National Institute Of Materials Physics - Romania

Arrays of magnetic Ni-Cu alloy nanowires with different compositions were prepared by a template-replication technique using electrochemical deposition into polycarbonate nanoporous membranes. Photolithography was employed for obtaining interdigitated metallic electrode systems of Ti/Au onto SiO2/Si substrates and subsequent electron beam lithography was used for contacting single nanowires in order to investigate their galvano-magnetic properties. The results of the magnetoresistance measurements made on single Ni-Cu alloy nanowires of different compositions have been reported and discussed in detail. A direct methodology for transforming the magnetoresistance data into the corresponding magnetic hysteresis loops was proposed, opening new possibilities for an easy magnetic investigation of single magnetic nanowires in the peculiar cases of Stoner-Wohlfarth-like magnetization reversal mechanisms. The magnetic parameters of single Ni-Cu nanowires of different Ni content have been estimated and discussed by the interpretation of the as derived magnetic hysteresis loops via micromagnetic modeling. It has been theoretically proven that the proposed methodology can be applied over a large range of nanowire diameters if the measurement geometry is suitably chosen.

Bio-waste eggshell membranes (ESM) present a unique micro-architecture consisting in an interwoven fibrous network which can be functionalized with metal oxides resulting in hybrid materials. ESM were covered with ZnO nanostructures by electroless deposition using Au as catalyst. The structural, optical, morphological and wetting properties of the pristine ESM and ESM/ZnO were evaluated. The ESM fibers were uniformly coated by ZnO hexagonal prisms, the hybrid ESM/ZnO preserving the water absorption characteristic of the pristine ESM. Combining an abundant bio-waste with a simple wet chemical synthesis method, flexible organic/inorganic hybrid networks based on ZnO-functionalized ESM can be designed for various applications. (C) 2018 Elsevier B.V. All rights reserved.

Ce3+ and Tb3+-doped silico-phosphate films were obtained by using the sol-gel method, followed by the spin-coating deposition on silicon substrate. The homogeneity of the films was investigated by the conoscopy method. It was observed that the analysed films are isotropic but relatively inhomogeneous due to the specificity of the deposition technique. The morphology of the sol-gel films was investigated by Scanning Electron Microscopy and Atomic Force Microscopy. The elemental composition was determined by Energy Dispersive X-ray analysis. The magneto-optical investigations evidenced the capability of Ce and Tb-doped films of less than 2 mu m thickness to produce measurable Kerr rotations of 1 mdeg/T and 0.28 mdeg/T, respectively. (C) 2018 Elsevier B.V. All rights reserved.

The sol-gel method was used to synthesize the silver doped hydroxyapatite (Ag:HAp) gels in order to produce the antifungal composite layers. The pure Ti disks were used as the substrate for the composite layers. Important information about suspensions used to make Ag:HAp composite layers were obtained from an ultrasonic technique. The identification of the phase composition of the Ag:HAp composite layers was accomplished X-ray diffraction (XRD). The morphology and the thickness of the layers was evaluated using scanning electron microscopy (SEM). The uniform distribution of the constituent elements (Ag, Ca, P, and O) in both analyzed samples was observed. The antifungal activity of the samples against Candida albicans ATCC 10231 microbial strain were investigated immediately after their preparation and six months later. SEM and confocal laser scanning microscopy (CLSM) images showed that the composite layers at the two time intervals exhibited a strong antifungal activity against Candida albicans ATCC 10231 and completely inhibited the biofilm formation.

The present study demonstrates the effectiveness of hydroxyapatite nanopowders in the adsorption of zinc in aqueous solutions. The synthesized hydroxyapatites before (HAp) and after the adsorption of zinc (at a concentration of 50 mg/L) in solution (HApD) were characterized using X-ray diffraction (XRD), and scanning and transmission electron microscopy (SEM and TEM, respectively). The effectiveness of hydroxyapatite nanopowders in the adsorption of zinc in aqueous solutions was stressed out through ultrasonic measurements. Both Langmuir and Freundlich models properly fitted on a wide range of concentration the equilibrium adsorption isotherms, allowing us to precisely quantify the affinity of zinc to hydroxyapatite nanopowders and to probe the efficacy of hydroxyapatite in removal of zinc ions from aqueous solutions in ultrasonic conditions.

This work is focused on the use of multilayer transparent conductive electrode (TCE) based on ZnO/Ag/ZnO in the fabrication of the organic heterostructures. The ZnO/Ag/ZnO obtained combining sputtering/thermal evaporation/sputtering techniques is featured by a good optical transmittance, a low electrical resistivity and a reduced roughness. All these characteristics recommend it as a viable alternative to indium tin oxide (ITO) for different applications. The organic materials, N,N' - diphenyl N,N' - bis (1 - aphthyl) 1,1' - biphenyl 4,4' - diamine (alpha-NPD), 5,12-Dihydro-5-12-dimethylquino [2,3-b]acridine-7,14dione (DMQA) and 4,7 diphenyl-1,10-phenanthroline (BPhen) were deposited by vacuum thermal evaporation (VTE) method, the properties of the obtained layers being investigated by FTIR, UV-VIS and PL) spectroscopy. The I-V characteristic (recorded in dark) of the organic heterostructure fabricated on the ZnO/Ag/ZriO electrode shows diode behavior, revealing its potential applications in the organic light emitting devices (OLED).

Eggshell membranes were employed as biological scaffolds for developing soft and versatile actuators. A particular architecture, consisting of eggshell membrane coated with polypyrrole, has been fabricated and has been found to be a green, inexpensive, lightweight, and easy to handle class of actuators. The polypyrrole-coated eggshell membrane devices were tested in liquid, ambient atmosphere and controlled humidity environment, with the recorded movements proving their versatility. In 1 M NaCl aqueous solution, by applying successive potential pulses, the actuator contracts/expands owing to the expulsion/insertion of the electrolyte ions out/into polypyrrole film, producing a displacement of similar to 0.1 cm. In air, upon application of voltages from 2 to 5 V on a V-shaped geometry actuator, it bends due to water desorption from its structure induced by Joule heating, generating a displacement which reaches similar to 0.4 cm at 5 V. In a chamber with controlled humidity, the decrease of humidity stimulates a bending/curling motion of the actuator, achieving a displacement of similar to 2.1 cm at 50% relative humidity. Upon modification of the humidity, these actuators move, hold, and release delicate and lightweight objects. Such polypyrrole-coated eggshell membrane actuators which operate in different environments and respond to multiple stimuli can have potential applications in biomimetic micromanipulators or artificial muscle fields.

Three phenacyl derivatives have been investigated as potential inhibitors for the aqueous oxidation of sphalerite (ZnS) in air-equilibrated solutions of HCl (pH 2.5 and 25 degrees C) using potentyodynamic polarization, aqueous batch experiments, scanning electron microscopy coupled with energy dispersive X-ray (SEM/EDX) analysis, Fourier transform infrared (FTIR) spectroscopy, Raman scattering and quantum chemical calculations. Findings show that the studied phenacyl derivatives are inhibitors of sphalerite aqueous oxidation. Quantum chemical calculations indicate that the adsorption of phenacyl derivatives on ZnS is energetically favorable and accounts for the observed inhibiting effects.

Lighting and display technologies are evolving at tremendous rates nowadays; new device architectures based on new, microscopic building blocks are being developed. Besides high light-emission efficiencies, qualities including low cost, low environmental impact, flexibility, or lightweightness are sought for developing new types of devices. Electrospun polymer fibers represent an interesting type of such microscopic structures that can be employed in developing new functionalities. White-light-emitting fiber mats were prepared by the electrospinning of different dye-doped polymer solutions. Two approaches were used in order to obtain white-light emissions: the overlapping of single-dye-doped electrospun fiber mats, and the electrospinning of mixtures of different ratios of single-dye-doped polymer solutions. Scanning electron microscopy (SEM) was used to investigate the morphologies of the electrospun fibers with diameters ranging between 300 nm and 1 mu m. Optical absorption and photoluminescence (PL) were evaluated for single-dye-doped submicronic fiber mats, for overlapping mats, and for fiber mats obtained from different compositions of mixtures. Depending on the ratios of the mixtures of different dyes, the luminance was balanced between blue and red emissions. Commission Internationale de L'Eclairage (CIE) measurements depict this fine-tuning of the colors' intensities, and the right composition for white-light emission of the submicronic fiber mats was found.

Herein, the spectral and transport properties in the finite phosphorene lattice are investigated using the tight-binding model in the presence of Anderson disorder potential. The focus is on the zig-zag edge states localization, provided by the numerically calculated inverse participation number. At low disorder, the zig-zag states undergo a localization process, keeping their 1D character, while further increasing the disorder leads to delocalization due to hybridization with the extended 2D states. The disorder-induced changes in the electronic conductance, from one zig-zag edge to the other, are also discussed.