Borate single crystals for polyfunctional applications: production and properties
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Materials Literature
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Stephanocostis chantaicus (Bacillariophyceae): morphology and population dynamics of a rare centric diatom growing in winter under ice in the oligotrophic Lake Stechlin, Germany
Phytoplankton succession was studied weekly based on integrated samples from the euphotic zone (0-25 m) of the deep oligotrophic Lake Stechlin (Germany, Brandenburg) between 1994-1999. The rare centric diatom Stephanocostis chantaicus appeared regularly int he winter plankton building up population maximum int he wint…
o-(Bromomethyl)-Substituted Tetraarylporphyrin Building Blocks
[structure: see text] A series of novel poly-o-(bromomethyl)ated tetraarylporphyrins was synthesized. Their usefulness as building blocks for porphyrinic materials is demonstrated.
Dendrimers Functionalized with a Single Fluorescent Dansyl Group Attached “Off Center”: Synthesis and Photophysical Studies
A series of three new fluorescent dendrimers containing a single, focally located dansyl group and 3 ( 1 ), 9 ( 2 ), and 27 ( 3 ) carboxylic acid groups in their peripheries were synthesized and characterized. The photophysical properties of these dendrimers were investigated in aqueous solution. The host−guest intera…
Multiple Expression of Molecular Information: Enforced Generation of Different Supramolecular Inorganic Architectures by Processing of the Same Ligand Information through Specific Coordination Algorithms
The multisubunit ligand 2 combines two complexation substructures known to undergo, with specific metal ions, distinct self-assembly processes to form a double-helical and a grid-type structure, respectively. The binding information contained in this molecular strand may be expected to generate, in a strictly predeter…
An Anthracene-Based Photochromic System That Responds to Two Chemical Inputs
Reversible intramolecular cyclization reactions to form crown ethers are possible with photoactive anthracene derivatives containing two binding sites (see scheme). Different chemical inputs in the form of HgCl2 and Na+ ions result in changes in the efficiency and rate of the forward and reverse processes.
Synthesis of Trioxane Using Heteropolyacids as Catalyst
A high formaldehyde feed concentration and a low reaction temperature are among the advantages of using heteropolyacids (phosphotungstic acid and silicotungstic acid) as catalysts in the formation of trioxane; this cyclic trimer of formaldehyde (see scheme) is used in the industrial production of acetal resins. Compar…
One-Pot Synthesis of Photochromic Naphthopyrans in the Solid State
p-TsOH-catalyzed condensation reactions of 1,1-diaryl-2-propyn-1-ol (1) and 2-naphthol (2) in the solid state gave 3, 3-diaryl-3H-naphtho[2,1-b]pyran (6) via Claisen rearrangement. Similar reactions of 1 with 2,6- (7) and 2,7-dihydroxynaphthalenes (8) afforded naphthodipyrane derivatives 9 and 10, respectively. Bis-na…
Photomagnetic Properties in a Series of Spin Crossover Compounds [Fe(PM-L)2(NCX)2] (X=S, Se) with Substituted 2′-Pyridylmethylene- 4-amino Ligands
The spin crossover (SC) compounds [Fe(PM-AzA)2(NCX)2] and [Fe(PM-FIA)2(NCX)2] (with PM-AzA = N-2'-pyridylmethylene-4-(phe-nylazo)aniline, PM-FIA = N-2'-pyridylmethylene-4-(2-amino)fluorene, and X = S, Se) have been prepared. The SC regimes have been deduced from variable-temperature magnetic susceptibility data. The e…
The characterization of Y2O2S:Sm powder as a thermographic phosphor for high temperature applications
Thermographic phosphors may be used to measure surface temperatures in hostile and high temperature environments and have applications in gas turbine combustors and high temperature regions of the turbine. Most phosphors are excited by UV light and exhibit a temperature sensitive exponential decay in emission once exc…
Rigidified Calixarenes Bearing Four Carbamoylmethylphosphineoxide or Carbamoylmethylphosphoryl Functions at the Wide Rim
Conformationally rigidified tetraCMPO derivatives have been prepared from calix[4]arene bis(crown ether) 4a in which adjacent oxygens are bridged at the narrow rim by two diethylene glycol links. Acylation of the tetraamine 4c with the CMPO-active ester 5b gave the tetraphosphine oxide 6a, while the tetraphosphinate 6…
Structure of Homoleptic CuI(CO)3 Cations in CuI-Exchanged ZSM-5 Zeolite: An X-ray Absorption Study
Interaction with the zeolitic walls changes the structure of zeolite-encapsulated CuI(CO)3 cations (see picture), which were synthesized in situ by treating CuI-ZSM-5 zeolite with CO at 80 K, from the planar D3h form, typical of homogeneous analogues such as [Cu(CO)3]+AsF6−, to a C3v-symmetric bent form. This conclusi…
Deposition of Highly Ordered CF2-Rich Films Using Continuous Wave and Pulsed Hexafluoropropylene Oxide Plasmas
The structure and composition of fluorocarbon materials deposited in pulsed and continuous wave (CW) hexafluoropropylene oxide (HFPO) plasmas were investigated. Results indicate substantial dependence on substrate position relative to the rf coil. When the substrate was placed 8 cm downstream from the rf coil (25 W CW…
Mixed Ferrocene-Cobaltocenium Dendrimers: The Most Stable Organometallic Redox Systems Combined in a Dendritic Molecule
Novel peripherally heterogeneous dendrimers in which both ferrocene and cobaltocenium units are attached to the surface of poly(propylene imine) dendritic frameworks (see picture) were prepared. The presence of the two redox-active moieties allows the heterometallic dendrimers to be used as novel types of mediator in…
Novel Electrostatic Attraction from Plasmon Fluctuations
In this Letter, we show that at low temperatures, zero-point fluctuations of the plasmon modes of two mutually coupled 2-D planar Wigner crystals give rise to a novel long-range attractive force. For the case where the distance $d$ between two planar surfaces is large, this attractive force has an unusual power-law de…
Electrostatic Attraction of Coupled Wigner Crystals: Finite Temperature Effects
In this paper, we present a unified physical picture for the electrostatic attraction between two coupled planar Wigner crystals at finite (but below their melting) temperature. At very low temperatures, we find a new regime where the attraction, arising from the long-wavelength excitation of the plasmon mode, scales…
Wavelength dependent negative and positive persistent photoconductivity in Sn delta-doped GaAs structures
The photoconductivity of GaAs structures delta-doped by Sn has been investigated for wavelengths lambda= 650-1200 nm in the temperature interval T= 4.2-300 K. The electron densities and mobilities, before and after illumination, have been determined by magnetoresistance, Shubnikov-de Haas effect and Hall effect measur…
Spin fluctuations in nearly magnetic metals from ab-initio dynamical spin susceptibility calculations:application to Pd and Cr95V5
We describe our theoretical formalism and computational scheme for making ab-initio calculations of the dynamic paramagnetic spin susceptibilities of metals and alloys at finite temperatures. Its basis is Time-Dependent Density Functional Theory within an electronic multiple scattering, imaginary time Green function f…
Spectroscopic fingerprints of a surface Mott-Hubbard insulator: the case of SiC(0001)
We discuss the spectroscopic fingerprints that a surface Mott-Hubbard insulator should show at the intra-atomic level. The test case considered is that of the Si-terminated SiC(0001) sqrt{3}xsqrt{3} surface, which is known experimentally to be insulating. We argue that, due to the Mott-Hubbard phenomenon, spin unpaire…
Detection of Nitrobenzene, DNT, and TNT Vapors by Quenching of Porous Silicon Photoluminescence
The detection of nitroaromatic molecules in air by the quenching of the photoluminescence of porous silicon (porous Si) films has been explored. Detection is achieved by monitoring the photoluminescence (PL) of a nanocrystalline porous Si film on exposure to the analyte of interest in a flowing air stream. The photolu…