bluuebunny/crossref_metadata_2025_split huggingface dataset:
Film Growth, by Seeded Supersonic Beams, of Thiophene-Based Oligomers with Controlled Optical, Structural and Morphological Properties
Authors: Toccoli Tullio , Ferrari Maurizio , Ronchin Sabina , Podestà Alessandro , Milani Paolo , Iannotta Salvatore 
Published: May 2011

ABSTRACTA novel approach for the deposition of high quality films of oligothiophenes has been developed. It is based on an original seeded supersonic molecular beam combined with a UHV deposition chamber. This method gives an unprecedented control on film properties. Several T4 films under different beams conditions have been prepared and characterized by optical absorption, photoluminescence and TMAFM. Morphology, structure and optical response are controlled by the beam's parameters. Highly ordered films, up to several hundreds of nm thick, show well resolved vibronic structures in low temperatures PL as only the best published data on films a few monolayers thick do.
Fluid Mechanics Model and Analysis for the Photofabrication of Surface Relief Grating on Azo Polymers
Authors: Fukuda Takashi , Matsuda Hiro , Sumaru Kimio , Yamanaka Tadae 
Published: May 2011

ABSTRACTThe mass transporting properties of the surface relief grating (SRG) photofabrication on azobenzene polymer films is discussed precisely using an existing fluid mechanics model. Formulation for the SRG inscription rate is derived analytically from Navier-Stokes equation. In consequence, the dependence of inscription rate of the SRG on the experimental and geometrical parameters was explained very well by the model. The photoinduced surface deformation with an onedimensional Gaussian laser beam was also carried out in order to establish the validity and the generality of our fluid mechanics model. The experimentally obtained surface deformation profile is well reproduced by the theoretical model generalized for arbitrary force field profile.
The Influence of Ordering on the Photoinduced Charge Transfer in Composites of Phenyl-type Substituted Polythiophenes with Methanofullerenes
Authors: Brabec Christoph J. , Winder Christoph , Scharber Markus C. , Sariciftci N. Serdar , Andersson Mats R. , Inganäs Olle , Hummelen Jan C. 
Published: May 2011

ABSTRACTRegioregular polythiophenes baring 3-(p-methoxyethoxyethoxy)-phenyl substituents (PEOPT) show high photoluminescence efficiencies. Exposing thin films of this polymer to vapors of chloroform or annealing them by heat treatment results in a red shift of the absorption maximum due to solvent or heat induced ordering which gives rise to more planar conformations. The fact, that annealed thin films of PEOPT exhibit absorption edges at relatively low energies and thus have an enhanced spectral range makes them suitable for use in photodiodes / solar cells. The photoinduced charge generation efficiency in PEOPT is significantly enhanced by the addition of a strong electron acceptor like fullerene, as observed by quenching of the luminescence and by photoinduced absorption measurements in the infrared and UV-Vis regime. The efficiency of the photoinduced charge transfer from PEOPT to a methanofullerene is found to depend on the ordering of PEOPT in thin films.
Linear and Nonlinear Optical Properties of Novel Ionic Chromophores
Authors: Duan Xuan-Ming , Wada Tatsuo , Okada Shuji , Oikawa Hidetoshi , Matsuda Hiro , Sasabe Hiroyuki , Nakanishi Hachiro 
Published: May 2011

ABSTRACTA series of novel ionic chromophores consisting of a carbazole moiety and pyridinium rings connected by a double bond have been designed and synthesized as nonlinear optical materials. Their linear and nonlinear optical properties were investigated by semiempirical calculation and experiment. The absorption maximum wavelengths (lmax) of these ionic chromophores showed shifting to longer wavelength region than their corresponding electrically neutral compounds. These ionic chromophores possess large first hyperpolarizabilities (b).
Multifunctional Dendrimers Incorporating Diphenylaminopolyenylic Chromophores
Authors: Ashworth K. , Reeves B. , Frost A. , Spangler C. , Sapochak L. , Padmaperuma A. , Schmett G. 
Published: May 2011

ABSTRACTWe have previously shown that diphenylpolyenes incorporating diphenylamino donor substituents form exceptionally stable bipolaronic dications in solution, even at the bis-(diphenylamino)-E-stilbene level, whereas most previously known polyenylic bipolarons were unstable at lengths shorter than the tetraene1. Most recently we have also demonstrated that replacement of one of the diphenylamino substituents in the stilbene substrate with a N-(hydroxyethyl), N-ethylaminophenyl group yields a functionalized polyene that can easily be attached to PMMA as a pendant group, or to 3,5-dihydroxy-benzyl alcohol to form reactive dendrons2. These functionalized materials also form extremely stable bipolarons and are intensely fluorescent. In this presentation we will discuss the formation of G-0 dendrimers incorporating a series of polyenes related to the stilbene structure, and possible photonic applications.
Photo and Electroluminescent Properties of a Porphyrin-Poly(p-Phenylene Vinylene) Derivative
Authors: Morgado J. , Iqbal R. , Yahioglu G. , Milgrom L. R. , Moratti S. C. , Holmes A. B. , Friend R. H. , Cacialli F. 
Published: May 2011

ABSTRACTThe solid state luminescent properties of new statistical copolymers of 2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylene vinylene and a porphyrin-substituted phenylene vinylene are reported. The photoluminescence, PL, emission shows an efficient energy transfer to the porphyrin, in spite of the small absorption coefficient of the porphyrin in the wavelength range of the poly [2-methoxy-5-(2'- ethylhexyloxy)-1,4-phenylene vinylene], MEH-PPV, emission. At a porphyrin content of 0.25%, by weight, the emission is already dominated by the porphyrin. The PL efficiency of these copolymers is significantly reduced from the value of 13% for MEH-PPV down to 3% for the copolymer with 10.84% of porphyrin. Efficient energy transfer is also observed in the emission spectra of light-emitting diodes.
Intermolecular Coupling Enhancement of the Molecular Hyperpolarizability in Multi-chromophoric Dipolar Dendrons
Authors: Yokoyama Shiyoshi , Otomo Akira , Mashiko Shinro 
Published: May 2011

ABSTRACTNonlinear optical dendritic macromolecules, called “azobenzene dendrons”, having a branching structure modified with a second-order nonlinear optical chromophore has been synthesized. An electron donor and acceptor azobenzene chromophore having a large molecular hyperpolarizability of β0=150E-30 esu, was chosen. The electronic structure of synthesized dendrons, which were expected to become dipolar due to their intermolecular attractive interaction, was proven by second-order nonlienar optical properties. The molecular hyperpolarizabilities of azobenzene dendrons were measured by the hypr-Rayleigh scattering technique. The highest molecular hyperpoalrizability was found to be 3,010E-30 esu for an azobenzene dendron having 15 chromophoric unit, where each chromophore coherently contribute to the second harmonic generation. This level of the molecular hyperpolarizability was much larger than that for a monomeric azobenzene chromophore.
Synthesis and Photo-Bleaching of Epoxy-Based Nonlinear Optical Polymers Containing Triene Chromophores
Authors: De B. B. , Kumar J. , Tripathy S. K. , Balasubramanian S. , Chittibabu K. G. , Li L. 
Published: May 2011

ABSTRACTBis(diglycidyl)ether of bisphenol-A-aniline (BP-AN) based second-order nonlinear optical (NLO) polymers containing triene chromophores have been developed through post-polymer functionalization reactions. One-pot aldol condensation reaction of dicyanomethylidene functionalized verbenone as well as isophorone compounds with aldehyde functionalized BP-AN polymer enabled the introduction of various chromophore moieties with high degree of functionalization. These polymers were studied using various structural (1H NMR, FTIR), linear (UV-Vis) and NLO characterization techniques. A d33 value of ca. 139 pm/V at 1.064 µm was determined for a representative polymer containing verbenone unit. We have observed fast photo-bleaching in these polymers. Detailed studies on the photophysical properties of this class of materials have been carried out using various analytical techniques, the structure-properties relationship and photo-bleaching mechanisms will be presented.
Control of Second-Order Nonlinear Optical Susceptibility in Ionically Self-Assembled Films by pH and Ionic Strength
Authors: Figura C. , Neyman P.J. , Marciu D. , Brands C. , Murray M.A. , Hair S. , Miller M.B. , Davis R.M. , Heflin J.R. 
Published: May 2011

ABSTRACTIonically self-assembled monolayers have been recently shown to spontaneously produce the noncentrosymmetric ordering that is required for a second order nonlinear optical (NLO) response. The precise thickness of each monolayer is determined by variables such as the pH and ionic strength of the immersion solutions. We show here that the relationship between polymer conformation and layer thickness dramatically affects the magnitude of the NLO response. The largest χ(2) values are found in the thinnest films, indicating that the NLO response is determined primarily by chromophores located at the layer interfaces, as opposed to those within the bulk of a layer.
The Interconnection Between Efficiency and Morphology of Two Component Systems in Plastic Solar Cells
Authors: Padinger Franz , Gebeyehu Desta , Brabec Christoph J. , Fromherz Thomas , Sariciftci N. Serdar , Hummelen Jan C. 
Published: May 2011

ABSTRACTUsing the ultrafast photoinduced electron transfer with long-living charge separation in the conjugated polymer/fullerene thin films, photovoltaic devices have been fabricated. The photoinduced charge separation happens with internal quantum efficiency near unity. The performance of such “bulk heterojunction” photovoltaic devices is critically dependent on the transport properties of the interpenetrating network. The influence of the variation of different donor / acceptor materials on the sample morphology is monitored by atomic force microscopy (AFM), while I/V characteristics have been studied to evaluate the conversion efficiency.
High Mobilities in Organic Molecular Crystals
Authors: Schön Jan Hendrik , Berg Steffen , Kloc Christian , Batlogg Bertram 
Published: May 2011

ABSTRACTThe charge transport in high quality single crystals of various organic molecular semiconductors is investigated. Band-like motion in delocalized states is observed in various polyacene and oligothiophene single crystals. The electric field dependence of the mobility is ascribed to acoustic phonon scattering. Furthermore, hot carrier effects can be observed at low temperatures and high electric fields. Band-like transport changes over to hopping motion when the effective bandwidth shrinks, i.e. at high temperatures or in crystallographic directions of small molecular orbital overlap.
Facile Deposition Processes for Semiconducting Molecular Solids
Authors: Katz H.E. , Li W. , Lovinger A.J. , Raju V.R. , King J.'A. , Lin Y.-Y. , Dodabalapur A. , Bao Z. , Rogers J. 
Published: May 2011

ABSTRACTFilms of end-substituted dihexyl-α-sexithiophene and –quinquethiophene were cast from solutions in aromatic solvents onto SiO2 and polyimide dielectrics at moderately elevated temperatures and reduced pressure. X-ray diffraction showed perpendicular orientation for most samples, while electron and optical microscopy revealed considerable variations in grain sizes, spacings, and uniformity depending on deposition conditions. For favorable morphologies, thin film transistor (TFT) mobilities were as high as those typically obtained from vacuum-deposited films, in the range of 0.01-0.2 cm2/Vs, with on/off ratios >1000 in accumulation mode.
Remedial Action for Radioactive Waste Rock Piles in China
Authors: Zhangru Chen , Yuanxin Jin , Lanying Song , Qingyan Wu 
Published: May 2011

ABSTRACTThe Chinese government has conducted remedial action for radioactive waste rock piles since 1990. The radioactive waste rocks produced in the course of geological exploration of uranium deposits are widely distributed over several hundreds of locations in more than 20 provinces in China.The following remedial actions for radioactive waste rock piles have been undertaken in China:1. Protecting dams for stabilizing the piles have been built. A total length of about 50,000 m of these dams has been completed.2. Soil layers have been emplaced on the radioactive waste rock piles. The focus of the action is to eliminate the radiation harmful to public health. A total area of 750,000 square meters of soil ahs been placed on the piles in China.3. Radioactive waste rock piles have been vegetated. Aesthetic shaping of the landscape in the exploratory district of the uranium deposits is our expectant goal. A total area of about 560,000 square meters of vegetation has been placed on the soil covering the piles.Through these remedial actions, the environmental situation has been extensively improved in the remedial districts. The individual annual effective dose equivalent is less than 1 Sv/a. The radon emission rate is less than 20 pCi/m2.s. The gamma ray external exposure rate has been greatly reduced.
Discussion on the Use of Matrix Diffusion Model after a Multidisciplinary Study of a Granitic Boulder Sample
Authors: Marcos N. , Siitari-Kauppi M. , Suksi J. , Rasilainen K. , Finch R. , Hellmuth K. -H. 
Published: May 2011

ABSTRACTThis paper aims to discuss the applicability of the classical matrix diffusion model against the integrated body of new data obtained by different methodologies on several samples of three granite boulders. The matrix diffusion model was tested against observations from the upper (most weathered in contact with air) and lower (fresh in contact with the ground) part of a boulder block. A U(VI) enrichment up to nearly 300 ppm (compared to about 10 ppm background concentration) mostly as uranophane was observed in the zone between the weathered and fresh rock. U-series disequilibrium studies indicated that most of U has been accumulated recently, about 10 000 years ago [1].High interconnected porosity (total porosity of > 1% and up to about 5.5% in altered minerals) characterizes the weathered zone (upper part), whereas the maximum porosity values in the fresh zone (lower part) of the rock are about 0.4 – 0.6%. Stable isotope studies δ18O and δ2H confirm that the mineralogical changes observed in the weathered upper part are due to old hydrothermal events. That is, the alteration is much older than uranium accumulation. Mössbauer spectroscopy showed that the Fe(III) content of the biotites from the upper to the lower part decreases from 30% in the weathered zone to 17% in the fresh rock, thus indicating possible redox control for the observed U precipitation. Fission track studies showed that secondary U(VI) also occurs within minerals grains (especially plagioclase) in the upper part.Mathematical simulations indicate that matrix diffusion alone is not enough to reconstruct the past U accumulation. The simulated concentrations derived from U concentration in pore water multiplied by Kd are clearly too small, indicating apparent insufficiency of the Kd approach. However, even with only matrix diffusion, the simulations roughly reconstruct the observation that U levels are clearly higher in the upper part of the boulder than in the lower part.
Brownian Simulation of Matrix Diffusion
Authors: Andersson Sofie , Emrén Allan T. 
Published: May 2011

ABSTRACTThe commonly used approach in dealing with matrix diffusion is to assign an effective diffusion constant for the radionuclide in the rock matrix. The idea behind this approach is that, on a scale much larger than the pore size, the irregularities tend to cancel out. Although it might look plausible at first sight, this approach has been questioned both for theoretical and experimental reasons.Here, Brownian simulation has been used to investigate the transport of dissolved material in a rock matrix modeled as a system of pores with a wide variability in size and shape. The Boltzmann distribution is used locally, although the system globally is far from equilibrium.The simulation consists of two main parts. First, the model rock is formed by precipitation of irregular mineral grains from a liquid phase. As the grains grow, they tend to form a mostly solid piece of rock.In the second part of the simulation, a dissolved species is introduced at one side of the rock and allowed to diffuse through its pore system. It is found that no apparent diffusion constant, D, can explain the properties of the system. Rather, D is found to be a function of both distance and time.
Radionuclide Movement during Unsteady, Unsaturated Soil Water Flow
Authors: Smiles D.E. , McOrist G.D. 
Published: May 2011

ABSTRACTAbsorption of aqueous solution by soil appears to result in piston-like displacement of the soil solution originally present by the invading solution. Diffusive redistribution of non-reactive solutes, relative to the water, occurs about that front when the solutions are of different chemical constitution. Adsorption of solute by the soil solid retards the solute front relative to the piston- front; it also reduces the effective diffusivity of the solute relative to the water. Such behavior tests prediction of radionuclide transport and retardation during non-steady water flow in unsaturated soil based on measured distribution coefficients.Experiments, where initially uniform soil columns absorbed tritiated water containing 60Co2+ from a source at constant water potential, illustrate these effects. Columns were sampled at significantly different elapsed times and the transient water content, water soluble salts, tritium and cobalt profiles determined. Theory anticipates, and experiment confirms, self- similarity of these profiles when data is graphed in terms of distance divided by the square root of time. Water, and soil solid-based, material coordinates facilitate data analysis; measurement of absorption isotherms is also discussed.
Migration Mechanisms of Americium(III) through Soil Layers
Authors: Tanaka T. , Ogawa H. , Muraoka S. 
Published: May 2011

ABSTRACTMigration experiments of 241Am(III) have been performed using a column system, to investigate migration behavior of 241Am through a column packed with porous sedimentary materials: a coastal sandy soil and a reddish soil. Sorption mechanisms of 241Am on the sedimentary materials were examined by a chemical extraction method.In the case of the reddish soil, most of 241Am sorbed on the influent edge of the column. The 241Am sorbed on the reddish soil was mainly controlled by a reversible ion exchange reaction. The migration of 241Am in the reddish soil could be evaluated by using the Kd concept. In the case of the sandy soil, on the other hand, considerable amount of particulate 241Am passed through the column. The 241Am sorbed on the sandy soil was controlled by irreversible reactions. The migration behavior of particulate 241Am in the sandy soil could be expressed by filtration theory.
Matrix Diffusion Measurements – Through Diffusion versus Electrical Conductivity Measurements
Authors: Ohlsson Y. , Neretnieks I. 
Published: May 2011

ABSTRACTMatrix diffusion laboratory experiments in dense porous rock are generally very time consuming and one is limited to rather short diffusion lengths, as well as to a small amount of samples. The large heterogeneity of rock, on the other hand, demands a large quantity of samples that are large enough to exclude effects from e.g. increases in interconnected porosity compared to that of the pristine rock.Electrical conductivity measurements are very fast and larger samples can be used than is practical in ordinary diffusion experiments. The effective diffusivity of a non-charged molecule is readily evaluated from the measurements, and influences from surface conductivity on diffusion of cations can be studied.In this study traditional through diffusion experiments as well as electrical conductivity measurements are carried out on the same rock samples. The formation factor is determined by both methods, and the methods are compared and discussed.The surface conductivity is studied by exchanging the surface sites with Na+, Sr2+ and Cs+. After leaching out the free pore ions the surface conductivity is measured.With the electrical conductivity method the formation factor is determined directly, whereas it has to be calculated using the bulk liquid diffusion coefficient in the diffusion experiments. This causes some uncertainties in the comparison between the experiments. In estimating the bulk liquid diffusivity, the value for infinitely diluted solutions and in pure water environment is commonly used. The calculated formation factor may therefore be somewhat underestimated.
Formation Factor Determinations byIn-SituResistivity Logging
Authors: Löfgren M. , Ohlsson Y. , Neretnieks I. 
Published: May 2011

ABSTRACTMatrix diffusion in bedrock is traditionally studied by laboratory liquid diffusion experiments, which are time consuming and expensive. A new way of studying matrix diffusion is to measure the electrical resistivity of the rock. This could be done either in laboratories orin-situ. A fast method of obtaining a formation factor log, later used in matrix diffusion calculations, for an entire borehole is proposed.It is a standard procedure in geophysical well logging to measure rock resistivity and there are well-developed tools for this in the oil industry. The SKB, Sweden, uses boreholes with a small diameter (56 mm) and this reduces the options in choosing resistivity tools. Therefore they have so far relied on the Normal log that only gives quantitative measurements in special cases, after corrections are made. Modern tools, such as the slimhole Dual-Laterolog, are accurate with a high vertical resolution.The pore fluid resistivity is required when obtaining a formation factor log. In previous work the borehole fluid resistivity has been used. A new method measures the resistivity in groundwater from local fractures. These values seem more appropriate to use as newin-situmeasurements show that there may be local groundwater resistivity differences.A preliminary study shows that the conductivity could be obtained in saline Swedish groundwater by measuring the chloride concentration only.Anomalies in the formation factor log have to be sorted out by using supporting core logging and non-electricalin-situmethods.
In-Situ Interaction between Cement and Clay: Implications for Geological Disposal
Authors: Sneyers A. , Paul M. , Tyrer M. , Glasser F.P. , Fays J. , Iseghem P. Van 
Published: May 2011

ABSTRACTThe extent and the consequences of interactions between cementitious materials used in radioactive waste management and clay host rock are described. In-situ tests were performed on seven cement formulations representing materials applied in repository construction, for backfilling or for solidification of radioactive waste. Samples were exposed to realistic repository conditions of the Boom Clay Formation in the HADES underground laboratory. Chemical, physical and mineralogical changes across the cement-clay interface were identified by combined observations from Electron Probe Microanalysis, Infrared microscopy and X-Ray powder diffraction. Significant interactions in both the cement and the clay part were found in a zone extending up to several hundreds of microns. The most prominent features are (1) leaching of cement with loss of calcium and/or silicon; (2) development of a calcium-rich zone in Boom Clay close to or at contact; (3) the formation of a contact zone marked by the precipitation of a (hydrated) magnesium aluminate phase; (4) reduction in apparent porosity of initially porous/permeable materials and (5) precipitation of calcite within the cement. This elemental exchange tends to diminish pH and reduce the buffering capacity of the cement. Although hydroxide will diffuse into the clay, the development of an extensive alkaline halo in the surrounding clay is unlikely owing to the buffering capacity of the Boom Clay pore water.