The study of the structure and bioactivity of the B2O3 • Na2O • P2O5 system

In this study, we have investigated calcium and silicate‐free samples over a wide compositional range in the xB₂O₃·30 Na₂O·(70−x)P₂O₅ system, with 0 ≤ x ≤ 70 mol%, in order to determine the influence of the chemical composition on their structure and bioactive response in simulated body fluid. Information related to the chemical structures present in the network was obtained by means of Raman and infrared spectroscopy. For samples containing small amounts of P₂O₅, boron structures are preponderant. Upon increasing the phosphorus content, the samples' network is based on phosphate chains linked by boron groups through ‘P–O–B’ bridges. For high concentration of P₂O₅, the Q³ units form three‐dimensional network, whereas Q² units assist the chain formation. Regarding the in vitro assessment of bioactivity, the clear print of PO₄ asymmetric bending vibrations of apatite‐like layer in the 540–680 cm⁻¹ spectral domain, the scanning electron micrographs and energy dispersive x‐ray analysis spectra demonstrate that the studied borophosphate samples exhibit good bioactive response only for certain chemical compositions. More exactly, the highest bioactivity is obtained for 30% and 20% B₂O₃ (mol%) after 3 and 11 days of immersion, respectively. Therefore, the samples with 20–30 mol% boron content are valuable candidates that can be used as materials for tissue engineering applications. Copyright © 2013 John Wiley & Sons, Ltd.     

La/B4C small period multilayer interferential mirror for the analysis of boron

An La/B₄C multilayer interferential mirror with small period d (4.8 nm) was produced by diode sputtering for the detection of the boron K emission by wavelength‐dispersive x‐ray spectrometry at a large Bragg angle (close to 45°). The structure of the mirror was characterized by grazing incidence x‐ray reflectometry and its performance at the energy of the boron K emission (183 eV) was evaluated by means of polarized synchrotron radiation. Spectrometric measurements showed that the La/B₄C mirror improved the detection limit of boron using by a factor of 2 with respect to similar Mo/B₄C mirrors and by a factor of 4 with respect to a lead stearate crystal. Copyright © 2005 John Wiley & Sons, Ltd.     

<Superscript>57</Superscript>Fe NMR study of amorphous and rapidly quenched crystalline Fe-B alloys

Amorphous and crystalline Fe-B alloys (5–25 at % B) were studied using pulsed ⁵⁷Fe nuclear magneticr esonance at 4.2 K. The alloy samples were prepared from a mixture of the ⁵⁷Fe and ¹⁰B isotopes by rapid quenching from the melt. In the microcrystalline Fe-(5–12 at %) B alloys, the resonance frequencies were measured for local states of ⁵⁷Fe nuclei in the tetragonal and orthorhombic Fe₃B phases and also in α-Fe. The resonance frequencies characteristic of ⁵⁷Fe nuclei in α-Fe crystallites with substitutional impurity boron atoms in the nearest neighborhood were also revealed. In the resonance frequency distribution P(f) in the amorphous Fe-(18–25) at % B alloys, there are frequencies corresponding to local Fe atom states with short-range order of the tetragonal and orthorhombic Fe₃B phases. As the boron content decreases below 18 at %, the P(f) distributions are shifted to higher frequencies corresponding to ⁵⁷Fe NMR for atoms exhibiting a short-range order of the α-Fe type. The local magnetic structure of the amorphous Fe-B alloys is also considered.     

Photocatalytic Activities of Boron Doped Titanium Dioxide Nanoparticles and its Composite with Polyaniline

Abstract

Titanium dioxide (TiO₂) was doped with a nonmetalic element, boron (B), and the boron doped TiO₂ (B-TiO₂) was combined with polyaniline (Pani) through an in-situ polymerization technique. The photocatalytic activity of the prepared samples was monitored by the degradation of methylene blue under UV light irradiation. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy were used to reveal the effect of boron doping on the crystalline and chemical structure of the photocatalyst, respectively. The morphological and elemental compositional characteristics of the samples were evaluated using field emission scaning electron microscopy (FE-SEM) and energy dispersive x-ray analysis. The optical band gap energy of the prepared samples was obtained by UV-Visible (UV-Vis) spectroscopy. B-TiO₂ exhibited enhanced photocatalytic performance compared to the undoped photocatalyst. Furthermore, compared with TiO₂ and B-TiO₂, Pani/B-TiO₂ displayed superior photocatalytic activity. The composite achieved almost 26% methylene blue degradation within 150?minutes. Although the boron doping enhanced the crystallinity of TiO₂ slightly, it did not affect the morphology. FTIR confirmed the presence of tri-coordinated interstitial boron in the Ti–O–B bonds. The UV-Vis spectra displayed a red shift with the incorporation of the boron atoms. The incorporation of the boron atoms in the TiO₂ crystal structure are suggested to promote the separation of the photoinduced electron-hole pairs, a possible reason for the enhanced photocatalytic activity. B-TiO₂ and its composite with polyaniline could be considered as a promising photocatalyst to remove organic dyes from the wastewater.     

An etched multilayer as a dispersive element in a curved‐crystal spectrometer: implementation and performance

Etched multilayers obtained by forming a laminar grating pattern within interferential multilayer mirrors are used in the soft X‐ray range to improve the spectral resolution of wavelength dispersive spectrometers equipped with periodic multilayers. We describe the fabrication process of such an etched multilayer dispersive element, its characterization through reflectivity measurement and simulations, and its implementation in a high‐resolution Johann‐type spectrometer. The specially designed patterning of a Mo/B₄C multilayer is found fruitful in the range of the C K emission as the diffraction pattern narrows by a factor 4 with respect to the non‐etched structure. This dispersive element with an improved spectral resolution was successfully implemented for electronic structure study with an improved spectral resolution by X‐ray emission spectroscopy. As first results, we present the distinction between the chemical states of carbon atoms in various compounds, such as graphite, SiC and B₄C, by the different shape of their C K emission band. Copyright © 2012 John Wiley & Sons, Ltd.     

Insight into growth of Au–Pt bimetallic nanoparticles: an in situ XAS study

Au–Pt bimetallic nanoparticles have been synthesized through a one‐pot synthesis route from their respective chloride precursors using block copolymer as a stabilizer. Growth of the nanoparticles has been studied by simultaneous in situ measurement of X‐ray absorption spectroscopy (XAS) and UV–Vis spectroscopy at the energy‐dispersive EXAFS beamline (BL‐08) at Indus‐2 SRS at RRCAT, Indore, India. In situ XAS spectra, comprising both X‐ray near‐edge structure (XANES) and extended X‐ray absorption fine‐structure (EXAFS) parts, have been measured simultaneously at the Au and Pt L₃‐edges. While the XANES spectra of the precursors provide real‐time information on the reduction process, the EXAFS spectra reveal the structure of the clusters formed in the intermediate stages of growth. This insight into the formation process throws light on how the difference in the reduction potential of the two precursors could be used to obtain the core–shell‐type configuration of a bimetallic alloy in a one‐pot synthesis method. The core–shell‐type structure of the nanoparticles has also been confirmed by ex situ energy‐dispersive spectroscopy line‐scan and X‐ray photoelectron spectroscopy measurements with in situ ion etching on fully formed nanoparticles.     

In situ observation of Ni–Mo–S phase formed on NiMo/Al2O3 catalyst sulfided at high pressure by means of Ni and Mo K‐edge EXAFS spectroscopy

To obtain direct evidence of the formation of the Ni–Mo–S phase on NiMo/Al₂O₃ catalysts under high‐pressure hydrodesulfurization conditions, a high‐pressure EXAFS chamber has been constructed and used to investigate the coordination structure of Ni and Mo species on the catalysts sulfided at high pressure. The high‐pressure chamber was designed to have a low dead volume and was equipped with polybenzimidazole X‐ray windows. Ni K‐edge k³χ(k) spectra with high signal‐to‐noise ratio were obtained using this high‐pressure chamber for the NiMo/Al₂O₃ catalyst sulfided at 613 K and 1.1 MPa over a wide k range (39.5–146 nm^?1). The formation of Ni–Mo and Mo–Ni coordination shells was successfully proved by Ni and Mo K‐edge EXAFS measurement using this chamber. Interatomic distances of these coordination shells were almost identical to those calculated from Ni K‐edge EXAFS of NiMo/C catalysts sulfided at atmospheric pressure. These results support the hypothesis that the Ni–Mo–S phase is formed on the Al₂O₃‐supported NiMo catalyst sulfided under high‐pressure hydrodesulfurization conditions.     

NMR study of rapidly quenched crystalline and amorphous Fe-B alloys

Amorphous and microcrystalline Fe-B alloys (4–25 at % B) obtained by rapid quenching of the melt were studied using the pulsed nuclear magnetic resonance (NMR) of ¹¹B nuclei at 4.2 K. Alloy samples were prepared from both a natural isotope mixture and a mixture of the ⁵⁶Fe and ¹¹B isotopes. The NMR spectra were measured as a function of the boron content. The maximum hyperfine fields at the ¹¹B nuclei sites are 25–29 kOe and overlap the values of the hyperfine fields at the ¹¹B nuclei sites in the tetragonal and orthorhombic Fe₃B phases and also in the α-Fe phase containing boron as a substitutional impurity. The short-range order and local atomic structure of the amorphous Fe-B alloys were determined. The amorphous alloys are found to consist of microregions (clusters) with a short-range order similar to that in the tetragonal or orthorhombic Fe₃B phase or the α-Fe phase.     

Acoustic characteristics of Ni–Nb–Zr–H glassy alloys by ultrasonic shear waves

The propagation characteristics of shear horizontally polarized (SH) waves passing through (Ni₄₂Nb₂₈Zr₃₀)_100–x H_x (x = 0–15.2) glassy alloys were investigated as a function of hydrogen content. With an increase in hydrogen content, the propagation time and main frequency of the receiving waves show increase and decrease, respectively, indicating expan‐ sion in average atomic distance which comes from solution of hydrogen. In sharp contrast to crystalline alloys, the decrease in damping ratio and the delay in phase with increasing hydrogen suggest a strong settlement of hydrogen into four‐coordination sites surrounded tetrahedrally by four Zr atoms and the resulting increase in dynamic elasticity, respectively. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Multivariate curve resolution alternating least squares in the quantitative determination of sulfur using overlapped S(Kα)–Mo(Lα) emission peaks by wavelength dispersive X‐ray fluorescence spectrometry

Spectral line overlap is a serious problem in quantitative X‐ray fluorescence analysis. In this study multivariate curve resolution alternating least squares (MCR‐ALS) approach was used to resolve the effect of overlapping S(K_α)–Mo(L_α) emission lines generated by standard‐less software of a wavelength dispersive X‐ray fluorescence spectrometer (WDXRF) for the quantitative monitoring of sulfur in mineral samples. Scan channel set contained Ge crystal, 550‐µm collimator, flow detector (Ar + CH₃) and rhodium (Rh) tube. The 18 calibration and 10 validation samples contain 0.00%–10.98% sulfate (SO₃) and 0.00%–92.40% MoO₃. The digitized spectral data were extracted in the range between 109° and 113.9° (2θ) at every 0.1 degree. Lack of fit percentage (LOF%) for experimental data and the variance explained at the optimum condition () were 2.32 and 99.94, respectively. The values of the root mean square error of prediction (RMSEP) for analyzing of sulfur were 0.23. MCR‐ALS was also compared with partial least squares (PLS) method for determination of sulfur in the presence of molybdenum. To evaluate the resolution and quantification performance of MCR‐ALS procedure, the method was used to determine sulfur in presence of molybdenum in two synthetic soil samples. Copyright © 2015 John Wiley & Sons, Ltd.     

Atomic and magnetic structures of Fe<Subscript>70</Subscript>Al<Subscript>5</Subscript>B<Subscript>25</Subscript> amorphous alloys

The short-range order around boron, aluminum, and iron atoms in Fe₇₅B₂₅ and Fe₇₀Al₅B₂₅ amorphous alloys has been studied by ¹¹B and ²⁷Al nuclear magnetic resonance at 4.2 K and ⁵⁷Fe Mössbauer spectroscopy at 87 and 295 K. The average magnetic moment of iron atoms μ(Fe) in these alloys has been measured by a vibrating sample magnetometer. It has been revealed that the substitution of aluminum atoms for iron atoms does not disturb μ(Fe) in the Fe₇₀Al₅B₂₅ alloy, gives rise to an additional contribution to the ¹¹B NMR spectrum in the low-frequency range, and shifts maxima of the distribution of hyperfine fields at the ⁵⁷Fe nuclei. In the Fe₇₀Al₅B₂₅ amorphous alloy, the aluminum atoms substitute for iron atoms in the nearest coordination shells of boron and iron atoms. This alloy consists of nanoclusters in which boron and iron atoms have a short-range order of the tetragonal Fe₃B phase type.     

Structural and electrical analysis of In–Sb–Te‐based PCM cells

Two In–Sb–Te compounds with low Te content (12 at.% and 17 at.%), deposited by metalorganic chemical vapour deposition, were implemented into prototype phase‐change memory devices of size 50 × 50 nm² and 93 × 93 nm². These chalcogenides yielded devices with higher threshold voltage than those based on Ge–Sb–Te alloys. The endurance and programming window were markedly improved (from 10³ to 10⁶ cycles and from 1 to 2 orders of magnitude, respectively) when employing the Te‐richer alloy. Moreover, in situ structural and electrical analysis on TiN/In–Sb–Te/dielectric stacks provided additional insight on the thermal stability of the two ternary phases In₃SbTe₂ and InSb_0.8Te_0.2, which were found to coexist in these compounds. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Study of interfacial charge transfer in nanosemiconductor–molecule composites

Interaction of sol–gel synthesized Ce–Ag‐codoped ZnO (CSZO) nanocrystals with (E)‐1‐(naphthalen‐1‐yl)‐2‐styryl‐1H‐phenanthro[9,10‐d]imidazole has been analysed. The synthesized nanocrystals and their composites with naphthyl styryl phenanthrimidazole have been characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X‐ray spectroscopy, X‐ray diffractometry, X‐ray photoelectron spectroscopy (XPS) lifetime and Fourier transform infrared spectroscopy and cyclic voltammetry. XPS shows doped silver and cerium in Ag⁰ and Ce⁴⁺ states, respectively_. SEM and TEM images of CSZO nanoparticles show that they appear to be 3D trapezoid and cocoon‐like shape. The selected area electron diffraction pattern supports the nanocrystalline character of the synthesized material. The percentages of doping of cerium and silver in CSZO are 0.54 (at.) and 0.34 (at.), respectively. From the energy levels of the materials used in the imidazole–CSZO composite, the dominant CT direction has been analysed. Theoretical investigation shows that the binding energy and energy gap of the imidazole composites are highly dependent on the nature of the silver oxide cluster and that charge transfer in the imidazole–Ag₄O₄ composite is faster than the same in other composites. Molecular docking technique has also been carried out to understand the imidazole–DNA interactions. Copyright © 2016 John Wiley & Sons, Ltd.     

Rapid,Microwave‐Assisted,and One‐Pot Synthesis of Magnetic Palladium–CoFe2O4–Graphene Composite Nanosheets and Their Applications as Recyclable Catalysts

Here, a microwave‐assisted approach has been demonstrated to rapidly prepare magnetic Pd–CoFe₂O₄–graphene (GE) composite nanosheets in ethylene glycol (EG) solvent. The generation of both Pd and CoFe₂O₄ nanoparticles is accompanied with the reduction process of graphene oxide (GO) by EG. The surface morphologies and chemical composition of the composite nanosheets are characterized by transmission electron microscopy (TEM), energy‐dispersive X‐ray spectrometer (EDS), powder X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR) measurements. The as‐prepared Pd–CoFe₂O₄–GE composite nanosheets exhibit a remarkable catalytic activity towards the reduction of 4‐nitrophenol by sodium borohydride (NaBH₄) at room temperature. The apparent kinetic rate constant (K _app) of this catalytic reaction could reach about 11.0 × 10^?3 s^?1. Moreover, the CoFe₂O₄ component exhibits a magnetic property, which could make the Pd–CoFe₂O₄–GE composite nanocatalysts separated from the suspension system. The catalytic conversion of the 4‐nitrophenol to 4‐aminophenol could reach 87.2% after four cycles. This work presents a simple, rapid, and versatile method to fabricate both metal and spinel‐type complex oxides on GE nanosheets, providing a new opportunity for their applications in the recyclable catalytic reaction.     

A New Method for Determining the Composition of Core–Shell Nanoparticles via Dual‐EDX+EELS Spectrum Imaging

Simultaneously acquired microanalytical X‐ray and electron energy loss signals are obtained from a bimetallic core–shell nanoparticle system (FePt@Fe₃O₄). The signals are decomposed using independent component analysis and the extracted components are used to separately quantify the composition of the spatially overlapping core and shell phases in the nanoheterostructure. The utilization of the complementary strengths of energy dispersive X‐ray and electron energy‐loss spectroscopy microanalysis has enabled the quantification of both light and heavy elements in a single spectrum image acquisition.     

Characterization of Pd/Y multilayers with B4C barrier layers using GIXR and X‐ray standing wave enhanced HAXPES

Pd/Y multilayers are high‐reflectance mirrors designed to work in the 7.5–11 nm wavelength range. Samples, prepared by magnetron sputtering, are deposited with or without B₄C barrier layers located at the interfaces of the Pd and Y layers to reduce interdiffusion, which is expected from calculating the mixing enthalpy of Pd and Y. Grazing‐incident X‐ray reflectometry is used to characterize these multilayers. B₄C barrier layers are found to be effective in reducing Pd–Y interdiffusion. Details of the composition of the multilayers are revealed by hard X‐ray photoemission spectroscopy with X‐ray standing wave effects. This consists of measuring the photoemission intensity from the samples by performing an angular scan in the region corresponding to the multilayer period and an incident photon energy according to Bragg's law. The experimental results indicate that Pd does not chemically react with B nor C at the Pd–B₄C interface while Y does react at the Y–B₄C interface. The formation of Y–B or Y–C chemical compounds could be the reason why the interfaces are stabilized. By comparing the experimentally obtained angular variation of the characteristic photoemission with theoretical calculations, the depth distribution of each component element can be interpreted.     

Correlation between local vibrations and metal mass in AlB2‐type transition‐metal diborides

Lattice vibrations have been investigated in TiB₂, ZrB₂ and HfB₂ by temperature‐dependent extended X‐ray absorption fine structure (EXAFS) experiments. Data clearly show that the EXAFS oscillations are characterized by an anomalous behavior of the Debye–Waller factor of the transition‐metal–boron pair, which is suggested to be associated with a superposition of an optical mode corresponding to phonon vibrations induced by the B sublattice and an acoustic mode corresponding to the transition‐metal (TM) sublattice. Data can be interpreted as a decoupling of the metal and boron vibrations observed in these transition‐metal diborides (TMB₂), a mechanism that may be responsible for the significant reduction of the superconducting transition temperature observed in these systems with respect to the parent MgB₂ compound. The vibrational behavior of TM–TM bonds has also been investigated to study the occurrence of anisotropy and anomalies in the lattice vibrational behavior of TM–TM bonds.     

Short-range order in amorphous ferromagnetic Fe-B alloys

Amorphous and quenched crystalline Fe-B alloys in the composition range of 4–25 at % B were prepared by melt spinning and investigated by ⁵⁷Fe Mössbauer spectroscopy at T = 87 K. The states of iron atoms in the α-Fe phases, including iron atoms having boron atoms in the nearest coordination sphere, and in the orthorhombic (o) and tetragonal (T) Fe₂B phases are detected in the microcrystalline alloys. The short-range order and the local atomic structure of the amorphous Fe-B alloys are determined. The amorphous alloys consist of microregions (clusters) with short-range order of the t- and o-Fe₂B and α-Fe types. The dependence of the content of various types of clusters on the alloy composition is quantitatively estimated.     

Higher reactivity of 3‐pyridinium boronic acid compared with 3‐pyridinium boronate ion toward 4‐isopropyltropolone in acidic aqueous solution: fundamental reaction analyses for an effective organoboron‐based chemosensor

The pK_as of 3‐pyridylboronic acid and its derivatives were determined spectrophotometrically. Most of them had two pK_as assignable to the boron center and pyridine moiety. The pK_a assignment performed by ¹¹B nuclear magnetic resonance spectroscopy revealed that both boron centers in 3‐pyridylboronic acid [3‐PyB(OH)₂] and the N‐methylated derivative [3‐(N‐Me)Py⁺B(OH)₂] have strong acidities (pK_a = 4.4 for both). It was found that introduction of a substituent to pyridine‐C atom in 3‐pyridylboronic acid drastically increased the acidity of the pyridinium moiety, but decreased the acidity of the boron center, whereas the introduction to pyridine‐N atom had no influence on the acidity of the boron center. Kinetic studies on the complexation reactions of 3‐pyridinium boronic acid [3‐HPy⁺B(OH)₂] with 4‐isopropyltropolone (Hipt) carried out in strongly acidic aqueous solution indicated that the positive charge on the boronic acid influenced little on its reactivity; 3‐HPy⁺B(OH)₂ reacts with Hipt and protonated H₂ipt⁺, and its reactivity was in line with those of a series of boronic acids. Kinetics in weakly acidic aqueous solution revealed that 3‐HPy⁺B(OH)₂ reacts with Hipt faster than its conjugate boronate [3‐HPy⁺B(OH)₃^–], which is consistent with our recent results. The reactivity of 3‐(N‐Me)Py⁺B(OH)₂ towards Hipt was also examined kinetically; the reactivities of 3‐(N‐Me)Py⁺B(OH)₂ and 3‐(N‐Me)Py⁺B(OH)₃^– are almost the same as those of their original 3‐HPy⁺B(OH)₂ and 3‐HPy⁺B(OH)₃^–, respectively. Copyright © 2012 John Wiley & Sons, Ltd.     

Spectroscopic characterization of cadion: UV–vis,resonance Raman and DFT calculations of a versatile metal complexing agent

The spectroscopic characterization of cadion or 1‐(4‐nitrophenyl)‐3‐(4‐phenylazophenyl)triazene, its anionic species and its complexes with Hg²⁺, Cd²⁺ and Ni²⁺ in DMSO solution is presented. Resonance Raman (RR) and UV–vis spectroscopy were the techniques of choice with results supported by density functional theory calculations. As previously reported, the UV–vis data indicate distinct absorption spectra for the five species mentioned, allowing for spectrophotometric metal differentiation. In order to understand the electronic spectra of such species, we performed a detailed RR investigation, where the spectral profiles revealed the vibrational modes mainly involved in the chromophoric moieties. The distinct enhancement profile observed for each species suggests that the charge transfer from the π‐system to the electron withdrawing NO₂ group is modulated by the electron donating triazene moiety, depending on the metal attached. The results reported herein show that RR spectroscopy can be potentially used in the metal detection of multicomponent samples by the proper choice of the excitation wavelength. Copyright © 2012 John Wiley & Sons, Ltd.