National Institute Of Materials Physics - Romania

Hybrid material based on PbI2 intercalated with 2,2'-bypiridine (BIPY) was investigated by correlated studies of photoluminescence. infrared absorption and Raman spectroscopy. The PbI2(BIPY) intercalated compound has been synthesized by the chemical reaction of K1 and Pb(NO3)(2) in aqueous BIPY solution The optical studies reveal different properties for the hybrid material in comparison with those of pure PbI2 and BIPY. In the photoluminescence spectrum of the intercalated compound. recorded at liquid nitrogen temperature a new intense hand emission with maximum at 2 07 eV is observed. The excitation spectrum reveals it broad hand featured by several maxima at 2.77, 3.34 and 3 70 eV. New absorption bands at about 1589, 1489, 1435, 1312, 1009 cm(-1) are observed in the IR spectrum of PbI2(BIPY). The Raman spectrum of intercalated compound discloses new lines at 67, 83, 127 cm(-1) and the shift of two Raman lines from 994 cm(-1) to 1010 cm(-1) and from 1045 cm(-1) to 1060 cm(-1). A charge transfer process, leading to the formation of lead-BIPY coordination complexes. is considered its responsible for the strong host-guest interaction revealed by almost all experimental data

Thin films of sucrose (C12H22O11) were deposited on thin cut glass substrates by thermal evaporation technique (p similar to 10-5 torr). The surface morphology was putted into evidence by FT-IR and SEM analysis. The experimental results confirm a uniform deposition of an adherent sucrose layer. The biological tests (e.g., cell morphology and cell viability evaluated by measuring mitochondrial dehydrogenise activity with MTT assay) confirm the properties of sucrose thin films as bioactive material. The human fetal osteoblast system grown on thin sucrose film was used for the determination of cell proliferation, cell viability and cell morphology studies.

In this paper results concerning the changes of the electric characteristics of langasite resonators irradiated with electron and gamma rays are reported. For both electron and gamma irradiations the quality factor increases significantly, presumably due to the re-distribution of the point defects. Preliminary optical investigations in UV-VIS domain confirm the modification of defect structure.

Functionalization of PbI2 with polyaniline-emeraldine base (PANI-EB) or polyaniline-emeraldine salt (PANI-ES) is demonstrated by Raman spectroscopy. Two functionalization methods were used: electrochemical polymerization of aniline onto the PbI2 modified Pt electrode and the mechanico-chemical reaction between PANI and PbI2. The functionalization induces changes in the Raman spectrum of PbI2 that consist in the appearance of new Raman lines with the peaks at 80, 144 and 170 cm(-1) The first line is the signature of the "stacking faults" that disrupt the stacking sequence of layers I-Pb-I atomic layers along the c crystalline axis by the intercalation of polymer molecules The bands at 144 and 170 cm(-1) are attributed to a vibrational mode associated to the Pb-NHR"(2) (R" = C6H4) bond.

We investigate the differential conductance dI/dV for the interacting T-shape model, using an approach based on the Keldysh formalism and the Lacroix solution for the equation of motion. A peak-dip crossover has been noticed by changing the hybridization between the two dots. For the same model, the combined interaction and interference processes give rise to the Fano-Kondo effect with an interesting crossing point of the isoterms below the Kondo temperature A tentative explanation of these effects is given in terms of the many-body spectral properties of the system.

We present the preparation, structural, and magnetic properties of a series of Fe-containing borosilicate glasses as a function of the ratio SiO2/Fe2O3 which is ranging from 1.49 to 2.68. The role of nucleators (Cr2O3 and P2O5) was also investigated. X-Ray diffraction has revealed the formation of magnetite as the major or unique crystalline phase. As SEM micrographs have revealed, the addition of P2O5 give rise to a finer structure as compared with Cr2O3. In addition, the same oxide decreases the temperature of structural transition with almost 100 degrees C. The magnetization data reveal a two step transition at low temperatures: a high temperature transition at T-v = 128 K, which we attribute to the Verwey transition, and a low temperature transition at T-s = 48 K which, most likely, is the result of change in the dynamic of the domain motion.

The influence of Pb2+ doping on the optical properties of LiF crystals before and after irradiation with X-ray was studied by using optical absorption and photoluminescence measurements. After irradiation it was observed an increase of the absorption due to primary and aggregate electronic defects together with a higher photoluminescence signals associated with the F-2 and F-3(+) colour centres in doped samples compared with the undoped ones.

Nanowires made of CdTe were produced by using a template method. Polymer ion track foils (30 micrometers thick) were used as templates, after a proper chemical etching. Nanowires were electrochemically grown in the resulting pores. A discussion of the observed correlations between the morphological/structural properties of the wires and the growth conditions is given. Electrical properties of the arrays of nanowires were studied in the temperature range of 40 K - 300 K, after contacting them by sputtering a gold layer on top of the membranes. Symmetric, non-linear I-V characteristics were recorded in the voltage range used and an activated electrical resistance was observed in the ohmic regime.

Fullerene C-60 has attracted attention due to its special chemical and physical properties. However, its poor solubility and processability arise difficulties in practical applications. These problems may be surpassed by grafting C-60 on polymers. This study presents the synthesis of the polyethylene/maleic anhydride copolymers and C-60 structures and their characterization by photoluminescence. The synthesis of the material is based upon the reaction of fullerene C-60 with amino groups containing in the polymer chains. In the first step, some polyethylene (PE)/maleic anhydride (MA) copolymers having 1, 3, 6 and 10 wt.% anhydride groups were reacted with an amine compound. The following step consists in the reaction of C-60 with the amine groups. A proof that the structures synthesized contain C-60 is given by the photoluminescence spectra.

ZnO is a wide band-gap (ca. 3.4 eV) semiconductor, piezoelectric, pyroelectric, biocompatible, transparent in the visible spectrum and UV light emitting material. The fabrication in 2001 of the first nanobelts of semiconductor oxide materials lead to a rapid expansion of researches concerning one dimensional nanostructures (nanotubes, nanowires, nanobelts), given their possible application in optics, optoelectronics, piezoelectricity, catalysis. Researches carried on up to date evidenced the possibility to obtain an extraordinary variety of ZnO nanostructures, in function of the experimental parameters and the used growth methods. In this work we present morphostructural results on nanostructured ZnO layers obtained by electrochemical deposition. The films have been grown on gold covered glass plates and Si wafers, in various experimental conditions such as: nature of the wetting agents, electrical polarization of the substrate (continuous, pulsed). The influence of the growth conditions on the crystalline structure and morphology of the films is revealed by scanning and transmission electron microscopy studies. The films show a variety of growth morphologies, from entangled-wires-like to honeycomb-like layers. These large-specific-surface layers will be tested as nanostructured substrates for photovoltaic cells with improved efficiency.