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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.

First-principles study on the energetic stability, electronic structure, and magnetic coupling in Mn-doped silicon with various configurations has been performed systematically. The results show that the poly-Mn atoms prefer to aggregate in the Mn-doped silicon dilute magnetic semiconductor. It is found that the tetrahedral interstitial Mn $({\text{Mn}}_{T})$ atoms assemble together via an intervening substitutional Mn $({\text{Mn}}_{\text{Si}})$ ion, subsequently forming the generally favored ${\text{Mn}}_{T}{\text{-Mn}}_{\text{Si}}{\text{-Mn}}_{T}$-type complexes. The dominant $d\text{\ensuremath{-}}d$ exchange interactions between the ${\text{Mn}}_{\text{Si}}$ and ${\text{Mn}}_{T}$ make all Mn ions in the ${\text{Mn}}_{T}{\text{-Mn}}_{\text{Si}}{\text{-Mn}}_{T}$ structures interact ferromagnetically with each other.

Structural studies become increasingly important for understanding the nature of magnetic properties in dilute magnetic semiconductors (DMSs) [K. Ando, Science 312, 1883 (2006)]. In this work, x-ray absorption fine structure (XAFS) at both Co and $\text{O}\text{ }K$ edges is used to investigate the Co occupation sites and distributions in ${\text{Zn}}_{1\ensuremath{-}x}{\text{Co}}_{x}\text{O}$ thin films with low Co concentrations $(x=0.005,0.02)$. $\text{Co}\text{ }K$-edge XAFS analysis indicates unambiguously that the doped Co ions are substantially incorporated into the ZnO host lattice. However, the $\text{O}\text{ }K$-edge XAFS spectral features are strikingly different from those of ZnO and ${\text{Zn}}_{1\ensuremath{-}x}{\text{Co}}_{x}\text{O}$ reported in the literature so far, and can be reproduced by the assembling of substitutional Co ions around intervening oxygen atoms. This provides experimental evidence for numerous theoretical predications that the substitutional Co ions in ZnO tend to gather together. It is expected that similar phenomenon can also be observed by XAFS in a number of other ZnO-, GaN-, and ${\text{TiO}}_{2}$-based DMSs for which the clustering of substitutional dopants have been previously predicted.

First-principles calculations were performed to study the electronic structure and magnetic interactions of ${\mathrm{Mn}}_{\mathrm{Ga}}\text{\ensuremath{-}}{\mathrm{Mn}}_{\mathrm{I}}$ dimer formed by the neighboring substitutional ${\mathrm{Mn}}_{\mathrm{Ga}}$ and interstitial ${\mathrm{Mn}}_{\mathrm{I}}$ ions in the zinc-blende structured $(\mathrm{Ga},\mathrm{Mn})\mathrm{N}$ dilute magnetic semiconductor. On the basis of the formation energy calculations, we show that the clustering of ${\mathrm{Mn}}_{\mathrm{Ga}}$ and ${\mathrm{Mn}}_{\mathrm{I}}$ in $(\mathrm{Ga},\mathrm{Mn})\mathrm{N}$ is energetically favored. The ${\mathrm{Mn}}_{\mathrm{Ga}}$ and ${\mathrm{Mn}}_{\mathrm{I}}$ ions in the ${\mathrm{Mn}}_{\mathrm{Ga}}\text{\ensuremath{-}}{\mathrm{Mn}}_{\mathrm{I}}$ dimer are antiferromagnetically coupled, but this cannot strikingly reduce the magnetic moments induced by ${\mathrm{Mn}}_{\mathrm{Ga}}$ due to the strong localization character of ${\mathrm{Mn}}_{\mathrm{I}}$ gap states. It is found that ${\mathrm{Mn}}_{\mathrm{Ga}}\text{\ensuremath{-}}{\mathrm{Mn}}_{\mathrm{I}}$ dimer in zinc-blende structured $(\mathrm{Ga},\mathrm{Mn})\mathrm{N}$ possesses unique electronic and magnetic properties, as compared with their counterparts in wurtzite structured $(\mathrm{Ga},\mathrm{Mn})\mathrm{N}$ or zinc-blende structured $(\mathrm{Ga},\mathrm{Mn})\mathrm{As}$. The present study can provide some insight into understanding the rather scattered magnetic moment per Mn ion observed experimentally.

XAFS technique is used to determine the atomic and electronic structures of NiP amorphous alloys with different P concentrations prepared by chemical reduction method. From the radial structural function (RSF) obtained from EXAFS, it is found that the amorphous alloys with P content less than 10 at.% still present strong peaks corresponding to high coordination shells just like crystalline Ni. This indicates the prominent existence of Ni‐rich phase with the fcc‐structure, which is not remarkably modified by the P atoms. As the P content is as large as 14 at.%, only the first shell peak in the RSF can be observed and the higher shell peaks disappear. Therefore the sample is totally amorphous. The XANES results show that as the P concentration is above 26 at.%, charge transfers from Ni atoms to P atoms. For P concentration lower than 20at.%, on the contrary, charge transfers from P atoms to Ni atoms, and 3d electron density of Ni atoms reaches the maximum when P concentration is about 14∼20 at.%.

The local structure of dilute Ge impurity in the Si host has been studied by fluorescence x‐ray absorption fine structure spectra through multiple‐scattering data analysis method. Contrary to the elongation of 0.029 A for the Ge‐Si distance in the first shell, the Ge‐Si interatomic distance in the second shell shows a contraction of about 0.013 A relative to the corresponding Si‐Si distance in the Si host. This coincides with the theoretical prediction by Mousseau and Thorpe [Phys. Rev. B 46, 15887 (1992)] which includes both the bond length mismatch and bond‐angle deviation. It turns out that the contraction of the second‐shell Ge‐Si distance is due to the deviation of Ge–Si–Si bond‐angle from the ideal tetrahedral angle. From the Ge‐Si distances within the first three shells, it is revealed that the dilute Ge doped into Si host can lead to the local distortion rather than the average lattice change.

The local structures of Si(20 monolayer)/Gen/Si(100) (n=1, 2, 4 and 8 monolayer) heterostructure films grown by molecular beam epitaxy (MBE) at 400 deg. C are investigated by grazing incidence fluorescence x-ray absorption fine structure. The Ge K-edge EXAFS analysis shows that the local structure of Ge atoms in the 1 or 2 monolayer (ML) Ge heterostructure film where the Ge atoms are dominantly surrounded by Si, is similar to that in Si0.95Ge0.05 alloy. With the thickness of the Ge monolayer increasing to 4 ML, the coordination environment around Ge atoms is close to that of Si70Ge30 alloy. Even for the 8-ML-thick Ge heterostructure film, the fraction of Ge-Si coordination pair in the first shell is as high as 55%, almost the same as that in Si0.50Ge0.50 alloy. These results clearly indicate the Ge migration effect in all Si/Gen/Si(100) heterostructure films, which is due to surface segregation of Ge atoms during growth process caused by large surface mobility of adatoms allowing for decreasing the surface strain.

There are many excellent charaters with adcanced ceramic composite materials, such as synthetical mechanic properties, wearability, anticorroseveness, heat resistance and high hardness. Therefore, these materials as an important part of the structural material are eagerly needed in modern industry, especialy for cutting tools, bearing, engine etc. It is common knowledge that composites are compounded by matrix and reinforced fibers or s, their physical, chemical and mechanical properties are of considerable difference. In order to achieve the optimum multiple qualities of composites, there must be an integral interface between fibers and matrix. The interface is the most important part of composite materials as following reason: (1) The interface directly affects the stress transmission and dispersion between the fiber and matrix, and affects the strength of the composite. (2) The interface controls the process of defect accumulation and transmission, and affects the breaking toughness of composite. (3) The interface strongly affects the stability via environmental and medium changes.1 The characterization and optimization of interface have been considered to be one of the main research techniques about composites, called the surface and interface engineering of composite.

ZnO-based nanogenerators with excellent performance and convenient functionalization are particularly desirable for self-powered technology, which is however difficult to achieve simultaneously in traditional piezoelectric ZnO nanogenerators. Here, we report a design of electrostatic ZnO nanogenerator by virtue of a type-II ZnO/ZnS core/shell nanostructure electrets, which can turn acoustic waves into electric power with an energy conversion efficiency of 2.2%. The ZnO/ZnS core/shell electrets are charged by ultraviolet irradiation with a long-term stability of the electrostatic charges under ambient condition. The electronic and atomic structure evolution in the charged ZnO/ZnS core/shell electrets are also discussed by detailed experimental and theoretical investigations. This design opens up an alternative path for fabricating robust ZnO-based nanogenerator for future nanotechnology application.

Electrochemical impedance spectroscopy has been used for the characterisation of electrodes modified with different polythiophenes, namely poly[4,4′-bis(butylsulfanyl)-2,2′-bithiophene], poly[4,4′-bis(methylsulfanyl)-2,2′-bithiophene] and poly(3-methylthiophene), at different applied potentials, using different supporting electrolytes. By comparison of the results obtained under experimental conditions in which n-doping is prevented and those obtained from tests where it does occur, some general features have been deduced, all of them being coherently described by a recently proposed ‘generalised transmission line circuit’ model: impedance plots at different applied potentials exhibit progressive changes which are well accounted for by the ‘evolving’ model. The results obtained on the n-doping process of S -alkyl substituted polymers suggest a behaviour interestingly similar to that exhibited in the p-doping; this supports a symmetry that was also found by us in a previous work, with respect to the incorporation and release of counterions during the n- and p-charge–discharge processes.

Bimetallic nanoparticles play an important role in potential industrial applications, such as catalysis, optoelectronics, information storage and biological labeling. Herein, homogeneous Cu-Pt core-shell nanoparticles with the averaged size of 8 nm have been synthesized by chemical methods. Cu atoms diffusion process, which motivated by heating, was observed in-situ by using temperature-dependent x-ray absorption fine-structure (XAFS) spectroscopy. Results show that Cu diffuse gradually from Cu core to Pt shell in these nanoparticles with increasing temperature. We also found the surface ligand (O) bonded Pt at the room temperature and were removed gradually by heating the sample. The analysis of the diffusion process in bimetallic nanoparticles will provide important guideline for their designing and tuning.

Pt-based alloys have recently triggered a lot of attentions due to their important potential industrial applications. They provide great opportunities for the development of low-cost and high-performance fuel-cell catalysts. Many studies have already pointed out the excellent physico-chemical properties of Pt-based alloys, intimately related to their internal structure. Great efforts have been spent to characterize shape, homogeneity, dispersion, alloying extent and kinetic growth of Pt-based nano-particles. Here, we present Cu-Pt bimetallic nano-particles synthesized by the thermal decomposition method under oleylamine and OE coordination. HRTEM images show that Cu-Pt nanostructures having size of about 1.2 nm includes about 35 atoms capped by the surfactant with OA. Accurate structural information of this system has been obtained by XRD and XAFS. A charge transfer mechanism has been observed and Pt occupied Cu sites in these Cu-Pt nanoparticles.

Purpose: 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. Methods: 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. Results: 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. Conclusions: 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. (C) 2013 American Association of Physicists in Medicine. [http://dx.doi.org/10.1118/1.4791672]

Understanding the kinetic mechanism during ligand adsorption on gold nanocrystals is important for designing and fine-tuning their properties and implications. Here, we report a kinetic study on the adsorption process of dodecanethiol ligands on Au nanocrystals of 3.3 nm by an in situ time-resolved X-ray absorption fine structure technique. A two-step process of dodecanethiol adsorption on Au NC surfaces is proposed based on the obtained ligand coverage, which shows a quick increase from 0 to 0.40 within the first 20 min, followed by a much slower increase to the limiting value of 0.94. In-depth analysis suggests that the first stage involves the quick adsorption of dodecanethiol to the corner and edge sites of Au NCs surfaces, leading to remarkable surface Au-Au bond length relaxation (from 2.79 to 2.81 angstrom) and pronounced gold-to-ligand charge transfer. The second step that corresponds to the much slower adsorption process to the surface facets could be described by the Langmuir kinetics equation with an adsorption rate constant of 0.0132 min(-1) and an initial coverage of 0.41, in good agreement with the initially preferable adsorption of thiols to the most favorable sites.

The controllable synthesis route of Co doped GaN nanowires was developed and the structural and magnetic properties of Co doped GaN nanowires were studied. The results indicate that Co atoms substitute Ga sites in GaN lattice, suggesting the intrinsic nature of ferromagentism at room temperature.

Homogeneous distribution of magnetic dopants in semiconductor hosts is highly desired for practical applications in spintronics. Herein, we show that codoping 2 at. % Cu with Zn0.98Co0.02O could change the magnetic behavior from paramagnetism to room temperature ferromagnetism. For Zn0.96Cu0.02Co0.02O nanocrystals prepared by a modified solid-state reaction method, the combination of x-ray absorption fine structure spectra at Co, Cu, and O K-edge reveals that the Cu and Co ions are substitutionally incorporated into the ZnO matrix and distribute randomly in the host. First-principles calculations further indicate strong hybridization between Co 3d states and Cu-induced donor impurity bands at the Fermi level, which effectively enhances the indirect ferromagnetic superexchange of Co ions and is responsible for the occurrence of ferromagnetism in (Co,Cu)-codoped ZnO.

The phase transition from tetragonal to hexagonal of crystalline BaTi1−xCoxO3 (0.01≤x≤0.20) powders prepared by solid state reaction has been studied by x-ray diffraction and x-ray absorption fine structure (XAFS). At the low Co doping level of x≤0.03, the structure of the samples is tetragonal, and it is transformed gradually to a hexagonal structure upon increasing Co content to ≥0.05. The detailed analysis of Co K-edge XAFS indicated unambiguously that the doped Co ions are substantially incorporated into the BaTiO3 host and likely serve as a trigger in leading the structure transition. On the basis of the formation energy calculations, we find that there exists a critical Co concentration in the x range of 0.027–0.055 for inducing the tetragonal-to-hexagonal structure transition of BaTi1−xCoxO3, in good agreement with the experimental observations.The phase transition from tetragonal to hexagonal of crystalline BaTi1−xCoxO3 (0.01≤x≤0.20) powders prepared by solid state reaction has been studied by x-ray diffraction and x-ray absorption fine structure (XAFS). At the low Co doping level of x≤0.03, the structure of the samples is tetragonal, and it is transformed gradually to a hexagonal structure upon increasing Co content to ≥0.05. The detailed analysis of Co K-edge XAFS indicated unambiguously that the doped Co ions are substantially incorporated into the BaTiO3 host and likely serve as a trigger in leading the structure transition. On the basis of the formation energy calculations, we find that there exists a critical Co concentration in the x range of 0.027–0.055 for inducing the tetragonal-to-hexagonal structure transition of BaTi1−xCoxO3, in good agreement with the experimental observations.

X-ray absorption near-edge structure (XANES) and first-principles calculations are employed to determine the Co spin state in the Co-doped TiO2 thin films. Based on the experiments and the theoretical calculations, we find that the transition of Co 1s electron to the unoccupied Co 3d eg states is clarified from the pre-edge single-peak in the Co K-edge XANES spectrum of the Co-doped TiO2 thin film, and that the Co 3d t2g states are occupied while the eg states are partially unoccupied. This suggests a low-spin configuration of the substitutional Co2+ in the Co-doped TiO2 thin film. The studies demonstrate the ability of Co K-edge XANES to provide information on spin state of Co ions in the Co-doped TiO2.

Substitutionally doped Si1−xMnx thin films were fabricated by a magnetron cosputtering method at a low growth temperature. X-ray absorption fine structure (XAFS) and x-ray diffraction (XRD) techniques were used to investigate the structures of the Si1−xMnx thin films. The XRD results exhibit that no secondary phases such as metallic Mn or Mn–Si compound can be detected. The detailed analysis of the extended XAFS together with the x-ray absorption near-edge structure spectra at the Mn K-edge unambiguously reveals that the doped Mn atoms are incorporated into the Si matrix and substitute for the Si sites in the Si lattice. The results clearly indicate that the Mn occupations in silicon thin films are quite sensitive to the growth conditions and the postannealing treatment.

The local structure of the doped Mn in the MnxSi1-x dilute magnetic semiconductors (DMSs) fabricated by magnetron cosputtering method are studied by fluorescence X-ray absorption fine structure (XAFS) at Mn K-edge. It is found that the occupation of Mn atoms in the MnxSi1-x DMS strongly depends on the Mn content. The Mn K-edge XAFS results indicate that for the sample with low Mn content (x = 0.03~0.08), the Mn atoms are incorporated into the lattice of Si, and substitute part of the Si sites. As the Mn content reaches 0.15, Mn atoms mainly form the phase of Mn1Si1 compound.

Fluorescence X-ray absorption fine structure (XAFS) technique was used to investigate the local structures of the doped Mn in the MnxGe1-x dilute magnetic semiconductors (DMSs) with different Mn content (x=0.07, 0.25, 0.36) prepared by magnetron cosputtering method. The results indicate that for the sample with low Mn content (x=0.07), the Mn atoms are mainly incorporated into the lattice of Ge, and locate at the substitutional sites of Ge atoms with the ratio of 75%. With the Mn content increasing to 0.25 or higher, only part of Mn atoms enter the lattice of Ge and the others exist in the form of the Mn5Ge3 phase whose content increases with the doped Mn concentration. It is found that, in the Mn0.07Ge0.93 the bond length of the first (Mn-Ge) shell is RMn-Ge = 2.50 A, which is bigger than the first (Ge-Ge) shell distance in Ge by about 0.05 A. These results imply that local structure expansion is induced by dilute Mn substituting into Ge sites.

X-ray absorption fine structure (XAFS) and first-principles calculations are effectively combined to establish correlations of fabrications, atomic and electronic structures as well as ferromagnetism for the Mn-doped dilute magnetic semiconductors (DMS), and to shed light on the magnetism origin for a variety of ZnO-, GaN-, and Si-based DMSs. The results of Mn:ZnO and (Mn,N):ZnO thin films reveal that either the existence of Zn vacancy or N substitution of O sites can stabilize the ferromagnetic interactions between neighboring Mn-Mn pairs, and enhance the magnetic moment per Mn. In a 2.5at.% Mn-doped GaN film, a part of substantial Mn ions is found to locate at the interstitial sites near the substitutional Mn ions, forming Mn-Mn dimers that possess unique electronic and magnetic properties. Similar phenomena have also been found in the Mn-doped Si system in which the interstitial Mn atoms intend to assemble together via an intervening substitutional Mn ion. We have proposed a pathway to understand the microscopic origin of ferromagnetism in the DMS materials from the viewpoint of experimental determination and theoretical calculations.

The x-ray absorption near-edge structure (XANES) and first-principles calculations were employed to study the local structure and magnetic origin of Co-doped rutile TiO2 thin film. It is found that the experimental Co K-edge XANES can be reproduced by the calculated spectrum of substitutional Co (CoTi) with O vacancy (VO), suggesting the coexistence of CoTi and VO in this system. First-principles total energy calculations further reveal that the O vacancy prefers to reside near the Co ion and substantially facilitates the impurity doping. The electronic structure analysis indicates that the O vacancy can mediate the ferromagnetic interaction between the CoTi ions and thus is responsible for the observed room-temperature ferromagnetism in the Co-doped TiO2-δ thin films.

We performed a first-principles study on the magnetism and electronic character of rutile Fe:TiO2(110) mediated by oxygen vacancies (OVs) and codopant. The results show the magnetic interaction between Fe ions is a ferromagnetic (FM) superexchange nature, while the presence of OV makes it turn to an antiferromagnetic behavior. It is found when the system is codoped with oppositely charged P, the interactions are rehabilitated to FM coupling. The electronic structure analysis reveals that this is principally attributed to the sp-d hybridizations between P and Fe, which finally activate a long-ranged FM interaction between the Fe ions, and substantially facilitate the electron transport.

The complicated three-dimensional interior structures of the polycrystalline hollow zinc oxide microspheres were clearly obtained by the nondestructive nanocomputed tomography (nano-CT) technique. The parameters such as diameter, volume, porosity, and surface area were calculated by the quantitative analysis of reconstructed data. Especially, three single selected particles with different typical structures were separated and compared. With these results, the distinction of the particles can be clearly understood in nanoscale. This study reveals that nano-CT is an effective and competent tool for investigating the three-dimensional interior structures of nanomaterials in the natural environment.

Cu and Co ions co-doped Zn0.95?xCuxCo0.05O (0 ? x ? 0.08) diluted magnetic semiconductors (DMSs) prepared by the sol?gel method were investigated by x-ray absorption fine structure (XAFS). Although the Co K-edge XAFS data indicate that the doped Co ions are located substitutionally at the Zn sites for all the Zn0.95?xCuxCo0.05O DMSs, the CuK-edge XAFS analysis combined with XRD results reveals that the doped Cu ions are separated to form a CuO phase for samples calcined at 1073?K. After being sintered at a higher temperature of 1473?K, the Cu ions with low Cu concentration (x ? 0.02) are substantially incorporated into the ZnO host lattice, while a small proportion of CuO clusters still coexist in the samples with a higher Cu concentration (x ? 0.05). The solubility of the doped Cu ions in Zn0.95Co0.05O DMS is estimated as about 0.04. The results provide experimental guidance in the synthesis of the co-doped ZnO based DMSs.

The x-ray absorption near edge structure spectroscopy and first-principles calculations were combined to study the local and electronic structures of rutile Co:TiO2 thin film with room-temperature ferromagnetism. It was revealed that the CoTi2+ substituting the Ti site forms CoTi2+-VO complex with the O vacancy generated in the annealing process. The O vacancy induces a spin-split donor impurity band with a t2g character within the gap region. We proposed that the strong exchange interaction between the localized carriers captured by O vacancy and the substitutional Co ions leads to the ferromagnetism of the Co:TiO2 thin film.

This work shows the structural evolution of a Au-Sn bimetallic system during the nanoscale diffusion process. Based on X-ray absorption fine structure (XAFS) spectroscopy, X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectrometry (EDX), insights were obtained into the detailed composition and structure of the Au-Sn bimetallic system, demonstrating the sequential formation of stable Au/AuSn, AuSn, AuSn/AuSn(2) and AuSn(2) nanocrystals (Au/AuSn and AuSn/AuSn(2) refer to core/shell structures) rather than disordered alloys or alloys with an equal Sn atomic distribution. Furthermore, the formation mechanism of Au-Sn intermetallic compounds and their core/shell structures are discussed. Through elucidating the structural evolution in the diffusion process, we can easily guide the design of other novel bimetallic phases and their core/shell structures which could be predicted between the noble metals (Cu, Ag, Au) and the IIIA or IVA (In, Sn, Pb) metallic elements owing to the rapid diffusion mechanism.

Rock-salt structured single-phase Ni0.98Fe0.02O and Ni0.93Fe0.02Li0.05O thin films with room temperature ferromagnetism were grown by pulsed laser deposition. It is found that the Li codoping into Ni0.98Fe0.02O significantly increases the saturation magnetic moment by a factor of 2, i.e., from 0.32μB∕Fe rising to 0.67μB∕Fe. The x-ray absorption fine structure spectral analyses at Fe and O K edge reveal that in both samples, the impurities are substitutionally incorporated into the NiO host. The first-principles calculations show that substitutionally doping Li ions into NiO leads to a strong hybridization between the Fe 3d states and the spin-split acceptor band at the Fermi level. As a result, the Fe 3d electron configuration is altered and the effective magnetic moment per Fe ion is enhanced.

X-ray absorption fine structure (XAFS) and first-principles calculations were employed to study the structure and ferromagnetism origin of Zn0.97Mn0.03O thin film grown by metal organic chemical vapor deposition. The magnetization measurements indicate that this sample is ferromagnetic at room temperature. The Mn ions are located at the substitutional Zn sites as revealed by the Mn K-edge XAFS spectroscopy. Moreover, the O K-edge XAFS analysis indicated the existence of numerous Zn vacancies. Based on first-principles calculations, the authors propose that the Zn vacancy can induce the room-temperature ferromagnetism in Mn-doped ZnO.

The porous Co3O4 nanowires have been successfully synthesized via modified template method. A possible growth mechanism governing the formation of such 1D nanowires is proposed. The as-prepared products have been characterized by X-ray Powder Diffraction (XRD), Extended X-ray Absorption Fine-structure (EXAFS), High-resolution Transmission Electron Microscopy (HRTEM) and N2 adsorption/desorption analysis. Our systematic studies have revealed that the porous Co3O4 nanowires show excellent gas sensing performances, which demonstrate the potential application of the 1D nanostructured Co3O4 in the detection of the ethanol gas as a sensor material. The improved performances are owing to its large specific surface area and porous morphology.