National Institute Of Materials Physics - Romania

This paper presents some investigations on the properties of guanine (G) and cytosine (C) based heterostructures deposited on flexible substrates. The effects of two types of maleic anhydride-aniline derivatives (maleic anhydride-cyano aniline or maleic anhydride-2,4 dinitroaniline) buffer layer, deposited between indium tin oxide and (G) or (C) layer, on the optical and electrical properties of the heterostructures have been identified. The heterostructures containing a film of maleic anhydride-2,4 dinitroaniline have shown a good transparency and low photoluminescence invisible range. This buffer layer has determined an increase in the conductance only in the heterostructures based on (G) and (C) deposited on biaxially-oriented polyethylene terephthalate substrate. (C) 2011 Elsevier B. V. All rights reserved.

Thin films of As2S3 doped with Eu3+ were prepared by vacuum evaporation. It was measured the fluorescence spectra before and after a heat treatment at 180 degrees C for 45 minutes in inert atmosphere. After the heat treatment the transitions D-5(1) -> F-7(1), D-5(0) -> F-7(1) and D-5(0) -> F-7(2) were evidenced in the luminescence spectrum.

Networks of dots made of As2S3 chalcogenide has been obtained by Vacuum Evaporation and Pulsed Laser Deposition from bulk glassy As2S3 by the adapted method of SCEV (screen evaporation method). A very thin layer of Eu2O3 was deposited from a different target in the final deposition process. After a heat treatment at 180 degrees C for 90 minutes in nitrogen atmosphere a structural transformation of the amorphous As2S3 to realgar (AsS) occurred in the PLD deposited dots and the network of dots develops a luminescence effect. (Received November 25, 2011; accepted December 2, 2011)

Thin films of arsenic sulphide have been obtained by Pulsed Laser Deposition from bulk As(2)S(3). A very thin layer of Eu(2)O(3) was deposited by PLD from a different target in the next deposition process. After a heat treatment at 180 degrees C for 45 minutes in inert atmosphere a structural transformation of the amorphous As(2)S(3) to realgar (As(2)S(2)) occurred and the film develops a strong luminescence effect.

The thermoluminescence (TL) response to gamma-ray irradiation of tooth enamel is reported. The tooth enamel was separated from dentine by using mechanical and physico-chemical procedures followed by grinding (grain size 100 urn) and etching. Then was attributed to the recombination of CO(2)(-) radicals incorporated into or attached to the surface of hydroxyapatite crystals. The growth of the 380 degrees C peak with absorbed dose was examined with irradiated tooth enamel samples and reconstructed doses evaluated for tooth enamel samples from four human subjects. (C) 2011 Elsevier Ltd. All rights reserved.

There was discovered a material with strong photoconduction effect. Langmuir-Blodgett film with barium stearate, and selenium carbazole has been prepared and tested for the change of conductivity (decrease) under the influence of UV-radiation. Change of resistance in a time scale of 0-400 seconds was evidenced. The UV radiation determines an increase of the electrical resistence and after switching off the illumination a slow decrease of the resistance occurs.

Simple and low cost biosensor based on screen-printed electrode for sensitive detection of some alkylphenols was developed, by entrapment of HRP in a nanocomposite gel based on single-walled carbon nanotubes (SWCNTs) and 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) ionic liquid. Raman and FTIR spectroscopy, CV and EIS studies demonstrate the interaction between SWCNTs and ionic liquid. The nanocomposite gel, SWCNT-[BMIM][PF6] provides to the modified sensor a considerable enhanced electrocatalytic activity toward hydrogen peroxide reduction. The HRP based biosensor exhibits high sensitivity and good stability, allowing a detection of the alkylphenols at an applied potential of -0.2 V vs. Ag/AgCl, in linear range from 5.5 to 97.7 mu M 4 for 4-t-octylphenol and respectively, between 5.5 and 140 mu M for 4-n-nonylphenol, with a response time of about 5s. The detection limit was 1.1 mu M for 4-t-octylphenol, and respectively 0.4 mu M for 4-n-nonylphenol (S/N = 3). (C) 2011 Elsevier B.V. All rights reserved.

Cotton/polyester woven fabrics were functionalized with ZnO thin films or nanoparticles by pulsed laser deposition, using a KrF* excimer laser source. Depending on the number of applied laser pulses, well-separated nanoparticles (for 10 pulses) or compact thin films (for 100 pulses) were deposited. The synthesized nanostructures were evaluated morphologically by scanning electron microscopy and atomic force microscopy, physico-chemically by x-ray diffraction and functionally by the contact angle method. By modifying the ambient gas nature and pressure in the deposition chamber, hydrophilic or hydrophobic surfaces were obtained. When using an oxygen flux, both the deposited thin films and nanoparticles were hydrophilic. After deposition in vacuum, the nanoparticles were hydrophobic, but the thin films were super-hydrophobic. This radical modification of wetting behavior was assigned to the differences in microstructure features and surface electrical charging in the two cases. (C) 2011 American Institute of Physics. [doi:10.1063/1.3639297]

Abnormal anti-Stokes Raman emission (AASRE) is defined by an anti-Stokes/Stokes intensity ratio much greater than expected on the basis of the equilibrium population of excited vibration states provided by the Boltzmann law. Using nonlinear optical materials such as LiNbO(3) and CdS in powder form, we demonstrate that under continuous single beam excitation it presents AASRE whose properties are similar to a single beam pumped Coherent Anti-Stokes Raman Scattering. We explain AASRE as resulting from a wave-mixing mechanism of the incident laser light with a Stokes shifted Raman light produced by a spontaneous Raman light scattering process, both strongly scattered inside the sample. (C) 2011 American Institute of Physics. [doi:10.1063/1.3633936]

In this study, we present the deposition of ZnPc, Alq3, and PTCDA thin films using Matrix Assisted Pulsed Laser Evaporation (MAPLE) technique. We also report the realisation of multilayer structures, made by the successive application of MAPLE. The films have been characterized by spectroscopic (UV-VIS and Photoluminescence) and microscopic (SEM and AFM) methods, and the effect of different deposition conditions such as fluence, number of pulses, and target concentration on the properties has been analysed. This paper also presents some investigations on the electrical conduction in sandwich type structures ITO or Si/organic layer/Au or Cu and ITO/double organic layer/Cu, emphasising the dominant effect of the height of the energetic barriers at the inorganic/organic and organic/organic interfaces.