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Ab initio study of the electronic and optical properties of sillimanite (Al(2)SiO(5)) crystal

Mamani, Nilo Francisco Cano; Watanabe, Shigueo
Fonte: ELSEVIER SCIENCE BV Publicador: ELSEVIER SCIENCE BV
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
65.96%
Ab initio calculations based on the density functional theory (DFT) are used to investigate the electronic and optical properties of sillimanite. The geometrical parameters of the unit cell, which contain 32 atoms, have been fully optimized and are in good agreement with the experimental data. The electronic structure shows that sillimanite has an indirect band gap of 5.18 eV. The complex dielectric function and optical constants, such as extinction coefficient, refractive index, reflectivity and energy-loss spectrum, are calculated. The optical properties of sillimanite are discussed based on the band structure calculations. It is shown that the O-2p states and Al-3s, Si-3s states play the major role in optical transitions as initial and final states, respectively. (C) 2011 Elsevier B.V. All rights reserved.; Fundacao de Amparo a Pesquisa do Estado de Sao Paulo - FAPESP[2007/08008-0]; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Theoretical investigation of electronic and optical properties of andalusite within density functional theory

Mamani, Nilo Francisco Cano; Watanabe, Shigueo
Fonte: PERGAMON-ELSEVIER SCIENCE LTD Publicador: PERGAMON-ELSEVIER SCIENCE LTD
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
65.96%
The electronic and optical properties of andalusite were studied by using quantum-mechanical calculations based on the density functional theory (DFT). The electronic structure shows that andalusite has a direct band gap of 5.01 eV. The complex dielectric function and optical constants, such as extinction coefficient, refractive index, reflectivity and energy-loss spectrum, are calculated. The optical properties of andalusite are discussed based on the band structure calculations. It is shown that the O-2p states and Al-3s states play a major role in optical transitions as initial and final states, respectively. (C) 2010 Elsevier Ltd. All rights reserved.; Fundacao de Amparo a Pesquisa do Estado de Sao Paulo - FAPESP[2007/08008-0]; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Electronic and optical properties of grossular garnet (Ca(3)Al(2)Si(3)O(12)): An ab initio study

Mamani, Nilo Francisco Cano; Ayta, Walter Elias Feria; Watanabe, Shigueo
Fonte: ELSEVIER SCIENCE BV Publicador: ELSEVIER SCIENCE BV
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
65.94%
The electronic and optical properties of grossular garnet are investigated using density functional theory (DFT) within generalized gradient approximation (GGA). The calculated lattice parameters are in good agreement with the experiment data. The electronic structure shows that grossular has a direct band gap of 5.22 eV. The dielectric functions, reflective index, extinction coefficient, reflectivity and energy-loss spectrum are calculated. The optical properties of grossular are discussed based on the band structure calculations. The O 2p states and Si 3s play a major role in these optical transitions as initial and final states, respectively. The absorption spectrum is localized in the ultraviolet range between 30 and 250 nm. Finally, we concluded that pure grossular crystal does not absorb radiation in the visible range. (c) 2009 Elsevier B.V. All rights reserved.; Fundacao de Amparo a Pesquisa do Estado de Sao Paulo - FAPESP[2007/08008-0]; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

HMDSO plasma polymerization and thin film optical properties

Mota, Rogério Pinto; Galvão, Douglas; Durrant, Steven F.; De Moraes, Mário A.Bica; de Oliveira Dantas, Socrates; Cantão, Mauricio
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 109-113
ENG
Relevância na Pesquisa
65.98%
Thin films were deposited from hexamethyldisiloxane (HMDSO) in a glow discharge supplied with radiofrequency (rf) power. Actino-metric optical emission spectroscopy was used to follow trends in the plasma concentrations of the species SiH (414.2 nm), CH (431.4 nm), CO (520.0 nm), and H (656.3 nm) as a function of the applied rf power (range 5 to 35 W). Transmission infrared spectroscopy (IRS) was employed to characterize the molecular structure of the polymer, showing the presence of Si-H, Si-O-Si, Si-O-C and C-H groups. The deposition rate, determined by optical interferometry, ranged from 60 to 130 nm/min. Optical properties were determined from transmission ultra violet-visible spectroscopy (UVS) data. The absorption coefficient α, the refractive index n, and the optical gap E04 of the polymer films were calculated as a function of the applied power. The refractive index at a photon energy of 1 eV varied from 1.45 to 1.55, depending on the rf power used for the deposition. The absorption coefficient showed an absorption edge similar to other non-crystalline materials, amorphous hydrogenated carbon, and semiconductors. For our samples, we define as an optical gap, the photon energy E04 corresponding to the energy at an absorption of 104 cm-1. The values of E04 decreased from 5.3 to 4.6 as the rf power was increased from 5 to 35 W. © 1995.

Rietveld refinement, morphology and optical properties of (Ba 1-xSrx)MoO4 crystals

Nogueira, I. C.; Cavalcante, L. S.; Pereira, P. F S; De Jesus, M. M.; Rivas Mercury, J. M.; Batista, N. C.; Li, M. Siu; Longo, Elson
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 1434-1446
ENG
Relevância na Pesquisa
65.94%
In this article, the structural refinement, morphology and optical properties of barium strontium molybdate [(Ba1-x Sr x )MoO4 with x = 0, 0.25, 0.50, 0.75 and 1] crystals, synthesized by the co-precipitation (drop-by-drop) method, are reported. The crystals obtained were structurally characterized by X-ray diffraction (XRD), Rietveld refinement, and Fourier transform-Raman (FT-Raman) and Fourier transform-infrared (FT-IR) spectroscopies. The shapes of the crystals were observed by means of field-emission scanning electron microscopy (FE-SEM). The optical properties were investigated using ultraviolet-visible (UV-Vis) absorption spectroscopy and photoluminescence (PL) measurements. XRD patterns, Rietveld refinement, and FT-Raman and FT-IR spectra showed that all of the crystals are monophasic with a scheelite-type tetragonal structure. The refined lattice parameters and atomic positions were employed to model the [BaO8], [SrO8] and [MoO4] clusters in the tetragonal lattices. The FE-SEM images indicate that increased x content produces a decrease in the crystal size and modifications in the crystal shape. UV-Vis spectra indicated a decrease in the optical band gap with an increase in x in the (Ba1-x Sr x )MoO4 crystals. Finally, a decrease in the intensity of PL emission is apparent with an increase in x up to 0.75 in the (Ba1-x Sr x )MoO4 crystal lattice when excited by a wavelength of 350nm...

Propriedades de pontos quânticos de InP/GaAs; Structural and optical properties of InP/GaAs type II quantum dots

Marcio Peron Franco de Godoy
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 19/05/2006 PT
Relevância na Pesquisa
65.96%
Neste trabalho estudamos as propriedade estruturais e ópticas de pontos quânticos auto-organizados de InP crescidos sobre o substrato de GaAs. Esta estrutura apresenta o alinhamento de bandas tipo-II na interface, confinando o elétron no ponto quântico, enquanto o buraco mantém-se na barreira, próximo à interface devido à interação coulombiana atrativa. As amostras foram crescidas por epitaxia de feixe químico (CBE) no modo Stranskii-Krastanov. Os pontos quânticos apresentam raio médio de 25 nm e grande dispersão de altura (1-5 nm) e ocorre a relaxação parcial do parâmetro de rede, chegando a 2 %, em pontos quânticos superficiais. Do ponto de vista de propriedades ópticas, a fotoluminescência de pontos quânticos superficiais exibe uma eficiente emissão óptica, devido a baixa velocidade de recombinação dos estados superficiais do InP, e reflete a densidade e distribuição bimodal de tamanhos. Além disso, sua emissão óptica em função da intensidade de excitação exibe comportamento diverso em comparação com pontos quânticos cobertos com uma camada de GaAs. Em pontos quânticos cobertos, determinamos a energia de ativação térmica, que varia de 6 a 8 meV, e é associada à energia de ligação do éxciton ou energia de ionização do buraco. O decaimento temporal da luminescência de pontos quânticos é de 1...

Optical properties of titanium oxycarbide thin films

Marques, L.; Pinto, H.; Fernandes, Ana C.; Banakh, O.; Vaz, F.; Ramos, Marta M. D.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em /03/2009 ENG
Relevância na Pesquisa
65.96%
The optical properties of TiC x O y thin films, deposited by reactive dc magnetron sputtering at different oxygen flow, were investigated by spectroscopic ellipsometry in the energy range of 0.75–4.5 eV. The dielectric functions measured in the energy range of intraband transitions were analyzed using the classical Drude theory. These results show that free plasma energy and the damping constant of the films depend strongly on film stoichiometry and on their oxygen content. The interband contribution to the optical conductivity of these films is in good agreement with the optical conductivity obtained from first principles calculations based on density functional theory. Both the experimental and the calculated results show that it is possible to significantly modify the optical properties of titanium oxycarbide by adjusting the oxygen content.; Fundação para a Ciência e a Tecnologia (FCT) – Programa Operacional “Ciência , Tecnologia, Inovação” – CONC-REEQ/443/EEI/2005, PTDC/CTM/69362 e SFRH/BD/27569/2006

Structural and optical properties of Ag : TiO2 nanocomposite films prepared by magnetron sputtering

Adochite, R.; Torrell, M.; Cunha, L.; Alves, E.; Barradas, N. P.; Cavaleiro, A.; Rivière, J. P.; Eyidi, D.; Vaz, F.
Fonte: INOE Publishing House Publicador: INOE Publishing House
Tipo: Artigo de Revista Científica
Publicado em /01/2011 ENG
Relevância na Pesquisa
65.98%
Three sets of nanocomposite films consisting of different atomic concentrations of Ag dispersed in a TiO2 dielectric matrix were deposited by DC reactive magnetron sputtering, and subjected to several thermal annealing experiments in vacuum, for temperatures ranging from 200 to 600 ºC. The main goal of the present study is to analyse the optical properties of the as-deposited and annealed films in order to clarify the role of Ag inclusions in the TiO2 dielectric matrix. The influence of the thermal annealing in the structural and morphological evolution was then correlated with the changes in the optical behavior of the samples. Significant structural and morphological changes were observed, consisting on the crystallization of Ag and their clustering. Clusters growth as a function of temperature was also observed by the evolution of the diffractograms with the temperature increase. The present study allowed to conclude that at certain concentrations (close to 10 at. %), the films revealed some important changes on the optical properties, commonly known as Surface Plasmon Resonance, SPR. This change in the optical behavior of the films was found to be in accordance with the clusters growth as concluded from the evolution of the diffraction patterns. The optical changes...

Optical properties of AlNxOy thin films deposited by DC magnetron sputtering

Borges, Joel; Alves, E.; Vaz, F.; Marques, L.
Fonte: SPIE Publicador: SPIE
Tipo: Artigo de Revista Científica
Publicado em /08/2011 ENG
Relevância na Pesquisa
65.96%
The aluminium oxynitride system offers the possibility to obtain a wide range of optical responses, by combining metallic aluminium, aluminium oxide and aluminium nitride properties, and thus opening a significant number of possible applications. The main purpose of the present work is to study the variation of the optical properties of AlN x O y thin films as a function of their composition (by varying both x and y coefficients), and the correspondent changes in their morphology and structure. The films were deposited by DC reactive magnetron sputtering, with the discharge parameters monitored during the deposition in order to control the chemical composition. The measurements reveal a smooth change of films Reflectance/Transmittance as a function of the concentration ratio of non metallic elements (O+N) to metallic Al, thus revealing the possibility to tailor the films optical properties according to the application envisaged.; Fundação para a Ciência e a Tecnologia (FCT) e ao Fundo Europeu de Desenvolvimento Regional (FEDER) – Programa Operacional “Ciência , Tecnologia, Inovação” – PTDC/CTM/69362/2006 e SFRH/BD/47118/2008

Influence of stoichiometry and structure on the optical properties of AlNxOy films

Borges, Joel; Barradas, N. P.; Alves, Eduardo; Beaufort, Marie France; Eyidi, Dominique; Vaz, F.; Marques, L.
Fonte: Institute of Physics Publishing (IOP) Publicador: Institute of Physics Publishing (IOP)
Tipo: Artigo de Revista Científica
Publicado em /11/2012 ENG
Relevância na Pesquisa
65.98%
The AlNxOy system offers the possibility to obtain a wide range of responses, by tailoring the properties between Al, AlN and Al2O3, opening a significant number of possible applications. The aim of this work is to correlate the optical properties of AlNxOy thin films with their composition and structural features, taking as reference the binary systems AlNx and AlOy. In the AlNx system, the increase of the nitrogen content induced a wide variation in the optical properties, ranging from the typical profile of a polycrystalline Al-type film towards nearly constant reflectance values as low as 5%, as well as a smooth increase in samples transparency as the ratio N/Al approached unit. In the case of the AlOy system, the reflectance also decreased as the oxygen content increased, however the transition to transparent films (Al2O3-like) was more abrupt. The ternary system AlNxOy, revealed optical responses that ranged from a typical profile of a polycrystalline Al-type film, towards low and constant reflectance values in a wide range of x and y coefficients, ending up as semi-transparent when Al2O3-like films were formed. The unusual low optical reflectance of some films reveals some potential applications in solar power systems and sensors.; This research is sponsored by FEDER funds through the program COMPETE-Programa Operacional Factores de Competitividade...

Microstructural, structural and optical properties of nanoparticles of PbO-CrO3 pigment synthesized by a soft route

Araújo,V. D.; Andreeta,M. R. B.; Maia,L. J. Q.; Nascimento,R. M.; Motta,F. V.; Bomio,M. R. D.; Paskocimas,C. A.; Bernardi,M. I. B.
Fonte: Associação Brasileira de Cerâmica Publicador: Associação Brasileira de Cerâmica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2015 EN
Relevância na Pesquisa
65.95%
PbCrO4 and Pb2CrO5 particles were synthesized by the polymeric precursor method. Structural and microstructural properties of the particles were characterized by scanning electron microscopy with field emission gun, X-ray diffraction, and Raman spectroscopy techniques. The diffuse reflectance technique was employed to study the optical properties in the 400-700 nm range. The optical bandgap of the samples was obtained indirectly. Colorimetric coordinates L*, a*, b* were calculated for the pigment powders as a function of the heat treatment (400-700 ºC). The powders displayed colors ranging from green to red. X-ray diffraction patterns showed the presence of monoclinic PbCrO4 phase in green samples, while red powders had a monoclinic Pb2CrO5 phase structure. The Raman spectra of the PbCrO4 and Pb2CrO5 powders were in good agreement with those reported in the literature. The synthesized compounds can be used as green and red pigments with high thermal stability.

Effect of cage configuration in structural and optical properties of tin films grown by cathodic cage discharge

Daudt,Natália de Freitas; Barbosa,Júlio César Pereira; Macêdo,Marina de Oliveira Cardoso; Pereira,Marcelo Barbalho; Alves Junior,Clodomiro
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/08/2013 EN
Relevância na Pesquisa
65.98%
Cathodic cage discharge was developed recently in order to eliminate phenomena as edge effect and overheating, which occurs during conventional processes. In this study, the effect of cage configuration in active species during the deposition process and optical properties of TiN film were studied. TiN compound was chosen because its optical properties are very sensitive to slight variations in microstructure and film thickness, becoming a good monitoring tool in fabrication process control. Cages were made of titanium and have different holes numbers and holes diameter. Electrical efficiency of the system and optical properties of TiN films were strongly influenced by experimental conditions. It was found that with more holes at the top of cage, deposition rate and crystallinity were higher, if compared to cages with a small number of holes at the top. On the other hand, the opposite behavior was observed when more holes were located at the sidewall of cage.

Continuous noninvasive monitoring of changes in human skin optical properties during oral intake of different sugars with optical coherence tomography

Zhang, Yuqing; Wu, Guoyong; Wei, Huajiang; Guo, Zhouyi; Yang, Hongqin; He, Yonghong; Xie, Shusen; Liu, Ying
Fonte: Optical Society of America Publicador: Optical Society of America
Tipo: Artigo de Revista Científica
Publicado em 28/02/2014 EN
Relevância na Pesquisa
65.99%
The objective of this study was to evaluate the effects of blood glucose concentration (BGC) on in vivo human skin optical properties after oral intake of different sugars. In vivo optical properties of human skin were measured with a spectral domain optical coherence tomography (SD-OCT). Experimental results show that increase of BGC causes a decrease in the skin attenuation coefficient. And the maximum decrements in mean attenuation coefficient of skin tissue after drinking glucose, sucrose and fructose solution are 47.0%, 36.4% and 16.5% compared with that after drinking water, respectively (p < 0.05). The results also show that blood glucose levels of the forearm skin tissue are delayed compared with finger-stick blood glucose, and there are significant differences in the time delays after oral intake of different sugars. The time delay between mean attenuation coefficient and BGC after drinking glucose solution is evidently larger than that after drinking sucrose solution, and that after drinking sucrose solution is larger than that after drinking fructose solution. Our pilot studies indicate that OCT technique is capable of non-invasive, real-time, and sensitive monitoring of skin optical properties in human subjects during oral intake of different sugars.

Caracterização das propriedades ópticas não lineares de vidros teluretos, líquidos orgânicos e colóides de nanopartículas de ouro.; Characterization of the nonlinear optical properties, nonlinear refraction, thermo-optical coefficient, photonics-nonlinear materials.

Souza, Rogerio Fernandes de
Fonte: Universidade Federal de Alagoas; BR; Física geral; Física teórica e computacional; Mecânica estatística; Ótica; Ótica não linear; Proprie; Programa de Pós-Graduação em Física da Matéria Condensada; UFAL Publicador: Universidade Federal de Alagoas; BR; Física geral; Física teórica e computacional; Mecânica estatística; Ótica; Ótica não linear; Proprie; Programa de Pós-Graduação em Física da Matéria Condensada; UFAL
Tipo: Tese de Doutorado Formato: application/pdf
POR
Relevância na Pesquisa
66.09%
In this thesis, we investigate the nonlinear optical properties of four different physical systems: tellurite glasses, castor oil, ionic liquids and colloids of gold nanoparticles. Using Zscan and I-scan techniques, it was possible to determine the values of the electronic (n2 e) and thermal (n2 t) contributions of nonlinear refractive index of these systems as well as evaluating their respective thermo-optical coefficients (dn/dT). We use the I-scan technique to characterize five tellurite glass samples with different compositions. In this experiment we employ a Ti:sapphire laser operating in the modelocked regime, tuned at , delivering pulses, with a repetition rate that was controlled by a pulse selector. These glasses presented an ultra-fast self-focusing nonlinearity. The figure of merit 810 nm 200 fs 1kHz max 0 W= Δn λα was evaluated, and the condition was obtained for four of the five studied samples, displaying the potentiality of these glasses for ultra-fast all-optical switching applications, for example. Castor oil is a natural organic compound with a wide range of applications in industry. In the nanotechnology field, this oil has been exploited as very efficient dispersant and stabilizer agent for metallic gold nanoparticles in colloidal systems. However...

Local-field effects and nanostructuring for controlling optical properties and enabling novel optical phenomena

Dolgaleva, Ksenia (1977 - ); Boyd, Robert W. (1948 - )
Fonte: University of Rochester. Publicador: University of Rochester.
Tipo: Tese de Doutorado
ENG
Relevância na Pesquisa
66.02%
Thesis (Ph. D.)--University of Rochester. Institute of Optics, 2009.; My Ph.D. thesis is devoted to the investigation of the methods for controlling and improving the linear and nonlinear optical properties of materials. Within my studies, two approaches are considered: nanostructuring and invoking local-field effects. These broad topics involve various projects that I have undertaken during my Ph.D. research. The first project is on composite laser gain media. It involves both nanostructuring and using local-field effects to control the basic laser parameters, such as the radiative lifetime, small-signal gain and absorption, and the saturation intensity. While being involved in this project, I have performed both theoretical and experimental studies of laser characteristics of composite materials. In particular, I have developed simple theoretical models for calculating the effective linear susceptibilities of layered and Maxwell Garnett composite materials with a gain resonance in one of their components. The analysis of the results given by the models suggests that local-field effects provide considerable freedom in controlling the optical properties of composite laser gain media. I have also experimentally measured the radiative lifetime of Nd:YAG nanopowder suspended in different liquids to extract information regarding local-field effects. The second project is devoted to the investigation of a not-well-known phenomenon that local-field effects can induce...

Set-up and evaluation of a mid-infrared reflectometer and investigation of the optical properties of doped tin telluride

Hawesa, Halima.
Fonte: Brock University Publicador: Brock University
Tipo: Electronic Thesis or Dissertation
ENG
Relevância na Pesquisa
65.96%
A system comprised of a Bomem interferometer and a LT3-110 Heli-Tran cryostat was set up to measure the reflectance of materials in the mid-infrared spectral region. Several tests were conducted to ensure the consistency and reliability of the system. Silicon and Chromium, two materials with well known optical properties were measured to test the accuracy of the system, and the results were found to be in good agreement with the literature. Reflectance measurements on pure SnTe and several Pb and Mn-doped alloys were carried out. These materials were chosen because they exhibit a strong plasma edge in the mid infrared region. The optical conductivity and several related optical parameters were calculated from the measured reflectance. Very low temperature measurements were carried out in the far-infrared on Sn9SMn2Te, and the results are indicative of a spin glass phase at 0.8 K. Resistivity measurements were made at room temperature. The resistivity values were found, as expected, to decrease with increasing carrier concentration and to increase with increasing manganese concentration.

Ex vivo investigation of tissue optical properties using an optical fibre sensor

Warncke, Dennis
Fonte: University of Limerick Publicador: University of Limerick
Tipo: info:eu-repo/semantics/doctoralThesis; all_ul_research; ul_published_reviewed; ul_theses_dissertations
ENG
Relevância na Pesquisa
66.07%
peer-reviewed; Biomedical research has become a strong growing sector in recent years. Moreover the interdisciplinary background involves novel possibilities and measurement techniques. Light propagation in turbid media like human tissue is a central aspect to many medical and biomedical applications. This is a very complex process and depends on parameters, which are called optical properties. The spatial distribution of light is determined by those optical properties. A major difficulty in this field can be explained by the forward and inverse problem. There are several theories and approximations that are used to describe the propagation of light in scattering media. Those approaches are often applied to get qualitative results that can be helpful in fields like laser surgery, photodynamic therapy and diagnostic purposes. This thesis presents the development of an optical fibre based system that uses diffuse reflectance data to determine the optical properties of tissue. The optical properties obtained are intended to be used as indicators in the characterization of burn wounds. Since the absorption of light by tissue has a minimum in the therapeutic window, which is situated in the visible to near-infrared region (600-1000 nm)...

Experiments and Monte Carlo Analysis for the Optical Properties of the Scintillator in SNO+

LIU, XU
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
Relevância na Pesquisa
65.96%
The SNO+ experiment will be the SNO detector filled with a neodymium-loaded liquid scintillator instead of heavy water. SNO+ will be used to detect neutrinos of much lower energy. Also, SNO+ will conduct a search for neutrinoless double beta decay with Nd-150. The Nd-loaded scintillator in SNO+ will be made from linear alkylbenzene (LAB). Both the LAB solvent and the Nd loading are new developments. The optical properties of this scintillator and information about radioactive backgrounds should be studied. A calibration source known as the scintillator bucket was deployed in the water-filled SNO detector in order to study some optical properties of Nd-loaded scintillator, raw LAB scintillator and distilled LAB scintillator. Using a neutron source attached to the bucket to produce events with known energy, with a model of the scintillator bucket simulated by an analysis tool called RAT, the light yield of the scintillator could be determined by comparing data measurements with simulations. This allowed the light yield, one of the main optical properties of the scintillator, to be measured and that value to be corrected in the Monte Carlo. The bucket was deployed both at the centre of the detector and at the bottom. After subtracting backgrounds from radon introduced in the scintillator during preparation and filling...

Preparation and optical properties of titania-doped hybrid polymer via anhydrous sol-gel process

Luo, Xinshi; Zha, Congji; Luther-Davies, Barry
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
66%
Incorporation of metal alkoxides (Ti, Zr, etc.) for tuning the optical properties of silica glasses by the sol-gel process is of significant interest for optical applications. In this paper, we report an anhydrous sol-gel process for preparation of photosensitive titania-doped hybrid glassy polymer with good homogeneity and high doping concentration (TiO2 up to 40mol%). The process consists of two steps: in the first step methacryloxypropyltrimethoxysilane (MPS) is hydrolyzed by boric acid through ligand exchange reaction (OH ↔ OR) under anhydrous conditions; and in the second step dimethyldimethoxysilane (DMDMS), diphenyldimethoxysilane (DPhDMS) and titanium ethoxide (TET) were added to condense with the silanols formed in the first step. The optical properties of the synthesized hybrid polymer were studied, and results showed that the hybrid material has low OH absorption, low optical losses (0.45dB/cm at 1550nm and 0.16dB/cm at 1310nm respectively), and good thermo-optical linearity with tuneable refractive index. The effect of TiO2 doping in reducing the OH concentration of the hybrid material was observed, and the mechanism for this effect is discussed.

Study of Structure and Spectral Characteristics of the Zinc(II) and Copper(II) Complexes With 5,5-Dimethyl-2-(2-(3-nitrophenyl) hydrazono)cyclohexane-1,3-dione and Their Effects on Optical Properties and the Developing of the Energy Band Gap and Investigation of Antibacterial Activity

Turan,Nevin; Gündüz,Bayram; Körkoca,Hanifi; Adigüzel,Ragip; Çolak,Naki; Buldurun,Kenan
Fonte: Sociedad Química de México A.C. Publicador: Sociedad Química de México A.C.
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2014 EN
Relevância na Pesquisa
65.96%
A new chelating ligand, 5,5-dimethyl-2-(2-(3-nitrophenyl) hydrazono)cyclohexane-1,3-dione (L), and four transition metal complexes were synthesized. The ligand and its complexes were characterized by IR, ¹H and 13C-NMR spectra, elemental analyses, magnetic susceptibility, mass spectra, UV-Vis. and thermogravimetry-differential thermal analysis (TGA-DTA). The metal complexes showed different geometric structures. Antibacterial tests of the ligand and complexes were also done. The Zn(II) complexes showed antibacterial activity against Staphylococcus aureus ATCC-25923 at middle level. The optical properties of the ligand and its complexes were extensively investigated by optical measurements. The average transmittance value of the ligand was the highest value, while the average transmittance value of the [CuL2(NO3)2]·6H2Ocomplex was the lowest value. The optical band gap of the ligand, [(Zn)2L(OH)4]·2DMF, [ZnL(NO3)2(H2O)2]·5H2O, [CuL2(OAc)]·OAc·3.5H2O and [CuL2(NO3)2]·6H2O complexes were calculated and 3.121 eV, 2.180 eV, 1.551 eV, 2.489 eV and 1.556 eV values were found, respectively. The complexes decreased the optical band gap of the ligand. The optical band gap value of the [ZnL(NO3)2(H2O)2]·5H2O complex is the lowest value. The optical band gap value of the ligand is the highest value. The complexes decrease the angle of incidence of the ligand...