			Home About us Contact

Refractive Indexes (refractive + indexes)

Distribution by Scientific Domains

Physics and Astronomy	50%
Chemistry	33%

Selected Abstracts

Bio-Inspired Bottom-Up Assembly of Diatom-Templated Ordered Porous Metal Chalcogenide Meso/Nanostructures

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 2 2009
Han Zhou
Abstract We put forward a novel and straightforward sonochemical process as a generic bottom-up assembly routeto produce ordered porous metal chalcogenide meso/nanostructures by templating of diatom frustules. We work with one of the most beautiful species of diatoms, Coscinodiscus lineatus, as a representative of diatoms with central symmetry, and with ZnS as the prototype, as it is a high refractive index material and is a typical material widely used in optics and photonics. ZnS replicas have been successfully synthesized from the interaction between the reactive surfaces of the frustules and the precursors under ultrasound. The inorganic replicas copy the morphology of the ordered porous structure and inherit its optical property, such as the existence of the photonic bandgap of the diatom frustules. It is possible to achieve tunable photonic properties in the replicas by assembly of various metal chalcogenide semiconductors of different refractive indexes. This bio-inspired discovery provides insight into the facile synthesis of elaborate meso/nanostructures from these marine microbes.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

Metal-Free Click Polymerization: Synthesis and Photonic Properties of Poly(aroyltriazole)s

ADVANCED FUNCTIONAL MATERIALS, Issue 12 2009
Anjun Qin
Abstract Regioselective 1,3-dipolar polycycloadditions of tetraphenylethene (TPE)-containing diazides 1,3 and bis(aroylacetylene) 4 are initiated by simple heating, affording poly(aroyltriazole)s (PATAs) PI,PIII with high molecular weights in high yields. The PATAs are completely soluble in common organic solvents and stable at temperatures up to 358,°C. Thanks to their TPE units, the polymers show aggregation-induced emission and work as explosive sensors with high sensitivity. The PATAs are optically transparent in the whole visible spectral region. Their refractive indexes can be tuned to a great extent (,n,,,0.08) by simply changing their alkyl spacer lengths. The modified Abbé numbers of the PATAs are very high (up to 273), indicative of very low optical dispersions in the telecommunication-important wavelength region. UV irradiation through a photomask quenches the light emissions of the polymers, enabling the generation of two-dimensional fluorescent images without development. The polymers can be readily photo-crosslinked, yielding three-dimensional patterns with high resolutions. [source]

Neural network modeling of physical properties of chemical compounds

INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 1 2001
J. Kozio
Abstract Three different models relating structural descriptors to normal boiling points, melting points, and refractive indexes of organic compounds have been developed using artificial neural networks. A newly elaborated set of molecular descriptors was evaluated to determine their utility in quantitative structure,property relationship (QSPR) studies. Applying two data sets containing 190 amines and 393 amides, neural networks were trained to predict physical properties with close to experimental accuracy, using the conjugated gradient algorithm. Obtained results have shown a high predictive ability of learned neural networks models. The fit error for the predicted properties values compared to experimental data is relatively small. © 2001 John Wiley & Sons, Inc. Int J Quant Chem 84: 117,126, 2001 [source]

Light propagation and scattering in porous silicon nanocomposite waveguides

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2005
P. Pirasteh
Abstract Planar waveguides have been achieved from oxidised porous silicon layers (OPS) which have been impregnated by solvents, Congo Red (CR) dye and poly(p-phenylene vinylene) (PPV) polymer. Optical loss has been investigated by a simple technique based on surface optical scattering measurements. Optical loss has been studied as a function of the wavelength, impregnation type and CR concentration. The main sources of attenuation, such as absorption, scattering from interface roughness, scattering from nano- crystallites and modification of the refractive indexes after filling are discussed. Optical loss measured at 0.633 µm is about 1.8 dB/cm for the OPS waveguides The optical loss decreases with wavelength. Otherwise, the optical loss increases with the concentration of Congo Red dye which is absorbent at this wavelength. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Optical properties of TiO2 thin films prepared by chemical spray pyrolysis from aqueous solutions

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3-4 2010
R. Ayouchi
Abstract Titanium dioxide (TiO2) is known to have three different kinds of polymorphous crystalline forms: rutile, anatase, and brookite. The rutile phase is always formed at higher temperatures, while the anatase phase is formed at lower temperatures and transformed into rutile phase above 800 ºC. Various deposition techniques have been developed for depositing TiO2 thin films, including evaporation, sputtering, chemical vapour deposition and thermal oxidation of titanium. Among them, the Chemical Spray Pyrolysis (CSP) technique has many advantages, such as good conformal coverage, the possibility of epitaxial growth and the application to large area deposition. Also, this method is low cost and it is easy to control the deposition growth parameters. In the present work, TiO2 thin films have been deposited on p-Si (001) and fused silica substrates by Chemical Spray Pyrolysis (CSP) method from aqueous solution containing titanium (IV) isopropoxide (Ti[OCH(CH3)2]4. As-deposited thin films show anatase polycrystalline structure, and rutile phase formed for films annealed at 750ºC. SEM images have confirmed a smooth and crack-free surface with low surface roughness. X-ray photoelectron spectroscopy (XPS) combined with 4 keV Ar+ depth profiling has shown that crystallized films correspond to TiO2. Residual carbon coming from the organic precursor solution is only detected at the surface of the film. Thin films deposited on fused silica were highly transparent (more than 85%), with an indirect optical band gap of 3,43 and 3,33 eV for as-deposited and annealed films, respectively, and refractive indexes in the range between 2.01,2.29. Spectroscopic Ellipsometry (SE) also has been used to extract optical parameters. SE data fitted to triple-layer physical model revealed the same tendency to increase refractive index in annealed films. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Omni-directional gap of 1-D photonic crystals based on porous silicon with a Gaussian profile refractive index

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2007
J. Arriaga
Abstract Using the transfer matrix method we calculate the omni-directional band gap of a 1-D photonic crystal consisting of alternating layers of two dielectric materials A and B with refractive index nA and nB, respectively. The refractive index of layer A is constant and the refractive index of layer B varies according to the envelope of a Gaussian function. We find that under certain circumstances it is possible to obtain 100% reflectivity for both polarizations and any value of the incident angle of the electromagnetic waves. Although the structure considered does not posses a higher omni-directional band gap than the periodic sequence of low and high constant refractive indexes, it can be used to produce a new type of omni-directional mirrors without abrupt interfaces. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]