National Institute Of Materials Physics - Romania

Publications

5714 articles found

1691. CdSe (quantum dots)-graphene oxide system for thiophene polymerization: a new strategy, a new material

Authors: Rusen, E; Diacon, A; Mocanu, A; Gavrila, R; Nistor, LC; Dinescu, A

Published: 2016, RSC ADVANCES, 6, 25583, DOI: 10.1039/c6ra00274a

This study presents a novel method for the oxidative polymerization of thiophene (T) by employing cadmium selenide (CdSe) quantum dots and CdSe-graphene oxide (GO) as activators of the polymerization system. The polymerization initiation mechanism is based on the difference between the HOMO-LUMO energy levels of the components, which permits the formation of a donor-acceptor exchange. Thus, T should act both as acceptor and donor for a component with suitable HOMO-LUMO energy levels. We have investigated the polymerization reaction evolution as well as the molecular weights of the obtained polymers. The resulting materials containing PT, CdSe quantum dots and GO have been characterized by FTIR, UV-vis, fluorescence, HRTEM, conductivity and AFM analyses.

1692. MEMORY PROPERTIES OF GE NANOCRYSTALS-BASED CAPACITORS WITH DIFFERENT COMPOSITION OF INTERMEDIATE LAYER

Authors: Lepadatu, AM

Published: OCT-DEC 2016, PROCEEDINGS OF THE ROMANIAN ACADEMY SERIES A-MATHEMATICS PHYSICS TECHNICAL SCIENCES INFORMATION SCIENCE, 17, 327, DOI:

In this work, the charge storage properties of trilayers with Ge nanocrystals (NCs) embedded in HfO2 matrix prepared by using two approaches for obtaining the intermediate layer with Ge NCs as nodes are investigated. Trilayer structures with tunnel and control oxides of HfO2, but with different intermediate layers of Ge and Ge-HfO2, respectively, were deposited by magnetron sputtering. Ge nanostructuring was achieved by subsequent rapid thermal annealing. Charge storage behaviour was studied by measurements of capacitance-voltage characteristics on MOS-like capacitors based on the annealed trilayers. The MOS samples with intermediate layer obtained by depositing a continuous Ge layer show hysteresis with memory windows up to similar to 1.3 V, while the ones with co-deposited Ge and HfO2 as intermediate layer present higher memory windows, similar to 1.8 V. In both cases, the memory windows are independent on the frequency demonstrating that the memory effect is due to storing the charge only inside Ge NCs. These show that the approach based on co-deposition of a Ge-HfO2 intermediate layer is more effective for charge storage with direct application in memory devices.

1693. POLYESTER FABRICS COVERED WITH AMORPHOUS TITANIUM DIOXIDE LAYERS: COMBINING WETTABILITY MEASUREMENTS AND PHOTOINDUCED HYDROPHILICITY TO ASSESS THEIR SURFACE PROPERTIES

Authors: Zgura, I; Frunza, S; Frunza, L; Enculescu, M; Florica, C; Cotorobai, VF; Ganea, CP

Published: 2016, ROMANIAN REPORTS IN PHYSICS, 68, 269, DOI:

Wettability properties of thin TiO2 amorphous layers obtained by sputtering or sol-gel onto polyester textile materials were investigated. Contact angle (CA) measurements by the sessile drop method were used to evaluate these properties. Comparison was performed with coated samples of related poly(lactic acid) material. The samples coated by sol gel have CAs a few degrees higher than those coated by sputtering. Wetting properties were conversely changed under alternate darkness/illumination conditions. Photoinduced hydrophilicity was observed even for these amorphous coating particles, being higher for sputtered samples than for sol gel ones.

1694. Effect of Mo/Ce ratio in Mo-Ce-Al catalysts on the hydrogen production by steam reforming of glycerol

Authors: Mitran, G; Pavel, OD; Mieritz, DG; Seo, DK; Florea, M

Published: 2016, , DOI: 10.1039/c6cy00999a

1695. Columnar Growth of Transparent Semiconducting Films: Learning from Nature

Authors: Wang, Y; Crisan, A; Mikheenko, P

Published: 2016, INTERNATIONAL CONFERENCE ON NANOMATERIALS: APPLICATION & PROPERTIES (NAP), DOI:

A two-dimensional array of a large number of identical densely-packed indium-oxide nano-columns was prepared by pulsed laser deposition. The structure closely mimics tubular structure of the under-cap layer of tubular mushrooms. The growth was initiated by a dense array of gold or silver nanodots. The resulting structure forms a transparent semiconducting layer whose resistance is highly sensitive to composition of gases in atmosphere. A simple device based on the array of nano-columns is able to accurately monitor gas balance in an open or closed-space environment. The simplicity of the device, its compactness and a well-established process of deposition would allow incorporating it in various equipment of general or personal use. The application of the sensor could range from health monitoring during the exhale to the check of the car exhaust or gas content in homes, offices, workplaces or in the dangerous and threatening environment.

1696. Bioactive glass thin films synthesized by advanced pulsed laser techniques

Authors: Mihailescu, N; Stan, GE; Ristoscu, C; Sopronyi, M; Mihailescu, IN

Published: 2016, INERA CONFERENCE: VAPOR PHASE TECHNOLOGIES FOR METAL OXIDE AND CARBON NANOSTRUCTURES, 764, DOI: 10.1088/1742-6596/764/1/012020

Bioactive materials play an increasingly important role in the biomaterials industry, and are extensively used in a range of applications, including biodegradable metallic implants. We report on Bioactive Glasses (BG) films deposition by pulsed laser techniques onto biodegradable substrates. The BG coatings were obtained using a KrF* excimer laser source (lambda= 248 nm, t(FWHM) <= 25 ns). Their thickness has been determined by Profilometry measurements, whilst their morphology has been analysed by Scanning Electron Microscopy (SEM). The obtained coatings fairly preserved the targets composition and structure, as revealed by Energy Dispersive X-Ray Spectroscopy, Grazing Incidence X-Ray Diffraction, and Fourier Transform Infra-Red Spectroscopy analyses.

1697. On the agent role of Mn2+ in redirecting the synthesis of Zn(OH)(2) towards nano-ZnO with variable morphology

Authors: Ghica, D; Vlaicu, ID; Stefan, M; Nistor, LC; Nistor, SV

Published: 2016, RSC ADVANCES, 6, 106741, DOI: 10.1039/c6ra23065b

One of the simplest routes to prepare polycrystalline Zn(OH)(2) is by coprecipitation, with zinc nitrate as a cation source. However, the addition of even minute amounts of manganese nitrate to the precursors used to prepare pure Zn(OH)(2) results in Mn2+ doped nanostructured ZnO. The comparison with other Mn2+ doped metal hydroxides prepared by the same coprecipitation method, involving metal nitrates precursors, shows that this behavior is unique, pertaining only to Zn(OH)(2). A systematic study of the samples prepared without and with variable amounts of Mn2+ ions, in the 1 to 5000 ppm nominal concentrations range showed that the re-routing of the reaction takes place even for the lowest nominal dopant concentration of 1 ppm. According to X-ray diffraction, transmission electron microscopy and Fourier transform infrared spectroscopy investigations, both crystallite size and morphology of the resulting nanostructured ZnO samples varied with the Mn2+ nominal concentration. Moreover, quantitative electron paramagnetic resonance investigations showed that the incorporation rate of the Mn2+ ions at different sites in the nanostructured ZnO depended on the nominal Mn2+ concentration. The results are discussed in terms of the coordination properties of the Mn2+ and Zn2+ ions and the nature of the reaction precursors.

1698. Carbon Nanotubes-Hydroxyapatite Nanocomposites for an Improved Osteoblast Cell Response

Authors: Constanda, S; Stan, MS; Ciobanu, CS; Motelica-Heino, M; Guegan, R; Lafdi, K; Dinischiotu, A; Predoi, D

Published: 2016, JOURNAL OF NANOMATERIALS, 2016, DOI: 10.1155/2016/3941501

An alternative and simple coprecipitation method was developed to obtain carbon nanotube-hydroxyapatite (CNTs:HAp) based nanocomposites. The incorporation of CNTs (in a concentration of 5% and 10% of total weight of the nanocomposite) and their impact on both structural and biological properties were studied by using a set of standard complementary biological, microscopic, and spectroscopic techniques. The characteristic peaks of carbon structure in CNTs were not observed in the CNTs-HAp composites by X-ray diffraction analysis. Moreover, FTIR and Raman spectroscopies confirmed the presence of HAp as the main phase of the synthesized CNTs: HAp nanocomposites. The addition of CNTs considerably affected the nanocomposite morphology by increasing the average crystallite size from 18.7 nm (for raw HAp) to 28.6 nm (for CNTs:HAp-10), confirming their proper incorporation. The biocompatibility evaluation of CNTs:HAp-5 and CNTs:HAp-10 nanocomposites included the assessment of several parameters, such as cell viability, antioxidant response, and lipid peroxidation, on human G-292 osteoblast cell line. Our findings revealed good biocompatibility properties for CNTs: HAp nanocomposites prepared by the coprecipitation method supporting their potential uses in orthopedics and prosthetics.

1699. Cerium-doped hydroxyapatite nanoparticles synthesized by the co-precipitation method

Authors: Ciobanu, CS; Popa, CL; Predoi, D

Published: 2016, JOURNAL OF THE SERBIAN CHEMICAL SOCIETY, 81, 446, DOI: 10.2298/JSC150824007C

The present work reports a simple adapted co-precipitation method for the synthesis of stable Ce-substituted Ca hydroxyapatite (HAp) nanoparticles. The structural and morphological properties of the Ce-doped hydroxyapatite (Ce:HAp) were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX). The optical properties of the Ce-doped hydroxyapatite were also investigated using Fourier transform infrared (FTIR) spectroscopy, Fourier transform Raman spectroscopy and photoluminescence analysis. The results of the XRD studies revealed the progressive increase in the a-and c-axes with increasing Ce concentration. In the FTIR studies of Ce: HAp powders, a structure similar to that of hydroxyapatite was observed. The IR and Raman wavenumbers and the peak strengths of the bands associated with the P-O and O-H bonds decreased progressively with increasing Ce concentration. All the emission maxima could be attributed to 5d-4f transitions of the Ce ions. The displacements of the maximum emission bands with increasing Cerium in the samples were in agreement with the results obtained by XRD studies. The Ce: HAp samples with x(Ce) = 0.03 and 0.05 exhibited significant antibacterial activity against Staphylococcus aureus and Escherichia coli bacterial strains compared to Ce: HAp samples with xCe = 0 (pure HAp) and 0.01.

1700. Preliminary Ultrasound Studies On Magnetic Fluids Based on Iron Oxide Nanoparticles

Authors: Popa, CL; Predoi, D; Soare, M; Petre, CC; Predoi, MV

Published: 2016, VIII INTERNATIONAL CONFERENCE ON TIMES OF POLYMERS AND COMPOSITES: FROM AEROSPACE TO NANOTECHNOLOGY, 1736, DOI: 10.1063/1.4949715

The study of various types of nanoparticles with different biomedical applications is of high interest in the last decades. For this purpose, among other techniques, ultrasounds have been used to characterize the aqueous solutions. A non-invasive method is preferable for the characterization of these materials, due to the fact that they are designed to be used for targeted delivery of a chemotherapeutic solution to the tumor site. The present research is focused on ultrasound characterization of solutions based on maghemite and 5-fluorouracil.