National Institute Of Materials Physics - Romania

In this study, we evaluate the feasibility of using quantum neural networks for classifying gravitational waveforms, using both simulators and quantum computers. The analysis is quite interdisciplinary in its nature, combining knowledge involving astrophysics, quantum information as well as quantum and classical machine learning. We showed that the quantum classifiers and hybrid classical-quantum layers give highly accurate results when tested on a simple dataset and ran on a simulator; also, adding a quantum layer to poorly performing classical neural network can highly improve its accuracy. When running on a real quantum computer, error minimizing algorithms need to be implemented in order to obtain a satisfying accuracy.

A multi-step ion-exchange methodology was developed for the fabrication of Cu(LaTa2O7)(2) lamellar architectures capable of wastewater depollution. The (001) diffraction line of RbLaTa2O7 depended on the guest species hosted by the starting material. SEM and TEM images confirmed the well-preserved lamellar structure for all intercalated layered perovskites. The UV-Vis, XPS, and photocurrent spectroscopies proved that Cu intercalation induces a red-shift band gap compared to the perovskite host. Moreover, the UV-Vis spectroscopy elucidated the copper ions environment in the Cu-modified layered perovskites. H-2-TPR results confirmed that Cu species located on the surface are reduced at a lower temperature while those from the interlayer occur at higher temperature ranges. The photocatalytic degradation of phenol under simulated solar irradiation was used as a model reaction to assess the performances of the studied catalysts. Increased photocatalytic activity was observed for Cu-modified layered perovskites compared to RbLaTa2O7 pristine. This behavior resulted from the efficient separation of photogenerated charge carriers and light absorption induced by copper spacer insertion.

Two novel fluorescent mesoporous silica-based hybrid materials were obtained through the covalent grafting of [4-hydrazinyl-7-nitrobenz-[2,1,3-d]-oxadiazole (NBDH) and N-1-(7-nitrobenzo[c][1,2,5]-oxadiazol-4-yl) benzene-1,2-diamine (NBD-PD), respectively, inside the channels of mesoporous silica SBA-15. The presence of fluorescent organic compounds (nitrobenzofurazan derivatives) was confirmed by infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), thermal analysis (TG), and fluorescence spectroscopy. The nitrogen physisorption analysis showed that the nitrobenzofurazan derivatives were distributed uniformly on the internal surface of SBA-15, the immobilization process having a negligible effect on the structure of the support. Their antioxidant activity was studied by measuring the ability to reduce free radicals DPPH (free radical scavenging activity), in order to formulate potential applications of the materials obtained. Cytotoxicity of the newly synthesized materials, SBA-NBDH and SBA-NBD-PD, was evaluated on human B16 melanoma cells. The morphology of these cells, internalization and localization of the investigated materials in melanoma and fibroblast cells were examined through fluorescence imaging. The viability of B16 (3D) spheroids after treatment with SBA-NBDH and SBA-NBD-PD was evaluated using MTS assay. The results showed that both materials induced a selective antiproliferative effect, reducing to various degrees the viability of melanoma cells. The observed effect was enhanced with increasing concentration. SBA-NBD-PD exhibited a higher antitumor effect compared to SBA-NBDH starting with a concentration of 125 mu g/mL. In both cases, a significantly more pronounced antiproliferative effect on tumor cells compared to normal cells was observed. The viability of B16 spheroids dropped by 40% after treatment with SBA-NBDH and SBA-NBD-PD at 500 mu g/mL concentration, indicating a clear cytotoxic effect of the tested compounds. These results suggest that both newly synthesized biomaterials could be promising antitumor agents for applications in cancer therapy.

The precursor method was employed to prepare ZnAl2_xCrxO4 (x = 0, 0.25, 0.5, 0.75, 1) using tartaric acid as a ligand. Five tartarate compounds were isolated as precursors for the obtaining of zinc aluminate and chromium -substituted zinc aluminate. These coordination compounds were characterized by elemental chemical analysis, infrared (IR) and ultraviolet visible (UV-Vis) spectroscopy, and thermal analysis. The influence of Cr3+ substi-tution on the structure, morphology and optical properties of the synthesized mixed oxides was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), infrared, Raman and UV-Vis spectroscopy, and nitrogen adsorption - desorption analysis. The XRD patterns and Raman spectra confirmed the formation of spinel structure. The mean crystallite size varied from 18 to 22 nm SEM and EDS showed uniform composition and microstructure of the ZnAl2_xCrxO4 nanocrystalline powders. The values of the optical energy bandgap for the samples were found to be in the 3.92 - 2.85 eV range. The photocatalytic performance in the degradation reaction of Eosin Y (EY) under visible light irradiation was evaluated. The Eosin Y degradation efficiency values were obtained between 48% and 80% after 75 min. The best photocatalytic result was obtained for the sample with the highest amount of chromium.

In this study, two alternative synthesis routes have been used in obtaining gas-sensitive NiO materials. The structural and morphological aspects were systematically investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM), revealing significant differences further mirrored in their sensing performances. Simultaneous electrical resistance and contact potential differences have been involved aiming to decouple the energetic contributions: work function (Delta phi), surface band bending (q Delta Vs) and electron affinity (Delta chi). Two sensing mechanism scenarios explained the enhancement and downgrading in the sensor response to carbon monoxide (CO) concerning the synthesis strategies. The role of relative humidity (RH) was considered throughout the electrical operando (in-field) investigations.

The aim of the present study was the development of Nb-doped ITO thin films for carbon monoxide (CO) sensing applications. The detection of CO is imperious because of its high toxicity, with long-term exposure having a negative impact on human health. Using a feasible sol-gel method, the doped ITO thin films were prepared at room temperature and deposited onto various substrates (Si, SiO2/glass, and glass). The structural, morphological, and optical characterization was performed by the following techniques: X-ray diffractometry (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV/Vis/NIR spectroscopic ellipsometry (SE). The analysis revealed a crystalline structure and a low surface roughness of the doped ITO-based thin films. XTEM analysis (cross-sectional transmission electron microscopy) showed that the film has crystallites of the order of 5-10 nm and relatively large pores (around 3-5 nm in diameter). A transmittance value of 80% in the visible region and an optical band-gap energy of around 3.7 eV were found for dip-coated ITO/Nb films on SiO2/glass and glass supports. The EDX measurements proved the presence of Nb in the ITO film in a molar ratio of 3.7%, close to the intended one (4%). Gas testing measurements were carried out on the ITO undoped and doped thin films deposited on glass substrate. The presence of Nb in the ITO matrix increases the electrical signal and the sensitivity to CO detection, leading to the highest response for 2000 ppm CO concentration at working temperature of 300 degrees C.

The morphology, structure, composition, and con-duction electron properties of quasi-spherical tin nanocrystals (NCs) of 2.5 nm average diameter, with unstrained, bulk-like alpha-Sn diamond cubic structure, observed in dark cubic boron nitride (cBN) crystallites, were determined by correlated analytical high-resolution scanning transmission electron microscopy and multifrequency electron spin resonance (ESR) investigations. The narrow Lorentzian ESR line with g = 2.0028 is attributed to the conduction ESR of the alpha- Sn NCs, consistent with the temperature-and frequency-independent small g-shift and intensity reduction under high temperature (950 degrees C) vacuum annealing when the alpha-Sn NCs are thermally dissolved in the host cBN crystallites. The ESR linewidth and line intensity vs temperature dependences recorded in the 20 to 295 K range are quantitatively described considering the presence of discrete, quantum confinement-induced conduction electron energy levels with Delta QC/kB = 125 K separation, close to the theoretical value for conductive alpha-Sn NCs of 2.5 nm in diameter. The observed properties are tentatively explained with the predicted nanosize induced band-gap opening and change of band ordering from bulk alpha-Sn to small unstrained alpha-Sn NCs, resulting in a topological phase transition that also explains the predominantly s-like character of the conduction band electron orbitals.

This letter highlights the role of synthesis temperature over the morpho-structural properties of SnO2. Specific crystalline nanoparticles with quasi-tetragonal and quasi-hexagonal morphologies are faceted, suggesting a high reactivity to atmospheric oxygen. This is a premise for the sensing ability of SnO2 in detecting CO2. The in-field conditions are ensured by dynamic synthetic air flow with variable relative humidity, a wide range of CO2 concentrations and potential interfering gases at their specific detection limits.

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.

Novel (1-x) SrFe12O19 - x BNT-BT0.08 (x = 0; 0.5; 0.8; 1) nanocomposites were explored in this study. The samples were produced by sol-gel method and compacted by conventional sintering. The composition, morphology, local structure, dielectric and magnetic properties were investigated by X-ray diffraction, Transmission Electron Microscopy, Impedance Analysis, Mossbauer spectroscopy, and SQUID magnetometry. The desired composition and the presence of the magnetoplumbite SrFe12O19 and perovskite BNT-BT structures were verified by X-ray diffraction. Irregular morphology and large size distributions are evidenced in the electron microscopy micrographs. The reported room temperature dielectric constants in this study are the highest values obtained in multiferroic composites at room temperature: giant dielectric constants (similar to 1.3 x 10(6)) were obtained, relative to 0.13 x 10(4) in BNT-BT. The hyperfine parameters allowed the identification of the Wyckoff positions of the Fe ions corresponding closely to the theoretical case. The hard magnetic character of the SrFe12O19 phase is evidenced from the magnetic measurements. For the first time in multifermic composites, superdielectric characteristics are evidenced at room temperature.