Publications

The paper is focused on the investigation of the properties of some organic heterostructures deposited on patterned AZO electrodes. In the first step, 2D patterned arrays based on commercially photoresist were fabricated on glass substrates using nanoimprint litography. Next, on these periodic nanostructures, the transparent AZO layers were deposited by pulsed laser deposition. Further, heterostructures consisting in organic thin films such as 4,7 diphenyl-1,10-phenanthroline (BPhen) (electron transport layer), N,N'-di(1-naftalenil)-N,N'-diafenil-(1,1'-bifenil)-4,4'-diamina (alpha-NPD) (hole transport layer) and arylenevinylene oligomers (3,3-bis (N-hexylcarbazole)vinylbenzene (P13) and 1,4-bis [4-(N,N-diphenylamino)phenylvinyl] benzene (P78)) were obtained by matrix assisted pulsed laser evaporation. The fabricated multilayer organic structures have been investigated from optical (UV-VIS spectroscopy), morphological (scanning electron microscopy and atomic force microscopy) and electrical (I-V characteristics) point of view. An improvement in the current value recorded on the samples prepared on nanostructured electrode was recorded. The results evidence the possibility to integrate these heterostructures in organic electronic devices.

MoO2-Fe2O3 nanoparticle system was successfully synthesized by mechanochemical activation of MoO2 and alpha-Fe2O3 equimolar mixtures for 0-12 hours of ball milling time. The study aims at exploring the formation of magnetic oxide semiconductors at the nanoscale. X-ray powder diffraction (XRD), Mossbauer spectroscopy and magnetic measurements were used to study the phase evolution of MoO2-Fe2O3 nanoparticle system under the mechanochemical activation process. The Mossbauer studies showed that the spectrum of the mechanochemically activated composites evolved from a sextet for hematite to sextet and a doublet upon duration of the milling process with molybdenum dioxide. Recoilless fraction was determined using our dual absorber method and was found to decrease with increasing ball milling time. Magnetic measurements recorded at 5 and 300 K in an applied magnetic field of 50,000 Oe showed the magnetic properties in the antiferromagnetic and canted ferromagnetic states. The Morin transformation was evidenced by zero-field cooling-field cooling (ZFC-FC) measurements in 200 Oe and the transformation characteristic temperatures were shifted to lower values.

Iron oxide-dextran nanoparticle suspensions (IOD-NPsS) have attracted attention for their considerable applications in various biomedical area such as cosmetics, water remediation, hyperthermia, drug delivery or magnetic resonance imaging (MRI) contrast enhancement. In these research we report the antimicrobial studies on iron oxide-dextran colloidal suspension against prokaryotic cells such as Escherichia coli (E. coli). The ultrasound studies and dynamic light scattering (DLS) of iron oxide-dextran nanoparticle suspensions. According colloidal studies of the iron oxide suspension, the nanoparticles was in dispersed state.

The present research is focused on the synthesis, structural and morphological characterization and antimicrobial evaluation of silver doped hydroxyapatite (AgHAp) in water. The preliminary ultrasonic characterizations of the AgHAp in water synthesized by an adapted co-precipitation method are also presented. X-ray diffraction result showed that silver ions were substituted in the hydroxyapatite structure. The lattice parameters increased when the silver substitution increased. The morphology of AgHAp were evaluated by Scanning Electron Microscopy (SEM). By EDX analysis the constituents elements of hydroxyapatite were detected in all analyzed samples. The silver was also found in the samples with x(Ag) = 0.5 and 0.2. The colloidal properties of the resulted AgHAp (x(Ag) = 0.0, 0.05 and 0.2) in water were analyzed by Dynamic Light Scattering (DLS) and zeta potential. On the other hand, the novelty of our research consists of preliminary ultrasonic measurements (US) conducted on AgHAp in water. Furthermore, the antimicrobial activity of AgHAp was evaluated and a decrease in the number of surviving cells was established.

Clean technologies using the principles of green chemistry have attracted the attention of scientists in the last decade. Our work was focused on building advanced silver-based materials using an eco-friendly and convenient method. Two types of silver nanoparticles were synthesized using aqueous extracts of orange (Citrus sinensis) and grapefruit (Citrus paradisi) peels. Hybrid entities consisting of these bionanosilver particles and biomimetic membranes were "green" prepared and studied by spectral methods (UV-Vis absorption and emission, and FTIR-ATR spectroscopy). The morphology of silver-containing materials was analyzed by AFM images and their physical stability was checked by zeta potential measurements. Also, their antioxidant and antimicrobial properties were evaluated.

We investigate the dynamic behavior of perovskite solar cells by focusing on the relaxation time tau, which corresponds to the slow de-polarization process from an initial bias pre-poled state. The dynamic electrical model (DEM) is employed for simulating the J-V characteristics for different bias scan rates and pre-poling conditions. Depending on the sign of the initial polarization normal or inverted hysteresis may be induced. For fixed pre-poling conditions, the relaxation time, in relation to the bias scan rate, governs the magnitude of the dynamic hysteresis. In the limit of large tau the hysteretic effects are vanishing for the typical range of bias scan rates considered, while for very small tau the hysteresis is significant only when it is comparable with the measurement time interval.

Low-loss dielectrics with various microstructure and, consequently, different extrinsic losses were investigated by using terahertz time-domain spectroscopy. The losses have been extrapolated and compared with those measured at microwave frequencies. The results showed that extrinsic factors have a considerably contribution in microwave domain. The intrinsic limit of dielectric loss of low absorption polycrystalline materials have been estimated by terahertz spectroscopy.

Mixed manganese iron oxides (Mn/Fe/O) as heterogeneous catalysts were prepared by hydrothermal treatment and citrate methods to be tested in the oxidation of p-xylene (PX) using as oxidation agent molecular oxygen, hydrogen peroxide, and tert-butyl hydroperoxide. Preparation of mixed Mn-Fe oxide by the citrate method releases materials with smaller particle size and lower degree of crystallinity as compared with the hydrothermal one, which further leads to a higher activity toward the oxidation of PX. A conversion of PX of 98% and a yield in p-toluic acid of 93% were obtained in the presence of Mn/Fe/O prepared by the citrate method using tert-butyl hydroperoxide as an oxidizing agent. (C) 2017 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.

Super paramagnetic iron oxide nanoparticles such as maghemite have been shown to exhibit antimicrobial properties [1-5]. Moreover, the iron oxide nanoparticles have been proposed as a potential magnetically controllable antimicrobial agent which could be directed to a specific infection [3-5]. The present research has focused on studies of the surface and structure of iron oxide dextran (D-IO) composite layers surface and structure. These composite layers were deposited on Si substrates. The structure of iron oxide dextran composite layers was investigated by X-Ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) while the surface morphology was evaluated by Scanning Electron Microscopy (SEM). The structural characterizations of the iron oxide dextran composite layers revealed the basic constituents of both iron and dextran structure. Furthermore, the in vitro evaluation of the antifungal effect of the complex layers, which have been shown revealed to be active against C. albicans cells at distinct intervals of time, is exhibited. Our research came to confirm the fungicidal effect of iron oxide dextran composite layers. Also, our results suggest that iron oxide dextran surface may be used for medical treatment of biofilm associated Candida infections.

This paper presents electric and electro-optic studies conducted on a new composite, namely hydroxypropylcellulose network with liquid crystal fillings. The composite was manufactured using the electrospinning method, and deposited on indium tin oxide glass. In terms of electric characterization, the samples were subjected to impedance spectroscopy, their equivalent circuit model was deduced, and the corresponding electric parameters were computed based on the Cole-Cole diagrams and frequency plots of the two impedance components. In terms of electro-optic studies, the optical transmission of the sample under a varying steady-state alternative regime voltage was recorded, and the saturation threshold field was determined. Also, the switching times of the sample with respect to a step signal were determined.