Time-resolved x-ray excited optical luminescence from SnO2 nanoribbons: Direct evidence for the origin of the blue luminescence and the role of surface states

2006 ◽  
Vol 89 (21) ◽  
pp. 213109 ◽  
Author(s):  
X. T. Zhou ◽  
F. Heigl ◽  
M. W. Murphy ◽  
T. K. Sham ◽  
T. Regier ◽  
...  
Keyword(s):  
Direct Evidence ◽  
Surface States ◽  
Blue Luminescence ◽  
Time Resolved ◽  
X Ray ◽  
Optical Luminescence

Green rust as a precursor for magnetite: an in situ synchrotron based study

2008 ◽  
Vol 72 (1) ◽  
pp. 201-204 ◽  
Author(s):  
A. Sumoondur ◽  
S. Shaw ◽  
I. Ahmed ◽  
L. G. Benning
Keyword(s):  
Direct Evidence ◽  
Green Rust ◽  
Stable Phase ◽  
X Ray Diffraction ◽  
Time Resolved ◽  
X Ray ◽  
Subsequent Transformation ◽  
Rapid Formation ◽  
Reaction Proceeds

AbstractIn this study, direct evidence for the formation of magnetite via a green rust intermediate is reported. The Fe(II) induced transformation of ferrihydrite, was quantified in situ and under O2-free conditions using synchrotron-based time-resolved energy dispersive X-ray diffraction. At pH 9 and Fe(II)/Fe(III) ratios of 0.5 and 1, rapid growth (6 min) of sulphate green rust and its subsequent transformation to magnetite was observed. Electron microscopy confirmed these results, showing the initial rapid formation of hexagonal sulphate green rust particles, followed by the corrosion of the green rust as magnetite growth occurred, indicating that the reaction proceeds via a dissolution-reprecipitation mechanism. At pH 7 and Fe(II)/Fe(III) ratio of 0.5, sulphate green rust was the stable phase, with no transformation to magnetite.

scholarly journals Titin strain contributes to the Frank–Starling law of the heart by structural rearrangements of both thin- and thick-filament proteins

2016 ◽  
Vol 113 (8) ◽  
pp. 2306-2311 ◽  
Author(s):  
Younss Ait-Mou ◽  
Karen Hsu ◽  
Gerrie P. Farman ◽  
Mohit Kumar ◽  
Marion L. Greaser ◽  
...  
Keyword(s):  
Thick Filament ◽  
Structural Rearrangements ◽  
X Ray Diffraction ◽  
Thin Filaments ◽  
Time Resolved ◽  
X Ray ◽  
Isolated Myocardium ◽  
Splice Isoform ◽  
Length Dependent Activation

The Frank–Starling mechanism of the heart is due, in part, to modulation of myofilament Ca2+ sensitivity by sarcomere length (SL) [length-dependent activation (LDA)]. The molecular mechanism(s) that underlie LDA are unknown. Recent evidence has implicated the giant protein titin in this cellular process, possibly by positioning the myosin head closer to actin. To clarify the role of titin strain in LDA, we isolated myocardium from either WT or homozygous mutant (HM) rats that express a giant splice isoform of titin, and subjected the muscles to stretch from 2.0 to 2.4 μm of SL. Upon stretch, HM compared with WT muscles displayed reduced passive force, twitch force, and myofilament LDA. Time-resolved small-angle X-ray diffraction measurements of WT twitching muscles during diastole revealed stretch-induced increases in the intensity of myosin (M2 and M6) and troponin (Tn3) reflections, as well as a reduction in cross-bridge radial spacing. Independent fluorescent probe analyses in relaxed permeabilized myocytes corroborated these findings. X-ray electron density reconstruction revealed increased mass/ordering in both thick and thin filaments. The SL-dependent changes in structure observed in WT myocardium were absent in HM myocardium. Overall, our results reveal a correlation between titin strain and the Frank–Starling mechanism. The molecular basis underlying this phenomenon appears not to involve interfilament spacing or movement of myosin toward actin but, rather, sarcomere stretch-induced simultaneous structural rearrangements within both thin and thick filaments that correlate with titin strain and myofilament LDA.

Influence of Electron-withdrawing Substituents on Photoelectrochemical Surface Phenomena at Phthalocyanine Thin Film Electrodes

1999 ◽  
Vol 03 (06) ◽  
pp. 444-452 ◽  
Author(s):  
TORSTEN OEKERMANN ◽  
DERCK SCHLETTWEIN ◽  
NILS I. JAEGER ◽  
DIETER WÖHRLE
Keyword(s):  
Charge Transfer ◽  
Steady State ◽  
Electrolyte Concentration ◽  
Surface States ◽  
Surface Phenomena ◽  
Time Resolved ◽  
Photogenerated Electrons ◽  
Millisecond Range ◽  
Electron Withdrawing Substituents

The influence of electron-withdrawing substituents on the photoelectrochemical properties of phthalocyanines is shown in a comparison between hexadecafluorophthalocyaninatozinc(II) ( F 16 PcZn ) and the unsubstituted phthalocyaninatozinc(II) ( PcZn ). The role of surface states in the photoelectrochemistry of both materials has been investigated by time-resolved photocurrent measurements in the millisecond range. The charging and discharging of surface states could clearly be seen as spikes at the beginning and the end of illumination. Surface states were filled with photogenerated electrons at PcZn and with photogenerated holes at F 16 PcZn . In the steady state under illumination only cathodic photocurrents were detected at PcZn , while at F 16 PcZn both cathodic and anodic photocurrents were observed. An adsorption step of electroactive species prior to the charge transfer was derived from the dependence of the steady state photocurrents on the electrolyte concentration for both materials. The concentration dependence of the charging and discharging currents, however, showed that charge transfer from surface states to the electrolyte occurs at PcZn , while at F 16 PcZn the surface states only represent recombination centres.

Time-Resolved X-Ray Absorption of An Amorphous Si Foil During Pulsed Laser Irradiation

1985 ◽  
Vol 51 ◽  
Author(s):  
Kouichi Murakami ◽  
Hans C. Gerritsen ◽  
Hedser Van Brug ◽  
Fred Bijkerk ◽  
Frans W. Saris ◽  
...  
Keyword(s):  
Laser Irradiation ◽  
Direct Evidence ◽  
Pulsed Laser ◽  
Time Resolved ◽  
Edge Structure ◽  
X Ray ◽  
Nanosecond Pulsed Laser ◽  
Amorphous Si ◽  
X Ray Absorption ◽  
Pulsed Laser Irradiation

ABSTRACTWe report time-resolved X-ray absorption and extended X-ray absorption fine structure (EXAFS) measurements on amorphous silicon under nanosecond pulsed-laser irradiation. Each measurement was performed with one laser shot in the X-ray energy range from 90 to 300 eV. An X-ray absorption spectrum for induced liquid Si (liq*Si) was first observed above an energy density of 0.17 J/cm2. It differs significantly from the spectrum for amorphous Si and characteristically shows the disappearance of the Si-L(II,III) edge structure at around 100 eV. This phenomenon is interpreted in terms of a significant reduction in the 3s-like character of the unfilled part of the conduction band of liq*Si compared to that of amorphous Si. This is the first direct evidence that liq*Si has a metallic-like electronic structure. Timeresolved EXAFS results are also discussed briefly.

scholarly journals Structural Transformations and Their Precursors

1983 ◽  
Vol 36 (4) ◽  
pp. 553 ◽  
Author(s):  
TR Finlayson
Keyword(s):  
Thermal Expansion ◽  
Electron Diffraction ◽  
Physical Properties ◽  
Elastic Constants ◽  
Direct Evidence ◽  
Indirect Evidence ◽  
Structural Transformations ◽  
X Ray ◽  
Kinetics Of

For a number of materials which exhibit a change of structure on being cooled below a certain temperature Tm, some physical properties display anomalous behaviour at temperatures above Tm. The particular structural transformations in mind have been broadly classified as 'martensitic' and the anomalous physical properties as 'precursive phenomena'. Some debate exists regarding the role of the precursive phenomenon in the kinetics of the structural transformation. The most direct evidence for 'martensite precursors' is obtained from electron diffraction, although various indirect evidence is contained in X-ray, neutron and y-ray diffraction and various physical properties, for example, elastic constants and thermal expansion. In this paper current understanding of 'martensite precursors' is reviewed and examples of data from the A15 structure compounds V 3Si and Nb3Sn,. In-TI and TiNi alloys are discussed.

Time-Resolved X-ray Excited Optical Luminescence from Tris(2-phenyl bipyridine)iridium

2006 ◽  
Vol 128 (12) ◽  
pp. 3906-3907 ◽  
Author(s):  
Franziskus Heigl ◽  
Simone Lam ◽  
Tom Regier ◽  
Ian Coulthard ◽  
Tsun-Kong Sham
Keyword(s):  
Time Resolved ◽  
X Ray ◽  
Optical Luminescence

scholarly journals Capabilities of time-resolved X-ray excited optical luminescence of the Taiwan Photon Source 23A X-ray nanoprobe beamline

2020 ◽  
Vol 27 (1) ◽  
pp. 217-221
Author(s):  
Bi-Hsuan Lin ◽  
Yu-Hao Wu ◽  
Xiao-Yun Li ◽  
Hsu-Cheng Hsu ◽  
Yu-Cheng Chiu ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
Decay Time ◽  
Streak Camera ◽  
Photonic Materials ◽  
Experimental Conditions ◽  
Time Resolved ◽  
X Ray ◽  
Optical Luminescence ◽  
Excellent Spatial Resolution ◽  
Photon Source

Time-resolved X-ray excited optical luminescence (TR-XEOL) was developed successfully for the 23A X-ray nanoprobe beamline located at the Taiwan Photon Source (TPS). The advantages of the TR-XEOL facility include (i) a nano-focused X-ray beam (<60 nm) with excellent spatial resolution and (ii) a streak camera that can simultaneously record the XEOL spectrum and decay time. Three time spans, including normal (30 ps to 2 ns), hybrid (30 ps to 310 ns) and single (30 ps to 1.72 µs) bunch modes, are available at the TPS, which can fulfil different experimental conditions involving samples with various lifetimes. It is anticipated that TR-XEOL at the TPS X-ray nanoprobe could provide great characterization capabilities for investigating the dynamics of photonic materials.

Soft X-ray excited colour-centre luminescence and XANES studies of calcium oxide

2007 ◽  
Vol 85 (10) ◽  
pp. 853-858 ◽  
Author(s):  
JY Peter Ko ◽  
Franziskus Heigl ◽  
Yun Mui Yiu ◽  
Xing-Tai Zhou ◽  
Tom Regier ◽  
...  
Keyword(s):  
Calcium Oxide ◽  
Density Functional ◽  
X Rays ◽  
Colour Centre ◽  
Time Resolved ◽  
Edge Structure ◽  
Colour Centres ◽  
X Ray ◽  
Optical Luminescence ◽  
X Ray Absorption

In this study, we show that colour centres can be produced by irradiating calcium oxide with soft X-rays from a synchrotron radiation source. Using the X-ray excited optical luminescence (XEOL) technique, two colour centres, F-centre, and F+-centre can be identified. These colour centres emit photons at characteristic wavelengths. In addition, by performing time-resolved XEOL (TRXEOL), we are able to reveal timing and decay characteristics of the colour centres. We also present X-ray absorption near-edge structure (XANES) spectra collected across oxygen K-edge, calcium L3,2-edge, and calcium K-edge. Experimental results are compared with density functional theory (DFT) calculations.Key words: calcium oxide, colour centre, synchrotron, X-ray excited optical luminescence, X-ray absorption near-edge structure.

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