Publications from 2010

Title Statistical analyses of repolarisation current of a PZT film deposited on ITO electrode with different thermal treatments
Author(s) Marino, S; Ionescu, AT; Alexe-Ionescu, AL; Nicastro, G; Strangi, G; Scaramuzza, N
Source PHILOSOPHICAL MAGAZINE 90 (12):1575-1584 2010
Abstract In the vast application fields of lead zirconate titanate (PZT) thin films, of particular interest are the interaction effects occurring at the ferroelectric-substrate interface [E. Bruno, M.P. De Santo, M. Castriota, S. Marino, G. Strangi, E. Cazzanelli and N. Scaramuzza, J. Appl. Phys. 103 (2008) p.064103; S. Dunn and R.W. Whatmore, J. Eur. Ceram. Soc. 22 (2002) p.825]. Relevant for this purpose are polarity-sensitive liquid crystals (LC) cells and micro- and nanoelectronic applications [S. Marino, M. Castriota, G. Strangi, E. Cazzanelli and N. Scaramuzza, J. Appl. Phys. 102, selected for Virtual Journal of Nanoscale Science Technology, 30 July 2007 (2007) p.013002]. The polarisation current was investigated of a PZT film (PbZr0.47Ti0.53O3) obtained by sol-gel synthesis and deposited by spin coating on an indium tin oxide (ITO) electrode. The different behaviour exhibited by such a system when the support electrode was previously submitted to a thermal treatment was attributed to the change of the electrical properties of the ITO layer. In particular, a higher negative charge in the conductive band of the ITO electrode seems to be responsible for a higher order in the ferroelectric film.
ISSN 1478-6435
DOI 10.1080/14786430903419091

Title Anomalous conductivity in PZT thin film deposited on copper substrate electrode
Author(s) Ionescu, AT; Alexe-Ionescu, AL; Marino, S; Castriota, M; Strangi, G; Nicastro, G; Scaramuzza, N
Source PHILOSOPHICAL MAGAZINE 90 (13):1733-1742 2010
Abstract Electrical properties of ferroelectric films are influenced by factors that include methods of synthesis and characteristics of the substrate electrode. Conductivity measurements were performed on PZT (lead zirconate titanate) thin films deposited by sol-gel synthesis on a copper electrode to investigate electric properties and isolate the principal charge carriers. A semiconducting PZT/Cu interface appears during thermal treatment, significantly influencing electric conduction. A power law, describing the transport mechanism across the PZT film, was found empirically.
ISSN 1478-6435
DOI 10.1080/14786430903463529

Title Automated Compensation of Light Attenuation in Confocal Microscopy by Exact Histogram Specification
Author(s) Stanciu, SG; Stanciu, GA; Coltuc, D
Abstract Confocal laser scanning microscopy (CLSM) enables us to capture images representing optical sections on the volume of a specimen. The images acquired from different layers have a different contrast: the images obtained from the deeper layers of the specimen will have a lower contrast with respect to the images obtained from the topmost layers. The main reasons responsible for the effects described above are light absorption and scattering by the atoms and molecules contained in the volume through which the light passes. Also light attenuation can be caused by the inclination of the observed surface. In the case of the surfaces that have a steep inclination, the reflected light will have a different direction than the one of the detector. We propose a technique of digital image processing that can be used to compensate the effects of light attenuation based on histogram operations. We process the image series obtained by CLSM by exact histogram specification and equalization. In this case, a strict ordering among pixels must be induced hi order to achieve the exact histogram modeling. The processed images will end up having exactly the specified histogram mid not a histogram with a shape that just resembles to the specified one, as in the case of classical histogram specification algorithms. Experimental results and theoretical aspects of the induced ordering are discussed, as well as a comparison between several histogram modeling techniques with respect to the processing of image series obtained by confocal microscopy. Microsc. Res. Tech. 73:165-175, 2010. (c) 2009 Wiley-Liss, Inc.
ISSN 1059-910X
DOI 10.1002/jemt.20767

Title CdS nanocrystals for laser scanning microscopy
Author(s) Savu, B; Peretz, S; Stanciu, GA
Abstract In this paper we report the synthesis and characterization of CdS semiconductor quantum dots for potential use in bioimaging. Nanocrystals structure and their mean size were determined by means of XRD. Photoluminescence characteristics of the nanocrystals were investigated using TPE laser scanning microscopy.
ISSN 1842-6573

Title Characterization of Langmuir-Blodgett films of a calix[8]arene and sensing properties towards volatile organic vapors
Author(s) Capan, R; Ozbek, Z; Goktas, H; Sen, S; Ince, FG; Ozel, ME; Stanciu, GA; Davis, F
Source SENSORS AND ACTUATORS B-CHEMICAL 148 (2):358-365 2010
Abstract: Within this article, we report the characterization and organic vapor sensing properties of Langmuir-Blodgett (LB) thin films of calix[8]arenes. Surface pressure-area isotherms show that very stable monolayers are formed at the air-water interface. The LB film could be deposited onto different substrates which allowed the films to be characterized by UV, quartz crystal microbalance (QCM), surface plasmon resonance (SPR) and atomic force microscopy (AFM). The results indicate that good quality, uniform LB films can be prepared with transfer ratios of over 0.95. QCM results showed that the deposited mass of calix[8]arene monolayer onto a quartz crystal decreased from 693 to 204 ng as the number of layers is increased. AFM studies showed a smooth, and void free surface morphology with a rms value of 1.202 nm. The sensing abilities of this LB film towards the development of room temperature organic vapor sensing devices are also studied. Responses of the LB films to various vapors are fast, large, and reversible. It was found that the obtained LB film is significantly more sensitive to chloroform than other vapors. It can be concluded that this molecule could have a potential application in the research area of room temperature vapor sensing devices. (C) 2010 Elsevier B.V. All rights reserved.
ISSN 0925-4005
DOI 10.1016/j.snb.2010.05.066
Title On the suitability of SIFT technique to deal with image modifications specific to confocal scanning laser microscopy

Stanciu SG, Hristu R, Boriga R, Stanciu GA.


Microsc Microanal. 2010 Oct;16(5):515-30. Epub 2010 Aug 5.

Computer vision tasks such as recognition and classification of objects and structures or image registration and retrieval can provide significant information when applied to microscopy images. Recently developed techniques for the detection and description of local features make the extraction and description of local image features that are invariant to various changes possible. The invariance and robustness of feature detection and description techniques play a key role in the design and implementation of object recognition, image registration, or image mosaicing applications. The scale-invariant feature transform (SIFT) technique is a widely used method for the detection, description, and matching of image features. In this article we present the results of our experiments regarding the repeatability of SIFT features, and to the precision of the SIFT feature matching, under image modifications specific to confocal scanning laser microscopy (CSLM). We have analyzed the behavior of SIFT while changing the pinhole aperture, photomultiplier gain, laser beam power, and electronic zoom. Our experiments, conducted on CSLM images, show that the SIFT technique is able to match detected key points between images acquired at different values of the acquisition parameters with good precision and represents a consistent tool for computer vision applications in CSLM

Author(s) Floroian, L; Mihailescu, I; Sima, F; Stanciu, G; Savu, B
Abstract We evaluated the scrach resistance, adherence and hardness for novel polymethyl methacrylat-bioglass (PMMA+BG) composites deposited by matrix assisted pulsed laser evaporation technique on medical titanium substrate, for applications in implantology. The bioactivity of the films was assessed in vitro by soaking the composite material films into simulated body fluid (SBF) followed by Fourier transform infrared spectrometry and confocal scanning laser microscopy analysis to determine the extent of hydroxyapatite formation on the bioactive surface. Interaction between human osteoblasts and tested material was studied by fluorescent mark of cellular proteins: actin and The human osteoblasts were shown to cover the entirely structures with which they strongly interact and this is an evidence of the PMMA+BG films biocompatibility.
ISSN 1223-7027

Title Structural and optical properties of Mn doped ZnS semiconductor nanostructures
Author(s) Gogoi, DP; Ahmed, GA; Mohanta, D; Choudhury, A; Stanciu, GA
Source INDIAN JOURNAL OF PHYSICS 84 (10):1361-1367 2010
Abstract Manganese doped zinc sulphide nanoparticles were fabricated by adopting an inexpensive solution growth route. Different samples were fabricated by varying Mn concentrations. UV-VIS study reveals blue-shift on the onset of absorption and hence enhancement in the optical band gap upto 0.75 eV, indicating strong quantum confinement. Photoluminescene study for all the samples display characteristic band edge peak at similar to 410 nm. The broad peak similar to 560-580 nm is ascribed to Mn incorporation. Further, structural investigations were carried out by using X-Ray diffraction and transmission electron microscopy (TEM).
ISSN 0973-1458
DOI 10.1007/s12648-010-0127-7

Title Two Photon Emission and Nonlinear Optical Imaging of Acetonitrile-Treated Quasi-Spherical Nanoscale PbS Systems
Author(s) Dutta, N; Mohanta, D; Ahmed, GA; Choudhury, A; Hristu, R; Stanciu, SG; Stanciu, GA
Source IEEE PHOTONICS JOURNAL 2 (6):1060-1068 2010
Abstract The fabrication and nonlinear optical imaging of similar to 5-nm-sized lead sulfide (PbS) nanoscale particles prepared in a water-soluble polymer matrix is reported. The two photon excitation fluorescence (TPEF) studies (using Ti:Sapphire laser, lambda(ex) similar to 706 nm, P 400 mW, pulse similar to 80 fs) clearly show the foremost band-edge and asymmetric trap-related emissions. The chain-like organization of PbS nanoparticles was evident from the electron microscopy studies, and the impression from a cluster of nanopatterns was observable through laser scanning confocal microscopy. We have observed adequate correspondence between the TPEF spectra-based nonlinear optical images and spots corresponding to PbS nanoparticle assemblies. In addition, the PbS nanoparticles that are capable of producing strong second harmonic signals were efficiently imaged along the forward direction of the nonlinear microscopy. Investigation of two photon absorption processes along with the second-harmonic-generated imaging indicates the possibility of using the nanoscale particles in single molecule fluorescence spectroscopy, biomolecular labeling, and/or imaging applications.
ISSN 1943-0655
DOI 10.1109/JPHOT.2010.2093513
Title Nonlinear optical absorption in inverse V-shaped quantum wells modulated by high-frequency laser field
Author(s) Niculescu, EC; Burileanu, LM
Source EUROPEAN PHYSICAL JOURNAL B 74 (1):117-122 2010
Abstract It is suggested that intersubband transition absorption coefficient in polarized inverse V-shaped quantum wells can be modulated through a non-resonant high-frequency laser field. This tuning mechanism is based on the variation of the quasi-bound states and corresponding wave functions of the quantum well with increasing intensity of the laser field. A transition between the strong absorption and induced laser transparency regimes is observed in one of the studied structures. The dependence of the saturation intensity on the laser parameter and the electric field strength is also investigated.
ISSN 1434-6028
DOI 10.1140/epjb/e2010-00060-3

Author(s) Eseanu, N; Niculescu, EC
Abstract We calculated the effects of the hydrostatic pressure and temperature on the binding energy for centric shallow donors in asymmetrical GaAs/AlGaAs quantum wells, within the effective mass approximation and variational approach. We found that the pressure, temperature and asymmetry effects are mainly observed when the quantum confinement due to the barrier potential are stronger.
ISSN 1223-7027

Title Intense THz laser effects on off-axis donor impurities in GaAs-AlGaAs coaxial quantum well wires
Author(s) Radu, A; Niculescu, EC
Source PHYSICS LETTERS A 374 (15-16):1755-1761 2010
Abstract The binding energy of an off-axis shallow-donor impurity in a GaAs coaxial cylindrical quantum well-wire under the action of an intense, high-frequency laser field is calculated using a variational procedure within the effective-mass approximation. We take into account the laser dressing effects on both the impurity Coulomb potential and the confinement potential. Numerical calculations of the ground state subband energy levels based on a finite element method are performed for different barrier thicknesses and laser field parameters. Our model indicates a possible tuning of the well potential shape along the laser polarization direction. Strong distortions of the electron probability density under intense laser field conditions are also predicted. The study proves that the presence of the laser field partially breaks down the degeneracy of the states for donors symmetrically positioned within the structure. The results obtained show that the impurity energy levels in coaxial quantum wires call be significantly modified and controlled by intense laser fields. (C) 2010 Elsevier B.V. All rights reserved.
ISSN 0375-9601
DOI 10.1016/j.physleta.2010.02.007

Title Laser-induced diamagnetic anisotropy of coaxial nanowires
Author(s) Niculescu, EC; Radu, A
Source CURRENT APPLIED PHYSICS 10 (5):1354-1359 2010
Abstract The diamagnetic susceptibility of the hydrogenic impurity in coaxial quantum well wires under high frequency laser field has been investigated taking into account the laser dressing effect on both the impurity Coulomb potential and confinement potential. The analysis revealed that a laser beam which is linearly polarized along the wire radial direction destroys the cylindrical symmetry of the donor Hamiltonian, leading to a strong dependence of the electron probability density on the laser field amplitude and orientation of the applied magnetic field. Thus, the direction of the magnetic field can be used as a tunable parameter in the variation of the diamagnetic susceptibility in low-dimensional structures under intense laser radiation. This phenomenon gives an additional degree of freedom in device applications. (C) 2010 Elsevier B.V. All rights reserved.
ISSN 1567-1739
DOI 10.1016/j.cap.2010.04.009

Title Hydrostatic pressure and electric field effects on the normalized binding energy in asymmetrical quantum wells
Author(s) Niculescu, EC; Eseanu, N
Source EUROPEAN PHYSICAL JOURNAL B 75 (2):247-251 2010
Abstract We have investigated the simultaneous effects of the hydrostatic pressure and electric field on the ground subband level and on normalized binding energy of an on-center donor in asymmetrical GaAs/AlGaAs quantum wells within the effective-mass approximation and a variational approach. We found that the well size at which the impurity energy changes from positive to negative value (turning point) strongly depends on the asymmetry and hydrostatic pressure. As a key result, we suggest that the study of the normalized binding energy for various values of the electric field in direct and inverse polarization regimes can be used to feel the quantum well asymmetry and to unambiguously find out the effective pressure acting on a given heterostructure.
ISSN 1434-6028
DOI 10.1140/epjb/e2010-00149-7

Author(s) Niculescu, EC; Carjeu, IG; Ionescu, RC
Abstract The polarization of the carriers in an electric field in GaAs/AlGaAs quantum well under the simultaneous action of the high-frequency laser filed and the hydrostatic pressure is investigated. The results show that the anomalous polarization of the first excited level is partially compensated by the presence of the laser radiation. The intersubband transition energy can be tuned by changing laser field intensity and hydrostatic pressure.
ISSN 1223-7027

Title Effect of UV Sunscreens Loaded in Solid Lipid Nanoparticles: A Combinated SPF Assay and Photostability
Author(s) Lacatusu, I; Badea, N; Murariu, A; Bojin, D; Meghea, A
Abstract The aim of this investigation was to obtain lipid nanoparticles loaded with different sunscreen agents in order to achieve enhanced photoprotection and to decrease the amount of UV – absorbers, with preserving at the same time a high sun protection factor. The developed formulations combined different types of additives including a mixture of non-ionic surfactant and lechitine with two lipids as solid matrix to obtain favourable stable lipid formulations. The research work could be concluded as successefully production of lipid nanoparticles loaded with UV-A and UV-B absorbers (with average size less than 100nm) that may represent useful UV-blocking systems in sunscreen products for cosmetical purpose.
ISSN 1542-1406
DOI 10.1080/15421401003719928

Title Antioxidant Capacity of Lipid Nanoparticles Loaded with Rosemary Extract
Author(s) Lacatusu, I; Badea, N; Murariu, A; Nichita, C; Bojin, D; Meghea, A
Abstract This work presents a simple, available and effective method for preparation of lipid nanoparticles loaded with a natural extract containing active principles. The purpose of the research is to synthesize new lipid nanoparticles with enhanced antioxidant activity, by using two types of lipid carriers. The lipid nanoparticles were produced by emulsification with high shear homogenisation method using biocompatible emulsifiers with excellent skin compatibility as surfactants. The developed nanoparticles were characterized for particle size, polydispersity index, zeta potential, morphology, crystallinity of the lipid matrices and antioxidant activity. Both types of synthesized lipid nanoparticles exhibit an improved antioxidant activity.
ISSN 1542-1406
DOI 10.1080/15421401003719886

Title Silica Polymeric Networks Templated with D-Fructose – as Host Matrices for Natural Extracts Immobilization
Author(s) Lacatusu, I; Badea, N; Bojin, D; Iosub, I; Meghea, A
Conference Title 10th International Conference on Frontiers of Polymers and Advanced Materials
Conference Date SEP 28-OCT 02, 2009
Conference Location Santiago, CHILE
Abstract In the present paper a non-surfactant templating route has been employed to prepare new fluorescence nanostructured materials, by combining some natural organic molecules present in vegetal extracts with three-dimensional silica and hybrid silica-silsesquioxane networks. The results obtained clearly indicated that organic chromophores like flavonoid compounds from two extracts with bio-active principles (orange peel extract and ornamental bush extract) can be efficiently immobilised in the host silica and hybrid matrices, using D-fructose as template. The confirmation of immobilization process was demonstrated by extensive characterization of final materials, achieved based on spectroscopy technique, fluorescence intensity measurements and transmission electron microscopy.
ISSN 1542-1406
DOI 10.1080/15421401003726774

Title Controlling the orientation of microgrooves and the depth of the ripple structure in dye-doped liquid crystal cells
Author(s) Palarie, I; Dascalu, C; Iacobescu, GE
Source LIQUID CRYSTALS 37 (2):195-199 2010
Abstract The permanent structure induced by an Ar+ linearly polarised laser beam on an asymmetric dye-doped nematic liquid crystal cell was investigated in a pump-probe experiment. The polarisation direction of the probe beam was parallel to the easy axis and two configurations of pump beam were used: polarisation directions perpendicular and parallel to the easy axis. The transmitted intensity of the probe beam was recorded during irradiation and it was observed that it depended both on the power and polarisation direction of the pump beam. We explained the evolution of the transmitted intensity and evaluated the start time of formation of the ripple structure. The induced permanent structure in the irradiated zones and the laser-induced surface morphology was studied using a polarising optical microscope and an atomic force microscope, respectively. The surface morphology in the irradiated zones was also dependent on both the power and polarisation of the Ar+ laser beam. The orientation of the microgrooves in the ripple structure was parallel to the polarisation direction of the pump laser beam in both configurations. For a given pump power, the depth of the ripple structure was greater in the case of an Ar+ beam polarised parallel to the easy axis. The induced azimuthal anchoring energy provided by the ripple structure was evaluated.
ISSN 0267-8292
DOI 10.1080/02678290903484222

Title Study on laser-induced ripple structures in dye-doped liquid crystal films in high-intensity regime
Author(s) Palarie, I; Dascalu, C; Iacobescu, GE
Abstract The photoalignment effect induced by an Ar+ linearly polarized laser beam on a dye-doped nematic liquid crystal in a pump-probe experiment is investigated. A symmetric capillary cell with two polymer coated glasses was used. An easy axis was induced by rubbing both surfaces in the same direction. The exciting Ar+ laser beam has the polarization direction perpendicular to the easy axis. The time dependent transmitted intensity of the probe He-Ne laser beam (polarized parallel to the easy axis) has been measured for various power of Ar+ laser in high-intensity regime and the beginning time of the ripple structure formation has been estimated. The spacing and the depth of the ripple structure were measured by using atomic force microscopy.
ISSN 1454-4164