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Background: Colorectal cancer (CRC) has high mortality, and 5-fluorouracil (5-FU) is a common clinical chemotherapeutic drug. The current study aimed to investigate the role of FAT4 in chemosensitivity of CRC cells treated by 5-FU. Methods: The immunohistochemistry and qRT-PCR was conducted to measure the FAT4 expression in CRC and adjacent tissues. The FAT4 expression was determined by qRT-PCR and Western blot, comparison of FAT expression between normal and several CRC cell lines was then made, so as to identify cell lines with the highest (LS174T) and the lowest (SW-620) expressions of FAT4 . The effects of 5-FU stimulation at various doses on cell viability were determined by CCK-8, and the level of FAT4 was also measured. After FAT4 knockdown in LS174T or FAT4 overexpression in SW-620 with or without pretreatment of 5-FU (30 µg/mL), cell growth, colony formation, cell migration and invasion, angiogenesis were determined by flow cytometry, wound-healing, transwell assay and tube formation assay, respectively. The expression levels of epithelial-mesenchymal transition (EMT) markers were detected by qRT-PCR and Western blot. Results: FAT4 was down-regulated in CRC tissues and cells, cell viability of CRC cells was decreased. The level of FAT4 was increased with the increase of 5-FU concentrations. Moreover, 5-FU stimulation increased FAT4 expression, and reduced cell proliferation, migration, invasion, angiogenesis and cell EMT process, furthermore, such effects of 5-FU stimulation could be enhanced by FAT4 overexpression but reversed by FAT4 knockdown. Conclusions: Upregulation of FAT4 could increase the sensitivity of CRC cells to 5-FU.

Exploration of the biological effects of transition metal ions in acupuncture points is essential to clarify the functional mechanism of acupuncture treatment. Here we show that in the SP6 acupuncture point (Sanyinjiao) the Fe ions are in a high-spin state of approximately t2g4.5eg1.5 in an Fe-N(O) octahedral crystal field. The Fe K-edge synchrotron radiation X-ray absorption fine structure results reveal that the Fe-N and Fe-O bond lengths in the SP6 acupuncture point are 2.05 and 2.13 A, respectively, and are 0.05-0.10 A longer than those in the surrounding tissue. The distorted atomic structure reduces the octahedral symmetry and weakens the crystal field around the Fe ions by approximately 0.3 eV, leading to the high-spin configuration of the Fe ions, which is favorable for strengthening the magnetotransport and oxygen transportation properties in the acupuncture point by the enhanced spin coherence. This finding might provide some insight into the microscopic effect of the atomic and electronic interactions of transition metal ions in the acupuncture point. Graphical Abstract ᅟ.

The Xpert MTB/RIF test (Cepheid, Sunnyvale, CA) can simultaneously detect the Mycobacterium tuberculosis (MTB) complex DNA and rifampicin (RFP) resistance and can rapidly determine RFP resistance and predict multidrug-resistant tuberculosis (MDR-TB). In this study, we analyzed clinical examination results of a hospital specializing in TB treatment in Wuhan, Hubei, China, and examined the use of traditional culture and drug-sensitive test (DST) results as a gold standard to assess the diagnosis value of the Xpert MTB/RIF test in RFP resistance and MDR-TB.A total of 2,910 specimens were received in the Mycobacteriology Laboratory, Wuhan Pulmonary Hospital, for Xpert MTB/RIF testing between December 2013 and December 2014. After the results were reviewed by exclusion criteria, 1,066 Xpert test results were eligible for our study. We then compared the Xpert test results with sputum acid-fast bacilli staining, cultures, and DST results.In total, Xpert correctly identified 96.71% (147/152) RFP-resistant TB and 98.25% (898/914) RFP-sensitive TB specimens. Of the 147 RFP-resistant TB specimens detected by Xpert, 122 MDR-TB (82.99%) were identified by traditional culture and DST techniques.Xpert can simultaneously detect MTB and RFP resistance with high sensitivity and specificity. Thus, Xpert testing aids in saving a considerable amount of time in the diagnosis and treatment of MDR-TB.

Direct and efficient photocatalytic water splitting is critical for sustainable conversion and storage of renewable solar energy. Here, we propose a conceptual design of two-dimensional C3N4-based in-plane heterostructure to achieve fast spatial transfer of photoexcited electrons for realizing highly efficient and spontaneous overall water splitting. This unique plane heterostructural carbon ring (Cring)–C3N4 nanosheet can synchronously expedite electron–hole pair separation and promote photoelectron transport through the local in-plane π-conjugated electric field, synergistically elongating the photocarrier diffusion length and lifetime by 10 times relative to those achieved with pristine g-C3N4. As a result, the in-plane (Cring)–C3N4 heterostructure could efficiently split pure water under light irradiation with prominent H2 production rate up to 371 μmol g–1 h–1 and a notable quantum yield of 5% at 420 nm.

Stanniocalcin 2 (STC2), a secretory glycoprotein hormone, regulates many biological processes including cell proliferation, apoptosis, tumorigenesis and atherosclerosis. However, the effect of STC2 on proliferation, migration and epithelial-mesenchymal transition (EMT) progression in human colorectal cancer (CRC) cells remains poorly understood. The expression level of STC2 was determined by quantitative real-time polymerase chain reaction (qPCR) and western blot analysis. Cell Counting Kit-8 (CCK-8) was used to detect the viability of SW480 cells. The invasion and migration of cells were identified by wound healing and Transwell assays. The mRNA and protein expression levels of β-catenin, matrix metalloproteinase (MMP)-2, MMP-9, E-cadherin and vimentin were assessed by qPCR and western blot analysis. In the present study, it was demonstrated that STC2 was highly expressed in the CRC cell lines. After silencing of STC2, the cell viability, migration and invasion were significantly reduced. Silencing of STC2 in the CRC Sw480 cells increased the expression of E-cadherin and decreased the expression of vimentin, MMP-2 and MMP-9, compared to those in the normal and empty vector group. Furthermore, the expression of β-catenin in the STC2 gene silenced group was suppressed, and the expression of β-catenin was reversed by Wnt activator, SB216763. These results demonstrated that STC2 participates in the development and progression of CRC by promoting CRC cell proliferation, survival and migration and activating the Wnt/β-catenin signaling pathway.

The facile electron-hole pair recombination in earth-abundant transition-metal oxides is a major limitation for the development of highly efficient hydrogen evolution photocatalysts. In this work, the thickness of a layered β-CoOOH semiconductor that contains metal/hydroxy groups was reduced to obtain an atomically thin, two-dimensional nanostructure. Analysis by ultrafast transient absorption spectroscopy revealed that electron-hole recombination is almost suppressed in the as-prepared 1.3 nm thick β-CoOOH nanosheet, which leads to prominent electron-hole separation efficiencies of 60-90 % upon irradiation at 350-450 nm, which are ten times higher than those of the bulk counterpart. X-ray absorption spectroscopy and first-principles calculations demonstrate that [HO-CoO6-x] species on the nanosheet surface promote H(+) adsorption and H2 desorption. An aqueous suspension of the β-CoOOH nanosheets exhibited a high hydrogen production rate of 160 μmol g(-1) h(-1) even when the system was operated for hundreds of hours.

Producing H2 by means of direct photocatalytic water splitting using suspension system is highly desired in efficiently transforming solar energy to chemical energy. Here, using an ultrathin β-CoOOH nanosheet as photocatalyst suspended in aqueous Na2SO3 solution, we realize highly efficient and stable photocatalytic hydrogen evolution under visible light irradiation. The as-prepared ultrathin β-CoOOH nanosheets suspension can directly photocatalyze hydrogen evolution in a high rate of 1200 μmol/g/h and large quantum efficiencies of 10.7% at 380 nm, 6.9% at 420 nm, and 2.3% at 450 nm. X-ray photoelectron and X-ray absorption measurements reveal that the excellent hydrogen evolution activity of the β-CoOOH nanosheet is attributed to the surface low-coordinated Co catalytic site, which results in a strong hybridization of Co 3d states with the S p states of SO32+, and facilitates the electron transfer to reduce H+. The results may be helpful for designing and understanding two-dimensional oxyhydroxide-based ...

Direct and efficient photocatalytic water splitting is critical for sustainable conversion and storage of renewable solar energy. Here, we propose a conceptual design of two-dimensional C

Control over the magnetic interactions in dilute magnetic semiconductor quantum dots (DMSQDs) is a key issue to future development of nanometer-sized integrated "spintronic" devices. However, manipulating the magnetic coupling between impurity ions in DMSQDs remains a great challenge because of the intrinsic quantum confinement effects and self-purification of the quantum dots. Here, we propose a hybrid structure to achieve room-temperature ferromagnetic interactions in DMSQDs, via engineering the density and nature of the energy states at the Fermi level. This idea has been applied to Co-doped ZnO DMSQDs where the growth of a reduced graphene oxide shell around the Zn(0.98)Co(0.02)O core turns the magnetic interactions from paramagnetic to ferromagnetic at room temperature, due to the hybridization of 2p(z) orbitals of graphene and 3d obitals of Co(2+)-oxygen-vacancy complexes. This design may open up a kind of possibility for manipulating the magnetism of doped oxide nanostructures.

Increasing the quantum conversion efficiency in visible-light region is a key issue for the efficient usage of solar energy in the process of photoelectrochemical (PEC) water splitting. Here, based on the N anion and S cation codoped TiO 2 thin film photoanodes, we find experimentally and theoretically that the transport ability of visible-light-induced carriers can be notably enhanced by engineering the dopant electronic energy states. The hole transport resistivity is decreased from 6.8 × 10 4 to 1.3 × 10 4 Ω m via delocalizing the introduced bands, leading to an evident increase of the internal quantum efficiency from 5% to 20% at the visible-light region of 450–550 nm. Further DFT calculations exhibit that the split of the isolated band is induced by a strong N and S hybridization, which favors to decrease the hole effective mass and to improve the hole mobility by three times. The photocurrent of N − S codoped TiO 2 thin film is thus twice that of monodoping cases, the best value for doping modified TiO 2 thin film photoanodes. This work may provide not only a design principle but also a candidate for tailoring and optimizing TiO 2 towards high PEC activity.

Enhancing catalytic water-splitting activity under mild environments is significant to solve the long-standing cost, safety and stability issues in photoelectrochemical cells. Here, we demonstrate the crucial role of improving surface H transfer in achieving efficient water-splitting catalytic activity of Co3O4 nanowire arrays in near-neutral pH working electrolytes. Under weak OH circumstances, the impedance of mass transfer quickly multiplies and the catalytic current declines to a current plateau in the region of 1.7–2.1 V vs. RHE, due to the surface H concentration approaching a threshold value in the range of 10−3–10−4 M. The proper choice of buffering agents to facilitate the mass transfer, with 0.1 M KPi as a prototype, would decrease the overpotential by 500 mV for neutral electrolyte and favors to achieve a catalytic current comparable to that under strong alkali environments (pH > 13). These results also provide a solid guideline for extending the electrocatalytic utility of other transition metal catalysts to near-neutral pH environments.

In this paper, a generalized reverse projection (RP) method for grating-based fan beam phase contrast imaging is presented. Compared to the original RP method, rays rather than projection images are taken into account during the information extraction process. We also discuss the influence of partial coherence on the extracted information. Theoretical derivations and numerical simulations are performed to confirm the validity of the method.

Elemental codoping has been an effective way to modify the structural and electronic properties of semiconductors. By use of X-ray diffraction and X-ray absorption fine structure spectroscopy, we s...

We report the microstructure, gas-sensing properties of the ordered mesoporous Co3O4 prepared by modified KIT-6 template method. Highly ordered mesoporous nanostructures of the as-prepared products have been characterized by X-ray diffraction (XRD), extended X-ray absorption fine structure (EXAFS), high-resolution transmission electron microscopy (HRTEM) and N2 adsorption/desorption analysis. We find that the ordered mesoporous Co3O4 enables a significant improvement of sensor response and selectivity to ethanol, which demonstrates the potential use of the ordered mesoporous Co3O4 as alcohol gas-sensing material. Through the analysis of microstructure including HRTEM and N2 adsorption/desorption, the sensing properties for the ordered mesoporous Co3O4 can be attributed qualitatively to its large specific surface area and porous morphology. Moreover, the results of EXAFS illustrate that the disorder degree and unsaturated bond of the ordered mesoporous Co3O4 increase, which agree well with the results observed in gas sensors. This makes the nanostructured ordered mesoporous Co3O4 a promising sensor material for detecting the alcohol gas.

Liver fibrosis is concomitant with monocyte infiltration, which has been highlighted as novel therapeutic targets for chronic liver diseases. We aimed to investigate whether curcumin might protect the liver from carbon tetrachloride (CCl4)-induced fibrosis by attenuating the recruitment of Gr1hi monocytes through inhibition of monocyte chemoattractant protein-1 (MCP-1).Mice were intraperitoneally injected with CCl4 to induce liver fibrosis. Curcumin was orally administrated to mice. Hepatic inflammation and fibrosis were evaluated by analysis of liver function and hepatic histopathology. Infiltration of the Gr1hi monocytes was assessed by flow cytometry and immunohistochemistry. Moreover, mRNA expression levels of tumor necrosis factor (TNF)-α, interleukin (IL)-6, IL-1β, and transforming growth factor (TGF)-β1 were determined by real time PCR. Hepatic expression of MCP-1 was determined by real time PCR and immunohistochemistry.Curcumin significantly attenuated inflammation and fibrosis, as revealed by histological and biochemical analysis. The intrahepatic infiltration of Gr1hi monocytes was attenuated by curcumin administration. T cells, NK cells, NKT cells, and dendritic cells were not affected by curcumin. Curcumin significantly reduced the expression of TNF-α and TGF-β1, which is in line with the decreased numbers of intrahepatic Gr1hi monocytes. Intrahepatic MCP-1 expression of CCl4-challenged mice was inhibited by curcumin.The anti-inflammatory and antifibrotic effects of curcumin could be contributed to its prevention of Gr1hi monocyte infiltration into the injured livers through inhibition of MCP-1. These new findings extend our understanding on the mechanisms of the anti-inflammatory and antifibrotic effects of curcumin.

Infiltrating monocytes have been demonstrated to contribute to tissue damage in experimental models of liver injury and fibrosis. However, less is known about monocyte infiltration in the livers of patients with chronic liver diseases (CLD). In the present study, we demonstrated that CD68+ hepatic macrophages and MAC387+ infiltrating monocytes were significantly increased in the livers of CLD patients with different etiologies as compared with normal liver tissue. In addition, CLD patients with higher inflammatory grading scores had more CD68+ macrophages and MAC387+ monocytes infiltration in their livers compared to those with lower scores. Significantly more MAC387+ infiltrating monocytes were found in the liver tissue of CLD patients with higher fibrotic staging scores compared to those with lower scores. Monocyte chemoattractant protein-1 (MCP-1) expression was significantly increased in the livers of CLD patients with different etiologies. MCP-1 staining scores were significantly positively associated with the numbers of MAC387+ infiltrating monocytes in CLD patients. Taken together, our results demonstrate that infiltrating monocytes may play a pathological role in exacerbating chronic liver inflammation and fibrosis in CLD. MCP-1 may be involved in the monocyte infiltration and progression of liver inflammation and fibrosis in CLD.

X-ray microscopy based on synchrotron radiation has become a fundamental tool in biology and life sciences to visualize the morphology of a specimen. These studies have particular requirements in terms of radiation damage and the image exposure time, which directly determines the total acquisition speed. To monitor and improve these key parameters, we present a novel X-ray microscopy method using a high-resolution zone plate as the objective and the matching condenser. Numerical simulations based on the scalar wave field theory validate the feasibility of the method and also indicate the performance of X-ray microscopy is optimized most with sub-10-nm-resolution zone plates. The proposed method is compatible with conventional X-ray microscopy techniques, such as computed tomography, and will find wide applications in time-resolved and/or dose-sensitive studies such as living cell imaging.

In this contribution we discuss the possibility of designing a modified transmission X-ray microscope by using fractal zone plates (Fzps) as diffractive optical elements. In the modified transmission X-ray microscope optical layout, we first introduced a fractal zone plate as the microscope objective. Indeed, a fractal zone plate cannot only be used as an image-forming component but also as a condenser element to achieve an extended depth of field. Numerical analysis reveals that fractal zone plates and conventional Fresnel zone plates have similar imaging capabilities under different coherent illumination. Using a fractal zone plate as a condenser we also simulated axial irradiance. Results confirm that fractal zone plates can improve focusing capability with an extended depth of field. Although preliminary, these simulations clearly reveal that fractal zone plates, when available, will be of great help in microscope layouts, in particular for foreseen high-resolution applications in the "water window" as strongly required in biological research.

The MFI/MCM-41 composite material with bimetallic Fe and Co incorporation was prepared using templating method via a two-step hydrothermal crystallization procedure. The obtained products were characterized by a series of techniques including powder X-ray diffraction, N2 sorption, transmission electron microscopy, scanning electron microscope, H2 temperature programmed reduction, thermal analyses, and X-ray absorption fine structure spectroscopy of the Fe and Co K-edge. The catalytic properties of the products were investigated by residual oil hydrocracking reactions. Characterization results showed that the FeCo-MFI/MCM-41 composite simultaneously possessed two kinds of stable meso- and micro-porous structures. Iron and cobalt ions were incorporated into the silicon framework, which was confirmed by H2 temperature programmed reduction and X-ray absorption fine structure spectroscopy. This composite presented excellent activities in hydrocracking of residual oil, which was superior to the pure materials of silicate-1/MCM-41.

In this study, we investigated the Cr(VI) uptake mechanism in an indigenous Cr(VI)-tolerant bacterial strain - Bacillus cereus through batch and microscopic experiments. We found that both the cells and the supernatant collected from B. cereus cultivation could reduce Cr(VI). The valence state analysis revealed the complete transformation from Cr(VI) into Cr(III) by living B. cereus. Further X-ray absorption fine structure and Fourier transform infrared analyses showed that the reduced Cr(111) was coordinated with carboxyl and amido functional groups from either the cells or supernatant. Scanning electron microscopy and atomic force microscopy observation showed that noticeable Cr(III) precipitates were accumulated on bacterial surfaces. However, Cr(111) could also be detected in bacterial inner portions by using transmission electron microscopy thin section analysis coupled with energy dispersive X-ray spectroscopy. Through quantitative analysis of chromium distribution, we determined the binding ratio of Cr(111) in supernatant, cell debris and cytoplasm as 22%, 54% and 24%, respectively. Finally, we further discussed the role of bacterium-origin soluble organic molecules to the remediation of Cr(Vi) pollutants. (C) 2011 Elsevier Ltd. All rights reserved.

Si 1− x Mn x diluted magnetic semiconductor films were deposited on the p-Si (100) single crystal wafer using magnetron sputtering method. Post-rapid thermal annealing treatments were performed at temperatures of 700 °C, 800 °C, and 900 °C in an argon atmosphere for approximately 5 min. Alternating gradient magnetometer, scanning electron microscope, atomic force microscope, X-ray diffraction and X-ray absorption near-edge structure spectra were employed to characterize magnetic properties and structure of the as-grown and annealed films. The films were about 2.8 μm thick and the RMS roughness of the surface was about 5–10 nm. All samples exhibit ferromagnetism at room temperature and the saturation magnetization reaches at the maximum value for the sample annealed at 700 °C. The silicide MnSi 1.7 was observed in the annealed samples. X-ray absorption near-edge structure spectra indicated that Mn atoms preferred to occupy substitutional or interstitial sites instead of precipitating to form silicide when annealing at 700 °C. It is inferred that the observed ferromagnetism is attributed to the interstitial and substitutional Mn dimers, which existed mostly in the sample annealed at 700 °C. The weaker ferromagnetism of the 900 °C annealed sample was closely related to the increased content of Mn 4 Si 7 compound.

Here we report that the occupation sites of Co atoms in ZnO matrix could be effectively tuned by the concentration of Cu codopant. The Co–Cu codoping effect has been revealed by a combination of X-ray diffraction and X-ray absorption fine structure spectroscopy techniques for Zn0.95–xCuxCo0.05O (0.005 ≤ x ≤ 0.08) thin films grown by pulse laser deposition at 923 K. Specifically, at the low Cu doping levels (x ≤ 0.02), the Co(+2) ions are substantially incorporated into the ZnO lattice; upon increasing the Cu concentration to 0.03 or higher, partial formation of Co(0) species occurs, and its proportion rises rapidly with the Cu concentration. Further analysis shows that the Cu codopants are precipitated to form Cu(0) metallic phase in all the samples. We propose a competition mechanism between the Co(0)–Cu(0) metallic interactions and the dissolution of Co ions in ZnO to interpret these findings.

The structures of selenium nanoparticles and nanotubes synthesized by the dismutation of precursor Na2SeSO3 under acidic condition in micellar solution are studied by transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray absorption fine structure spectroscopy (XAFS). Spherical-like nanoparticles contain both amorphous and crystalline parts while, as shown by XRD patterns, nanotubes have the crystal structure of trigonal selenium (t-Se). They display quite different XANES spectral features indicating different local atomic arrangements. Theoretical XANES calculations show that the local structure around Se atom in the nanotubes is similar to a hexangular cylinder. Quantitative extended XAFS (EXAFS) analysis further shows that the average Se–Se bond length for both nanotubes and nanoparticles is 2.35 A.

The Morlet wavelet transformation (MT) was used to analyze Mn K-edge extended X-ray absorption fine structure (EXAFS) spectra of Mn-doped Si-based diluted magnetic semiconductor (DMS) thin films grown by the magnetron co-sputtering method. MT of EXAFS data shows that the Mn–Mn scattering path can be distinguished by the Mn–Si scattering path in the spectra of Mn x Si1−x DMS thin films. In all DMS thin films Mn atoms fill Si sites without forming Mn–Si compounds while Mn–Si compounds are present in the annealed analogues. From the analysis of experimental data we point out that low-concentration Mn-doped samples are characterized by a more symmetric structure.

The efficient absorption of visible light is crucial for improving the photocatalytic activity of foreign species-doped TiO2. With first-principles calculations, we explore the effects of phosphorus doping on mediating the photocatalytic activity of anatase. It is found that the P impurity tends to occupy the cation site in TiO2; more importantly, there exists a critical phosphorus concentration of about 0.7% for maximizing the absorption of solar light. The optical energy gap is narrowed by ∼0.3 eV at the low doping concentration of 0.7%, whereas it increases with P concentration at the higher P concentration region of 0.7−3.1 atm. %. These results suggest that the dopant concentration dependence might be responsible for numerous seeming controversies of optical absorption observed in experiments. This finding points to a possibility of tailoring the optical absorption of TiO2 by varying the dopant content.

The Co100−xNix (x = 0, 30, 50, and 70) bimetallic nanoparticles (NPs) synthesized by a solvothermal method show interesting shape changes from aggregated clusters to ordered nanorings with increasing Ni concentration. A comprehensive structural study of these Co100−xNix NPs is performed with X-ray diffraction and X-ray absorption fine structure spectroscopy. It is shown that the pure Co NPs consist of a majority of the fcc structure and a minority of the hcp phase. When 30% Ni is added, alloyed Co−Ni NPs with an inhomogenous atomic distribution are formed. The further addition of Ni to ≥50% could considerably improve the crystallinity and homogeneity of the alloyed NPs, as suggested by the fact that the disorder degree (σ2) is gradually lowered and the coordination number ratios NCo−Co/NCo−Ni and NNi−Ni/NNi−Co gradually approach the stoichiometry of the NPs. The ordered and homogeneous fcc structure helps to strengthen the magnetocrystalline anisotropic interactions, which may facilitate the head-to-tail ...

Protein splicing is a unique post-translational process in which an intein excises itself from a precursor with the concomitant ligation of flanking sequences. The binding of zinc to intein inhibits protein splicing reversibly and EDTA relieves the inhibition. Copper was found to inhibit protein trans splicing; however, the recovery of intein splicing required both EDTA and TCEP, suggesting a different inhibition mechanism for copper compared to zinc. In this work, we have investigated the binding properties and inhibition effects of copper ions on the RecA intein from Mycobacterium tuberculosis. Both Cu(+) and Cu(2+) exhibited high binding affinity to inteins, while different binding sites were identified. Cu(2+) coordinates to Cys1, the key residue involved in the mechanism of protein splicing, however, Cu(+) does not coordinate to cysteine. An in vitro inhibition assay indicated that monovalent Cu(+) demonstrates reversible inhibition to protein splicing, and the inhibitory efficiency is comparable to Zn(2+). Redox reaction between Cu(2+) and cysteine in inteins were observed and the rate constants were determined. The results suggested a dual role for Cu(2+) in the inhibition of intein splicing: strong coordination of Cu(2+) to key residues (including Cys1) in the intein, and subsequent oxidation of Cys1, the residue required for the N-->S acyl shift step in protein splicing. A kinetic study suggested that the coordination could be the major cause of inhibition effect of Cu(2+) initially, whereas the redox reaction could play an additional role in inhibition at a later stage.

Single phase Co-doped ZnO dilute magnetic semiconductor nanowire was synthesized by a chemical solution method and characterized by X-ray absorption fine structure (XAFS). The Co K-edge XAFS spectroscopy reveals that the doped Co ions are substantially incorporated into the ZnO host lattice. Moreover, the spatial occupation of Co dopants in Zn0.98Co0.02O nanowire is resolved further by the detailed O K-edge XANES analysis. We suggest that the Co ions are randomly doped into the ZnO matrix and located at the Zn sites. The magnetization measurement of the Co-doped ZnO nanowire shows the room temperature ferromagnetic characteristic with a relatively larger saturation magnetization. Furthermore, we suggest that the enhanced ferromagnetism can be ascribed to the coeffect of the size effect and the homogeneity of Co dopants for Zn0.98Co0.02O nanowire, which will make it useful in nanometer spintronic devices.

Hybrid-nanostructure Ag−Zn0.92Co0.08O dilute magnetic semiconductors synthesized by a solvothermal method show that the magnetic property of the nanorods is changed from paramagnetism to room-temperature ferromagnetism when 2% Ag is codoped into Zn0.92Co0.08O nanorods. The detailed analysis of the X-ray absorption fine structure spectra at both Co and Ag K-edge reveals that a substantial part of Ag atoms exists in the tetrahedral interstitial sites of (Zn, Co)O matrix in the Ag(2%)−Zn0.92Co0.08O. We suggest that the interstitial Ag atoms, together with Ag nanoparticles, play a most important role in mediating the high-temperature ferromagnetism of Ag(2%)−Zn0.92Co0.08O, due to the strong hybridization between the Co 3d states and the spin-split impurity band at the Fermi level.

Infrared-to-visible upconversion emission intensities are investigated in Li+ and Er3+ codoped ZnO nanocrystals. Li+ ions doped in ZnO/Er3+ nanocrystals can greatly enhance the upconversion emission intensity of Er3+ ions. The extended X-ray absorption fine structure spectroscopy data show that both the Er−O bond length and coordination number of the Er−Er bond have been altered by introducing Li+ ions in the ZnO/Er3+ nanocrystals. The variation of Er−O bond length leads to the change in the local asymmetry around Er3+ ions. Meanwhile, the greater coordination number of the Er−Er bond causes stronger interaction between neighboring Er3+ ions and, hence, strengthens the reaction Er3+ (4F7/2) + Er3+ (4I11/2) → 2Er3+ (4F9/2). In this process, the 4F9/2 state is a metastable state that could be excited to the 2H9/2 state by absorbing one photon at high excitation power. Li+ ions also can reduce the OH groups in specimen, which is the other reason for enhancing the upconversion emission intensities.

The structural evolutions of the mechanically alloyed ternary Al 70 Cu 20 Fe 10 powders with the milling times and the annealing treatment were studied by X-ray diffraction (XRD) and X-ray absorption fine structure (XAFS). It was found that during the milling process, only Cu can incorporate into the lattice of Al to form an Al 2 Cu compound or an AlCu solid solution, depending on the milling times. However, Fe remains the original structure of bcc α-Fe. Annealing treatment at 700 °C for 4 h can drive the α-Fe to react with the Al 2 Cu compounds and AlCu solid solution, and the main products of the annealed Al 70 Cu 20 Fe 10 (10 h) and the annealed Al 70 Cu 20 Fe 10 (40 h) are the icosahedral Al 65 Cu 20 Fe 15 quasicrystal and the Al(Cu, Fe) solid solution, respectively. The local structural disorders around Fe and Cu atoms in the icosahedral QC phase is about 50% larger than those of the Al(Cu, Fe) solid solution.

The interfacial and surface structures of CeO2−TiO2 mixed oxides prepared by the sol−gel method have been investigated in detail by means of X-ray diffraction (XRD), BET surface area measurement, X-ray absorption spectroscopy (XAS), high-resolution transmission electron microscope (HRTEM), and selective chemisorption of methyl orange. TiO2 and CeO2 are in the anatase phase and the cubic fluorite phase in CeO2−TiO2 mixed oxides, respectively. The mixed oxides exhibit much higher surface areas than the individual oxides and are with both mesopores and micropores. XAS results suggest that Ce atoms nucleate as cubic [CeO8] polyhedrons with the formation of a Ce−O−Ti interface in mixed oxides. With the increasing Ce/TiO2 weight ratio, the cubic fluorite CeO2 crystallites gradually develop. TiO2 anatase forms ultrafine particles in mixed oxides, whose local structure is stabilized by the presence of CeO2. HRTEM results reveal that the exposed surfaces of mixed oxides depend on the Ce concentration. Chemisorptio...

Endowing transition-metal oxide electrocatalysts with high water oxidation activity is greatly desired for production of clean and sustainable chemical fuels. Here, we present an atomically thin cobalt oxyhydroxide (γ-CoOOH) nanosheet as an efficient electrocatalyst for water oxidation. The 1.4 nm thick γ-CoOOH nanosheet electrocatalyst can effectively oxidize water with extraordinarily large mass activities of 66.6 A g(-1), 20 times higher than that of γ-CoOOH bulk and 2.4 times higher than that of the benchmarking IrO2 electrocatalyst. Experimental characterizations and first-principles calculations provide solid evidence to the half-metallic nature of the as-prepared nanosheets with local structure distortion of the surface CoO(6-x) octahedron. This greatly enhances the electrophilicity of H2O and facilitates the interfacial electron transfer between Co ions and adsorbed -OOH species to form O2, resulting in the high electrocatalytic activity of layered CoOOH for water oxidation.

X-ray absorption fine structure (XAFS) has experienced a rapid development in the last three decades and has proven to be a powerful structural characterization technique nowadays. In this review, the XAFS basic principles including the theory, the data analysis, and the experiments have been introduced in detail. To show its strength as a local structure probe, the XAFS applications in semiconductors are summarized comprehensively, that is, thin films, quantum wells and dots, dilute magnetic semiconductors, and so on. In addition, certain new XAFS-related techniques, such as in-situ XAFS, micro-XAFS, and time-resolved XAFS are also shown.

Fluorescence x-ray absorption fine structure and x-ray diffraction are used to study the structures of super-hard TiN/Si3N4 multilayer films deposited by reactive magnetron sputtering at temperatures of 20, 200, 500 and 800 °C. The results clearly reveal the presence of interfacial intermixing between adjacent TiN and Si3N4 layers. And the interlayer is composed of TiSixN1−x solid solution with an NaCl-like structure. Increasing the growth temperature from 20 to 500 °C, the crystalline quality of the pure TiN layer improves significantly, and the thickness of the interlayer rises from 2.5 to 5.0 A. For the TiN/Si3N4 multilayer film grown at 500°C, the interfacial layer is composed of TiSi0.24N0.76 solid solution, where the Ti–N bond length (2.07 A) is largely shrunk as compared with the value (2.12 A) in the pure TiN layer. When growth temperature rises to 800°C, the composition of the interfacial layer becomes TiSi0.3N0.7 and reaches a thickness of 7.8 A. We propose that the TiSixN1−x interlayer with obviously contracted Ti–N bond length is an important hardening factor for the crystalline/amorphous TiN/Si3N4 multilayer films grown at high temperatures.

A method of incorporating iron onto the mesoporous silica network using potassium ferricyanide (K 3 Fe (CN) 6 ) as the iron source was established. The Fe (CN) 6 3 + ions interact with the template and attached onto the silica network after the as-synthesized sample calcined at 823 K. FT-IR spectroscopy provided a clear evidence for the interaction between cyanide ligands and template. XANES spectroscopic displayed that the Fe 3 + changed from octahedral to tetrahedral coordinated during thermal treatment. XRD and HRTEM results indicated that the iron ions incorporated onto the silica network without destroying the lattice structure of the parent MCM-41. The synthesized material exhibited a good activity for phenol hydroxylation.

There remains a pressing challenge in the efficient utilization of visible light in the photoelectrochemical applications of water splitting. Here, we design and fabricate pseudobrookite Fe2TiO5 ultrathin layers grown on vertically aligned TiO2 nanotube arrays that can enhance the conduction and utilization of photogenerated charge carriers. Our photoanodes are characterized by low onset potentials of ~0.2 V, high photon-to-current efficiencies of 40–50% under 400–600 nm irradiation and total energy conversion efficiencies of ~2.7%. The high performance of Fe2TiO5 nanotube arrays can be attributed to the anisotropic charge carrier transportation and elongated charge carrier diffusion length (compared with those of conventional TiO2 or Fe2O3 photoanodes) based on electrochemical impedance analysis and first-principles calculations. The Fe2TiO5 nanotube arrays may open up more opportunities in the design of efficient and low-cost photoanodes working in visible light for photoelectrochemical applications. Metal oxides are desirable photoanode materials due to their low cost and chemical stability, but they only work in the ultraviolet range. Here, Liu et al. design anode architecture that can absorb the visible light, while maintaining photon-to-current efficiency of 40% at an onset potential of 0.2 V.

The growth mechanism of glutathione (GSH) capped ZnSe quantum dots (QDs) obtained from the aqueous synthesis method is studied by in situ X-ray absorption fine structure (XAFS) utilizing a flow reactor and synchrotron radiation. Detailed analysis of the Se K-edge EXAFS data reveals that the growth of ZnSe QDs from aqueous synthesis undergoes a fast nucleation process and then a slow growth stage, which follows the two-stage growth mechanism. The ZnSe QDs are strained to minimize the total free energy, and the contraction of Se-Zn bond relaxes with time. This shows the promising capability of in situ XAFS to investigate the growth process of nano-materials synthesized by chemical solution method. (C) 2010 Elsevier B.V. All rights reserved.

We present a x-ray microscopy technique based on structured illumination in a microscope that characterizes the size of the subresolution-limit features. The technique is effective for characterizing fine structures substantially beyond the Rayleigh resolution of the microscope. We carried out optical experiments to demonstrate the basic principle of this new technique. Experimental results show good agreement with theoretical predictions. This technique should find a wide range of important imaging applications with a feature size down to nanometer scale, such as oil and gas reservoir rocks, advanced composites, and functional nanodevices and materials.

We report the microstructure, gas-sensing properties of the ordered mesoporous Co3O4 prepared by modified KIT-6 template method. Highly ordered mesoporous nanostructures of the as-prepared products have been characterized by X-ray diffraction (XRD), extended X-ray absorption fine structure (EXAFS), high-resolution transmission electron microscopy (HRTEM) and N2 adsorption/desorption analysis. We find that the ordered mesoporous Co3O4 enables a significant improvement of sensor response and selectivity to ethanol, which demonstrates the potential use of the ordered mesoporous Co3O4 as alcohol gas-sensing material. Through the analysis of microstructure including HRTEM and N2 adsorption/desorption, the sensing properties for the ordered mesoporous Co3O4 can be attributed qualitatively to its large specific surface area and porous morphology. Moreover, the results of EXAFS illustrate that the disorder degree and unsaturated bond of the ordered mesoporous Co3O4 increase, which agree well with the results observed in gas sensors. This makes the nanostructured ordered mesoporous Co3O4 a promising sensor material for detecting the alcohol gas.

Sample radiation damage is one of the main drawbacks limiting applications of the x-ray phase-contrast imaging method. Recently, for x-ray grating-based phase contrast imaging, the reverse projection (RP) method has been proposed by Zhu et al. [Proc. Natl. Acad. Sci. U.S.A. 107, 13576-13581 (2010)]. Compared to the conventional phase stepping technique, the RP method allows a strong reduction of the exposure time and minimization of the errors induced by mechanical vibrations. However, so far, it has only been considered for parallel beam illumination, typical of a synchrotron radiation source. In this paper, a generalization of the RP method from parallel beam geometry to fan beam geometry was presented and discussed.Within parallel beam geometry, the RP method utilizes the conjugate characteristic between reverse projection images. Nevertheless, this characteristic is not directly satisfied for fan beam geometry. In this study, a phantom composed of known materials was constructed and the projection images of the phantom were calculated in a fan beam geometry. By considering single ray, the conjugate images of the projection images were derived from the projection dataset. After that, using the modified RP method the authors retrieved phase and absorption information from paired images.Extracted phase and absorption information of the phantom were in good agreement with theoretical values. Additionally, the slice reconstruction was performed and the results turned out to be in the authors' expectation.Theoretical calculations and numerical simulations confirm both feasibility and validity of the RP method under fan beam illumination. Because this method is simple, fast, and releases a relatively low dose, the authors believe that this research is very useful for the x-ray phase contrast imaging applications in clinical diagnosis, bioresearch, and industrial nondestructive testing.

Elemental codoping has been an effective way to regulate the structural and electronic properties of semiconductors. By using x-ray diffraction and x-ray absorption fine structure spectroscopy, we investigate the local structure and spatial occupations of Co dopants in Cu-doped ZnO thin films prepared by pulsed-laser deposition method. It is revealed that the Co dopants are substantially incorporated into ZnO matrix when the deposition temperature is increased up to 650 °C, although the preferential orientation of ZnO film is changed. The results provide experimental guidance in the synthesis of the co-doped ZnO based dilute magnetic semiconductors.

Cosmic dust grains (CD) are part of the evolution of stars and planetary systems and pervade the interstellar medium. Thus, their spectral signature may be used to deduce the physical features of the observed astronomical objects or to study many physical and chemical processes in the interstellar medium. However, CD samples are available only from sample-and-return space missions. Thus, they are rare and not sufficient to be used to perform laboratory experiments of astrophysical interest, such as to produce reference spectra. In this contribution, we describe a new physical vapor deposition (PVD) technique that allows the production of amorphous samples with controlled chemical and morphological characteristics. In particular, this technique was developed to grow uniform or microstructured layers of Mg-Fe amorphous silicates (olivine or pyroxene) that are materials of wide interest for laboratory experiments. We discuss the first results that were achieved by applying this new synthesis method. The layers were studied by combining infrared spectroscopy, scanning electron microscopy, and X-ray spectroscopy. The X-ray microscopy was used for the first time to characterize the internal structure of the grains in these synthetic samples. Finally, future improvements of the technique and foreseen applications are discussed.

The driving mechanism of the metal-insulator transition (MIT) in VO(2) has always attracted attention, in particular with regards to understanding if and how the doping mechanism may tune the MIT transition temperature. However, due to the lack of detailed local structural information, in this oxide the underlying MIT mechanism is still matter of debate. In this contribution on the V(1-x)W(x)O(2) system, we attempt to clarify the origin of the MIT induced by tungsten doping. Combining W L(3)-edge and V K-edge extended X-ray absorption fine-structure (EXAFS) spectroscopy, the local structures around both V and W have been obtained. The data point out the occurrence of internal stress along the V-V chains induced by doping. It reaches a critical value that remains constant during the transition. The main effect of the internal stress on the vanadium local structure has also been identified. Actually, upon increasing the dopant concentration, the tilt of the V-V pairs towards the apex oxygen atoms in the VO(6) octahedron decreases while the V-V bond lengths remain unchanged. The electronic structure has also been investigated by O K-edge X-ray absorption near-edge structure (XANES) spectroscopy. Actually, at high doping concentrations the interaction of O(2p) and the V d(∥) state increases, while the hybridization of O(2p) and V π* decreases. The O(2p)-V(3d) hybridization is therefore an essential parameter correlated with the decreasing transition temperature in the V(1-x)W(x)O(2) system.

Understanding the formation process in the controlled synthesis of nanocrystals will lead to the effective manipulation of the morphologies and properties of nanomaterials. Here, in-situ UV-vis and X-ray absorption spectroscopies are combined to monitor the tracks of the nucleation pathways in the solution synthesis of platinum nanocrystals. We find experimentally that the control over nucleation pathways through changing the strength of reductants can be efficiently used to manipulate the resultant nanocrystal shapes. The in-situ measurements show that two different nucleation events involving the formation of one-dimensional "Pt(n)Cl(x)" complexes from the polymerization of linear "Cl(3)Pt-PtCl(3)" dimers and spherical "Pt(n)(0)" clusters from the aggregation of Pt(0) atoms occur for the cases of weak and strong reductants; and the resultant morphologies are nanowires and nanospheres, respectively. This study provides a crucial insight into the correlation between the particle shapes and nucleation pathways of nanomaterials.

The mesoporous ferrisilicates (MFS) with high iron content were synthesized by pH-modification method, and the iron content could be up to 10.5 wt.% (Si/Fe = 8). The pH was kept less than 2 at pre-hydrothermal synthesis step and was adjusted to 11 during hydrothermal step. The samples were characterized by XRD, HRTEM, N2-sorption, XRF, FTIR, DRUV–vis, Fe K-edge EXAFS, EPR, and DSC. The results suggested that the MFS materials were ordered 2D hexagonal mesophase of MCM-41, and the iron atoms were tetrahedral coordinated in the silica framework. This material could efficiently catalyze the hydroxylation of phenol in water medium using H2O2 as an oxidant, and the phenol conversion could be up to 52% under the optimal experimental conditions.

Understanding the initial nucleation mechanism of monodisperse nanocrystals (NCs) during synthesis process is an important prerequisite to control the desired sizes and to manipulate the properties of nanoscale materials. The acquisition of information for the small nanocluster nucleation process, however, still remains challenging. Here, using a continuous-flow in situ X-ray absorption fine structure (XAFS) spectroscopy for time-resolved studies, we have clarified the initial kinetic nucleation of Au clusters under the grain size of 1 nm for the classical Au NCs synthesis via the reduction of AuCl(4)(-) in aqueous solution. The in situ XAFS results present the experimental revelation of the formation of intermediate Cl(3)(-)Au-AuCl(3)(-) dimer and the subsequent higher complexes 'Au(n)Cl(n+x)' in the initial nucleation stage. We propose a kinetic three-step mechanism involving the initial nucleation, slow growth, and eventual coalescence for the Au NCs formation, which may be helpful for the synthesis of metallic nanomaterials.

Synchrotron radiation (SR) is a fundamental tool for X-ray research. In particular, X-ray absorption spectroscopy (XAS) accesses information as electronic properties, local structure or chemical-physical state in condensed-matter studies. Ionization chambers (ICs) are the most widely used XAS detectors for transmission measurements because of their reliability, high linearity and good stability. Recently, solid-state detectors have been considered and Si p-i-n has been applied to high fluxes (10{sup 11} ph/s), where the linearity of ICs is no longer guaranteed. Silicon photodiodes exhibit an extremely linear response in at least 5 decades but show diffraction peaks. Diamond is an ideal substrate to produce radiation-hard, low dark current (

Single-walled carbon nanotubes (SWNTs) synthesized with different methods are investigated by using multiple characterization techniques, including Raman scattering, optical absorption, and X-ray absorption near edge structure, along with X-ray photoemission by following the total valence bands and C 1s core-level spectra. Four different SWNT materials (produced by arc discharge, HiPco, laser ablation, and CoMoCat methods) contain nanotubes with diameters ranging from 0.7 to 2.8 nm. The diameter distribution and the composition of metallic and semiconducting tubes of the SWNT materials are strongly affected by the synthesis method. Similar sp 2 hybridization of carbon in the oxygenated SWNT structure can be found, but different surface functionalities are introduced while the tubes are processed. All the SWNTs demonstrate stronger plasmon resonance excitations and lower electron binding energy than graphite and multiwalled carbon nanotubes. These SWNT materials also exhibit different valence-band X-ray photoemission features, which are considerably affected by the nanotube diameter distribution and metallic/ semiconducting composition.