Francisco Brown

Charge-transfer complexes of benzylviologen (1,1′-dibenzyl-4,4′-bipyridinium(2+) cation) with cyanocuprate(I) and the structure of (BzV)3Cu9(CN)15·H2O

Reactions between 1,1′-dibenzyl-4,4′-bipyridinium(2+) (benzylviologen, BzV) chloride and cyanocuprates(I) gave two charge-transfer complexes having different colors: dark brown (BzV)3Cu9(CN)15·H2O and light brown (BzV)Cu(CN)3·2H2O. An X-ray crystal analysis of the former compound showed that nine crystallographically nonequivalent Cu atoms form three kinds of triad Cu(CN)Cu screws, which are linked by CN groups resulting in a unique three-dimensional network structure. Three of the nine Cu atoms have distorted tetrahedral (td) coordination geometries while the others have triangular plane (tp) geometries. Each screw consists of a (-tp-td-tp-)n array. There are three crystallographically nonequivalent viologen molecules. Certain CuCN moieties are located above a viologen ring or by the side of a viologen ring, with close interatomic contacts. These close contacts are characteristic of the charge-transfer complex and are responsible for the deep color of the complex.

Modulated structure of the pseudohexagonal InFe1−x−4δTix+3δO3+x/2 (x = 0.61) composite crystal

The structure of pseudohexagonal-type InFe1−x−4δTix+3δO3+x/2 (x = 0.61, δ = 0.04), indium iron titanium oxide, was refined on the basis of a four-dimensional superspace group. The crystal has a compositely modulated structure consisting of two orthorhombic subsystems mutually incommensurate in b. The first subsystem InFe1−x−4δTix+3δO2 has a delafossite structure with lattice parameters a = 5.835 (3), b1 = 3.349 (1) and c = 12.082 (7) A. The second subsystem with b2 = 2.568 (6) A consists of O atoms. The superspace group of the overall structure is Ccmm(1, 1.305, 0)s00, which can be converted to Amam(0, 0, 0.305)0s0 (No. 63.8). Refinement on 1105 unique reflections converged to R = 0.0303 and wR = 0.0325 with 63 structural parameters. The structure of the first subsystem is the alternate stacking of an edge-shared InO6 octahedral layer and an Fe/Ti triangle-lattice plane along c. A sheet of O atoms in the second subsystem is also extending on the Fe/Ti plane, where displacive modulation of atoms is prominent.

Orthorhombic InFe0.33Ti0.67O3.33

The title compound, indium iron titanium oxide, is closely related to InFeO 3 , having a hexagonal structure which consists of alternating layers of InO 6 octahedra and FeO 5 trigonal bipyramids. According to substitution of Ti 4+ for Fe 3+ , excess O atoms are introduced into the Fe-O trigonal lattice plane of InFeO 3 . The inplane arrangement of O atoms can be described as partial occupation on a honeycomb lattice, although large displacement parameters indicate local shifts of 0 atoms due to repulsive interactions between them.

PHOTOCHEMICAL SYNTHESES OF FULLERENE-AMINE ADDUCTS AND THEIR CHARACTERIZATION WITH 1H NMR SPECTROSCOPY

Abstract Photoreactions of C 60 with aromatic or aliphatic amines in contact with air gave a new type of amine adduct with a general compound formula of C 60 (amine) x (OH) y O z ; the amine was di-2-pyridylamine, morpholine or N , N -dimethylethylenediamine. The N , N -dimethylethylenediamine adduct was obtained as a hydrochloride. Its 1 H NMR spectrum showed that the adduct cation, obtained after functionalizing C 60 , formed an ion pair with a benzenesulfonate anion.

Study of the glow curve structure of the minerals separated from black pepper (Piper nigrum L.)

The inorganic mineral fraction extracted from black pepper (Piper nigrum L.) has been analysed using a thermoluminescence (TL) method, investigating the glow curve structure, including an evaluation of the kinetic parameters. Different grain sizes, i.e. 10, 74, and 149 μm, were selected from commercial black pepper. The X-ray diffraction of the inorganic fraction shows that quartz is the main mineral present in it. The samples were exposed to 1–25 kGy doses by gamma rays of 60Co in order to analyse the thermally stimulated luminescence response as a function of the delivered dose. The glow curves show a complex structure for different grain sizes of the pepper mineral samples. The fading of the TL signal at room temperature was obtained after irradiation, and it was observed that the maximum peaks of the glow curves shift towards higher values of the temperature when the elapsed time from irradiation increases. It seems that the fading characteristic may be related to a continuous trap distribution responsible for the complex structure of the glow curve. Similar glow curves structure behaviour was found under ultraviolet irradiation of the samples. The activation energy and the frequency factor were determined from the glow curves of different grain sizes using a deconvolution programme because of the evident complexity of the structure.

Polymerization of anilines by the use of copper(II) perchlorate as an oxidative coupling agent

SummaryPolyaniline and polyalkylaniline perchlorates were prepared by oxidative coupling polymerization of anilines by the use of copper(II) perchlorate in acetonitrile as an oxidant. The corresponding polymer bases obtained by treating the perchlorates with alkaline solution were soluble in dimethylsulfoxide and partly soluble in tetrahydrofuran. The molecular weights of the THF-soluble components were 2000–6000. The charge transport of the perchlorates is influenced by the chain length and the steric effect of alkyl substituents.

Thermoluminescence response and glow curve structure of Sc2TiO5 ß-irradiated

Discandium titanate (Sc2TiO5) powder was synthesized in order to analyze its thermoluminescence (TL) response. The TL glow curve structure shows two peaks: at 453-433 K and at 590-553 K. The TL beta dose-response has a linear behavior over the dose range 50-500 Gy. The T(stop) preheat method shows five glow peaks that were taken into account to calculate the kinetic parameters using the CGCD procedure. TL results support the possible use of Sc2TiO5 as a new phosphor in high ß-dose dosimetry.

Structural Characterization and Dielectric Properties of Hexagonal Lu(Fe,Ti)O3

We investigated the average crystal structure and microstructures of LuFe0.56Ti0.44O3 by transmission electron microscopy (TEM) in combination with dielectric measurements. In this work, high-quality polycrystalline samples of LuFe0.56Ti0.44O3 were successfully synthesized in air by the conventional solid-state reaction. The average crystal structure at room temperature is characterized by a hexagonal structure (space group: P63cm). Dielectric measurements revealed that LuFe0.56Ti0.44O3 shows broad dielectric peaks at approximately 450 and 580 K, one of which is considered to originate from the formation of polar domains at the nanometer scale.

Thermoluminescence characterization of LiMgF3:DyF3 phosphors exposed to beta radiation

LiMgF3:DyF3 phosphors were obtained as polycrystalline solids from the melting of component salts, with two DyF3 concentrations, 2.02% mol and 4.04% mol. In order to guarantee the homogeneity of the composition, the samples were crushed and the resulting powder was pressed to form pellet-shaped phosphors, some of which were sintered at 700 °C for 5 h, under atmospheric air. Thermoluminescence measurements of beta irradiated samples show that these phosphors exhibit adequate properties to be considered for development of thermoluminescence dosimeters. Integrated thermoluminescence as a function of dose displays a linear dependence with dose for doses below 20.0 Gy.

Afterglow dosimetry performance of beta particle irradiated lithium zirconate

In this work, we report for the very first time on the thermoluminescence (TL) and afterglow (AG) properties of Li2ZrO3. The ternary oxide Li2ZrO3 was synthesized by solid state reaction of a mixture of Li2CO3 and ZrO2 subjected to thermal annealing at 400°C for 2h and 1000°C during 24h in air. The characteristic glow curves of beta particle irradiated samples exhibit an intense TL emission located around 150°C. From the shape of the TL curve, a 0.4 form factor was determined, suggesting that first order kinetics processes are involved. The afterglow decay curves were recorded after exposure to beta particle irradiation in the dose range from 0.5 up to 2kGy. The AG integrated in the time interval from 510 to 600s after radiation exposure shows a linear dependence as a function of the irradiation dose from 0.5 up to 256Gy. A method is proposed to compute the lower detection limit and the AG sensitivity and applied to the studied phosphors. Structural and morphological characterization were carried out by X-ray diffraction and Scanning Electron Microscopy, respectively. From the results presented, it is concluded that the AG response of the synthesized Li2ZrO3 presents features suitable to develop radiation detectors and dosimeters.