National Institute Of Materials Physics - Romania

The purpose of this study was to investigate the effectiveness in photodynamic therapy of iron oxide nanoparticles (gamma-Fe2O3 NPs), synthesized by laser pyrolysis technique, functionalized with 5,10,15,20-(Tetra-4-sulfonatophenyl) porphyrin tetraammonium (TPPS) on human cutaneous melanoma cells, after only 1 min blue light exposure. The efficiency of porphyrin loading on the iron oxide nanocarriers was estimated by using absorption and FTIR spectroscopy. The singlet oxygen yield was determined via transient characteristics of singlet oxygen phosphorescence at 1270 nm both for porphyrin functionalized nanoparticles and rose bengal used as standard. The irradiation was performed with a LED (405 nm, 1 mW/cm(2)) for 1 min after melanoma cells were treated with TPPS functionalized iron oxide nanoparticles (gamma-Fe2O3 NPs_TPPS) and incubated for 24 h. Biological tests revealed a high anticancer effect of gamma-Fe2O3 NPs_TPPS complexes indi-cated by the inhibition of tumor cell proliferation, reduction of cell adhesion, and induction of cell death through ROS generated by TPPS under light exposure. The biological assays were combined with the pharmacokinetic prediction of the porphyrin.

Plasmonic nanostructures based on AuAg nanoalloys were fabricated by thermal annealing of metallic films in an argon atmosphere. The nanoalloys were chosen because they can extend the wavelength range in which plasmon resonance occurs and thus allow the design of plasmonic platforms with the desired parameters. The influence of initial fabrication parameters and experimental conditions on the formation of nanostructures was investigated. For the surface morphology studies, chemical composition analysis and nanograin structure, Scanning Electron Microscopy (SEM), X-Ray Photoelectron Spectroscopy (XPS), Energy Dispersive X-Ray Spectroscopy (EDS) and High-Resolution Transmission Electron Microscopy (HR TEM) measurements were performed. The position of the resonance band was successfully tuned in the 100 nm range. The EDS together with the XPS analysis confirmed the formation of an alloy with the aspect ratio of individual metals in a single nanoisland similar to the ratio of the thicknesses of the initially sputtered layers. The experimental research was complemented by the neural network model, which enables the calculation of the absorbance peak depending on the thickness of Au and Ag layers and the annealing time. The proposed model of machine learning makes it possible to fine-tune the desired position of the plasmon resonance.

The dependencies of the BiOi defect concentration on doping, irradiation fluence and particle type in p-type silicon diodes have been investigated. We evidenced that large data scattering occurs for fluences above 10(12) 1 MeV neutrons/cm(2), becoming significant larger for higher fluences. We show that the BiOi defect is metastable, with two configurations A and B, of which only A is detected by Deep Level Transient Spectroscopy and Thermally Stimulated Currents techniques. The defect' electrical activity is influenced by the inherent variations in ambient and procedural experimental conditions, resulting not only in a large scattering of the results coming from the same type of measurement but making correlation between different types of experiments difficult. It is evidenced that the variations in [BiOiA] are triggered by subjecting the samples to an excess of carriers, by either heating or an inherent short exposure to ambient light when manipulating the samples prior to experiments. For the samples investigated in this work both, the [BiOiA] as determined from electrical spectroscopic measurements and the full depletion voltage as measured from Current-Voltage characteristics reach a steady state in similar to 7h. Any electrical measurement performed before will give a different result. The bi-stable behavior of the BiOi defect fully accounts for these variations.

Zirconia- and hafnia-based thin films have attracted tremendous attention in the past decade because of their unexpected ferroelectric behavior at the nanoscale, which enables the downscaling of ferroelectric devices. The present work reports an unprecedented ferroelectric rhombohedral phase of ZrO2 that can be achieved in thin films grown directly on (111)-Nb:SrTiO3 substrates by ion-beam sputtering. Structural and ferroelectric characterizations reveal (111)-oriented ZrO2 films under epitaxial compressive strain exhibiting switchable ferroelectric polarization of about 20.2 mu C/cm(2) with a coercive field of 1.5 MV/cm. Moreover, the time-dependent polarization reversal characteristics of Nb:SrTiO3/ZrO2/Au film capacitors exhibit typical bell-shaped curve features associated with the ferroelectric domain reversal and agree well with the nucleation limited switching (NLS) model. The polarization-electric field hysteresis loops point to an activation field comparable to the coercive field. Interestingly, the studied films show ferroelectric behavior per se, without the need to apply the wake-up cycle found in the orthorhombic phase of ZrO2. Overall, the rhombohedral ferroelectric ZrO2 films present technological advantages over the previously studied zirconia- and hafnia-based thin films and may be attractive for nanoscale ferroelectric devices.

Amino-derivatized lignocomposite (ADL-composite) has been designed as an artificial lignin polymer (P1) of monolignol (coniferyl alcohol, CA) enhanced by aniline insertion (P2). The derivatized lignopolymeric (P2) layer covered the surface of a methacrylate particles (SC2/SC6) functionalized previously with amino phenolic crosslinker (p-phenylenediamine (p-Ph-2-NH2) or p-amino-2-hydroxybenzoic acid (p-NH2-SalA)). One-pot biocatalytic approach allowed to combine the preparation of the polymeric materials and also its attachment on the particles surface. Thus, the monolignol (CA) will be oxi-copolymerized together with aniline on the amino prefunctionalized support surface. The oxidation process was performed using H2O2 reagent and catalyzed by peroxidase enzyme (horseradish peroxidase, HRP). The biocatalytic process was evaluated in term of aromatic monomers (CA and aniline) conversion. The chemical structure and properties of the resulted ADL-composites were investigated using specific techniques (e.g. FTIR, TPD, TGA, static contact angle, elemental analysis, and gel permeation chromatography). Attachment of P1/P2 polymer on the particles improved the hydrophobicity and also the basicity of the composite surface. Lipase enzyme was immobilized on the ADL-composites for testing the applicability of ADL-composites for biocatalyst preparation. SEM analysis allowed to notice the modification of ADL-composites surface after enzyme immobilization. Immobilized lipase exhibited better activity compared with free lipase demonstrating the efficiency of ADL-composite as support for enzyme immobilization.

Novel complexes of type [Cu(N-N)(dmtp)(2)(OH2)](ClO4)(2)& BULL;dmtp ((1) N-N: 2,2 & PRIME;-bipyridine; (2) L: 1,10-phenantroline and dmtp: 5,7-dimethyl-1,2,4-triazolo[1,5-a]pyrimidine) were designed in order to obtain biologically active compounds. Complexes were characterized as mononuclear species that crystallized in the space group P-1 of the triclinic system with a square pyramidal geometry around the copper (II). In addition to the antiproliferative effect on murine melanoma B16 cells, complex (1) exhibited low toxicity on normal BJ cells and did not affect membrane integrity. Complex (2) proved to be a more potent antimicrobial in comparison with (1), but both compounds were more active in comparison with dmtp-both against planktonic cells and biofilms. A stronger antimicrobial and antibiofilm effect was noticed against the Gram-positive strains, including methicillin-resistant Staphylococcus aureus (MRSA). Both electron paramagnetic resonance (EPR) and Saccharomyces cerevisiae studies indicated that the complexes were scavengers rather than reactive oxygen species promoters. Their DNA intercalating capacity was evidenced by modifications in both absorption and fluorescence spectra. Furthermore, both complexes exhibited nuclease-like activity, which increased in the presence of hydrogen peroxide.

The chemical precipitation was used to obtain carbon fibers (CF) with surface modified by magnetite particles (Fe3O4). Processing was carried out by employing up to three subsequent coating stages of ultrasonic treatments. After each sonication stage, the coating was 17, 33, and 47 wt. % of the total weight of the modified fibers. Raman spectroscopy indicates the presence in the coating of a mixture of iron II and III states. As-decorated fibers were used to fabricate composites with an epoxy resin (ED-20) matrix cured with PEPA. The quantity of the carbon fiber filler was of 1, 3, and 6 wt %. At room temperature, the saturation magnetization of the soft magnetic samples was 0.37, 0.83, and 1.72 emu/g for the indicated compositions. Carbon fiber reinforced polymer materials with extra functions such as magnetic in this case, are expected to be useful in applications from the power and energy industries.

Rare-earth doped oxyfluoride glass ceramics represent a new generation of tailorable optical materials with high potential for optical-related applications such as optical amplifiers, optical waveguides, and white LEDs. Their key features are related to the high transparency and remarkable luminescence properties, while keeping the thermal and chemical advantages of oxide glasses. Sol-gel chemistry offers a flexible synthesis approach with several advantages, such as lower processing temperature, the ability to control the purity and homogeneity of the final materials on a molecular level, and the large compositional flexibility. The review will be focused on optical properties of sol-gel derived nano-glass ceramics related to the RE-doped luminescent nanocrystals (fluorides, chlorides, oxychlorides, etc.) such as photoluminescence, up-conversion luminescence, thermoluminescence and how these properties are influenced by their specific processing, mostly focusing on the findings from our group and similar ones in the literature, along with a discussion of perspectives, potential challenges, and future development directions.

Alloys possessing nominal compositions Mn53Al45C2 and Mn52Al46C2 were prepared by the melt spinning method and were subjected to complex structural, morphological and magnetic investigations. As these alloys can exhibit tetragonal L1(0)-type and tau phase, they have good potential as rare earth (RE)-free magnets. It is, therefore, important to monitor the epsilon-tau phase transformation and the stability and the magnetic features of the tetragonal phase in an entire temperature interval. By using synchrotron X-ray diffraction, it has been proven that the epsilon-tau phase transformation occurs gradually, with the tau phase becoming predominant only after 450 & DEG;C. Moreover, this phase has been proven to be quite stable without any grain growth even at the highest temperature investigated at 800 & DEG;C. Low temperature behavior was thoroughly investigated by using a complex combination of major and minor hysteresis loops combined with the zero field cooled-field cooled magnetization protocols (ZFC-FC). Two different regimes, blocking and superparamagnetic, were documented. A spin reorientation transition was proven to occur at 55 K while a maximum magnetization observed in ZFC-FC curves proved that at about 75 K, a transition from ferro to superparamagnetic state occurs. The existence of a blocking regime below 55 K that is characteristic to nanogranular systems with superparamagnetic behavior has shown further development towards obtaining RE-free magnets.

In order to prove the usefulness of having a structurally disordered precursor to the formation of FePt L1(0) phase and to facilitate the co-existence of exchange coupled hard and soft magnetic phases with optimized magnetic properties in various conditions of annealing, a Fe-Pt-Zr-B melt spun alloy has been synthesized and detailed structural and magnetic investigations have been undertaken to probe its phase evolution during annealing. The dynamics of formation of the hard magnetic L1(0) phase during the gradual disorder-order phase transformation has been monitored by using a complex combination of X-ray diffraction methods and Fe-57 Mossbauer spectroscopy methods, over a wide range of annealing temperatures. Multiple phases co-existing in the annealed sample microstructures, observed in XRD, have been reconfirmed by the Mossbauer spectra analysis and, moreover, accurate quantitative data have been acquired in what concerns the relative abundance of each of the observed crystalline phases in every stage of annealing. It is shown that the formation of the hard magnetic phase, emerging from the chemically disordered precursor, is gradual and occurs via complex mechanisms, involving the presence of a disordered Fe-Zr-B-rich intergranular region which contributes to an increase in the abundance of the L1(0) phase for higher annealing temperatures. Magnetic measurements have confirmed the good performances of these alloys in terms of coercivity and remanence. These results contribute to the development of these alloys as the next generation of rare earth, free permanent magnets.