National Institute Of Materials Physics - Romania

Publications

907 articles found

71. Anticoagulant Properties of Coated Fe-Pd Ferromagnetic Shape Memory Ribbons

Authors: Bunge, A; Chiriac, A; Sofronie, M; Craciunescu, I; Porav, AS; Turcu, R

Published: FEB 2023, INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES, 24, 2452, DOI: 10.3390/ijms24032452

Shape memory alloys, especially ferromagnetic shape memory alloys, are interesting new materials for the manufacturing of stents. Iron-palladium alloys in particular can be used to manufacture self-expanding temporary stents due to their optimum rate of degradation, which is between that of magnesium and pure iron, two metals commonly used in temporary stent research. In order to avoid blood clotting upon the introduction of the stent, they are often coated with anticoagulants. In this study, sulfated pectin, a heparin mimetic, was synthesized in different ways and used as coating on multiple iron-palladium alloys. The static and dynamic prothrombin time (PT) and activated partial thromboplastin time (APTT) of the prepared materials were compared to samples uncoated or coated with polyethylene glycol. While no large differences were observed in the prothrombin time measurements, the activated partial thromboplastin time increased significantly with all alloys coated with sulfated pectin. Aside from that, sulfated pectin synthesized by different methods also caused slight changes in the activated partial thromboplastin time. These findings show that iron-palladium alloys can be coated with anticoagulants to improve their utility as material for temporary stents. Sulfated pectin was characterized by nuclear magnetic resonance (NMR) and Fourier-transform infrared (FTIR) spectroscopy, and the coated alloys by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX).

72. Chiral and Catalytic Effects of Site-Specific Molecular Adsorption

Authors: Borca, B; Michnowicz, T; Aguilar-Galindo, F; Petuya, R; Pristl, M; Schendel, V; Pentegov, I; Kraft, U; Klauk, H; Wahl, P; Arnau, A; Schlickum, U

Published: FEB 2023, JOURNAL OF PHYSICAL CHEMISTRY LETTERS, DOI: 10.1021/acs.jpclett.2c03575

The changes of properties and preferential interactions based on subtle energetic differences are important characteristics of organic molecules, particularly for their functionalities in biological systems. Only slightly energetically favored interactions are important for the molecular adsorption and bonding to surfaces, which define their properties for further technological applications. Here, prochiral tetracenothiophene molecules are adsorbed on the Cu(111) surface. The chiral adsorption configurations are determined by Scanning Tunneling Microscopy studies and confirmed by first-principles calculations. Remarkably, the selection of the adsorption sites by chemically different moieties of the molecules is dictated by the arrangement of the atoms in the first and second surface layers. Furthermore, we have investigated the thermal effects on the direct desulfurization reaction that occurs under the catalytic activity of the Cu substrate. This reaction leads to a product that is covalently bound to the surface in chiral configurations.

73. Synthesis and Anti-Melanoma Activity of L-Cysteine-Coated Iron Oxide Nanoparticles Loaded with Doxorubicin

Authors: Toderascu, LI; Sima, LE; Orobeti, S; Florian, PE; Icriverzi, M; Maraloiu, VA; Comanescu, C; Iacob, N; Kuncser, V; Antohe, I; Popescu-Pelin, G; Stanciu, G; Ionita, P; Mihailescu, CN; Socol, G

Published: FEB 2023, NANOMATERIALS, 13, 621, DOI: 10.3390/nano13040621

In this study, we report on the synthesis of L-Cysteine (L-Cys)-coated magnetic iron oxide nanoparticles (NPs) loaded with doxorubicin (Dox). The Fe3O4-L-Cys-Dox NPs were extensively characterized for their compositional and morpho-structural features using EDS, SAED, XRD, FTIR and TEM. XPS, Mossbauer spectroscopy and SQUID measurements were also performed to determine the electronic and magnetic properties of the Fe3O4-L-Cys-Dox nanoparticles. Moreover, by means of a FO-SPR sensor, we evidenced and confirmed the binding of Dox to L-Cys. Biological tests on mouse (B16F10) and human (A375) metastatic melanoma cells evidenced the internalization of magnetic nanoparticles delivering Dox. Half maximum inhibitory concentration IC50 values of Fe3O4-L-Cys-Dox were determined for both cell lines: 4.26 mu g/mL for A375 and 2.74 mu g/mL for B16F10, as compared to 60.74 and 98.75 mu g/mL, respectively, for unloaded controls. Incubation of cells with Fe3O4-L-Cys-Dox modulated MAPK signaling pathway activity 3 h post-treatment and produced cell cycle arrest and increased apoptosis by 48 h. We show that within the first 2 h of incubation in physiological (pH = 7.4) media, similar to 10-15 mu M Dox/h was released from a 200 mu g/mL Fe3O4-L-Cys-Dox solution, as compared to double upon incubation in citrate solution (pH = 3), which resembles acidic environment conditions. Our results highlight the potential of Fe3O4-L-Cys-Dox NPs as efficient drug delivery vehicles in melanoma therapy.

74. Kinetics and the Effect of Thermal Treatments on the Martensitic Transformation and Magnetic Properties in Ni49Mn32Ga19 Ferromagnetic Shape Memory Ribbons

Authors: Tolea, F; Popescu, B; Bartha, C; Enculescu, M; Tolea, M; Sofronie, M

Published: JAN 2023, MAGNETOCHEMISTRY, 9, 7, DOI: 10.3390/magnetochemistry9010007

In our work, the kinetics of martensitic transformations and the influence of thermal treatments on martensitic transformations, as well as the related magnetic properties of the Ni49Mn32Ga19 ferromagnetic shape memory melt-spun ribbons, have been investigated. Thermal treatments at 673 K for 1, 4 and 8 h can be considered an instrument for fine-tuning the performance parameters of alloys. One-hour thermal treatments promote an improvement in the crystallinity of these otherwise highly textured ribbons, reducing internal defects and stress induced by the melt-spinning technique. Longer thermal treatments induce an important magnetization rise concomitantly with a slight and continuous increase in martensitic temperatures and transformation enthalpy. The activation energy, evaluated from differential scanning calorimeter experimental data with a Friedman model, significantly increases after thermal treatments as a result of the multi-phase coexistence and stabilization of the non-modulated martensitic phase, which increases the reverse martensitic transformation hindrance.

75. Measurements of Surface Impedance in MgB2 in DC Magnetic Fields: Insights in Flux-Flow Resistivity

Authors: Alimenti, A; Torokhtii, K; Garcia, PV; Silva, E; Grigoroscuta, MA; Badica, P; Crisan, A; Pompeo, N

Published: JAN 2023, MATERIALS, 16, 205, DOI: 10.3390/ma16010205

We present the multifrequency measurements of the surface resistance of spark-plasma-sintered MgB2 performed through a dielectric loaded resonator operating at 16.5 and 26.7 GHz. By normally applying magnetic fields <= 1.2 T to the sample surface, we drove it in the mixed state. By means of data-rooted analysis, we found that the sample vortex dynamics could be fully described within a single-component approach. Pinning phenomena were present and characterized by a depinning frequency smaller than the measurement ones. The multiband nature of the superconductor emerged in the flux-flow resistivity, whose field dependence could be interpreted well within theoretical models. By exploiting them, the upper critical field was extracted in the low-temperature range, which exhibited a consistent temperature trend with the values obtained at the onset of the resistive transition near Tc, and was well in line with literature data on other polycrystalline samples.

76. Multifunctional Magnetic Nanocomposites: Innovative Processing and Applications

Authors: Kuncser, V

Published: JAN 2023, NANOMATERIALS, 13, 206, DOI: 10.3390/nano13010206

Multifunctional magnetic nanocomposites are among those heterogeneous nanosized systems where at least one phase component is magnetic and can act as an intermediate of either the actuation or the response of the overall system. The main advantage of heterogeneous nanosystems is the possibility of combining and inter-influencing the electronic properties of constituent interfaced nanophases. Consequently, unique physico-chemical properties of the hybrid materials of interest in various applications can be obtained. This Special Issue of Nanomaterials highlights the most advanced processing and characterization tools of some multifunctional magnetic nanocomposites and heterogeneous systems of interest in various applications, from biomedicine to sensoristics and energy-saving materials.

77. Kinetics and the Effect of Thermal Treatments on the Martensitic Transformation and Magnetic Properties in Ni₄₉Mn₃₂Ga₁₉ Ferromagnetic Shape Memory Ribbons

Authors: Tolea, F; Popescu, B; Bartha, C; Enculescu, M; Tolea, M; Sofronie, M

Published: JAN 2023, MAGNETOCHEMISTRY, 9, 7, DOI: 10.3390/magnetochemistry9010007

78. Paving the Way to the Fuel of the Future-Nanostructured Complex Hydrides

Authors: Comanescu, C

Published: JAN 2023, INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES, 24, 143, DOI: 10.3390/ijms24010143

Hydrides have emerged as strong candidates for energy storage applications and their study has attracted wide interest in both the academic and industry sectors. With clear advantages due to the solid-state storage of hydrogen, hydrides and in particular complex hydrides have the ability to tackle environmental pollution by offering the alternative of a clean energy source: hydrogen. However, several drawbacks have detracted this material from going mainstream, and some of these shortcomings have been addressed by nanostructuring/nanoconfinement strategies. With the enhancement of thermodynamic and/or kinetic behavior, nanosized complex hydrides (borohydrides and alanates) have recently conquered new estate in the hydrogen storage field. The current review aims to present the most recent results, many of which illustrate the feasibility of using complex hydrides for the generation of molecular hydrogen in conditions suitable for vehicular and stationary applications. Nanostructuring strategies, either in the pristine or nanoconfined state, coupled with a proper catalyst and the choice of host material can potentially yield a robust nanocomposite to reliably produce H-2 in a reversible manner. The key element to tackle for current and future research efforts remains the reproducible means to store H-2, which will build up towards a viable hydrogen economy goal. The most recent trends and future prospects will be presented herein.

79. Synthesis of Nickel and Cobalt Ferrite-Doped Graphene as Efficient Catalysts for Improving the Hydrogen Storage Kinetics of Lithium Borohydride

Authors: Palade, P; Comanescu, C; Radu, C

Published: JAN 2023, MATERIALS, 16, 427, DOI: 10.3390/ma16010427

Featuring a high hydrogen storage content of up to 20 wt%, complex metal borohydrides remain promising solid state hydrogen storage materials, with the real prospect of reversible behavior for a zero-emission economy. However, the thermodynamic barriers and sluggish kinetics are still barriers to overcome. In this context, nanoconfinement has provided a reliable method to improve the behavior of hydrogen storage materials. The present work describes the thermodynamic and kinetic enhancements of LiBH4 nanoconfined in MFe2O4 (M=Co, Ni) ferrite-catalyzed graphene host. Composites of LiBH4-catalysts were prepared by melt infiltration and investigated by X-ray diffraction, TEM, STEM-EDS and TPD. The role of ferrite additives, metal precursor treatment (Ar, Ar/H-2) and the effect on hydrogen storage parameters are discussed. The thermodynamic parameters for the most promising composite LiBH4-graphene-NiFe2O4 (Ar) were investigated by Kissinger plot method, revealing an E-A = 127 kJ/mol, significantly lower than that of neat LiBH4 (170 kJ/mol). The reversible H-2 content of LiBH4-graphene-NiFe2O4 (Ar) after 5 a/d cycles was similar to 6.14 wt%, in line with DOE's target of 5.5 wt% storage capacity, while exhibiting the lowest desorption temperature peak of 349 degrees C. The composites with catalysts treated in Ar have lower desorption temperature due to better catalyst dispersion than using H-2/Ar.

80. Measurements of Surface Impedance in MgB₂ in DC Magnetic Fields: Insights in Flux-Flow Resistivity

Authors: Alimenti, A; Torokhtii, K; García, PV; Silva, E; Grigoroscuta, MA; Badica, P; Crisan, A; Pompeo, N