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Optical Spectroscopy (optical + spectroscopy)

Distribution by Scientific Domains

Physics and Astronomy	46%
Chemistry	35%
Polymers and Materials Science	15%
2 Other Domains	4%

Distribution within Physics and Astronomy

Astronomy & Astrophysics	54%
Solid State Physics	39%

Selected Abstracts

New trends and recent advances in coherent Raman microscopy and nonlinear optical spectroscopy: introduction to the special issue

JOURNAL OF RAMAN SPECTROSCOPY, Issue 7 2009
A. Volkmer
Abstract This special issue highlights 20 papers, presenting the latest theoretical and experimental developments and achievements in coherent anti-Stokes Raman scattering (CARS) microscopy and nonlinear optical spectroscopy. Most of them were presented at the seventh European Conference on Nonlinear Optical Spectroscopy (ECONOS 2008) jointly held with the first European Conference on CARS Microscopy (microCARS 2008) in Igls, Austria, May 25,27, 2008. Copyright © 2009 John Wiley & Sons, Ltd. [source]

New developments in nonlinear spectroscopy: ECONOS meeting in St. Petersburg

JOURNAL OF RAMAN SPECTROSCOPY, Issue 6 2008
A. M. Zheltikov
Abstract The sixth European Conference on Nonlinear Optical Spectroscopy(ECONOS) took place in St. Petersburg, Russia, in May 2007. This special issue includes ten contributions from ECONOS authors, presenting the latest developments and achievements in nonlinear optical spectroscopy. Copyright © 2008 John Wiley & Sons, Ltd. [source]

ECONOS in the epoch of CARS renaissance

JOURNAL OF RAMAN SPECTROSCOPY, Issue 8 2007
A. M. Zheltikov
Abstract The fifth European Conference on Nonlinear Optical Spectroscopy (ECONOS), continuing a long-standing tradition of European CARS Workshops (ECWs), was held in Smolenice, Slovakia, in April 2006. This special issue includes 15 contributions from ECONOS authors, giving a flavor of the most interesting topics covered by ECONOS'2006. Copyright © 2007 John Wiley & Sons, Ltd. [source]

New developments in non-linear optical spectroscopy

JOURNAL OF RAMAN SPECTROSCOPY, Issue 6 2006
P. P. Radi
Abstract This paper gives a brief summary of the proceedings of the European Conference on Non-Linear Optical Spectroscopy (ECONOS 2005) held at the University of Oxford, United Kingdom, from April 10 to 12, 2005. It demonstrates the progress made in recent years in this research area. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Metastable alumina formation during oxidation of FeCrAl and its suppression by surface treatments

MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 12 2005
E. N'Dah
Abstract The influence of various surface treatments of industrial FeCrAl grades was investigated in order to reduce the formation of transition aluminas during thermal oxidation in the 800,950°C temperature range. High temperature gas phase annealing in H2 -H2O mixtures promoted the initial formation of an alpha thin film and no transition alumina formed during subsequent oxidation at lower temperatures, showing very low weight gains compared to non-treated grades. Such a treatment was shown to be efficient for isothermal oxidation in oxygen of laboratory foil specimens but also for cyclic air exposure of fiber mats in near-real operating conditions. Surface modification by application of a slurry TiO2 coating before oxidation was also shown to greatly reduce the amount of transition alumina, observed by X-Ray Diffraction and Laser Induced Optical Spectroscopy. For both treatments, the optimal conditions were determined and the influence on oxidation rate was assessed. [source]

Characterisation of Nanohybrids of Porphyrins with Metallic and Semiconducting Carbon Nanotubes by EPR and Optical Spectroscopy

CHEMPHYSCHEM, Issue 13 2008
Sofie Cambré
Abstract Single-walled carbon nanotubes (SWCNTs) are noncovalently functionalised with octaethylporphyrins (OEPs) and the resulting nanohybrids are isolated from the free OEPs. Electron paramagnetic resonance (EPR) spectroscopy of cobalt(II)OEP, adsorbed on the nanotube walls by ,,,-stacking, demonstrates that the CNTs act as electron acceptors. EPR is shown to be very effective in resolving the different interactions for metallic and semiconducting tubes. Moreover, molecular oxygen is shown to bind selectively to nanohybrids with semiconducting tubes. Water solubilisation of the porphyrin/CNT nanohybrids using bile salts, after applying a thorough washing procedure, yields solutions in which at least 99,% of the porphyrins are interacting with the CNTs. Due to this purification, we observe, for the first time, the isolated absorption spectrum of the interacting porphyrins, which is strongly red-shifted compared to the free porphyrin absorption. In addition a quasi-complete quenching of the porphyrin fluorescence is also observed. [source]

Collapsed But Not Folded: Looking with Advanced Optical Spectroscopy at Protein Folding

CHEMPHYSCHEM, Issue 11 2007
Jörg Enderlein Prof. Dr.
The intermediate folding step: The highlight discusses a recent study by Hoffman et al. on the collapsed but still unfolded state of a small protein under close to native conditions. This collapsed unfolded state (see picture) is an important intermediate between the completely denatured, unfolded and the completely folded, native protein structure and is thought to be of paramount importance for the final folding. [source]

Optical Spectroscopy of Biomolecular Dynamics

CHEMPHYSCHEM, Issue 9 2004
Peter Vöhringer Prof.
Of visible interest: At the Minerva-Gentner Symposium on Optical Spectroscopy of Biomolecular Dynamics, which took place between 21st and 25th March 2004 at Banz, Germany, scientists from many disciplines came together to compare the study of single molecules to that of ensembles. Fluorescent proteins, time-resolved IR, and protein folding dynamics were among the main topics discussed. [source]

One-Dimensional Plasmon Coupling by Facile Self-Assembly of Gold Nanoparticles into Branched Chain Networks,

ADVANCED MATERIALS, Issue 21 2005
S. Lin
Short chains and complex networks of interconnected Au nanoparticle chains (see Figure) are produced by a simple template-free approach. Optical spectroscopy and computer simulations show that surface plasmons from individual non-contacting nanoparticles are strongly coupled in the resulting 1D superstructures. These chains may provide a unique way to fabricate complex subwavelength optical waveguides. [source]

Label free optical sensor for Avidin based on single gold nanoparticles functionalized with aptamers

JOURNAL OF BIOPHOTONICS, Issue 4 2009
Frank Jeyson Hernandez
Abstract Optical spectroscopy of a single gold nanoparticle, functionalized with an aptamer, is used to sense the specific binding of avidin. Herewith, the field of single noble metal nanoparticle biosensors is extended to the important field of aptamer based assays. The sensitivity of this initial, but not yet optimized apta-nano-sensor is in the range of 20 nM. Due to its nanoscopic size, this single nanoparticle based apta-sensor may be used in nanoscopic volumes such as in array type assays or even inside cells. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Optical spectroscopy of high proper motion stars: new M dwarfs within 10 pc and the closest pair of subdwarfs

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2006
C. Reylé
ABSTRACT We present spectra of 59 nearby star candidates, M dwarfs and white dwarfs, previously identified using high proper motion catalogues and the DENIS database. We review the existing spectral classification schemes and spectroscopic parallax calibrations in the near-infrared J band and derive spectral types and distances of the nearby candidates. Forty-two stars have spectroscopic distances smaller than 25 pc, three of them being white dwarfs. Two targets lie within 10 pc, one M8 star at 10.0 pc (APMPM J0103,3738), and one M4 star at 8.3 pc (L 225,57). One star, LHS 73, is found to be among the few subdwarfs lying within 20 pc. Furthermore, together with LHS 72, it probably belongs to the closest pair of subdwarfs we know. [source]

Optical spectroscopy of GX 339,4 during the high,soft and low,hard states , II.

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2001
Line ionization, emission region
We have carried out observations of the X-ray transient GX 339,4 during its high,soft and low,hard X-ray spectral states. Our high-resolution spectroscopic observation in 1999 April suggests that the H, line has a single-peaked profile in the low,hard state as speculated in our previous paper. The He ii,4686 line, however, has a double-peaked profile in both the high,soft and low,hard states. This suggests that the line-emission mechanism is different in the two states. Our interpretation is that double-peaked lines are emitted from a temperature-inversion layer on the accretion disc surface when it is irradiatively heated by soft X-rays. Single-peaked lines may be emitted from outflow/wind matter driven by hard X-ray heating. We have constructed a simple plane-parallel model and we use it to illustrate that a temperature-inversion layer can be formed at the disc surface under X-ray illumination. We also discuss the conditions required for the formation of temperature inversion and line emission. Based on the velocity separations measured for the double-peaked lines in the high,soft state, we propose that GX 339,4 is a low-inclination binary system. The orbital inclination is about 15° if the orbital period is 14.8 h. [source]

Swift observations of CSS081007:030559+054715

ASTRONOMISCHE NACHRICHTEN, Issue 2 2010
A.P. Beardmore
Abstract CSS081007:030559+054715 was discovered by the Catalina Real-time Transient Survey. Optical spectroscopy revealed a multi-peaked H, emission line profile with radial velocities exceeding 1500 km/s, as well as strong Ne emission, suggestive of a neon nova. We monitored the source extensively with the Swift satellite, obtaining a unique dataset spanning 270 days in the soft X-ray and UV bands. The data reveal a soft, blackbody-like spectrum with a temperature around 55 eV (though dependent on the modelling), variable X-ray and UV light curves with a 1.77 day period in both the X-ray and UV bands, a longer timescale modulation of , 50 days, followed by a slowly declining trend in the soft X-ray and UV flux. We highlight the Swift observations and their implications for the SSS nature of this object (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Optical spectroscopy of novae in M 31,,

ASTRONOMISCHE NACHRICHTEN, Issue 2 2010
F. Di Mille
Abstract We report results of a spectrophotometric survey of novae in M 31. The observations were carried out using the TNG at La Palma and the 1.82 m telescope of the INAF/OAPD at Asiago observatory. Low resolution spectra of the novae, obtained mainly in the early decline phase, allow us to classify the objects following the Tololo scheme (Williams 1992) (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Most supermassive black hole growth is obscured by dust

ASTRONOMISCHE NACHRICHTEN, Issue 2-3 2006
A. Martínez-Sansigre
Abstract We present an alternative method to X-ray surveys for hunting down the high-redshift type-2 quasar population, using Spitzer and VLA data on the Spitzer First Look Survey. By demanding objects to be bright at 24 µm but faint at 3.6 µm, and combining this with a radio criterion, we find 21 type-2 radio-quiet quasar candidates at the epoch at which the quasar activity peaked. Optical spectroscopy with the WHT confirmed 10 of these objects to be type-2s with 1.4 , z , 4.2 while the rest are blank. There is no evidence for contamination in our sample, and we postulate that our 11 blank-spectrum candidates are obscured by kpc-scale dust as opposed to dust from a torus around the accretion disk. By carefully modelling our selection criteria, we conclude that, at high redshift, 50,80% of the supermassive black hole growth is obscured by dust. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Characterization of a nif-regulated flavoprotein (FprA) from Rhodobacter capsulatus

FEBS JOURNAL, Issue 3 2000
2S] ferredoxin, Redox properties, molecular interaction with a [2Fe
A flavoprotein from Rhodobacter capsulatus was purified as a recombinant (His)6 -tag fusion from an Escherichia coli clone over-expressing the fprA structural gene. The FprA protein is a homodimer containing one molecule of FMN per 48-kDa monomer. Reduction of the flavoprotein by dithionite showed biphasic kinetics, starting with a fast step of semiquinone (SQ) formation, and followed by a slow reduction of the SQ. This SQ was in the anionic form as shown by EPR and optical spectroscopies. Spectrophotometric titration gave a midpoint redox potential for the oxidized/SQ couple of Em1 = +20 mV (pH 8.0), whereas the SQ/hydroquinone couple could not be titrated due to the thermodynamic instability of SQ associated with its slow reduction process. The inability to detect the intermediate form, SQ, upon oxidative titration confirmed this instability and led to an estimate of Em2 , Em1 of > 80 mV. The reduction of SQ by dithionite was significantly accelerated when the [2Fe,2S] ferredoxin FdIV was used as redox mediator. The midpoint redox potential of this ferredoxin was determined to be ,275 ± 2 mV at pH 7.5, consistent with FdIV serving as electron donor to FprA in vivo. FdIV and FprA were found to cross-react when incubated together with the 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, giving a covalent complex with an Mr of , 60 000. Formation of this complex was unaffected by the redox states of the two proteins. Other [2Fe,2S] ferredoxins, including FdV and FdVI from R. capsulatus, were ineffective as electron carriers to FprA, and cross-reacted poorly with the flavoprotein. The possible function of FprA with regard to nitrogen fixation was investigated using an fprA -deleted mutant. Although nitrogenase activity was significantly reduced in the mutant compared with the wild-type strain, nitrogen fixation was apparently unaffected by the fprA deletion even under iron limitation or microaerobic conditions. [source]

Investigation of molecule chemisorption on Si(001)2 × 1 surfaces by surface reflectance spectroscopies

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 13 2005
O. Pluchery
Abstract Several examples are given on the investigation of adsorption of atoms and molecules on Si(001)2 × 1 in ultra-high vacuum, by means of two different surface optical spectroscopies, the Surface Differential Reflectance Spectroscopy and the Reflectance Anisotropy Spectroscopy. Hydrogen, water, oxygen, benzene and pyridine adsorptions are presented. Specific spectra are obtained, which are interpreted as a function of the mode of adsorption of the adsorbates. In particular, it is possible to discriminate between adsorption on the dangling bonds of the Si dimers and adsorption inducing a breaking of the dimers. Moreover, quantitative information is obtained from these optical techniques which yields the determination of the absolute number of surface Si atoms involved in the bonding. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Secondary conformation of short lysine- and leucine-rich peptides assessed by optical spectroscopies: Effect of chain length, concentration, solvent, and time

BIOPOLYMERS, Issue 1 2006
Belén Hernández
Abstract Solution secondary structures of three synthetic cationic peptides, currently used in antisense oligonucleotide delivery into living cells, have been analyzed by means of circular dichroism (CD) and Raman scattering in different buffers as a function of concentration and time. All three peptides are of minimalist conception, i.e., formed by only two types of amino acids (leucine: L and lysine: K). Two of these peptides contain 15 aminoacids: Nter - KLLKLLLKLLLKLLK (L10K5), Nter -KLKLKLKLKLKLKLK (L7K8), and the third one has only 9 residues: Nter -KLKLKLKLK (L4K5). The conformational behavior of the 15-mers in pure water differs considerably one from another. Although both of them are initially disordered in the 50,350 ,M range, L10K5 gradually undergoes a disordered to , -helix transition for molecular concentrations above 100 ,M. In all other solvents used, L10K5 adopts a stable , -helical conformation. In methanol and methanol/Tris mixture, nonnative , -helices can be induced in both KL-alternating peptides, i.e., L7K8 and L4K5. However, in major cases and with a time delay depending on peptide concentration, , -like structures can be gradually formed in both solutions. In PBS and methanol/PBS mixture, the tendency for L7K8 and L4K5 is to form structures belonging to , -family. A discussion has been undertaken on the effect of counterions as well as their nature in the stabilization of ordered structures in both KL-alternating peptides. © 2005 Wiley Periodicals, Inc. Biopolymers 81: 8,19, 2006 This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source]

Oxido Pincer Ligands , Exploring the Coordination Chemistry of Bis(hydroxymethyl)pyridine Ligands for the Late Transition Metals

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 15 2009
Axel Klein
Abstract Coordination of the 2,6-bis(hydroxymethyl)pyridine-based oxido pincer ligands RR,pydimH2 [R = R, = H (pydimH2); R = R, = Me (pydipH2); R = 2-tolyl, R, = Me (pydotH2)] towards late transition metals CoII, NiII, CuII, ZnII, PdII and PtII allows the formation of molecular species (complexes), which exhibit three main structural motifs in the solid state. The two main species are pentacoordinate [(RR,pydimH2)MCl2] and hexacoordinate [(RR,pydimH2)2M]X2, both of which are stable in solution and can be interconverted by changing the solvent polarity. The disproportionation equilibrium [(RR,pydimH2)MCl2] [rlhar2] [(RR,pydimH2)2M]2+ + [MCl4]2, was studied by optical spectroscopy. The chiral ligand pydotH2 allows the formation of chiral complexes. In the square-planar complexes [(pydimH2)2MCl2] (M = PdII or PtII) the oxido donor functions of the ligands do not take part in the coordination.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

Close Proximity Dibenzo[a,c]phenazine,Fullerene Dyad: Synthesis and Photoinduced Singlet Energy Transfer

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 18 2010
Rajeev K. Dubey
Abstract A dibenzo[a,c]phenazine,fullerene (DBPZ-C60) dyad in which two chromophores are linked in close proximity to each other has been synthesized and studied in detail by optical spectroscopy to explore a new energy donor,acceptor system. The dyad was prepared by Prato reaction between 11-formyldibenzo[a,c]phenazine and fullerene. 3,5-Di- tert -butylbenzyl group was introduced onto the fulleropyrrolidine unit to achieve adequate solubility of the dyad. A thorough study of the photophysical properties of the dyad and relevant reference compounds, performed by means of steady state and time resolved spectroscopic measurements, has revealed the presence of highly efficient (ca. 98,%) and extremely fast (ken = 5,×,1011 s,1) intramolecular photoinduced singlet,singlet energy-transfer process from singlet excited state of the DBPZ moiety to fullerene. In both polar and nonpolar environment transduction of singlet excited state energy governs the excited state deactivation, but the efficiency and rate of energy transfer were found to be higher in nonpolar solvents in comparison to polar. The DBPZ singlet excited state decays within 2 and 4.7 ps in toluene andbenzonitrile, respectively, via singlet,singlet energy transfer to produce a fullerene singlet excited state which decays with a life time of 1.5 ns to give a very long-lived fullerene triplet state as final populated excited state. [source]

Highly Emissive and Electrochemically Stable Thienylene Vinylene Oligomers and Copolymers: An Unusual Effect of Alkylsulfanyl Substituents

ADVANCED FUNCTIONAL MATERIALS, Issue 10 2010
Shehzad Jeeva
Abstract The synthesis, unexpected efficient photoluminescence, and reversible electrochemical p- and n-doping of new conjugated thienylene vinylene materials functionalized with alkylsulfanyl substituents poly(trithienylene vinylene) (PTTV) and poly(dithienylvinyl- co -benzothiadiazole) (PDTVB) along with dithienylvinylene-based oligomers is reported. The materials are studied by thermal and X-ray diffraction analysis, optical spectroscopy, cyclic voltammetry, and spectroelectrochemistry. Organic field-effect transistors (OFETs) are fabricated with PTTV and PDTVB. The polymers, prepared by Stille polycondensation, exhibit good thermal stability and a photoluminescent quantum yield in the range 34%,68%. Low bandgaps (1.5,1.8,eV), estimated by optical and electrochemical measurements along with high stability of both redox states, suggest that these structures are promising materials for photovoltaic applications. OFETs fabricated with PDTVB reveal a hole mobility of 7,×,10,3,cm2 V,1 s,1 with on/off ratio 105, which are comparatively high values for completely amorphous polymer semiconductors. [source]

The Influence of Alkyl-Chain Length on Beta-Phase Formation in Polyfluorenes

ADVANCED FUNCTIONAL MATERIALS, Issue 1 2009
Daniel W. Bright
Abstract Di- n -alkyl substituted polyfluorenes with alkyl chain lengths of 6, 7, 8, 9, and 10 carbon atoms (PF6, PF7, PF8, PF9, and PF10) are studied in dilute solution in MCH using optical spectroscopy. Beta-phase is formed upon cooling in solutions (, 7,µg mL,1) of PF7, PF8, and PF9 only, which is observed as an equilibrium absorption peak at , 437,nm and strong changes in the emission spectra. Beta-phase is formed upon thermal cycling to low temperature in solutions (,7,µg mL,1) of PF7, PF8, and PF9, which is observed as an equilibrium absorption peak at , 437,nm and strong changes in the emission spectra. Beta phase is found to occur more favorably in PF8 than in PF7 or PF9, which is attributed to a balance between two factors. The first is the dimer/aggregate formation efficiency, which is poorer for longer (more disordered) alkyl chain lengths, and the second is the Van der Waals bond energy available to overcome the steric repulsion and planarize the conjugated backbone, which is insufficient in the PF6 with a shorter alkyl chain. Beta phase formation is shown to be a result of aggregation, not a precursor to it. A tentative value of the energy required to planarize the fluorene backbone of (15.6,±,2.5) kJ mol,1 monomer is suggested. Excitation spectra of PF6, PF7, PF8, and PF9 in extremely dilute (, 10,ng mL,1) solution show that beta phase can form reversibly in dilute solutions of PF7, PF8 and PF9, which is believed to be a result of chain collapse or well dispersed aggregates being present in solution from dilution of more concentrated solutions. PF7, PF8, and PF9 also form beta phase in thermally cycled solid films spin-cast from MCH. However, in the films the PF7 formed a larger fraction of beta phase than the PF9, in contrast to the case in solutions, because it is less likely that the close-packed chains in the solid state will allow the formation of planarized chains with the longer PF9 side chains. [source]

Effects of Annealing on the Nanomorphology and Performance of Poly(alkylthiophene):Fullerene Bulk-Heterojunction Solar Cells,

ADVANCED FUNCTIONAL MATERIALS, Issue 7 2007
H. Nguyen
Abstract The evolution of nanomorphology within thin solid-state films of poly(3-alkylthiophene):[6,6]-phenyl-C61 butyric acid methyl ester (P3AT:PCBM) blends during the film formation and subsequent thermal annealing is reported. In detail, the influence of the P3AT's alkyl side chain length on the polymer/fullerene phase separation is discussed. Butyl, hexyl, octyl, decyl, and dodecyl side groups are investigated. All of the P3ATs used were regioregular. To elucidate the nanomorphology, atomic force microscopy (AFM), X-ray diffraction, and optical spectroscopy are applied. Furthermore, photovoltaic devices of each of the different P3ATs have been constructed, characterized, and correlated with the nanostructure of the blends. It is proposed that the thermal-annealing step, commonly applied to these P3AT:PCBM blend films, controls two main issues at the same time: a),the crystallization of P3AT and b),the phase separation and diffusion of PCBM. The results show that PCBM diffusion is the main limiting process for reaching high device performances. [source]

The Effect of Polymer Optoelectronic Properties on the Performance of Multilayer Hybrid Polymer/TiO2 Solar Cells

ADVANCED FUNCTIONAL MATERIALS, Issue 4 2005
P. Ravirajan
Abstract We report a study of the effects of polymer optoelectronic properties on the performance of photovoltaic devices consisting of nanocrystalline TiO2 and a conjugated polymer. Three different poly(2-methoxy-5-(2,-ethylhexoxy)-1,4-phenylenevinylene) (MEH-PPV)-based polymers and a fluorene,bithiophene copolymer are compared. We use photoluminescence quenching, time-of-flight mobility measurements, and optical spectroscopy to characterize the exciton-transport, charge-transport, and light-harvesting properties, respectively, of the polymers, and correlate these material properties with photovoltaic-device performance. We find that photocurrent is primarily limited by the photogeneration rate and by the quality of the interfaces, rather than by hole transport in the polymer. We have also studied the photovoltaic performance of these TiO2/polymer devices as a function of the fabrication route and device design. Including a dip-coating step before spin-coating the polymer leads to excellent polymer penetration into highly structured TiO2 networks, as was confirmed through transient optical measurements of the photoinduced charge-transfer yield and recombination kinetics. Device performance is further improved for all material combinations studied, by introducing a layer of poly(ethylene dioxythiophene) (PEDOT) doped with poly(styrene sulfonic acid) (PSS) under the top contact. Optimized devices incorporating the additional dip-coated and PEDOT:PSS layers produced a short-circuit current density of about 1,mA,cm,2, a fill factor of 0.50, and an open-circuit voltage of 0.86,V under simulated AM,1.5 illumination (100,mW,cm,2, 1,sun). The corresponding power conversion efficiency under 1,sun was ,,0.4,%. [source]

Reversible Conductance Switching of Single Diarylethenes on a Gold Surface,

ADVANCED MATERIALS, Issue 11 2006
N. Katsonis
Light-controlled conductance switching of diarylethenes attached to Au(111) is reported (see figure). First, scanning tunneling microscopy is used to demonstrate reversible photoswitching for individual molecules. Second, reversible switching in self-assembled monolayers is established by means of optical spectroscopy. [source]

New trends and recent advances in coherent Raman microscopy and nonlinear optical spectroscopy: introduction to the special issue

New developments in nonlinear spectroscopy: ECONOS meeting in St. Petersburg

New developments in non-linear optical spectroscopy

Synthesis and Characterization of Bulk, Vitreous Cadmium Germanium Arsenide

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2009
Bradley R. Johnson
Cadmium germanium diarsenide glasses were synthesized in bulk form (,2.4 cm3) using procedures adapted from the literature. Several issues involved in the fabrication and quenching of amorphous CdGexAs2 (x=0.45, 0.65, 0.85, and 1.00, where x is the molar ratio of Ge to 1 mol of Cd) are described. An innovative processing route is presented to enable fabrication of high-purity, vitreous, crack-free ingots with sizes up to 10 mm diameter, and 30,40 mm long. Specimens from selected ingots were characterized using thermal analysis, optical microscopy, scanning electron microscopy, energy dispersive spectroscopy, particle-induced X-ray emission, Rutherford backscattering, secondary ion mass spectrometry, X-ray diffraction, density, and optical spectroscopy. Variations in properties as a function of processing conditions and composition are described. Results show that the density of defect states in the middle of the band gap and near the band edges can be decreased three ways: through suitable control of the processing conditions, by doping the material with hydrogen, and by increasing the concentration of Ge in the glass. [source]

The remarkable properties of the symbiotic star AE Circinus

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2008
R. Mennickent
ABSTRACT We present new optical spectroscopy and photometry, Two-Micron All-Sky Survey (2MASS) infrared observations and 24 yr of combined American Association of Variable Star Observers (AAVSO) and Association Francaise des Observateurs d'Etoiles Variables (AFOEV) photometry of the symbiotic star candidate AE Cir. The long-term light curve is characterized by outbursts lasting several years and having a slow decline of ,2 × 10,4 mag d,1. The whole range of variability of the star in the V band is about 4 mag. The periodogram of the photometric data reveals strong signals at ,342 and 171 d. The presence of the emission feature at ,6830 Å at minimum and the detection of absorption lines of a ,K5 type star confirm the symbiotic classification and suggest that AE Cir is a new member of the small group of s-type yellow symbiotic stars. We estimate a distance of 9.4 kpc. Our spectrum taken at the high state shows a much flatter spectral energy distribution, the disappearance of the ,6830 Å emission feature and the weakness of the He ii 4686 emission relative to the Balmer emission lines. Our observations indicate the presence of emission-line flickering in time-scales of minutes in 2001. The peculiar character of AE Cir is revealed in the visibility of the secondary star at the high and low state, the light curve resembling a dwarf nova superoutburst and the relatively short low states. The data are hard to reconciliate with standard models for symbiotic star outbursts. [source]