Electronic structures of CdSe nanocrystals — An X-ray absorption near-edge structure (XANES) investigation

2007 ◽  
Vol 85 (10) ◽  
pp. 756-760 ◽  
Author(s):  
Jigang Zhou ◽  
Xingtai Zhou ◽  
Xuhui Sun ◽  
Michael Murphy ◽  
Franziskus Heigl ◽  
...  
Keyword(s):  
Electronic Structures ◽  
Quantum Confinement Effect ◽  
Chemical Properties ◽  
Trioctylphosphine Oxide ◽  
Cdse Nanocrystals ◽  
Edge Structure ◽  
X Ray ◽  
Vis Spectroscopy ◽  
Capping Ligands ◽  
X Ray Absorption

CdSe nanocrystals (NCs), capped with trioctylphosphine oxide and 1-octadecanamine, have been synthesized with colloidal methods. Both UV–vis absorption and photoluminescence spectra show that the prepared nanostructures exhibit a quantum confinement effect. X-ray absorption near–edge structure (XANES) at Se K-edge recorded in fluorescence yield mode have been carried out on these NCs, with different size and capping ligands to gain insight into how their electronic structures are affected by the NC size and chemical properties of the ligands. The results indicate that XANES are sensitive to both the NC size and the nature of the capping ligands. The whiteline intensity in XANES spectra can be related to the photoluminescence properties of these NCs.Key words: CdSe nanocrystals, capping ligands, X-ray absorption near-edge structure, UV–vis spectroscopy, photoluminescence.

Crystalline Phases and Electronic Structures in Superconducting Bi – Sr – Ca – Cu Oxides

1997 ◽  
Vol 12 (8) ◽  
pp. 2009-2013
Author(s):  
M. D. Giardina ◽  
R. Feduzi ◽  
D. Inzaghi ◽  
A. Manara ◽  
C. Giori ◽  
...  
Keyword(s):  
Microwave Absorption ◽  
Photoelectron Spectroscopy ◽  
Electronic Structures ◽  
Theoretical Interpretation ◽  
Nominal Composition ◽  
X Ray Diffraction ◽  
Edge Structure ◽  
X Ray ◽  
Quantum Percolation ◽  
X Ray Absorption

Two classes of samples, designated A and B, of layered Bi–Sr–Ca–Cu oxides having the same nominal composition 4 : 3 : 3 : 4, but different thermal histories, were investigated by using field modulated microwave absorption (ESR), powder x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and x-ray absorption near the edge structure (XANES). Previous electrical resistivity measurements showed that the B samples presented only two superconducting phases with midpoints of the transition temperatures at ∼80 K and ∼105 K. The microwave absorption technique indicated instead the presence of islands which became superconducting at the above-mentioned temperatures also in the A samples. The crystalline and electronic structures of the two types of samples are illustrated and discussed. A plausible theoretical interpretation of the experimental results, based on a quantum percolation model with Coulomb interaction, is also given.

scholarly journals Effect of thickness and Si substrate morphology in La0.7Sr0.3MnO3/Si thin films

2014 ◽  
Vol 70 (a1) ◽  
pp. C1532-C1532
Author(s):  
Hsiao-Tsu Wang ◽  
Mau- Kuen Wu ◽  
Yu-Cheng Shao ◽  
Yu-Fu Wang ◽  
Shang-Hsien Hsieh ◽  
...  
Keyword(s):  
Thin Films ◽  
Magnetic Properties ◽  
Electronic Structures ◽  
Magnetic Circular Dichroism ◽  
Magnetic Behavior ◽  
Si Substrate ◽  
Edge Structure ◽  
X Ray ◽  
X Ray Absorption ◽  
Different Thickness

Investigation has been made on atomic, electronic structures and magnetic properties of La0.7Sr0.3MnO3 (LSMO) on Si substrate. The effect of different thickness of LSMO and different morphological [flat and nano-pyramid (NP)] of Si substrate are studied in present work. The result of Mn K-edge extended x-ray absorption fine structure indicates the more disorder of local atomic structure of first shell (Mn-O bound) in the thinner LSMO/Si film. The Mn L3,2-edge x-ray absorption near-edge structure shows the presence of Mn2+ ion on the sample. Furthermore, the Mn L3,2-edge x-ray magnetic circular dichroism reveals that the thinner film (LSMO/Si) has highest magnetic moment, in comparison to that of thick LSMO/Si and LSMO/Si-NP samples. This finding suggests that the appearance Mn2+ may play an important role in magnetic behavior of hetero-junction LSMnO/Si and Si-NP.

ELECTRONIC STRUCTURES OF La0.7Ca0.3MnO3 AND La0.7Ce0.3MnO3 BY X-RAY ABSORPTION SPECTROSCOPY

2002 ◽  
Vol 09 (02) ◽  
pp. 1053-1057 ◽  
Author(s):  
K. ASOKAN ◽  
K. V. R. RAO ◽  
J. C. JAN ◽  
J. W. CHIOU ◽  
W. F. PONG ◽  
...  
Keyword(s):  
Absorption Spectroscopy ◽  
Electronic Structures ◽  
Spectral Features ◽  
Electron Hole ◽  
Edge Structure ◽  
X Ray ◽  
Strong Hybridization ◽  
Doped Manganites ◽  
X Ray Absorption ◽  
Tetravalent State

Electronic structures of hole-doped and electron hole-doped manganites, La 0.7 Ca 0.3 MnO 3 and La 0.7 Ce 0.3 MnO 3, have been elucidated by X-ray absorption near-edge structure (XANES) spectra of O K- and Mn L3,2-edges. In the electron-doped system, La 0.7 Ce 0.3 MnO 3, the spectral features of O K-edge spectra are shifted by ~ 1 eV towards the higher energy side and reduction of Mn valency from 4+ and 3+ to 3+ and 2+ is expected when compared to hole-doped manganite. The XANES of Ce M5,4-edges indicates a tetravalent state for Ce, similar to that in CeO 2. Ce 4+ is incorporated into the lattice of LaMnO 3, resulting in the modification of MnO 6 octahedra and also indicating strong hybridization of Ce 5d and/or Ce 4f states with O 2p states.

Extraction of local coordination structure in a low-concentration uranyl system by XANES

2016 ◽  
Vol 23 (3) ◽  
pp. 758-768 ◽  
Author(s):  
Linjuan Zhang ◽  
Jing Zhou ◽  
Jianyong Zhang ◽  
Jing Su ◽  
Shuo Zhang ◽  
...  
Keyword(s):  
Structural Information ◽  
Chemical Properties ◽  
Edge Structure ◽  
X Ray ◽  
Low Concentration ◽  
Simplified Approach ◽  
Bond Lengths ◽  
Uranyl Carbonate ◽  
X Ray Absorption ◽  
Xanes Analysis

Obtaining structural information of uranyl species at an atomic/molecular scale is a critical step to control and predict their physical and chemical properties. To obtain such information, experimental and theoreticalL3-edge X-ray absorption near-edge structure (XANES) spectra of uranium were studied systematically for uranyl complexes. It was demonstrated that the bond lengths (R) in the uranyl species and relative energy positions (ΔE) of the XANES were determined as follows: ΔE1= 168.3/R(U—Oax)2− 38.5 (for the axial plane) and ΔE2= 428.4/R(U—Oeq)2− 37.1 (for the equatorial plane). These formulae could be used to directly extract the distances between the uranium absorber and oxygen ligand atoms in the axial and equatorial planes of uranyl ions based on the UL3-edge XANES experimental data. In addition, the relative weights were estimated for each configuration derived from the water molecule and nitrate ligand based on the obtained average equatorial coordination bond lengths in a series of uranyl nitrate complexes with progressively varied nitrate concentrations. Results obtained from XANES analysis were identical to that from extended X-ray absorption fine-structure (EXAFS) analysis. XANES analysis is applicable to ubiquitous uranyl–ligand complexes, such as the uranyl–carbonate complex. Most importantly, the XANES research method could be extended to low-concentration uranyl systems, as indicated by the results of the uranyl–amidoximate complex (∼40 p.p.m. uranium). Quantitative XANES analysis, a reliable and straightforward method, provides a simplified approach applied to the structural chemistry of actinides.

Chemical Properties of Superfine Pulverized Coal Particles. Part 4. Sulfur Speciation by X-ray Absorption Near-Edge Structure Spectroscopy

2020 ◽  
Vol 34 (11) ◽  
pp. 13686-13697
Author(s):  
Jiaxun Liu ◽  
Xiuchao Yang ◽  
Yuanzhen Jiang ◽  
Hai Zhang ◽  
Xue Jiang ◽  
...  
Keyword(s):  
Chemical Properties ◽  
Pulverized Coal ◽  
Edge Structure ◽  
X Ray ◽  
Coal Particles ◽  
Sulfur Speciation ◽  
X Ray Absorption

Study of MgXZn1-XO Alloys (0

2013 ◽  
Vol 663 ◽  
pp. 361-365 ◽  
Author(s):  
Wei Zheng ◽  
Zhe Chuan Feng ◽  
Fan Hsiu Chang ◽  
Jyh Fu Lee ◽  
Rui Sheng Zheng ◽  
...  
Keyword(s):  
Fine Structure ◽  
High Resolution ◽  
Detailed Analysis ◽  
Absorption Spectroscopy ◽  
Electronic Structures ◽  
Chemical Bonds ◽  
Absorption Data ◽  
Edge Structure ◽  
X Ray ◽  
X Ray Absorption

High-resolution K-edge x-ray absorption data are presented for Mg, Zn and O of Mg1-xZnxO films. A detailed analysis of the extended x-ray absorption fine structure by using the IFEFFIT program is given, and the Zn form chemical bonds with O are obtained. The x-ray absorption near-edge structure of Mg, Zn and O K-edge are investigated, and the electronic structures of Mg1-xZnxO with various compositions are studied.

Oxidative Degradation Monitoring of Natural Rubber Using S K-Edge X-Ray Absorption near-Edge Spectroscopy (XANES)

2012 ◽  
Vol 620 ◽  
pp. 440-445 ◽  
Author(s):  
Wirach Taweepreda ◽  
Wanwisa Limphirat ◽  
Prayoon Songsiriritthigul
Keyword(s):  
Natural Rubber ◽  
Oxidative Degradation ◽  
Chemical Properties ◽  
Oxidative Process ◽  
Tetramethylthiuram Disulfide ◽  
Edge Structure ◽  
X Ray ◽  
Degradation Monitoring ◽  
Zinc Diethyldithiocarbamate ◽  
X Ray Absorption

In this work, we present the results of sulfur crosslinking and degradation in natural rubber (NR) studied by X-ray absorption near-edge structure spectroscopy (XANES). Sulfur K-edge XANES spectra has been collected and analyzed to provide the geometry and electronic environment of sulfur crosslinks during vulcanization and degradation processes by ozone aging. We found that reversion took place before the onset of oxidative process at the sulfur bridge. Parallel to the oxidative process, the production of cyclic sulfanes took places. This physico-chemical properties which were calculated from S K-edge XANES spectra were correlated with the mechanical of NR films by varying accelerator type. The accelerator zinc diethyldithiocarbamate (ZDEC) gave highest film strength when compared with other accelerators: N-cyclohexylbenzothiazole sulfenamide (CBS), 2,2' dibenzothiazyl disulfide (MBTS), and tetramethylthiuram disulfide (TMTD).

scholarly journals X-ray absorption near-edge structure spectroscopy research on electronic structures and magnetic properties of (Fe1-xNix)2P

2008 ◽  
Vol 57 (6) ◽  
pp. 3868
Author(s):  
Ma Chen-Yan ◽  
Cui Ming-Qi ◽  
Zhang Ling-Yun ◽  
Wu Xiang ◽  
Zhou Ke-Jin ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Electronic Structures ◽  
Edge Structure ◽  
X Ray ◽  
X Ray Absorption ◽  
Spectroscopy Research
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