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near-IR Region (near-ir + region)
Selected AbstractsMulticomponent Supramolecular Devices: Synthesis, Optical, and Electronic Properties of Bridged Bis-dirhodium and -diruthenium Complexes,EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 19 2006Anne 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] Metallodielectric Photonic Crystals Assembled from Monodisperse Spherical Colloids of Bismuth and Lead,ADVANCED MATERIALS, Issue 4 2006Y. Wang Monodisperse metallic and metallodielectric spherical colloids have been synthesized in large quantities and explored as building blocks for fabricating three-dimensional metallodielectric photonic crystals. Both measurements and calculations revealed large photonic bandgaps covering optical wavelengths from the visible up to the near-IR region for the metallic (Bi and Pb) and metallodielectric (with a silica coating) colloids (see Figure). [source] Fabrication of Polyimide-Blend Thin Films Containing Uniformly Oriented Silver Nanorods and Their Use as Flexible, Linear PolarizersADVANCED MATERIALS, Issue 18 2005S. Matsuda Fully aromatic polyimide films containing uniformly oriented Ag nanorods (see Figure) have been prepared by a simple method consisting of thermal curing and uniaxial drawing of submicrometer-scale phase-separated polyimide-blend films containing dissolved AgNO3. The films exhibit outstanding optical dichroism, over 20,dB (see inset), in the near-IR region due to the high aspect ratio of the nanorods and the high transparency of the matrix. [source] Laser and nonlinear-laser properties of undoped and Nd3+ -doped orthorhombic Ca(NbO3)2 single crystals: new stimulated-emission performance and high-order picosecond stimulated Raman scattering covering more than two octave Stokes and anti-Stokes wavelengthsLASER PHYSICS LETTERS, Issue 11 2009A.A. Kaminskii Abstract We report new laser and nonlinear-laser properties of Nd3+ -ion doped and undoped orthorhombic calcium niobate. In particular, we show that: Nd3+:Ca(NbO3)2 is a promising gain medium for LD-pumped microchip lasers and undoped Ca(NbO3)2 can give rise to high-order lasing covering more than two-octave Stokes and anti-Stokes frequency comb in the visible and near-IR region. We measured also the main spectroscopic intensity characteristics related to the observed laser performance and identified their physical nature. (© 2009 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Solid-State Gas Sensors Developed from Functional Difluoroboradiazaindacene DyesCHEMISTRY - A EUROPEAN JOURNAL, Issue 6 2009Raymond Ziessel Dr. Abstract This article describes the synthesis and characterization of several new difluoroboradiazaindacene (BODIPYÔ) dyes functionalized at the central 8-position by a phenyliodo, phenylheptynoate or phenylheptynoic fragment and at the 3- or 3/5-position(s) by 4-dimethylaminophenylstyryl residue(s). Single-crystal structural determinations confirm the planarity of the dyes, while the absorption and fluorescence spectroscopic properties are highly sensitive to the state of protonation (or alkylation) of the terminal anilino donor group(s). Reversible color tuning from green to blue for absorption and from colorless (i.e., near-IR region) to red for fluorescence is obtained on successive addition of acid and base. The difunctionalized derivative is especially interesting in this respect and shows two well-resolved pKa values of 5.10 and 3.04 in acetonitrile. Addition of the first proton causes only small spectral changes and deactivates the molecule towards addition of the second proton. It is this latter step that accommodates the large change in absorption and emission properties, due to the reversible extinction of the intramolecular charge-transfer character inherent to this type of dye. The main focus of the work is the covalent anchoring of the dyes to inert, porous polyacrylate beads so as to form a solid-state sensor suitable for analysis of gases or flowing liquids. The final material is highly stable,its performance is undiminished after more than one year,and fully reversible over many cycles. The sensitivity is such that reactions can be followed by the naked eye and the detection limit is about 600,ppb for HCl and about 80,ppb for ammonia. Trace amounts of diphosgene can be detected, as can alkylating agents. The sensing action is indiscriminate and also operates when the beads are dispersed in aqueous media. Ce manuscrit décrit la synthèse et la caractérisation de nouvelles sondes fluorescentes communément appelées BODIPY qui ont été ciselées en position centrale par un groupe phényl-iodo, phénylheptynoate ou phénylheptanoic acide et en positions 5 ou 3/5 avec des fragments 4-diméthylaminostyryle. Ces derniers fragments favorisent une excellente conjugaison qui est à l'origine de la couleur verte des sondes. Des structures moléculaires obtenues par diffraction aux rayon X sur monocristal confirment la planarité des ces objets, tandis que les propriétés d'absorption et de fluorescence sont sensibles à la protonation ou l'alkylation des groupements aminés terminaux. Un changement de couleur réversible du vert au bleu par absorption et de l'invisible au rouge en fluorescence est obtenu en présence d'un flux d'air pimenté avec des traces d'acides. La réversibilité est observée en présence de traces de base. Le dérivé di-fonctionnalisé est particulièrement intéressant dans la mesure ou deux pKa sont bien résolus à 5,10 et 3,04 unités dans l'acétonitrile. L'addition du premier proton induits des changements spectroscopiques modestes et diminue la basicité du deuxième groupe amino. Cette dernière protonation induit des changements majeurs en absorption et émission et inhibe le transfert de charge intramoléculaire. L'intérêt majeur de ces sondes réside dans leur potentiel d'être lié de façon covalente à des billes de polymères et d'utiliser ces billes pour la détection d'éléments toxiques dans des effluents gazeux. En particulier il a été démontré que la détection visuelle de trace de HCl (environ 600 ppb) ou d'ammoniaque (environ 80 ppb) est possible sans l'utilisation de systèmes de détection particuliers. De façon similaire des traces de diphosgène et d'autre agent vésicant et alkylant est possible. Ces systèmes sont très stables (durée supérieure à un an) et fonctionnent également en phase aqueuse. Aucune sélectivité de détection n'a été obtenue mais conceptuellement les systèmes sont particulièrement sensibles et peuvent être modifiés à façon. [source] | ||||||||||