Materials Literature
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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…
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…
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.
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…
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…
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…
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…
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…
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…
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…
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…
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…
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…
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…
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…
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…
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…
New aspects of a relation between lattice and dislocation structures are examined within a physically transparent theoretical scheme. Predicted features originating from the lattice discreteness include: (i) multiple core dislocation structures and (ii) their dependence on the position of the dislocation axis. These e…
Programmed chemical systems rest on the structural information stored in a molecular framework and on its reading and processing through non-covalent interactional algorithms to yield specific supramolecular entities. Beyond single-code self-assembly, which generates exclusively a single, specific superstructure, seve…
A correlation between the electron spin−orbital angular momentum coupling and the superparamagnetic properties has been established in MgFe 2 O 4 and CoFe 2 O 4 spinel ferrite nanoparticles. The contribution to the magnetic anisotropy from the Fe 3+ lattice sites is almost the same in both nanocrystallites as neutron…