Distribution by Scientific Domains
Distribution within Physics and Astronomy

Kinds of Optical

  • longitudinal optical
  • non-linear optical
  • nonlinear optical
  • second-order nonlinear optical

  • Terms modified by Optical

  • optical aberration
  • optical absorbance
  • optical absorption
  • optical absorption measurement
  • optical absorption spectroscopy
  • optical absorption spectrum
  • optical action potential
  • optical activity
  • optical amplifier
  • optical analysis
  • optical anisotropy
  • optical application
  • optical band gap
  • optical bandgap
  • optical bands
  • optical behavior
  • optical behaviour
  • optical biopsy
  • optical biosensor
  • optical cavity
  • optical change
  • optical characteristic
  • optical characterization
  • optical clarity
  • optical clearing
  • optical coherence tomography
  • optical coherence tomography study
  • optical communication
  • optical component
  • optical conductivity
  • optical constant
  • optical contrast
  • optical counterpart
  • optical crystal
  • optical data
  • optical data storage
  • optical density
  • optical density value
  • optical depth
  • optical design
  • optical detection
  • optical device
  • optical effects
  • optical element
  • optical emission
  • optical emission spectrometry
  • optical emission spectroscopy
  • optical excitation
  • optical feature
  • optical fiber
  • optical fiber probe
  • optical fibre
  • optical field
  • optical filament
  • optical filter
  • optical function
  • optical gain
  • optical identification
  • optical image
  • optical imaging
  • optical imaging methods
  • optical information
  • optical interference
  • optical interferometer
  • optical investigation
  • optical isomer
  • optical kerr effect
  • optical laryngoscope
  • optical lattice
  • optical limiting
  • optical limiting property
  • optical lithography
  • optical loss
  • optical luminescence
  • optical mapping
  • optical material
  • optical measurement
  • optical media
  • optical methods
  • optical microcavity
  • optical micrograph
  • optical microscope
  • optical microscope image
  • optical microscopes
  • optical microscopy
  • optical microscopy image
  • optical mode
  • optical network
  • optical nonlinearity
  • optical observation
  • optical parameter
  • optical path length
  • optical performance
  • optical phenomenoN
  • optical phonon
  • optical phonon mode
  • optical polarization
  • optical power
  • optical probe
  • optical property
  • optical pulse
  • optical purity
  • optical quality
  • optical recording
  • optical resolution
  • optical response
  • optical rotation
  • optical rotatory dispersion
  • optical scanning
  • optical section
  • optical sensor
  • optical signal
  • optical spectroscopy
  • optical spectrum
  • optical structure
  • optical studies
  • optical study
  • optical susceptibility
  • optical switch
  • optical switching
  • optical system
  • optical technique
  • optical techniques
  • optical telescope
  • optical thickness
  • optical transition
  • optical transmission
  • optical transmittance
  • optical transparency
  • optical transport network
  • optical trapping
  • optical tweezers
  • optical waveguide
  • optical waveguide device
  • optical wavelength

  • Selected Abstracts


    ABSTRACT The mechanical, optical and barrier properties of chitosan films containing polygodial (0.0, 2.7, 13.9, 25.0 mg/g of chitosan) were studied. Water vapor permeability (WVP), tensile strength, percentage elongation at break, CIELab color parameters, hue angle and chroma of films were determined. Fourier transform infrared (FTIR) was also performed to determine functional group interaction between the matrix and polygodial added. The use of polygodial resulted in stronger films without losing their extensibility and with low WVP. Films became darker with yellow-green coloration with increasing polygodial concentration. Polygodial added to chitosan films did not have any interaction with the amino groups of chitosan as measured by FTIR. Polygodial as a natural dialdehyde can effectively be applied to enhance some physical properties of edible films prepared with chitosan. PRACTICAL APPLICATIONS There has been an increased interest in the study of edible,biodegradable packaging films during the last decade, offering an alternative and partial solution to the problem of accumulation of solid waste composed of synthetic inert polymers, and chitosan films has been studied with this purpose. Furthermore, replacing synthetic additives by natural compounds such us polygodial can be a suitable manner to improve some physical properties of those chitosan films. [source]

    Optical and dielectric studies on pure and Ni2+, Co2+ doped single crystals of bis thiourea cadmium chloride

    R. Uthrakumar
    Abstract Good quality single crystals of Ni2+, Co2+ ions doped Bisthiourea Cadmium Chloride (BTCC) are some of the excellent and efficient non-linear optical materials grown from aqueous solution by slow evaporation method. The lattice parameters of the grown crystals are determined by single crystal X-ray analysis. UV spectral analyses on these samples reveal the improved transparency of the doped crystals ascertaining the inclusion of metal ion in the lattice. FTIR spectral analysis carried out on the materials confirm the presence of functional groups. Dielectric measurements reveal that the dielectric constant of pure and doped crystals decreases with increase of frequency. ( 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Optical and electrical studies on spray deposited ZnO thin films

    P. P. Sahay
    Abstract ZnO thin films were prepared by spray pyrolytic decomposition of zinc acetate onto a glass substrate. These films were analyzed for the optical and electrical properties. Optical studies show that in these films the electronic transition is of the direct transition type. The optical energy gap for the films of different thicknesses is estimated to be in the range 2.98 , 3.09 eV. Electrical studies indicate that the films exhibit thermally activated electronic conduction and the activation energies are found to be dependent on the film thickness. The complex impedance measurements were carried out over a wide range of frequencies at room temperature (300 K). All the impedance spectra contain only a single arc, but the arc has a non-zero intersection with the real axis in the high frequency region. Also, the arc has its centre lying below with the real axis which indicates the multirelaxation behavior of the films. ( 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Growth and properties of ferroelectric potassium ferrocyanide trihydrate single crystals

    R. Kanagadurai
    Abstract Single crystals of potassium ferrocyanide trihydrate, K4[Fe(CN)63H2O (KFCT), a ferroelectric material with Curie temperature 251K were grown in silica gel at room temperature for the first time by the solubility reduction method. Resorcinol and ethyl alcohol were used for the purpose of gel setting and supernatant liquid respectively. Optical and mechanical properties were studied for the grown crystal. The structure of the grown crystal was confirmed by X-ray diffraction analysis. Fourier Transform Infrared (FTIR) and FT Raman spectral analysis of the crystalline samples reveal that the crystalline sample consist consists of all functional groups. Thermal analysis of the crystalline sample was performed by TGA and DTA methods. The Vicker's micro hardness value was measured for KFCT crystals. The square etch pits with a hopper-like structure is an indicative of 2D nucleation mechanism. ( 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Growth and optical characterization of Cd1- xBexSe and Cd1- xMgxSe crystals

    F. Firszt
    Abstract Cd1- xBexSe and Cd1- xMgxSe solid solutions were grown from the melt by the high pressure Bridgman method. Optical, luminescence and photothermal properties of these materials were investigated. Spectroscopic ellipsometry was applied for determination of the spectral dependence of the complex dielectric function (E) and refractive index n(E) at room temperature in the photon energy range 0.75-6.5 eV for samples with optic axis (c-axis) perpendicular to the air-sample interface. The critical point (CP) parameters for E0 and E1 transitions were determined using a standard excitonic CP function to fit the numerically calculated differential spectra ,2,2/,E2. The dispersion of the refractive index of the alloys was modelled using a Sellmeier-type relation. The values of fundamental and exciton band-gap energies were estimated from the ellipsometric and photoluminescence measurements. The origin of luminescence in Cd1- xBexSe and Cd1- xMgxSe was discussed. ( 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Dewetted growth of CdTe in microgravity (STS-95)

    M. Fiederle
    Abstract Two CdTe crystals had been grown in microgravity during the STS-95 mission. The growth configuration was dedicated to obtain dewetting of the crystals and to achieve high quality material. Background for the performed experiments was based on the theory of the dewetting and previous experience. The after flight characterization of the crystals has demonstrated existance of the dewetting areas of the crystals and their improved quality regarding the earth grown reference sample. The samples had been characterized by EDAX, Synchrotron X-ray topography, Photoluminescence and Optical and IR microscopy. ( 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Study on minute surface structures of the depressed-type early gastric cancer with magnifying endoscopy

    Kouji Tobita
    Background: Gastric surface patterns and morphology of minute surface vessels in depressed lesions were analyzed using a magnifying endoscope with high resolving power to contribute to qualitative diagnosis of gastric cancer. Methods: Subjects were diagnosed with depressed-type early gastric cancer (pT1), there were 63 lesions, 38 differentiated-type lesions, and 25 undifferentiated-type lesions. There were also 40 benign depressed lesions found. After routine observations with an endoscope, amplifying observations of lesions were made by EG-410CR (Fuji Photo Optical; Saitama, Japan) (CR). The images were compared with macroscopic patterns and histopathological patterns of the surgical specimens and endoscopic mucosal resection specimens. Results: Surface patterns of gastric depressed lesions were classified as irregular protrusion, normal papilla, pseudopapilla and amorphia. Irregular protrusion was found only in cancerous lesions. Characteristic minute vessels were observed in amorphia. Their patterns were classified into the following six types: sand, fence, round net, flat net, branch and coil. Irregular protrusion and minute vessels in amorphia (round net, flat net, branch and coil) were specific to cancers. There was a tendency for round net and flat net patterns to be found often in differentiated cancers and for branch and coil patterns to be found often in undifferentiated cancers. Conclusion: This magnifying endoscopic classification is considered useful for the qualitative diagnosis of depressed-type early gastric cancer. [source]

    Holocene valley aggradation driven by river mouth progradation: examples from Australia

    Paul Rustomji
    Abstract Since the end of the post-glacial sea level rise 6800 years ago, progradation of river mouths into estuaries has been a global phenomenon. The responses of upstream alluvial river reaches to this progradation have received little attention. Here, the links between river mouth progradation and Holocene valley aggradation are examined for the Macdonald and Tuross Rivers in south-eastern Australia. Optical and radiocarbon dating of floodplain sediments indicates that since the mid-Holocene sea level highstand 6800 years ago vertical floodplain aggradation along the two valleys has generally been consistent with the rate at which each river prograded into its estuary. This link between river mouth progradation and alluvial aggradation drove floodplain aggradation for many tens of kilometres upstream of the estuarine limits. Both rivers have abandoned their main Holocene floodplains over the last 2000 years and their channels have contracted. A regional shift to smaller floods is inferred to be responsible for this change, though a greater relative sea level fall experienced by the Macdonald River since the mid-Holocene sea level highstand appears to have been an additional influence upon floodplain evolution in this valley. Copyright 2006 John Wiley & Sons, Ltd. [source]

    Comparison of Different Strategies on DNA Chip Fabrication and DNA-Sensing: Optical and Electrochemical Approaches

    ELECTROANALYSIS, Issue 22 2005
    Sabine Szunerits
    Abstract New strategies for the construction of DNA chips and the detection of DNA hybridization will be discussed in this review. The focus will be on the use of polypyrrole as a linker between a substrate and oligonucleotide probes. The modification step is based on the electrochemical copolymerization of pyrrole and oligonucleotides bearing a pyrrole group on its 5, end. This strategy was employed for the immobilization of oligonucleotides on millimeter-sized electrodes, microelectrode arrays, as well as for the local structuring of homogeneous gold surfaces. Our approaches for the localized patterning of gold surfaces will be also discussed. Localized immobilization was achieved by using an electrospotting technique, where a micropipette served as an electrochemical cell where spot sizes with 800,,m diameters were fabricated. The use of a microcell using a Teflon covered metal needle with a cavity of 100,,m resulted in immobilized probe spots of 300,,m. Scanning electrochemical microscopy (SECM) was also used, and surface modifications of 100,,m were obtained depending on the experimental conditions. Different detection methods were employed for the reading of the hybridization event: fluorescence imaging, surface plasmon resonance imaging (SPRI), photocurrent measurements, and voltamperometric measurements using intercalators. Their advantages concerning the various immobilization strategies will also be discussed. [source]

    Optical, Magnetic and Structural Properties of the Spin-Crossover Complex [Fe(btr)2(NCS)2]H2O in the Light-Induced and Thermally Quenched Metastable States

    Vincent Legrand
    Abstract [Fe(btr)2(NCS)2]H2O [btr = 4,4,-bis(1,2,4-triazole)] is thearchetype of highly cooperative and low-dimensional spin-crossover complexes, which exhibit low-spin (LS) to high-spin (HS) light-induced conversion at very low temperature. The structural reorganizations related to the light-induced and thermally induced LS,HS transitions were characterized by single-crystal X-ray diffraction below the relaxation temperature (T = 15 K < TLIESST) and at 130 K within the thermal hysteresis loop. We show that the LIESST and thermal spin transitions lead to the same structural variations, namely an elongation of the Fe,N bonds by 0.18 (Fe,NNCS) and 0.20 (Fe,Nbtr), on going from LS to HS, together with a reorientation of the NCS group by nearly 13. The atomic displacement amplitudes, derived from the crystal structures, indicate lattice vibration modes of larger amplitudes and correlatively lower vibration frequencies in the HS state. The deformation of the crystal lattice as a function of temperature and laser excitation was quantitatively analyzed in terms of the HS and LS thermal-expansion (,HS and ,LS) and spin-transition spontaneous-strain (,) tensors. The eigendirections and eigenvalues of the , and , tensors correlate well with the weak and strong interactions in the solid and are responsible for the high cooperativity and low-dimensional behaviour. Magnetic and spectroscopic measurements were performed in all the different spin states and related to the structural findings. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

    A Series of Lithium Rare Earth Polyphosphates [LiLn(PO3)4] (Ln = La, Eu, Gd) and Their Structural, Optical, and Electronic Properties

    Jing Zhu
    Abstract The structural, optical, and electronic properties of a series of lithium rare earth polyphosphates [LiLn(PO3)4] [Ln = La (1), Eu (2), Gd (3)] have been investigated by means of single-crystal X-ray diffraction, elemental analyses, and spectroscopic measurements, as well as calculations of energy-band structures, density of states, and optical response functions by density functional methods. These LiLn(PO3)4 systems are monoclinic with space group C2/c and Z = 4. Their unit-cell parameters decrease as the ionic radius of Ln3+ decreases (La3+ > Eu3+ > Gd3+). Both (PO4)3, zig-zag chains and infinite chains formed by the alternate connection of LnO8 polyhedra and LiO4 tetrahedra run parallel to the b -axis in the structure. The energy-band structures, density of states, the chemical bonds, and optical properties have been investigated by density functional methods for some of the title compounds. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

    Multicomponent Supramolecular Devices: Synthesis, Optical, and Electronic Properties of Bridged Bis-dirhodium and -diruthenium Complexes,

    Anne Petitjean
    Abstract Four ruthenium- and rhodium-based metal,metal-bonded multicomponent systems have been synthesized, and their absorption, redox, spectroelectrochemical and structural properties have been studied. The absorption spectra of the four bis-dimetallic compounds M2LM2, where L is a bridging ligand and M is rhodium or ruthenium, exhibit very strong bands in the UV, visible and, for the diruthenium species, near-IR region. The low-energy absorption bands are assigned to charge-transfer transitions involving a metal,metal bonding orbital as the donor and an orbital centered on the bis-tetradentate aromatic ligands as the acceptor (metal,metal to ligand charge transfer, M2LCT). Each compound exhibits reversible bridging-ligand-centered reductions at mild potentials and several reversible oxidation processes. The oxidation signals of the two equivalent dimetallic centers of each bis-dimetallic compound are split, with the splitting , a measure of the electronic coupling , depending on both the metal and bridging ligand. The mixed-valence species of the dirhodium species was investigated, and the electronic coupling matrix element calculated from the experimental intervalence band parameters for one of them (86 cm,1) indicates a significant inter-component electronic interaction which compares well with good electron conducting anionic bridges such as cyanides. Although none of these compounds is luminescent, the M2LCT excited state of one of the bis-dirhodium complexes is relatively long-lived (about 6 ,s) in degassed acetonitrile at room temperature. The results presented here are promising for the development of linear poly-dimetallic complexes built on longer naphthyridine-based strands, with significant long-range electronic coupling and molecular-wire-like behavior. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]

    A Comparative Study of the Optical and Electroluminescent Properties of EuIII Complexes with TTA and 2-(2,-Pyridyl)azoles: The Crystal Structure of [Eu(TTA)3(PBO)]

    Li-Hua Gao
    Abstract Two EuIII mixed-ligand complexes, namely [Eu(TTA)3(PBO)]and [Eu(TTA)3(PBT)] [TTA = 1,1,1-trifluoro-3-(2-thenoyl)acetonato, PBO = 2-(2,-pyridyl)-1,3-benzoxazole, and PBT = 2-(2,-pyridyl)-1,3-benzothiazole], have been synthesized. [Eu(TTA)3(PBO)] has been structurally characterized by single-crystal X-ray diffraction analysis. The complex crystallizes in the monoclinic space group C2/c. The lattice parameters are a = 41.346(4), b = 10.0538(8), c = 20.3793(16) , , = 110.922(2), Z = 8. The EuIII ion is eight-coordinate, with three bidentate TTA, anions and one bidentate N,O-chelated PBO molecule. A comparative study by UV and emission spectroscopy was carried out and electroluminescent properties of the related complexes [Eu(TTA)3(PBO)] and [Eu(TTA)3(PBT)] are reported as well. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]

    Aligning Single-Walled Carbon Nanotubes By Means Of Langmuir,Blodgett Film Deposition: Optical, Morphological, and Photo-electrochemical Studies

    Gabriele Giancane
    Abstract An alkoxy-substituted poly(phenylene thiophene) is used in order to suspend single-walled carbon nanotubes in an organic solvent. The suspension is spread on the air,water interface of a Langmuir trough and the floating film is characterized by means of Brewster angle microscopy and UV-visible reflection spectroscopy and the compression isotherm is recorded. The polymer/carbon-nanotube blend is transferred onto different substrates using the Langmuir,Blodgett technique. AFM measurements indicate the formation of globular structures for the samples transferred at low surface-pressure values and a tubular morphology for high-pressure-deposited samples. AFM analysis is repeated on a sample exposed to soft X-rays for about 5,h and a highly organized structure of bundles of carbon nanotubes rises up. Samples with different numbers of layers are transferred onto ITO substrates by means of the Langmuir,Blodgett method and are tested as photocathodes in a photo-electrochemical cell. A Voc of 0.18,V, an Isc of 85.8,mA, FF of 40.0%, and , of (6.23,,10,3)% are obtained. [source]

    An actualistic perspective into Archean worlds , (cyano-)bacterially induced sedimentary structures in the siliciclastic Nhlazatse Section, 2.9 Ga Pongola Supergroup, South Africa

    GEOBIOLOGY, Issue 1 2008
    ABSTRACT Extensive microbial mats colonize sandy tidal flats that form along the coasts of today's Earth. The microbenthos (mainly cyanobacteria) respond to the prevailing physical sediment dynamics by biostabilization, baffling and trapping, as well as binding. This biotic,physical interaction gives rise to characteristic microbially induced sedimentary structures (MISS) that differ greatly from both purely physical structures and from stromatolites. Actualistic studies of the MISS on modern tidal flats have been shown to be the key for understanding equivalent fossil structures that occur in tidal and shelf sandstones of all Earth ages. However, until now the fossil record of Archean MISS has been poor, and relatively few specimens have been found. This paper describes a study location that displays a unique assemblage with a multitude of exceptionally preserved MISS in the 2.9-Ga-old Pongola Supergroup, South Africa. The ,Nhlazatse Section' includes structures such as ,erosional remnants and pockets', ,multidirected ripple marks', ,polygonal oscillation cracks', and ,gas domes'. Optical and geochemical analyses support the biogenicity of microscopic textures such as filamentous laminae or ,orientated grains'. Textures resembling filaments are lined by iron oxide and hydroxides, as well as clay minerals. They contain organic matter, whose isotope composition is consistent with carbon of biological origin. The ancient tidal flats of the Nhlazatse Section record four microbial mat facies that occur in modern tidal settings as well. We distinguish endobenthic and epibenthic microbial mats, including planar, tufted, and spongy subtypes. Each microbial mat facies is characterized by a distinct set of MISS, and relates to a typical tidal zone. The microbial mat structures are preserved in situ, and are consistent with similar features constructed today by benthic cyanobacteria. However, other mat-constructing microorganisms also could have formed the structures in the Archean tidal flats. [source]

    Combined Optical and MR Bioimaging Using Rare Earth Ion Doped NaYF4 Nanocrystals

    Rajiv Kumar
    Abstract Here, novel nanoprobes for combined optical and magnetic resonance (MR) bioimaging are reported. Fluoride (NaYF4) nanocrystals (20,30,nm size) co-doped with the rare earth ions Gd3+ and Er3+/Yb3+/Eu3+ are synthesized and dispersed in water. An efficient up- and downconverted photoluminescence from the rare-earth ions (Er3+ and Yb3+ or Eu3+) doped into fluoride nanomatrix allows optical imaging modality for the nanoprobes. Upconversion nanophosphors (UCNPs) show nearly quadratic dependence of the photoluminescence intensity on the excitation light power, confirming a two-photon induced process and allowing two-photon imaging with UCNPs with low power continuous wave laser diodes due to the sequential nature of the two-photon process. Furthermore, both UCNPs and downconversion nanophosphors (DCNPs) are modified with biorecognition biomolecules such as anti-claudin-4 and anti-mesothelin, and show in vitro targeted delivery to cancer cells using confocal microscopy. The possibility of using nanoprobes for optical imaging in vivo is also demonstrated. It is also shown that Gd3+ co-doped within the nanophosphors imparts strong T1 (Spin-lattice relaxation time) and T2 (spin-spin relaxation time) for high contrast MR imaging. Thus, nanoprobes based on fluoride nanophosphors doped with rare earth ions are shown to provide the dual modality of optical and magnetic resonance imaging. [source]

    Supported Lipid Bilayer on Nanocrystalline Diamond: Dual Optical and Field-Effect Sensor for Membrane Disruption

    Priscilla Kailian Ang
    Abstract It is demonstrated that a good biomimetic model lipid membrane with dynamic fluidity can be established on optically transparent nanocrystalline diamond (OTND) with surface roughness below 10,nm. Maigainin II, an antimicrobial peptide, is chosen to investigate the permeation of artificial bacterial membranes constructed on OTND. Due to the unique combination of optical transparency and highly sensitive surface conducting channel, intrinsic OTND affords the possibility of dual-mode sensing based on optical and field effect properties. This opens up new possibilities for making integrated biomolecule,semiconductor microdevices, or sensors where the binding of biomolecules can be tracked using confocal microscopy whilst the associated changes in charge density during membrane perforation can be tracked using the space charge effect in the semiconductor. Such a synergistic approach may provide a powerful methodology for the screening of specific bactericidal activity on biomimetic membrane systems. [source]

    Nanoparticle Coating for Advanced Optical, Mechanical and Rheological Properties,

    F. Hakim
    Abstract Primary titania nanoparticles were coated with ultrathin alumina films using Atomic Layer Deposition (ALD). The deposited films were highly uniform and conformal with an average growth rate of 0.2,nm per coating cycle. The alumina films eliminated the surface photocatalytic activity of titania nanoparticles, while maintained their original extinction efficiency of ultraviolet light. Deposited films provided a physical barrier that effectively prevented the titania surface from oxidizing organic material whereas conserving its bulk optical properties. Parts fabricated from coated powders by pressureless sintering had a 13,% increase in surface hardness over parts similarly fabricated from uncoated particles. Owing to its homogeneous distribution, the secondary alumina phase suppressed excessive grain growth. Alumina films completely reacted during sintering to form aluminum titanate composites, as verified by XRD. Coated particles showed a pseudoplastic behavior at low shear rates due to modified colloidal forces. This behavior became similar to the Newtonian flow of uncoated nanoparticle slurries as the shear rate increased. Suspensions of coated particles also showed a decreased viscosity relative to the viscosity of uncoated particle suspensions. [source]

    Substituent Effects on Crosslike Packing of 2,,7,-Diaryl- spiro(cyclopropane-1,9,-fluorene) Derivatives: Synthesis and Crystallographic, Optical, and Thermal Properties,

    Z. Wang
    Abstract A series of 2,,7,-diarylspiro(cyclopropane-1,9,-fluorene) derivatives are efficiently synthesized and characterized to determine the reason for the "green-light" emission of these compounds. These compounds exhibit bright-violet to blue photoluminescence (PL) (,PLmax,=,353,419,nm) with excellent PL quantum efficiencies (,PL,=,83,100,%) in solution and show high thermal stabilities (Td,=,267,474,C). The variation of the optical properties of these molecules in the solid state depends on the different stacking modes of these compounds containing different substituents, which are revealed by crystallographic analysis. CH,, hydrogen bonds instead of intermolecular ,,, interactions act as the driving force between adjacent fluorenes, even though a very small dialkyl group (cyclopropane) is introduced at the C-9 position of fluorene. The crosslike molecular stacking efficiently reduces the energy transfer between the herring-like aggregates and therefore results in the absence of a "green-light" emission tail. In order to determine the cause of the "green-light" emission tails, the fluorescence spectra of the films annealed in N2 or in air are recorded. Broad green-light emission tails were observed for the films annealed in air, which might be caused by fluorenone defects generated during processing or during the course of the photophysical analysis by reaction with residual oxygen. [source]

    Fourier analysis methodology of trabecular orientation measurement in the human tibial epiphysis

    JOURNAL OF ANATOMY, Issue 2 2001
    Methods to quantify trabecular orientation are crucial in order to assess the exact trajectory of trabeculae in anatomical and histological sections. Specific methods for evaluating trabecular orientation include the ,point counting' technique (Whitehouse, 1974), manual tracing of trabecular outlines on a digitising board (Whitehouse, 1980), textural analysis (Veenland et al. 1998), graphic representation of vectors (Shimizu et al. 1993; Kamibayashi et al. 1995) and both mathematical (Geraets, 1998) and fractal analysis (Millard et al. 1998). Optical and computer-assisted methods to detect trabecular orientation of bone using the Fourier transform were introduced by Oxnard (1982) later refined by Kuo & Carter (1991) (see also Oxnard, 1993, for a review), in the analysis of planar sections of vertebral bodies as well as in planar radiographs of cancellous bone in the distal radius (Wigderowitz et al. 1997). At present no studies have applied this technique to 2-D images or to the study of dried bones. We report a universal computer-automated technique for assessing the preferential orientation of the tibial subarticular trabeculae based on Fourier analysis, emphasis being placed on the search for improvements in accuracy over previous methods and applied to large stereoscopic (2-D) fields of anatomical sections of dried human tibiae. Previous studies on the trajectorial architecture of the tibial epiphysis (Takechi, 1977; Maquet, 1984) and research data about trabecular orientation (Kamibayashi et al. 1995) have not employed Fourier analysis. [source]

    Optical and thermo electrical properties of ZnO nano particle filled polystyrene

    Mulayam S. Gaur
    Abstract The study of optical and thermally stimulated electrical properties such as optical band gap, refractive index, X-ray spectra, SEM spectra, thermally stimulated discharge current (TSDC), differential scanning calorimetry (DSC) have been undertaken in ZnO nanoparicle filled polystyrene nanocomposite thin film of 30 ,m thickness. The appearance of single TSDC peak at temperature 408 5 K in nanocomposite samples shows the charge carriers injected from deeper trapping levels. It is due to the modification of surface and bulk properties of polystyrene by filling of ZnO nanoparticles. In other hand, the strong interaction of nanoparticles with polymer matrix is the expected reason of improvement of crystallite size, optical energy band gap, refractive index, TSDC, glass transition temperature, and charge storage. It is confirmed from SEM images that the modifications of these properties are caused by creation of clusters in amorphous,crystalline boundaries of pristine polystyrene. 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

    Optical and physicochemical properties of silica-supported TiO2 photocatalysts

    AICHE JOURNAL, Issue 8 2006
    Javier Marugn
    Abstract Commercial applications of photocatalysis in slurry reactors employing titanium dioxide particles present the disadvantage of the additional cost associated with the downstream catalyst separation. In past years a significant effort has been made to develop supported titania photocatalysts on particles of larger size in order to facilitate the sedimentation recovery process. In this work, two different silica materials have been used for preparing immobilized catalysts. Their physicochemical characteristics have been compared with those corresponding to two commercially available unsupported titanium dioxide catalysts. However, for reaction kinetics and reactor design purposes, three additional properties must be known: (i) the spectral specific radiation absorption coefficient, (ii) the spectral specific radiation scattering coefficient, and (iii) the asymmetry factor of a model for the angular distribution of the scattered photons (the phase function). They have been determined with specially designed spectrophotometer transmission, diffuse transmittance, and diffuse reflectance experiments and constitute the most significant addition to this contribution. 2006 American Institute of Chemical Engineers AIChE J, 2006 [source]

    Optical and electrochemical properties of copoly(aryl ether)s consisting of alternate 2,5-distyrylbenzene and electron-transporting oxadiazole or triazole derivatives

    Shinn-Horng Chen
    Abstract New copoly(aryl ether) P1 consisting of alternate electron-transporting 2-(3-(trifluoromethyl)phenyl)-5-(4-(5-(3-(trifluoromethyl)phenyl)-1,3,4-oxadiazol-2-yl)-2,5-bis(hexyloxy)phenyl)-1,3,4-oxadiazole and hole-transporting 2,5-distyrylbenzene (DSB) was synthesized via nucleophilic substitution polymerization. We investigated the optical and electrochemical properties of alternate copoly(aryl ether)s P1,P6, which contain the same hole-transporting DSB segments, but with different electron transporting segments. The effect of trifluoromethyl groups in electron transporting segments is also discussed. Referencing to the spectra of their model compounds M1,M4, the emissions of P1,P3 are dominated exclusively by the hole-transporting fluorophores with longer emissive wavelength about 452,453 nm via efficient excitation energy transfer. Furthermore, P1,P3 also exhibit unique variations in energy transfer in acidic media and solvatochromism in organic solvents. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of P1,P4, estimated from electrochemical data, are ,5.12, ,5.15, ,5.18, ,5.00 eV and ,2.93, ,3.39, ,3.49, ,2.76 eV, respectively. The electron and hole affinity of P1,P6 can be enhanced simultaneously by introducing isolated hole- and electron-transporting segments in backbone. 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5083,5096, 2005 [source]

    Metal-Ceramic Interface Evaluation of a Gold-Infiltrated Alloy

    Rupal Vasani BDS
    Abstract Purpose: The success of metal-ceramic systems partially depends on the formation of a stable bond between metal and porcelain. The purpose of this study was to investigate the porcelain/metal interface and the mechanism of interfacial bonding in a gold-infiltrated alloy (Captek). Materials and Methods: Captek specimens with feldspathic porcelain were evaluated by optical microscopy, scanning electron microscopy (SEM), electron probe microanalysis (EPMA), X-ray diffraction (XRD), and the Schwickerath crack initiation test for metal-ceramic bond compatibility. Specimens were processed with or without Capbond, a bonding agent. A traditional metal-ceramic alloy was also analyzed with microscopy for comparative purposes. Results: Optical and scanning electron micrographs of Captek specimens processed with Capbond revealed close adaptation of porcelain to the surface of the metal with sporadic nodules extending from the Captek surface. In contrast, the specimens of Captek without Capbond showed a much flatter porcelain/metal interface. Comparatively, the porcelain/metal interface of the traditional metal-ceramic crown showed greater surface roughness than the Captek specimens. No metal oxides were observed at the porcelain/metal interface of the Captek specimens with XRD. During the Schwickerath test, the Captek specimens permanently deformed, not allowing for crack initiation at the porcelain/metal interface. Conclusions: Microscopy and XRD analysis showed that micromechanical interlocking is the primary mechanism of porcelain adherence to Captek metal. The use of Capbond prior to porcelain application to Captek results in gold nodules on the surface to aid retention. Existing metal-ceramic bond compatibility standardized tests are not sufficient for evaluating Captek, primarily due to the flexibility of the material. [source]

    Characterisation of carbonaceous materials using Raman spectroscopy: a comparison of carbon nanotube filters, single- and multi-walled nanotubes, graphitised porous carbon and graphite

    H. M. Heise
    Abstract Multi-walled carbon nanotube (MWCNT) filters have been recently synthesised which have specific molecular filtering capabilities and good mechanical strength. Optical and scanning electron microscopy (SEM) reveals the formation of highly aligned arrays of bundles of carbon nanotubes having lengths up to 500 m. The Raman spectra of this material along with four other carbonaceous materials, commercially available single-walled carbon nanotubes (SWCNTs) and MWCNTs, graphitised porous carbon (Carbotrap) and graphite have been recorded using two-excitation wavelengths, 532 and 785 nm, and analysed for band positions and shape with special emphasis paid to the D-, G- and G,-bands. A major difference between the different MWCNT varieties analysed is that G-bands in the MWCNT filters exhibit almost no dispersion, whereas the other MWCNTs show a noticeable dispersive behaviour with a change in the excitation wavelength. Spectral features similar to those of the MWCNT filter varieties were observed for the Carbotrap material. From the line shape analysis, the intensity ratio, ID/IG, of the more ordered MWCNT filter material using the integral G-band turns out to be two times lower than that of the less ordered MWCNT filter product at both excitation wavelengths. This parameter can, therefore, be used as a measure of the degree of MWCNT alignment in filter varieties, which is well supported also by our SEM study. Copyright 2008 John Wiley & Sons, Ltd. [source]

    Optical and Mechanical Properties of Glasses and Glass,Ceramics Based on the Ge,Ga,Se System

    Mathieu Roz
    In this paper, the mechanical and thermo-mechanical properties of glasses and glass,ceramics belonging to the Ge,Ga,Se system are studied. Pure glasses slightly transparent in the visible range up to 16 ,m have been synthesized. Glass,ceramics were made using an appropriate heat-treatment time and temperature from the 80GeSe2,20Ga2Se3 base glass in order to improve the mechanical properties. The optical and mechanical properties of glasses and glass,ceramics such as hardness and toughness were investigated. X-ray diffraction (XRD) versus temperature experiments were performed to understand the crystallization evolution as a function of heat-treatment time. GeGa4Se8 and GeSe2 crystalline phases have been determined with XRD. As a result, glass,ceramics with 40% density of crystals present a very low thermal expansion coefficient (11.8 10,6 0.5 K,1) and an excellent infrared transmission in the 3,5 and 8,13 ,m regions. [source]

    Magnetic and Electrical Properties of (Mn, La)-Codoped SrTiO3 Thin Films

    Song-Yin Zhang
    Mn-doped SrTiO3 -based thin films have been prepared by a simple sol,gel spin-coating method on silicon substrate. X-ray diffraction and high-resolution transmission electron microscopy reveal that these thin films are composed of amorphous and crystalline SrTiO3 phases. Optical and electrical measurements indicate that La codoping can make the band gap of SrTiO3 narrow and cause the leakage current to increase. Ferromagnetic behavior can be observed in these Mn- and/or La-codoped SrTiO3 -based thin films at room temperature, which should be ascribed to the magnetic coupling between the induced free electrons and Mn 3d spins. [source]

    Optical and Electrical Properties of Amorphous and Nanocrystalline (La0.8Sr0.2)0.9MnO3 Thin Films Prepared from Low-Temperature Processing Technique

    Toshio Suzuki
    The results of a study on the optical and electrical properties of (La0.8Sr0.2)0.9MnO3 (LSM) thin films obtained by a polymeric precursor spin coating technique were presented. This method allowed preparation of optical quality thin films at annealing temperatures around 800C. Amorphous and crystalline LSM thin films were studied by optical and electrical conductivity measurements. The energy-dependent absorption coefficients for the crystalline specimen were calculated from optical spectra and extra absorption was observed in the range of 1.8,2.5 eV with the exchange-gap excitation behavior in the 3,5 eV range. In comparison to the amorphous specimens, the electrical conductivity of the nanocrystalline specimen increased two to three orders of magnitude with decreasing activation energy. The charge carrier absorption model suggested an increase of the carrier concentration in the nanocrystalline specimen which may be a reason for the change in the electrical conductivity. [source]

    Multilayer Thin Films by Layer-by-Layer Assembly of Hole- and Electron-Transport Polyelectrolytes: Optical and Electrochemical Properties

    Kyungsun Choi
    Abstract Summary: In this paper, we present the synthesis of a series of p-type and n-type semiconducting polyelectrolytes with triarylamine, oxadiazole, thiadiazole and triazine moieties. The synthesized polymeric hole and electron transport materials were examined optically and electrochemically using UV/Vis spectroscopy, PL spectroscopy and CV. Based on the optical and electrochemical data, each of the energy levels were calculated and all values suggested that they were promising hole- (p-type) or electron-transport (n-type) materials for devices. Moreover, the synthesized ionic polymers were suitable for LBL thin film deposition from dilute polymer solutions and the multilayers were fully characterized by UV/Vis, PL spectroscopy and CV. [source]

    Miscibility in Blends of Isotactic/Syndiotactic Polystyrenes at Melt or Quenched Amorphous Solid State

    Shu Hsien Li
    Abstract Summary: Miscibility in amorphous phase and behavior in a crystalline phase of blends of two semicrystalline and isomeric polymers, isotactic polystyrene (iPS) and syndiotactic polystyrene (sPS), was probed. Optical and scanning electron microscopy results indicate no discernible heterogeneity in iPS/sPS blends in either melt state or rapidly quenched amorphous super-cooled state, while the Tg behavior of the quenched amorphous blends shows an intimately mixed state of two polymer chains. The crystal forms of the blends were further analyzed to provide additional evidence of miscibility in the amorphous domain. The sPS in the iPS/sPS blends upon melt crystallization was found to predominantly exist as the more stable , -form (rather than mixed , -form and , -form in neat sPS), which also suggests evidence of miscibility in the iPS/sPS blends. The melting behavior of semicrystalline sPS in the iPS/sPS mixtures was analyzed using the Flory-Huggins approach for estimation of interactions. By measuring the equilibrium melting point of the higher-melting sPS species in the sPS/iPS blends, a small negative value, for the interaction parameter (,,,,,0.11) was found. Further, by introducing a third polymer, poly(2,6-dimethyl- p -phenylene oxide) (PPO), a ternary iPS/sPS/PPO blend system was also proven miscible, which constituted a further test for stable phase miscibility in the iPS/sPS blend. General nature of miscibility in blends composed of two crystalline isomeric polymers is discussed. Issues in dealing with blends of polymers of the same chemical repeat unit but different tacticities were addressed. X-ray diffractograms for neat sPS and iPS/sPS blends, each having been isothermally crystallized at 245,C for 4 h. [source]