National Institute Of Materials Physics - Romania

A series of LaPO4:Ce3+/Mn2+/xZr(4+) (LPOCM:xZr(4+)) (0% <= x <= 30%) emission-tunable phosphors were synthesized by a cost-efficient co-precipitation method. The samples presented a monoclinic phase structure and a macroscopic rod-like shape. Photoluminescence (PL) and electron paramagnetic resonance spectroscopy were employed, the Zr4+ concentration-dependent excitation, emission, decay time, and energy transfer (Ce3+ -> Mn2+) being discussed in detail. Under UV-excitation of Ce3+, typical green-red PL emission is observed for the LPOCM:xZr(4+) phosphors, which is attributed to the T-4(1)(G) -> (6)A(1)(S) transition of the Mn2+ ion. The charge compensation strategy achieved the Mn2+ PL-enhancement and color-tuning effect in LPOCM:xZr(4+) phosphors. A strong blue emission with color purity of up to 97% is observed in the Ce3+ singly-doped sample. Cold white light emission can be obtained by doping 5% Zr4+ in LPOCM phosphor under UV irradiation. The corresponding CIE 1931 coordinates were inferred to be (0.309, 0.329), close to the standard white emission (0.330, 0.330). The color was tuned towards whitish-orange/red emissions for higher Zr4+ concentrations (15% and 30%). These findings indicate that the charge compensation approach can greatly improve the PL and color-tunable properties of LPOCM:xZr(4+) phosphors.

Azathioprine (AZA) is a pharmacologic immunosuppressive agent administrated in various conditions such as autoimmune disease or to prevent the rejection of organ transplantation. The mechanism of action is based on its biologically active metabolite 6-mercaptopurine (6-MP), which is converted, among others, into thioguanine nucleotides capable of incorporating into replicating DNA, which may act as a strong UV chromophore and trigger DNA oxidation. The interaction between azathioprine and DNA, before and after exposure to solar simulator radiation, was investigated using UV-vis spectrometry and differential pulse voltammetry at a glassy carbon electrode. The results indicated that the interaction of AZA with UV radiation was pH-dependent and occurred with the formation of several metabolites, which induced oxidative damage in DNA, and the formation of DNA-metabolite adducts. Moreover, the viability assays obtained for the L929 cell culture showed that both azathioprine and degraded azathioprine induced a decrease in cell proliferation.

The current consumption trends of plant based functional products have encouraged researchers and industry to study the production of protein enriched bakery products as a source of protein. In the context of the circular economy, the press cakes remaining after extraction of juices/oil from plants such as sea buckthorn or hemp can be valorized as they are rich in proteins, fibers and many bioactive compounds. Their use in bread making is a good solution to enrich the nutritional value of bread. Pea protein concentrate, hemp and sea buckthorn ingredients from press cakes by-products were added to whole wheat flour in different percentages and combinations (2% pea protein concentrate; 1% pea + 2% sea buckthorn ingredients; 1% pea + 2% hemp ingredients). Bread samples were obtained through three technological methods: one phase baking process (dough), two phases (sponge and dough) and one phase with dried sourdough added directly into the dough. A control sample (100% wheat whole flour) was considered. The mixtures of whole wheat flour and plant protein ingredients were rheologically tested. The bread samples were physicochemically analyzed (protein, fat, carbohydrates, energy value) and sensory characteristics were evaluated (texture, color and overall acceptability). The changes in the physicochemical characteristics, rheology behavior, microstructure and sensory quality were evaluated and compared. The energy from protein varied from 17.26 to 19.34% which means that all the samples can be considered "a source of protein". Hardness decreased in samples with sponge and dried sourdough which reflect the importance of technology in keeping the freshness of the product. The most appreciated were the samples with pea protein concentrate, with hemp ingredient obtained through an indirect bread making process and the sample with sea buckthorn ingredient prepared through a direct bread making process using dried sourdough.

To obtain highly homogeneous cobalt-nickel aluminate spinels with small crystallite sizes, CoNiAl alloy thin films were primarily deposited using Laser-induced Thermionic Vacuum Arc (LTVA) as a versatile method for performing processing of multiple materials, such as alloy/composite thin films, at a nanometric scale. Following thermal annealing in air, the CoNiAl metallic thin films were transformed into ceramic oxidic (Co,Ni)Al2O4 with controlled composition and crystallinity suitable for thermal stability and chemical resistance devices. Structural analysis revealed the formation of (Co,Ni)Al2O4 from the amorphous CoNiAl alloys. The mean crystallite size of the spinels was around 15 nm. Thermal annealing induces a densification process, increasing the film thickness together with the migration process of the aluminum toward the surface of the samples. The sheet resistance changed drastically from 200-240 omega/sq to more than 10(6) omega/sq, revealing a step-by-step conversion of the metallic character of the thin film to a dielectric oxidic structure. These cermet materials can be used as inert anodes for the solid oxide fuel cells (SOFCs), which require not only high stability with respect to oxidizing gases such as oxygen, but also good electrical conductivity. These combination metal-ceramics are known as bi-layer anodes. By controlling the crystallite size and the interplay between the oxide/metal composite, a balance between stability and electrical conductivity can be achieved.

Understanding the phonon anharmonicity and temperature-dependent behavior of phonons that affect the thermal transport properties in 2D materials is crucial for developing efficient thermoelectric and memristor devices. SnSe has attracted significant interest because of its potential applications for developing such novel devices. Here, orthorhombic SnSe nanoflakes with a thickness of less than 100 nm and oriented along the [100] crystal axis were obtained using physical vapor transport at atmospheric pressure. Polarization-resolved Raman spectroscopy of SnSe nanoflakes was performed at a temperature of 5 K. Temperature-dependent frequencies and linewidths of Raman modes in tin selenide were fitted according to the anharmonic phonon coupling theory. The results indicate that both two and three order processes are responsible for the phonon decay in tin selenide. The memristive property was confirmed by electrical measurements of SnSe devices. SnSe memristors have an operating current of 10-4 A, similar to other transition-metal dichalcogenide memristors, but are more energy efficient than memristors based on defect migration, with a threshold voltage of 3 V.

Designing complex electrochemical artificial muscles aims towards novel devices which besides excellent actuation capabilities should also present the ability to self-sense the modification of environmental parameters. In order to improve efficiency, mimicking the structure of natural muscles, synthetic actuators should have a similar fibrillary morphology. The importance of using materials based on fiber building blocks in actuators aimed at soft robotics field was demonstrated in the present report by comparing a fibrillary artificial muscle with one based on a classical film structure. Nylon electrospun fiber meshes and films were covered in the same conditions with a thin polypyrrole (PPy) layer. The fibrillary electrospun web morphology mimics that of natural muscles and the structure performs a fast, ample bending movement in liquid electrolyte when switching an applied electric potential between -0.6 and +0.6 V. Using the same actuation conditions, no movement of a film based artificial muscle was observed. In order to check the sensing ability of both fibrillary and film like electroactive architectures, their response i.e. PPy reaction when potential cycles were applied in different concentrations of LiClO4 electrolyte were recorded. The obtained results suggest that the ion exchange of the fibrillary artificial muscle is more efficient due to its higher active surface and such devices could work also as dual device (sensor/artificial muscle).

The influence of processing on the martensitic transformation and related magnetic properties of the Ni55Fe18Nd2Ga25 ferromagnetic shape memory alloy, as bulk and ribbons prepared by the melt spinning method and subjected to different thermal treatments, is investigated. Structural, calorimetric, and magnetic characterizations are performed. Thermal treatment at 1173 K induces a decrease in both the Curie and the martensitic transformation temperatures, while a treatment at 673 K produces the structural ordering of the ribbons, hence an increase in T-C. A maximum value of the magnetic entropy variation of -5.41 J/kgK was recorded at 310 K for the as quenched ribbons. The evaluation of the magnetoresistive effect shows a remarkable value of -13.5% at 275 K on the bulk sample, which is much higher than in the ribbons.

In the present study, we report the development and characterization of composite layers (by spin coating) based on magnesium-doped hydroxyapatite in a chitosan matrix, (Ca10-xMgx(PO4)(6)(OH)(2); x(Mg) = 0, 0.08 and 0.3; HApCh, 8MgHApCh and 30MgHApCh). The MgHApCh composite layers were investigated using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS) techniques. The in vitro biological evaluation included the assessment of their cytotoxicity on MG63 osteoblast-like cells and antifungal activity against Candida albicans ATCC 10231 fungal cell lines. The results of the physico-chemical characterization highlighted the obtaining of uniform and homogeneous composite layers. In addition, the biological assays demonstrated that the increase in the magnesium concentration in the samples enhanced the antifungal effect but also decreased their cytocompatibility. However, for certain optimal magnesium ion concentrations, the composite layers presented both excellent biocompatibility and antifungal properties, suggesting their promising potential for biomedical applications in both implantology and dentistry.

Titanium dioxide nanoparticles (TiO2-NPs) are increasingly used in consumer products for their particular properties. Even though TiO2 is considered chemically stable and insoluble, studying their behavior in biological environments is of great importance to figure their potential dissolution and transformation. The interaction between TiO2-NPs with different sizes and crystallographic forms (anatase and rutile) and the strong chelating enterobactin (ent) siderophore was investigated to look at a possible dissolution. For the first time, direct evidence of anatase TiO2-NP surface dissolution or solubilization (i.e., the removal of Ti atoms located at the surface) in a biological medium by this siderophore was shown and the progressive formation of a hexacoordinated titanium-enterobactin (Ti-ent) complex observed. This complex was characterized by UV-visible and Fourier transform infrared (FTIR) spectroscopy (both supported by Density Functional Theory calculations) as well as electrospray ionization mass spectrometry (ESI-MS) and X-ray photoelectron spectroscopy (XPS). A maximum of ca. 6.3% of Ti surface atoms were found to be solubilized after 24 h of incubation, releasing Ti-ent complexes in the micromolar range that could then be taken up by bacteria in an iron-depleted medium. From a health and environmental point of view, the effects associated to the solubilization of the E171 TiO2 food additive in the presence of enterobactin and the entrance of the Ti-enterobactin complex in bacteria were questioned.