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Structural analysis of hybrid titania-based mesostructured composites

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 2005年第27期127卷 9721-9730页

作者： Boettcher, SW Bartl, MH Hu, JG Stucky, GD Univ Calif Santa Barbara CNSI Dept Chem & Biochem Santa Barbara CA 93106 USA Univ Calif Santa Barbara Mat Res Lab Santa Barbara CA 93106 USA

High-optical-quality titania-based mesostructured films with cubic or 2D-hexagonal symmetry were fabricated by combining trifluoroacetate (TFA)-modified titanium precursors with amphiphilic triblock poly(ethylene oxide)-poly(propylene oxide) -poly(ethylene oxide) (PEO-PPO-PEO) copolymers. The distribution, dynamics, and local environments of the TFA-modified titania, PEO, and PPO components of the hybrid were investigated. IR/Raman spectroscopy, in situ small-angle X-ray scattering, and transmission electron microscopy studies indicate that TFA coordinates the titanium center and forms a stable complex that is subsequently organized by the block copolymer species into ordered mesostructures. Solid-state NMR F-19 -> H-1 cross-polarization, C-13{H-1} two-dimensional heteronuclear correlation, and H-1 relaxation techniques were used to determine that PEO is predominantly incorporated within the TFA-modified titania, and that PPO environments encompass both microphase separated regions and interfacial regions composed of mixed PPO and TFA-modified titania. NMR F-19 multiple-quantum spin counting measurements suggest that -CF3 groups of the trifluoroacetate ligands do not form clusters but instead randomly distribute within the inorganic component of the hybrid.

关键词： SOLID-STATE-NMR MULTIPLE-QUANTUM NMR MESOPOROUS MOLECULAR-SIEVES THIN-FILMS TRIFLUOROACETIC-ACID METAL-OXIDES POLY(ETHYLENE OXIDE) VIBRATIONAL-SPECTRA CROSS-POLARIZATION wave-guides

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Hole-assisted energy deposition in dielectrics and clusters in the multiphoton regime

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JOURNAL OF MODERN OPTICS 2005年第7期52卷 1019-1030页

作者： Gaier, LN Lein, M Stockman, MI Yudin, GL Corkum, PB Ivanov, MY Knight, PL Univ London Imperial Coll Sci Technol & Med Blackett Lab London SW7 2BW England Max Planck Inst Phys Komplexer Syst D-01187 Dresden Germany Georgia State Univ Dept Phys & Astron Atlanta GA 30303 USA Natl Res Council Canada Steacie Inst Mol Sci Femtosecond Sci Program Ottawa ON K1A 0R6 Canada

We propose a novel mechanism of energy absorption in dielectric materials with ultrashort infrared laser pulses of intensities below the damage threshold. Analytical theory, generalized to hole-assisted processes in arbitrarily polarized laser fields, is validated using one-dimensional numerical simulations of the time-dependent Schrodinger equation. Large enhancements in the multiphoton transition rates are found both numerically and analytically. The one-dimensional calculations are extended to two dimensions via a forest. re percolation model, in which nanoplasma-like structures have been identified.

关键词： LASER-INDUCED DAMAGE FEMTOSECOND-LASER TRANSPARENT MATERIALS SUBPICOSECONDPULSES INDUCED BREAKDOWN wave-guides NANOSECOND IONIZATION DYNAMICS GLASSES

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Tuned graft copolymers as controlled coatings for DNA microarrays

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ANALYTICAL CHEMISTRY 2005年第18期77卷 5831-5838页

作者： De Paul, SM Falconnet, D Pasche, S Textor, M Abel, AP Kauffmann, E Liedtke, R Ehrat, M ETH Swiss Fed Inst Technol Dept Mat Surface Sci & Technol Lab CH-8093 Zurich Switzerland Zeptosens AG CH-4108 Witterswil Switzerland

DNA microarrays have become a powerful tool for expression profiling and other genomics applications. A critical factor for their sensitivity is the interfacial coating between the chip substrate and the bound DNA. Such a coating has to embrace the divergent requirements of tightly binding the capture probe DNA during the spotting process and of minimizing the nonspecific binding,of target DNA during the hybridization assay. To fulfill these conditions, most coatings require a passivation step. Here we demonstrate how the chain density of a graft copolymer with a polycationic backbone, poly(L-lysine)-graft-poly(ethylene glycol), can be tuned such that the binding capacity during capture probe deposition is maximized while the nonspecific binding during hybridization assays is kept to a minimum, thus alleviating the requirement for a separate passivation procedure. Evidence for the superior performance of such coatings in terms of signal-to-noise ratio and spot quality is presented using an evanescent field-based fluorescent sensing technique (the ZeptoREADER). The surface architecture is further characterized using optical waveguide lightmode spectroscopy and time-of-flight secondary ion mass spectrometry. Finally, in a model assay, we demonstrate that expression changes can be detected from 1 mu g of total mRNA sample material with a limit of detectable differential expression of +/- 1.5.

关键词： METAL-OXIDE SURFACES POLY(L-LYSINE)-G-POLY(ETHYLENE GLYCOL) LAYERS PROTEIN ADSORPTION GENE-EXPRESSION wave-guides RESISTANCE ARCHITECTURE MONOLAYERS INTERFACE CDNA Monolayers Graft copolymers Interfaces waveguide Device Component Chromosomal Probes ARCHITECTURE Protein adsorption tuning Building construction Complementary DNA Passivation metal oxides Interface

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Fabrication and characterization of two-photon polymerized features in colloidal crystals

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ADVANCED FUNCTIONAL MATERIALS 2005年第12期15卷 1995-2004页

作者： Pruzinsky, SA Braun, PV Univ Illinois Dept Mat Sci & Engn Beckman Inst Adv Sci & Technol Urbana IL 61801 USA Univ Illinois Frederick Seitz Mat Res Lab Urbana IL 61801 USA

The fabrication and characterization of two photon polymerized features written within and outside of colloidal crystals is presented. Two-photon polymerization (TRP) response diagrams are introduced and developed to map the polymerization and damage thresholds for features written via modulated beam rastering. The use of tris[4-(7-benzothiazol-2-yl-9,9-diethylfluoren-2-yl)phenyl]amine (AF 350) as an initiator for TPP is demonstrated for the first time and TPP reponse diagrams illustrate the polymerization window. These diagrams also demonstrate that the polymerization behavior within and outside of colloidal crystals is similar and electron microscopy reveals nearly identical resolution. Fluorescence confocal microscopy further enables visualization of non-self-supporting, three-dimensional TPP features within self-assembled photonic crystals. Finally, microspot spectroscopy is collected from a two photon feature written within a colloidal crystal and this is compared with simulation.

关键词： PHOTONIC CRYSTALS SILICA SPHERES DIFFRACTION RESPONSE NUMERICAL-APERTURE wave-guides PHOTOPOLYMERIZATION ABSORPTION MICROFABRICATION EXCITATION MICROSCOPY

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Study of filamentary damage in synthesized silica induced by chirped femtosecond laser pulses

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS 2005年第11期22卷 2437-2443页

作者： Onda, S Watanabe, W Yamada, K Itoh, K Nishii, J Osaka Univ Grad Sch Engn Dept Mat & Life Sci Suita Osaka 5650871 Japan Natl Inst Adv Ind Sci & Technol Photon Res Lab Osaka 5638577 Japan

Different filamentary tracks in synthesized silica were induced by varying both the pulse duration and the incident energy of chirped laser pulses under slow-focusing conditions. Short-duration pulses induced filamentary refractive-index change, whereas longer pulses produced scattering damage in filamentary tracks. We report a systematic study on the morphology and birefringence of filamentary refractive-index change and scattering damage. (c) 2005 Optical Society of America.

关键词： REFRACTIVE-INDEX CHANGE FUSED-SILICA TRANSPARENT MATERIALS OPTICAL-BREAKDOWN wave-guides GLASS IRRADIATION ABLATION DIELECTRICS STORAGE

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Peptide nanotubes: Simple separation using size-exclusion columns and use as templates for fabricating one-dimensional single chains of an nanoparticles

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ADVANCED MATERIALS 2005年第14期17卷 1753-+页

作者： Gao, XY Djalali, R Haboosheh, A Samson, J Nuraje, N Matsui, H CUNY Hunter Coll Dept Chem & Biochem New York NY 10021 USA CUNY Hunter Coll Grad Ctr New York NY 10021 USA

Straight single chains of An nanoparticles have been synthesized using 10 nm diameter peptide nanotubes as templates (see Figure). The 6 nm An nanoparticles grow in the gaps between the synthetic peptide coating the nanotubes which regulates the size, dispersity, interparticle distance, and crystallinity of the nanoparticles. The use of longer nanotubes results in longer chains.

关键词： HISTIDINE-RICH PEPTIDE ELECTRON TRANSISTORS QUANTUM DOTS NANOCRYSTALGROWTH PACKING DISORDER wave-guides NANOWIRES ARRAYS DNA ELECTROMIGRATION

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Plasmon Bragg reflectors and nanocavities on flat metallic surfaces

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APPLIED PHYSICS LETTERS 2005年第1期87卷 013107-1-013107页

作者： Wang, B Wang, GP Wuhan Univ Dept Phys Wuhan 430072 Peoples R China

Metal heterostructures constructed surface plasmon polaritons (SPPs) Bragg reflectors and nanocavities on flat metallic surfaces are proposed and demonstrated numerically. A metal heterowaveguide structured by alternately stacking two kinds of metal gap waveguides (MGWs) shows periodically effective refraction index modulation to SPPs and produces SPP propagation on flat metallic surfaces a band gap in certain frequencies, known as plasmonic band gap, in which SPP propagation is forbidden. Changing the width of one MGW in the heterowaveguide, a SPP nanocavity with high quality factor can be created. Our results imply a broad possibility of constructed SPP-based Bragg reflectors, emitter, and filters, etc., on flat metallic surfaces for planar nanometeric photonic networks. (c) 2005 American Institute of Physics.

关键词： wave-guides BAND-GAP LIGHT LASER

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Three-dimensional photonic devices fabricated in glass by use of a femtosecond laser oscillator

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OPTICS LETTERS 2005年第9期30卷 1060-1062页

作者： Kowalevicz, AM Sharma, V Ippen, EP Fujimoto, JG Minoshima, K MIT Dept Elect Engn & Comp Sci Cambridge MA 02139 USA MIT Elect Res Lab Cambridge MA 02139 USA AIST Tsukuba Ibaraki 3058563 Japan

Three-dimensional photonic waveguide devices are fabricated in glass by use of femtosecond pulses from an extended-cavity laser oscillator. Three-dimensional devices, including a symmetric three-waveguide directional coupler and a three-dimensional microring resonator, are fabricated and tested. waveguides can be fabricated at depths of -1 mm inside a glass substrate, thus demonstrating the capability of achieving dramatic increases in device density. These results demonstrate the potential to fabricate new classes of devices that are not possible in two dimensions. (c) 2005 Optical Society of America.

关键词： wave-guides PULSES WRITTEN SILICA

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Er³⁺-doped tellurofluorophosphate glasses for lasers and optical amplifiers

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JOURNAL OF PHYSICS-CONDENSED MATTER 2005年第48期17卷 7705-7715页

作者： Jayasimhadri, M Moorthy, LR Kojima, K Yamamoto, K Wada, N Wada, N Sri Venkateswara Univ Dept Phys Tirupati 517502 Andhra Pradesh India Ritsumeikan Univ Fac Sci & Engn Dept Appl Chem Shiga 5258577 Japan

Absorption, fluorescence and decay properties of erbium-doped alkali tellurofluorophosphate glasses (RTFP) with the molar compositions of 50 (NaPO3)(6)-1 0 TeO2-20 AlF3-19 RF-1 Er2O3 (R = Li, Na or K) have been investigated in order to utilize these materials for the development of fibre amplifiers and lasers. The Judd-Ofelt (JO) model was applied to the absorption intensities of Er3+ (4f(11)) transitions to determine the JO intensity parameters Omega(lambda) (lambda = 2, 4 or 6). These evaluated intensity parameters are used to calculate the spontaneous emission probabilities and branching ratios from the excited state J manifolds to the lower lying J' manifolds of Er3+ emission transitions. The radiative lifetimes of these excited states are determined from their respective spontaneous emission probabilities. Visible and NIR emission spectra have been studied for all three Er3+-doped tellurofluorophosphate glasses. In particular, for the emission at 1.5 mu m corresponding to the 4I(13/2) -> I-4(15/2) transition, radiative parameters like the full width at half maximum (FWHM), emission cross-sections (sigma(e)) and figure of merit (FWHM x sigma(e)) were determined and compared with other hosts. The measured lifetimes of the 4S(3/2) level are compared with predicted radiative lifetimes calculated from the JO theory. The potentiality of Er3+-doped tellurofluorophosphate glasses for devices such as lasers and optical amplifiers is discussed.

关键词： ERBIUM-DOPED FIBER RARE-EARTH IONS FREQUENCY UP-CONVERSION JUDD-OFELTANALYSIS ER3+ IONS ABSORPTION INTENSITIES ENERGY-TRANSFER GERMANATE GLASSES TELLURITE GLASS wave-guides

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Switching in coupled nonlinear photonic-crystal resonators

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS 2005年第8期22卷 1778-1784页

作者： Maes, B Bienstman, P Baets, R Univ Ghent Dept Informat Technol Interuniv Microelect Ctr B-9000 Ghent Belgium

Using coupled-mode theory we examine the linear and Kerr nonlinear behavior of multiple consecutive photonic-crystal switches. Two types of resonators are considered, those with the cavity inside and those adjacent to the waveguide. We observe gap solitons in both structures and examine a nonlinear mode with energy localized near the boundaries of the finite system. Finally, we propose a device with two side-coupled resonators and a judiciously chosen intercavity distance that demonstrates switching at low powers. In addition to coupled-mode theory, rigorous simulations are performed for this structure. (c) 2005 Optical Society of America.

关键词： wave-guides PROPAGATION EXPANSION SOLITONS MODES

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