependence of m (irr)(t), with a well-defined time t exponent.

2057. Antifungal activity of Ag:hydroxyapatite thin films synthesized by pulsed laser deposition on Ti and Ti modified by TiO2 nanotubes substrates

Authors: Erakovic, S; Jankovic, A; Ristoscu, C; Duta, L; Serban, N; Visan, A; Mihailescu, IN; Stan, GE; Socol, M; Iordache, O; Dumitrescu, I; Luculescu, CR; Janackovic, D; Miskovic-Stankovic, V

Published: FEB 28 2014, APPLIED SURFACE SCIENCE, 293, 45, DOI: 10.1016/j.apsusc.2013.12.029

Hydroxyapatite (HA) is a widely used biomaterial for implant thin films, largely recognized for its excellent capability to chemically bond to hard tissue inducing the osteogenesis without immune response from human tissues. Nowadays, intense research efforts are focused on development of antimicrobial HA doped thin films. In particular, HA doped with Ag (Ag:HA) is expected to inhibit the attachment of microbes and contamination of metallic implant surface. We herewith report on nano-sized HA and Ag:HA thin films synthesized by pulsed laser deposition on pure Ti and Ti modified with 100 nm diameter TiO2 nanotubes (fabricated by anodization of Ti plates) substrates. The HA-based thin films were characterized by SEM, AFM, EDS, FUR, and XRD. The cytotoxic activity was tested with HEp2 cells against controls. The antifungal efficiency of the deposited layers was tested against the Candida albicans and Aspergillus niger strains. The Ti substrates modified with TiO2 nanotubes covered with Ag:HA thin films showed the highest antifungal activity. (C) 2013 Elsevier B.V. All rights reserved.

2058. Nanomechanical characterization of bioglass films synthesized by magnetron sputtering

Authors: Popa, AC; Marques, VMF; Stan, GE; Husanu, MA; Galca, AC; Ghica, C; Tulyaganov, DU; Lemos, AF; Ferreira, JMF

Published: FEB 28 2014, THIN SOLID FILMS, 553, 172, DOI: 10.1016/j.tsf.2013.10.104

Bioactive glasses are osteoproductive-type inorganic materials possessing the highest indices of bioactivity in both bulk and thin film forms. The prerequisites for reliable implant-type coatings are both their biological and mechanical performances. Whilst the bioglass films' structural, chemical and biological properties have been studied extensively, information about their mechanical performance is scarce. Here, transmission electron microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, nanoindentation and pull-out measurements were employed to assess the morphological, chemical, structural and mechanical properties of the bioglass films deposited onto Ti substrates by radio-frequency magnetron sputtering (RF-MS). The biological safety of the thin bioglass films was evaluated preliminarily in vitro by investigating the adherence, proliferation and cytotoxicity of fibroblast cells cultivated on their surface. Our study emphasize the versatility of RF-MS, showing how bioglass films' features such as composition, structure, bonding strength, hardness, elastic modulus and biological response can be conveniently adapted by tuning the RF-MS working conditions, and therefore demonstrating the unexplored potential of this deposition technique for preparing quality biomimetic glass coatings. (C) 2013 Elsevier B. V. All rights reserved.

2059. Polarization-Control of the Potential Barrier at the Electrode Interfaces in Epitaxial Ferroelectric Thin Films

Authors: Pintilie, I; Teodorescu, CM; Ghica, C; Chirila, C; Boni, AG; Hrib, L; Pasuk, I; Negrea, R; Apostol, N; Pintilie, L

Published: FEB 26 2014, ACS APPLIED MATERIALS & INTERFACES, 6, 2939, DOI: 10.1021/am405508k

Electrode interface is a key element in controlling the macroscopic electrical properties of the ferroelectric capacitors based on thin films. In the case of epitaxial ferroelectrics, the electrode interface is essential in controlling the leakage current and the polarization switching, two important elements in the read/write processes of nonvolatile memories. However, the relation between the polarization bound charges and the electronic properties of the electrode interfaces is not yet well understood. Here we show that polarization charges are controlling the height of the potential barriers at the electrode interfaces in the case of Pb(Zr,Ti)O-3 and BaTiO3 epitaxial films. The results suggest that the height is set to a value allowing rapid compensation of the depolarization field during the polarization switching, being almost independent of the metals used for electrodes. This general behavior open a new perspective in engineering interface properties and designing new devices based on epitaxial ferroelectrics.

2060. Synthesis, structural characterization and dielectric properties of Nb doped BaTiO3/SiO2 core-shell heterostructure

Authors: Cernea, M; Vasile, BS; Boni, A; Iuga, A

Published: FEB 25 2014, JOURNAL OF ALLOYS AND COMPOUNDS, 587, 559, DOI: 10.1016/j.jallcom.2013.10.228

Perovskite complex ceramic oxides, BaTiO3 doped with 0.5 mol% Nb2O5 and then nanocoated with SiO2 (abbreviated as BT-Nb-0.005/SiO2) was successful prepared using conventional sol-gel processing. Phase composition, particle morphology, structure, and electric properties of BT-Nb-0.005 core and BT-Nb-0.005/SiO2 core-shell were examined and compared, using X-ray diffraction, transmission electron microscopy and, dielectric and ferroelectric measurements. Core-shell composite with well-defined perovskite tetragonal phase of BaTiO3 was achieved. Furthermore, single crystalline BT-Nb-0.005/SiO2 core-nanoshell heterostructure with similar to 34 nm shell thick was prepared, which is a novelty in ferroelectrics field. The ferroelectric quality of BT-Nb-0.005 has suffered an alteration when the (BT-Nb-0.005)/SiO2 core-shell heterostructure was realized. One-dimensional BT-Nb-0.005/SiO2 core-shell heterostructure exhibits an improvement of dielectric losses and a decrease of dielectric constant, compared to uncoated BT-Nb-0.005. The (BT-Nb-0.005)/SiO2 core-shell material could be interesting for application in the composite capacitors. (C) 2013 Elsevier B.V. All rights reserved.