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Broad Bands (broad + bands)
Selected AbstractsRaman microscopy of formamide-intercalated kaolinites treated by controlled-rate thermal analysis technologyJOURNAL OF RAMAN SPECTROSCOPY, Issue 10 2001Ray L. Frost Raman spectroscopy of formamide-intercalated kaolinites treated using controlled-rate thermal analysis technology (CRTA), allowing the separation of adsorbed formamide from intercalated formamide in formamide-intercalated kaolinites, is reported. The Raman spectra of the CRTA-treated formamide-intercalated kaolinites are significantly different from those of the intercalated kaolinites, which display a combination of both intercalated and adsorbed formamide. An intense band is observed at 3629 cm,1, attributed to the inner surface hydroxyls hydrogen bonded to the formamide. Broad bands are observed at 3600 and 3639 cm,1, assigned to the inner surface hydroxyls, which are hydrogen bonded to the adsorbed water molecules. The hydroxyl-stretching band of the inner hydroxyl is observed at 3621 cm,1 in the Raman spectra of the CRTA-treated formamide-intercalated kaolinites. The results of thermal analysis show that the amount of intercalated formamide between the kaolinite layers is independent of the presence of water. Significant differences are observed in the CO stretching region between the adsorbed and intercalated formamide. Copyright © 2001 John Wiley & Sons, Ltd. [source] Spectroscopic Investigation of the Europium(3+) Ion in a New ZnY4W3O16 MatrixHELVETICA CHIMICA ACTA, Issue 11 2009bieta Tomaszewicz Abstract A new Zn and Eu tungstate was characterized by spectroscopic techniques. This tungstate, of the formula ZnEu4W3O16, crystallized in the orthorhombic system and was synthesized by a solid-state reaction. It melts incongruently at 1330°. The luminescent properties, including excitation and emission processes, luminescent dynamics, and local environments of the Eu3+ ions in ZnEu4W3O16 and ZnY4W3O16,:,Eu3+ diluted phases (1, 5, and 10,mol-% of Eu3+ ion) were studied basing on the f6 -intraconfigurational transitions in the 250,720,nm spectral range. The excitation spectra of this system (,em 615 and 470,nm) show broad bands with maxima at 265 and 315,nm related to the ligand-to-metal charge-transfer (LMCT) states. The emission spectra under excitation at the O,W (265,nm) and O,Eu3+ (315,nm) LMCT states present the blue-green emission bands. The emission of tungstate groups mainly originate from the charge-transfer state of excited 2p orbitals of O2, to the empty orbitals of the central W6+ ions. On the other hand, in the emission of the Eu3+ ions, both the charge transfer from O2, to Eu3+ and the energy transfer from W6+ ions to Eu3+ are involved. The emission spectra under excitation at the 7F0,5L6 transition of the Eu3+ ion (394,nm) of ZnY4W3O16,:,Eu3+ diluted samples show narrow emission lines from the 5D3, 5D2, and 5D1 emitting states. The effect of the active-ion (Eu3+) concentration on the colorimetric characteristic of the emissions of the compound under investigation are presented. [source] A Japanese case of Kindler syndromeINTERNATIONAL JOURNAL OF DERMATOLOGY, Issue 4 2000Yasushi Suga MD A 25-year-old Japanese woman presented with contracture of the fingers and toes, and difficulty in opening her mouth. Her grandparents are first cousins, but none of the other members of the family are affected. Bulla formation started at birth on areas of the skin that received pressure, and in infancy and early childhood the lesions were limited only to the acral areas. She also had bilateral, incomplete syndactylies involving all web spaces ( Fig. 1a). The formation of blisters ceased after the age of 15 years, but a generalized progressive poikiloderma then appeared with accompanying cutaneous atrophy of the skin of the neck, trunk, and extremities ( Fig. 1b). The patient experienced mild photosensitivity of the face and neck. At age 18 years, surgical removal of the webbing of all her fingers was performed. Oral examination showed atrophy of the buccal mucosa, and an inability to fully open the mouth. The patient also suffered from poor dentition and easily bleeding gums, but had no symptoms of esophageal dysfunction. Figure 1. Clinical manifestations of the patient with Kindler syndrome. (a) Dorsal surface of the patient's hands. Note the marked cutaneous atrophy with a severely wrinkled appearance on the dorsal surface of the hands, as well as the proximal fusion of the fingers. (b) Lower left leg of the patient. Atrophic thinning of the skin and poikiloderma with reticular pigmentation are evident Histology of separate biopsy specimens, taken from the poikilodermatous pretibial and trunk skin, showed classical features of poikiloderma, namely epidermal atrophy with flattening of the rete ridges, vacuolization of basal keratinocytes, pigmentary incontinence, and mild dermal perivascularization ( Fig. 2a). Interestingly, dyskeratotic cells ( Fig. 2b) and eosinophilic rounded bodies (colloid bodies) ( Fig. 2c) were frequently found at the basal keratinocyte layer and in the upper dermis, respectively. Pigment was also present in the upper epidermis. Figure 2. Hematoxylin and eosin staining of a biopsy specimen taken from pretibial skin. (a) Epidermal atrophy with flattening of the rete ridges. Note the dyskeratotic cells (arrowheads) and vacuolar degeneration of the basal layer in the epidermis. Bar = 50 ,m. (b) Higher magnification of dyskeratotic cells (arrowheads). Bar = 10 ,m. (c) Higher magnification of colloid bodies (arrowheads) in the superficial dermis. Bar = 10 ,m To rule out the possibility of a congenital epidermolysis bullosa, ultrastructural and immunofluorescence studies were performed. Ultrastructural studies demonstrated the reduplication of the basal lamina with branching structures within the upper dermis and cleavage between the lamina densa and the cell membrane of the keratinocytes ( Fig. 3a). The numbers of associated anchoring fibrils did not seem to be reduced, and colloid bodies and dyskeratotic cells were detected. Immunofluorescence studies with the antibody against type VII collagen (LH 7 : 2) were subsequently carried out. The results showed extensive broad bands with intermittently discontinuous and reticular staining at the dermo-epidermal junction (DEJ) ( Fig. 3b), whereas a linear distribution is typically seen in healthy tissue (data not shown). Interestingly, direct immunofluorescence studies revealed intracellular accumulation of immunoglobulin G (IgG), IgM, IgA, and C3 in colloid bodies under the basement membrane ( Fig. 3c). Figure 3. Ultrastructural and immunohistochemical findings of the patient with Kindler syndrome. (a) Ultrastructural study of the dermo-epidermal junction. The branching structures of the lamina densa (arrowheads) were frequently seen. The asterisks show the cleavage in the lamina lucida. Bar = 1 ,m. (b) Immunohistochemical studies with the antibody to type VII collagen (LH 7 : 2). An extensive broad band with reticular patterns is evident. Bar = 50 ,m. E, epidermis; D, dermis. (c) Direct immunofluorescence study. Intracytoplasmic deposition of IgM in the basal keratinocytes is evident (arrowheads). Bar = 50 ,m. E, epidermis; D, dermis [source] Micro-Raman study of iridium silicidesJOURNAL OF RAMAN SPECTROSCOPY, Issue 2 2002A. Almendra The micro-Raman spectra of three iridium silicides, IrSi, IrSi1.75 and IrSi3, were obtained. The silicides were prepared by rapid thermal annealing of iridium films deposited on Si substrates. The three phases were identified by Rutherford backscattering spectrometry. The main bands observed in the micro-Raman spectra are described in order to provide a simple characterization method for these silicides with high spatial resolution. The three silicides present phonon bands around 165 and 200 cm,1. Some additional broad bands between 240 and 500 cm,1 were also observed. Copyright © 2002 John Wiley & Sons, Ltd. [source] Observation of new defect levels in nanodiamond membranesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 11 2005R. Kravets Abstract This paper reports on a new set of defect features in thin membrane nanodiamond. The samples were stud-ied using Fourier transform photocurrent spectroscopy. We have observed four dominant new peaks in nanocrystalline diamond: two sharp peaks at 0.36 and 0.40 eV and broad bands at 0.27 and 0.57 eV. The first of these peaks is suggested to originate from a currently unknown bulk impurity; the other three are surface-related and are especially prone to surface effects such as absorption/desorption over time. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Cathodoluminescent characteristics of Sm-doped ZnAl2O4 nanostructured powdersPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2005E. Martinez-Sanchez Abstract Cathodoluminescent (CL) powders of zinc aluminate activated with samarium ions have been prepared by a co-precipitation chemical process. Different doping concentrations in the start mixture and sintering temperatures for the precipitated powder were studied. It was observed that the crystalline characteristics of the powders depend upon the sintering temperature. For temperatures higher than 450 °C, the powders presented the cubic spinel phase with a lattice parameter value of 8.0756 Å, and grain sizes from 50 to 100 nm with semispherical shape. The CL emission spectra showed broad bands localized at 564, 602, 644, and 703 nm associated with 4G5/2 , 6H5/2, 4G5/2 , 6H7/2, 4G5/2 , 6H9/2, and 4G5/2 , 6H11/2 transitions in the Sm3+ ions, respectively. Concentration quenching of the cathodoluminescence occurred at about 4.26 at% of the activator (Sm) concentration inside the sintered powders. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Compositional dependence of optical and vibrational properties of strontium barium niobate (SrxBa1,xNb2O6)PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 6 2007C. David Abstract The index of refraction, the optical band edge and the Raman scattering of strontium barium niobate, SrxBa1,xNb2O6 with 0.38 < x < 0.77 have been studied. The ordinary refractive index does not depend on x, while the extra-ordinary one increases with increasing x. The band edge is almost unaffected by the Ba- or Sr-content and shows a weak band bowing. Both the index of refraction and the band edge may be used for an optical determination of the composition of the crystal. Raman spectra show the typical behavior of tungsten bronze type crystals with broad bands and complicated spectral shapes. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Optical absorption and photoluminescence of CuAlTe2PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 8 2006B. V. Korzun Abstract The bulk crystals of the CuAlTe2 semiconductor ternary compound with the chalcopyrite structure were prepared, and their optical properties were investigated. It was determined that the value of band gap energy equals 1.69 and 1.65 eV at 105 and 293 K, respectively. The photoluminescence spectra were measured for the first time and contain broad bands with peaks at 1.09 eV (78 K) and 1.03 eV (293 K). The full width at half maximum (FWHM) for both temperatures is 0.28 eV. The origin of this band is associated with band to deep acceptor optical transition. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Low-Energy-Barrier Proton Transfer Induced by Electron Attachment to the Guanine,,,Cytosine Base PairCHEMPHYSCHEM, Issue 4 2010Anna Szyperska Abstract The photoelectron spectrum of the anion of the guanine,,,cytosine base apair (GC)., is recorded for the first time. The observed variation in the spectral peak-height ratios with the source conditions suggests the presence of two or more anionic isomers. Two maxima of the broad bands in the photoelectron spectrum were measured at about 1.9 and about 2.6 eV. These values are very well reproduced by the vertical detachment energies of the B3LYP/6-31++G(d,p) calculated low-energy anionic structures, which are 1) the Watson,Crick base-pair anion with proton transferred from N1 of guanine to N3 of cytosine, 2) its analogue in which the proton is transferred from N9 of guanine to N7 of guanine, and 3) the global minimum geometry, which is formed from the latter anion by rotation of guanine about the axis approximately defined by C2 of guanine and C4 of cytosine. Furthermore, a minor difference in the stabilities of the two lowest energy anions explains the experimentally observed source (temperature) dependence of the PES spectrum. A rational procedure, based on the chemistry involved in the formation of anionic dimers, which enables the low-energy anions populated in the photoelectron spectrum to be identified is proposed. In contrast to the alternative combinatorial approach, which in the studied case would lead to carrying out quantum chemical calculations for 2000,2500 structures, the procedure described here reduces the computational problem to only 15 geometries. [source] Electron Transfer from Photoexcited TiO2 to Chelating Alizarin Molecules: Reversible Photochromic Effect in Alizarin@TiO2 under UV IrradiationCHEMPHYSCHEM, Issue 7 2009Yesica Di Iorio Abstract Reduction of alizarin molecules coupled to TiO2 nanoparticles occurs on UV irradiation in the presence of a sacrificial electron donor. Reduction is mediated by conduction-band electrons and yields a 1,2,9,10-tetrahydroxyanthracene species which remains coupled to the TiO2 nanoparticles (see figure). The process can be reversed by addition of an acceptor (i.e. oxygen). Reduction of alizarin molecules coupled to TiO2 nanoparticles (A@TiO2) occurs on UV irradiation in the presence of a sacrificial electron donor. Evidence is presented that reduction is mediated by conduction-band electrons and yields a 1,2,9,10-tetrahydroxyanthracene species which remains coupled to the TiO2 nanoparticles. The spectrum of the reduced complex displays two overlapping broad bands centred at 480 and 650 nm which can harvest visible photons besides 900 nm, in agreement with theoretical predictions by TDDFT. The potential relevance of the dual-redox behaviour of strongly TiO2 coupled anthraquinone dyes in the field of photocatalysis and in connection with their utilization in the development of dye-sensitized TiO2 solar cells is briefly discussed. [source] | |||||||||||||