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Background and Aim: Organophosphate compounds, including nerve agents, pesticides, chemical agent analogs, and Novichok, pose a serious health hazard to humans. Their use against humans was banned by 192 countries in 1993 under the Chemical Weapons Convention. The toxic effects of these compounds involve the phosphorylation and subsequent inhibition of the enzyme acetylcholinesterase, leading to the accumulation of acetylcholine in the synapses of the central and peripheral nervous systems, resulting in neurotoxic poisoning symptoms. The drugs used to treat this poisoning are compounds that can cross the blood-brain barrier by a maximum of 10% and therefore do not effectively detoxify the central nervous system. This research aims to design and synthesize a superparamagnetic nano-reactivator to activate the inhibited enzyme in the central nervous system. Methods: In this study, iron oxide nanoparticles conjugated with 2-pyridinium aldoxime were designed and synthesized in four steps. The characteristics of the nanoparticles were determined by infrared spectroscopy, energy-dispersive X-ray spectroscopy (EDS), elemental analysis, dynamic light scattering (DLS), and electron microscopy (SEM). Their activation effect was compared with pralidoxime, a commercially available drug, using the Ellman method in vitro. Results: The results of the Ellman method showed that the percentage of activation of the paraoxon-inhibited enzyme by pralidoxime as a commercially available antidote and the synthesized nanoparticles at a concentration of 5 mM over 30 minutes was 88.6% and 39.3%, respectively. Conclusion: This study demonstrated that the designed iron oxide nanoparticles conjugated with 2-pyridinium aldoxime can be synthesized and activate acetylcholinesterase inhibited by paraoxon. Therefore, future studies should investigate the effect of other groups such as 4-pyridinium aldoxime, 2,4-pyridinium aldoxime, etc., on the enzyme activation performance and the ability of these nanoparticles to cross the blood-brain barrier. [ABSTRACT FROM AUTHOR]

The study aimed to develop a potential biomaterial for neuroregeneration by the electrospinning of the biocompatible polymer polyvinylidene fluoride (PVDF) with innovative functionalized boron nitride quantum dots (F-BNQDs) synthesized via green chemistry using the amino acid taurine as a functionalization. The F-BNQDs were characterized and were found to be 16-21 nm in diameter, showed good photoluminescent characteristics, and their elemental composition was confirmed by x-ray photoelectron spectroscopy, Fourier-transform infrared (FTIR), and ultraviolet spectroscopy. The PVDF with F-BNQDs was prepared at three different concentrations, and the resulting electrospun fibers were characterized by scanning electron microscopy, FTIR, thermogravimetric analysis, contact angle, biodegradation, water uptake, Schwann cell cytotoxicity, and cell behavior studies. The results of the study showed that the addition of F-BNQDs to PVDF resulted in enhanced mechanical properties, decreased contact angle, increased degradability, and water uptake. The lactate dehydrogenase assay revealed that 5% BN-PVDF had the lowest cytotoxicity. Fluroscent 4',6-diamidino-2-phenylindole (DAPI) staining showed that the increase in F-BNQD concentration up to 5% BN-PVDF enhanced cell behavior on the electrospun fibers. Therefore, the study concluded that 5% BN-PVDF would be suitable for further testing as a potential biomaterial for neuroregeneration in vivo. Highlights * Functionalized boron nitride quantum dots (F-BNQDs) were prepared using amino acid taurine. * The F-BNQDs were characterized and electrospun with polyvinylidene fluoride (PVDF). * The incorporation of F-BNQDs to PVDF has enhanced its physicochemical properties. * All samples showed a single [beta]phase PVDF. * Schwann cells showed excellent compatibility and cell adhesion on F-BNQDs/PVDF. KEYWORDS electrospinning, functionalized boron nitride quantum dots, PVDF, Schwann cells, taurine, 1 | INTRODUCTION Peripheral nerve injuries have the potential to cause total transection of the nerve, necessitating surgical intervention to enable the regrowth of axons from the injured site to [...]

Background: This study evaluated the interface between fresh eugenol/bioceramic sealer-conditioned coronal dentin and high-viscous glass-ionomer cement (HVGIC), treated with various dentin conditioners (saline, 10% polyacrylic acid, and 37% phosphoric acid). Materials and Methods: Standard endodontic access preparation and instrumentation were done in 21 freshly extracted mandibular molar teeth in this in vitro study. Teeth were divided into two interventional groups (n = 9/group), based on the type of sealer (zinc oxide eugenol [ZOE]/ bioceramic [BioRoot RCS] sealer) used for obturation. Samples were further subdivided based on the type of dentin-conditioning procedures performed (saline/10% polyacrylic acid/37% phosphoric acid). Post dentin conditioning, the access cavity was sealed with HVGIC. Later, material-dentin interfacial analysis and elemental analysis were done using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy. Results: The interfacial SEM images of HVGIC layered over B-RCS/ZOE sealer-conditioned dentin, treated with saline, showed predominantly adhesive debonding failures, whereas cohesive debonding was observed with polyacrylic and phosphoric acid. In the elemental analysis, the intensity of zirconium (depicting the residue of B-RCS)/zinc (depicting ZOE sealer) was very high on the dentin side treated with saline, in comparison to the dentin treated with polyacrylic and phosphoric acid. Furthermore, the intensity of elements from HVGIC was low on the dentin side of the groups with saline, whereas these elements showed maximum penetration into the dentin when treated with phosphoric acid. Conclusion: Conditioning of the endodontic access cavity using 37% phosphoric acid immediately postobturation resulted in higher penetration of HVGIC into the dentin, in comparison to the other dentin conditioners. [ABSTRACT FROM AUTHOR]

Simple Summary: In this study, X-ray Photoelectron Spectroscopy (XPS) is used as a fast technique to characterize the composition of nanosized small extracellular vesicles (EVs), with the aim of evaluating its possible application in cancer screening and diagnosis. This spectroscopic technique is an ideal approach to characterize membranes due to its sensitivity and its penetration depth, in the nanometric range, meaning that the results will mainly correspond to the membrane composition, with little interference from the biomolecules in the EV´s lumen. We propose the use of XPS to analyze the membranes of small extracellular vesicles isolated from bodily fluids of cancer patients and compared them to those of healthy cells and donors. Notably, we have focused our analysis on the N chemical environment of EV membranes, as this can be related to previous complex chemical analyses of lipid and protein contents in EVs. We provide preliminary results on a fast and non-invasive novel strategy, as a method or tool for research-based EV investigations with potential application in cancer screening and monitoring. Small extracellular vesicle (EV) membranes display characteristic protein-lipidic composition features that are related to their cell of origin, providing valuable clues regarding their parental cell composition and real-time state. This could be especially interesting in the case of cancer cell-derived EVs, as their membranes could serve as valuable tools in liquid biopsy applications and to detect changes in the tumor malignancy. X-Ray Photoelectron Spectroscopy (XPS) is a powerful surface analysis technique able to detect every chemical element present, being also sensitive to their chemical environment. Here we explore the use of XPS as a fast technique to characterize EV membrane composition, with possible application in cancer research. Notably, we have focused on the nitrogen environment as an indicator of the relative abundance of pyridine-type bonding, primary, secondary and tertiary amines. Specifically, we have analyzed how tumoral and healthy cells have different nitrogen chemical environments that can indicate the presence or absence of malignancy. In addition, a collection of human serum samples from cancer patients and healthy donors was also analyzed. The differential XPS analysis of EVs collected from patients confirmed that the patterns of amine evolution could be related to markers of cancer disease, opening the possibility of their use as a non-invasive blood biomarker. [ABSTRACT FROM AUTHOR]

In energy dispersive X‐ray fluorescence analysis (EDXRF), many baseline estimation algorithms have been proposed for the accurate characteristic peak area. However, the true value of the characteristic peak area of measured spectrum is unknown and cannot be used to evaluate the accuracy of the baseline estimation algorithms. In this article, an assessment method was proposed based on Monte Carlo simulation, which can obtain the characteristic peak area, and evaluate the accuracy of the baseline estimation algorithms directly. Meanwhile, the accuracy and practicality of four baseline estimation algorithms were evaluated by the assessment method, which include statistics‐sensitive nonlinear iterative peak‐clipping (SINP), fast Fourier transform (FFT), adaptive iteratively reweighted penalized least squares (AirPLS), and automated iterative moving averaging (AIMA). Comparing the relative error of the characteristic peak area, AirPLS gave the best performance for baseline estimation in EDXRF. [ABSTRACT FROM AUTHOR]

One new clerodane-type diterpenoid, together with one known, was isolated from the leaves and twigs of C. krabas. The structures of these compounds were elucidated as krabasinolide A (1) and taraxerol (2) by spectroscopic methods (UV, IR, HRESIMS, 1 D, and 2 D NMR), and the relative stereochemistry was confirmed by X-ray diffraction analysis with graphite monochromated Mo-Kα (λ = 0.71073 Å) radiation at 296(2) K. Extracts and compounds 1-2 were evaluated for in vitro antiviral activity. [ABSTRACT FROM AUTHOR]

Nanoarchitectonics is a widespread concept to construct functional materials from nanoscale building units. Based on this concept, fabrications of KMgSO4Cl:Eu phosphor with hierarchical structural motifs and their photo-physical properties after γ-ray exposure from 60Co source are described in this manuscript. The photo-physical properties of γ-ray-exposed KMgSO4Cl:Eu phosphor such as oxidation state of Eu ion, thermoluminescence (TL) kinetic parameters and fading response have been evaluated and reported herein. The KMgSO4Cl:Eu phosphor was synthesized using wet-chemistry method and the nanoarchitectonics concept behind the nanostructured fabrication has been illustrated. The formation of the compound was reported using X-ray diffraction (XRD) analysis and the presence of individual elements using energy-dispersive X-ray spectroscopy (EDS). The spherical but faceted highly agglomerated morphology of KMgSO4Cl nano-crystallite was shown using NanoSAM analysis. The bandgap (Eg) value of KMgSO4Cl was reported to be 3.4 ± 0.1 eV from diffused reflectance spectrum analysis. Photoluminescence (PL) analysis reveals that Eu is present in both divalent (Eu2+) and trivalent (Eu3+) oxidation states. The two oxidation states were detected as EuCl2+ and EuCl3+ species using XPS analysis, essentially Eu(II) and Eu(III) oxidation states, respectively. The TL glow curve consists of major broadband at 450 K and a minor peak at 542 K. The TL glow curve was deconvoluted to calculate the kinetic parameters and quasi-continuous distribution of trap levels. The kinetic parameters of the TL glow curve were estimated using Chen peak shape method, Ilich's method and Initial Rise method, respectively. The fading response indicates that TL intensity over 30 days of storage period was reduced to 25‒30%. [ABSTRACT FROM AUTHOR]

This paper focuses on the authigenic mineralization processes acting on "Tufo Rosso a Scorie Nere" (TRS), i.e. one of the main pyroclastic units of the Vico stratovolcano (Latium, Italy). The pyroclastic deposits appear in general massive and made of "black vitreous vesiculated juvenile scoriae", immersed in an ashy matrix lithified after zeolitization processes. The main minerals are chabazite and phillipsite, and the zeolitic content is locally variable, reaching 68%wt. Zeolites grow replacing both amorphous fraction and pre-existing phases, occurring inside both matrix and scoriae. Concerning scoriae, zeolitization moves from the rim to the core of the scoriaceous fragment as a function of (a) temperature of the fluids and (b) permeability (primary or secondary). Composition of parental fresh glass and that of zeolitized rocks is compatible with trachyte chemistry, lightly undersaturated in SiO2, and the alteration processes modified the parental rock chemical features. Zeolites genesis is ascribed to a "geoautoclave-like system", and zeolites display a Si=Al ratio similar to that of the parental glasses. TRS presents promising mineralogical characteristics as supplementary cementitious material in the production of mixed cements. [ABSTRACT FROM AUTHOR]

Raman spectra of three natural carbonophosphates (sidorenkite, bonshtedtite, and bradleyite) with the general formula Na3MCO3PO4 (M is Mn, Fe, and Mg) were studied and compared. These spectra showed from 21 to 24 vibrational bands, of which the two most intense (964±5 and 1074±3 cm-1) correspond to the v1(P-O) and v1(C-O) modes. These two bands split into doublet peaks due to the occurrence of isomorphic impurities. It was found that the crystallographic orientation of the sample influences the intensity of most bands. Most bands assigned to the same vibrations showed a regular shift (the smallest in sidorenkite spectra, an intermediate in bonshtedtite, and the largest in bradleyite). We propose an algorithm that allows for diagnostics of carbonophosphates in inclusions by their Raman spectra, providing a reliable result even in the absence of energy-dispersive X-ray spectroscopy (EDX) data. [ABSTRACT FROM AUTHOR]

The reversible amorphous-crystalline phase change in a chalcogenide material, specifically the Se1-xTex alloy, has been investigated for the first time using ultrafast differential scanning calorimetry. Heating rates and cooling rates up to 5000 K/s were used. Repeated reversible amorphouscrystalline phase switching was achieved by consecutively melting, melt-quenching, and recrystallizing upon heating. Using a well-conditioned method, the composition of a single sample was allowed to shift slowly from 15 at. %Te to 60 at. %Te, eliminating sample-to-sample variability from the measurements. Using Energy Dispersive X-ray Spectroscopy composition analysis, the onset of melting for different Te-concentrations was confirmed to coincide with the literature solidus line, validating the use of the onset of melting Tm as a composition indicator. The glass transition Tg and crystallization temperature Tc could be determined accurately, allowing the construction of extended phase diagrams. It was found that Tm and Tg increase (but Tg/Tm decrease slightly) with increasing Te-concentration. Contrarily, the Tc decreases substantially, indicating that the amorphous phase becomes progressively unfavorable. This coincides well with the observation that the critical quench rate to prevent crystallization increases about three orders of magnitude with increasing Te concentration. Due to the employment of a large range of heating rates, non-Arrhenius behavior was detected, indicating that the undercooled liquid SeTe is a fragile liquid. The activation energy of crystallization was found to increase 0.5-0.6 eV when the Te concentration increases from 15 to 30 at. % Te, but it ceases to increase when approaching 50 at. % Te. [ABSTRACT FROM AUTHOR]

The local vibrational dynamics of hematite (α-Fe2O3) has been investigated by temperature-dependent extended x-ray absorption fine structure spectroscopy and molecular dynamics simulations. The local dynamics of both the short and long nearest-neighbor Fe–O distances has been singled out, i.e., their local thermal expansion and the parallel and perpendicular mean-square relative atomic displacements have been determined, obtaining a partial agreement with molecular dynamics. No evidence of the Morin transition has been observed. More importantly, the strong anisotropy of relative thermal vibrations found for the short Fe–O distance has been related to its negative thermal expansion. The differences between the local dynamics of short and long Fe–O distances are discussed in terms of projection and correlation of atomic motion. As a result, we can conclude that the short Fe–O bond is stiffer to stretching and softer to bending than the long Fe–O bond. [ABSTRACT FROM AUTHOR]

We report on a novel slow dynamics of polymer xerogels, aerogels, and nanocomposite aerogels with iron oxide nanoparticles, as revealed by X-ray photon correlation spectroscopy. The polymer aerogel and its nanocomposite aerogels, which are porous in nature, exhibit hyper-diffusive dynamics at room temperature. In contrast, non-porous polymer xerogels exhibit an absence of this peculiar dynamics. This slow dynamical process has been assigned to a relaxation of the characteristic porous structure of these materials and not to the presence of nanoparticles. [ABSTRACT FROM AUTHOR]

The improvement of the software UNIFIT 2020 from an analysis processing software for photoelectron spectroscopy (XPS) only to a powerful tool for XPS, Auger electron spectroscopy (AES), X‐ray absorption spectroscopy (XAS), and Raman spectroscopy requires new additional programme routines. Particularly, the implementation of the analysis of Raman spectra needs a well‐working automatic spike correction. The application of the modified discrete Laplace operator method allows for a perfect localization and correction of the spikes and finally a successful peak fit of the spectra. The theoretical basis is described. Test spectra allow for the evaluation of the presented method. A comparison of the original and spike‐corrected real measurements demonstrates the high quality of the method used. [ABSTRACT FROM AUTHOR]

We report in-plane Cu-O atomic displacements as a function of doping in the La2-xSrxCuO4 system, determined by polarized Cu K-edge extended x-ray absorption fine structure measurements. We find a wide distribution of the Cu-O bonds showing a single peak asymmetric function for the system at low doping, which gets two peak function for the underdoped and optimally doped superconducting phases before turning to a single peak function for the overdoped phase. The results provide a direct evidence of critical local lattice fluctuations for an optimum transition temperature in the superconducting phases hosting quantum stripes. [ABSTRACT FROM AUTHOR]

We report recent results on top-emitting organic light-emitting diodes (OLEDs) using color conversion layers (CCLs) embedded into the electron transport layer of the OLED structure. The method of color conversion provides the possibility to generate a color stable emission with operating lifetime. Due to a constant ratio between absorbed blue emission and converter emission, the spectral shape remains for all time. This guarantees constant color coordinates of the OLED, which is essential for lighting applications. It is shown that OLEDs using conversion layers reach external quantum efficiencies (EQE) which can be higher than the corresponding blue top-emitting OLED. The used conversion layer thickness is below 100 nm, reaching Commission Internationale de l'Éclairage (CIE) coordinates of (0.23; 0.27) close to the Planckian locus at a maximum EQE of 3.16% using a blue fluorescent emitter system. Furthermore, we show that the excitation mechanism of the conversion layer is caused by absorption and no parasitic electrical excitation is taking place. Investigations on the emission color over the lifetime show color-stability over a period of up to 2200 h. [ABSTRACT FROM AUTHOR]

X-ray excited optical luminescence (XEOL) spectroscopy has been used to investigate the optical emission properties of Ce3+ activated Ba2Ca(BO3)2 with a charge-compensating Na+ and the results are compared with the optical emission properties from UV excitation. Further, x-ray absorption near-edge structure (XANES) has been employed to study the chemical environment and energy transfer efficiency to optical emission upon x-ray excitation. XEOL results agree well with optical emission with UV excitation. XANES results across various absorption edges show that while the chemical environment of host materials does not change significantly with doping, luminescence yield decreases significantly at absorption edges due to an abrupt change in the de-excitation mechanism. [ABSTRACT FROM AUTHOR]

SnO2:Eu is a well-known luminescent material, emitting red and orange lines. The intensity ratio of red to orange emission, being sensitive to the deviation of Eu3+ ions from symmetric location, finds wide application as sensor. The luminescence intensity of such lanthanide-doped sensors is generally optimized by high temperature annealing. However, for the present system (SnO2:Eu) it had been found that the red emission suddenly disappears while annealing beyond 900 °C, which can however be recovered by dispersing the system in a secondary host matrix of Y2O3. Understanding the mechanism of this recovery has important implication for designing of phosphor. In this work, we structurally explain this spectral evolution, by employing x-ray absorption fine structure technique. The initial disappearance of the red line is realized to be due to the formation of Eu2Sn2O7 and the recovery, to the intercalation of the Eu3+ ions from the SnO2 surface into Y2O3. Oxygen vacancy in Y2O3 creates the asymmetric environment required for red line emission. The design implications of these findings are discussed. [ABSTRACT FROM AUTHOR]

This letter reports on the site configuration of implanted Mn cations in ZnO. The samples studied were obtained by means of ion implantation in m-plane ZnO single crystals. Synchrotron radiation based fluorescence shows no contamination during the implantation process. The results of micro-x-ray absorption spectroscopy indicate that Mn ions are located in substitutional sites without detectable traces of secondary phases. The postgrowth thermal annealing in O2 atmosphere induces a change in the coordination of a large amount of Mn cations, corresponding to α-Mn2O3. [ABSTRACT FROM AUTHOR]

We present the first femtosecond soft x-ray spectroscopy in liquids, enabling the observation of changes in hydrogen bond structures in water via core-hole excitation. The oxygen K-edge of vibrationally excited water is probed with femtosecond soft x-ray pulses, exploiting the relation between different water structures and distinct x-ray spectral features. After excitation of the intramolecular OH stretching vibration, characteristic x-ray absorption changes monitor the conversion of strongly hydrogen-bonded water structures to more disordered structures with weaker hydrogen-bonding described by a single subpicosecond time constant. The latter describes the thermalization time of vibrational excitations and defines the characteristic maximum rate with which nonequilibrium populations of more strongly hydrogen-bonded water structures convert to less-bonded ones. On short time scales, the relaxation of vibrational excitations leads to a transient high-pressure state and a transient absorption spectrum different from that of statically heated water. [ABSTRACT FROM AUTHOR]

The efficiency of resonance energy transfer can be used to determine nanometer-scale separations between dye molecules in a donor-acceptor pair. We argue that the standard method for making this determination in single-pair experiments is valid only when excitation by the applied field is much slower than the other photophysical processes in the system. We derive a simple relation between measured transfer efficiency and interdye distance that is valid regardless of excitation rate for a broad class of currently accepted models for dye photophysics. Significant deviations from weak-field results are predicted for typical experimental conditions. [ABSTRACT FROM AUTHOR]

We present here the results of time-resolved absorption and emission experiments for 4-(dimethylamino)benzonitrile in solution, which suggest that the fluorescent intramolecular charge transfer (ICT) state may differ from the twisted ICT (TICT) state observed in transient absorption. [ABSTRACT FROM AUTHOR]

A method for the analysis of time-resolved x-ray absorption near edge structure (XANES) spectra is proposed. It combines principal component analysis of the series of experimental spectra, multidimensional interpolation of theoretical XANES as a function of structural parameters, and ab initio XANES calculations. It allows to determine the values of structural parameters for intermediates of chemical reactions and the concentrations of different states as a function of time. This approach is tested using numerically generated data and its possibilities and limitations are discussed. The application of this method to a reaction with methylrhenium trioxide catalyst in solution, for which experimental data were measured using stopped-flow energy-dispersive x-ray absorption spectroscopy technique, is demonstrated. Possibilities and limitations of this experimental technique are also discussed. [ABSTRACT FROM AUTHOR]

The chemical short-range structure was studied in liquid Al–Ni alloys by x-ray absorption spectroscopy as a function of temperature and composition. A containerless technique, combining aerodynamic levitation and inductive heating, was used to position and melt the samples. The fluorescence yield x-ray absorption at the Ni K edge was measured by a multichannel solid-state Ge detector. The number of heteroatomic pairs around the scatterer is higher than for a homogeneous alloy. [ABSTRACT FROM AUTHOR]

Two-dimensional x-ray correlation spectra (2DXCS) obtained by varying two delay periods in a time-resolved coherent all-x-ray four-wave-mixing measurement are simulated for the N 1s and O 1s transitions of aminophenol. The necessary valence and core-excited states are calculated using singly and doubly substituted Kohn–Sham determinants within the equivalent-core approximation. Sum-over-states calculations of the 2DXCS signals of aminophenol isomers illustrate how novel information about electronic states can be extracted from the 2D spectra. Specific signatures of valence and core-excited states are identified in the diagonal and off-diagonal peaks arising from core transitions of the same and different types, respectively. [ABSTRACT FROM AUTHOR]

Indium was substituted at gallium site in chalcopyrite AgGaS2 structure by using a simple solid solution method. The spectroscopic analysis using extended x-ray absorption fine structure and x-ray photoelectron spectroscopy confirmed the indium substitution in AgGaS2 lattice. The band gap energy of AgGa1-xInxS2 (x=0–1) estimated from the onset of absorption edge was found to be reduced from 2.67 eV (x=0) to 1.9 eV (x=1) by indium substitution. The theoretical and experimental studies showed that the indium s orbitals in AgGa1-xInxS2 tailored the band gap energy, thereby modified the photocatalytic activity of the AgGa1-xInxS2. [ABSTRACT FROM AUTHOR]

Ce1-x-yTixPtyO2-δ (x=0.15; y=0.01) and Ce1-x-yTixPdyO2-δ (x=0.25; y=0.02 and 0.05) are found to be good CO oxidation catalysts [T. Baidya et al., J. Phys. Chem. B 110, 5262 (2006); T. Baidya et al., J. Phys. Chem. C 111, 830 (2007)]. A detailed structural study of these compounds has been carried out by extended x-ray absorption fine structure along with x-ray diffraction and x-ray photoelectron spectroscopy. The gross cubic fluorite structure of CeO2 is retained in the mixed oxides. Oxide ion sublattice around Ti as well as Pt and Pd ions is destabilized in the solid solution. Instead of ideal eight coordinations, Ti, Pd, and Pt ions have 4+3, 4+3, and 3+4 coordinations creating long and short bonds. The long Ti–O, Pd–O, and Pt–O bonds are ∼2.47 Å (2.63 Å for Pt–O) which are much higher than average Ce–O bonds of 2.34 Å. [ABSTRACT FROM AUTHOR]

Cd1-xZnxTe alloys have been studied by surface photovoltage spectroscopy (SPS) and energy dispersive spectroscopy (EDS). The analyses of surface photovoltage spectra have been perfomed at near and above band gap energies. Surface recombination effects on the surface photovoltage have been investigated. SPS analyses of Cd1-xZnxTe alloys with different surface conditions have shown that the surface recombination velocity significantly affects the SPS determination of the material band gap. Accounting for this and preparing the surfaces accordingly, SPS spectra of Cd1-xZnxTe samples have allowed an accurate determination of the optical band gap as a function of the Zn concentration, determined via EDS analyses. The local increases in the density of states associated with band structure features in Cd1-xZnxTe alloys have been investigated by SPS spectra in the above band gap energy range. [ABSTRACT FROM AUTHOR]

We report the nearest-neighbor oxygen-oxygen radial distribution function (NN O–O RDF) of room temperature liquid water and polycrystalline ice Ih (-16.8 °C) obtained by x-ray Raman based extended x-ray absorption fine structure (EXAFS) spectroscopy. The spectra of the two systems were taken under identical experimental conditions using the same procedures to obtain the NN O–O RDFs. This protocol ensured a measurement of the relative distance distribution with very small systematic errors. The NN O–O RDF of water is found to be more asymmetric (tail extending to longer distances) with longer average distance (2.81 Å for water and 2.76 Å for ice) but a slightly shorter peak position (2.70 Å for water and 2.71 Å for ice). The refinement also showed a small but significant contribution from the linear O–H–O multiple scattering signal. The high sensitivity to short range distances of the EXAFS probe will set further restrictions to the range of possible models of liquid water. [ABSTRACT FROM AUTHOR]

We have investigated the structural and electrical properties of GaInP/GaAs epilayers implanted with Fe atoms to produce a shallow high resistivity layer. Proton-induced x-ray emission channeling measurements indicate that the substitutional fraction of the Fe implanted atoms decreases with increasing postimplant annealing temperatures. However, current-voltage analyses as a function of temperature indicate that a high temperature postimplantation annealing is necessary for the removal of the implantation-induced damage and for the activation of an efficient and stable electrical compensation process, which we have ascribed to the interplay between a deep donor and a deep acceptor, located at EC-0.50 eV and EV+0.74 eV, respectively. We have focused our attention on the latter deep level, attributed to the Fe2+/3+ related acceptor trap, which we have directly identified and characterized by spectral photocurrent analyses and by capacitance transient spectroscopy carried out under below-band-gap illumination, which stimulated the direct emission/trapping of carriers from the deep trap. [ABSTRACT FROM AUTHOR]

Nowadays charged-coupled device (CCD) detectors are widely used for the registration of multicharged ions x-ray spectra. These spectra are generated in a plasma during interaction of ultrashort, ultraintense laser pulses with solid targets. Strong parasitic radiation from the plasma affects CCD detectors and contaminates resulting spectra, so that spectral features can be completely covered by noise even during measurements with a very short accumulation time. In this work we propose a “mean to median” (M2M) algorithm for noise suppression in femtosecond laser plasma x-ray spectra. Series of spectra is necessary for the identification of corrupted data points by the developed method. The algorithm was tested with model spectra which reflect main features of experimental data. In practice we used it for extracting information about spectral lines of Ne-like Fe ions and He-like Al ions which allowed us to calculate plasma parameters. It is demonstrated that M2M method is able to clean spectra with more than 10% of corrupted pixels. Fluctuations in intensity of spectral lines induced by laser instability do not affect validity of the proposed method. [ABSTRACT FROM AUTHOR]

Theoretical foundation of rate kernel equation approaches for diffusion-influenced chemical reactions is presented and applied to explain the kinetics of fluorescence quenching reactions. A many-body master equation is constructed by introducing stochastic terms, which characterize the rates of chemical reactions, into the many-body Smoluchowski equation. A Langevin-type of memory equation for the density fields of reactants evolving under the influence of time-independent perturbation is derived. This equation should be useful in predicting the time evolution of reactant concentrations approaching the steady state attained by the perturbation as well as the steady-state concentrations. The dynamics of fluctuation occurring in equilibrium state can be predicted by the memory equation by turning the perturbation off and consequently may be useful in obtaining the linear response to a time-dependent perturbation. It is found that unimolecular decay processes including the time-independent perturbation can be incorporated into bimolecular reaction kinetics as a Laplace transform variable. As a result, a theory for bimolecular reactions along with the unimolecular process turned off is sufficient to predict overall reaction kinetics including the effects of unimolecular reactions and perturbation. As the present formulation is applied to steady-state kinetics of fluorescence quenching reactions, the exact relation between fluorophore concentrations and the intensity of excitation light is derived. [ABSTRACT FROM AUTHOR]

We present measurements of the Zr and Si core level photoelectron binding energies relative to the Fermi level and the vacuum level under a ZrO2 growth series on Si(100). It is shown that the Zr core level binding energy is most properly referenced to the local vacuum level already from the monolayer regime. This confirms the insulating properties of ZrO2. The Si core levels are referenced to the Fermi level and undergo shifts consistent with the disappearance of the mid-band-gap states originating from the (2×1) reconstruction on the clean Si(100) surface. The use of O 1s x-ray absorption spectroscopy (XAS) to determine the location of the conduction band edge of ZrO2 is discussed with the aid of ab initio calculations. It is demonstrated that the conduction band edge is located at the XAS peak position and that the position relative to the valence band can be determined by aligning the O 1s XAS spectrum to the O 1s photoelectron spectrum. The study thus establishes that photoelectron spectroscopy in conjunction with x-ray absorption spectroscopy forms a most powerful tool for studies of the band alignment at metal oxide–silicon interfaces. [ABSTRACT FROM AUTHOR]

V2O5 nanotubes synthesized via the sol-gel route has been studied by electron energy loss spectroscopy (EELS), x-ray absorption spectroscopy (XAS), and energy dispersive x-ray analysis, in order to understand the local structure of vanadium in the nanotubes. Contrary to our expectation, all the features of the XAS and EELS spectra of the V2O5 nanotubes are in line with that of bulk layered vanadium oxide revealing that vanadium is present in the 5+ oxidation state in the nanotubes. However, V2O5 nanotubes exhibit additional surface states in their electronic structure in comparison with bulk V2O5. A comparison of measured and calculated spectra allows us to distinguish single-wall from multiwall V2O5 nanotubes. [ABSTRACT FROM AUTHOR]

We report experimental evidence for the segregation and preferential localization of C atoms at the surface and substrate interfaces in thin Ge1-xCx films deposited directly on Si (100). The results are interpreted in the context of C segregation providing a mechanism for strain relaxation. Four different experimental techniques, including energy-dispersive spectroscopy, electron energy loss spectroscopy (EELS), energy-filtering transmission electron microscopy, and secondary ion mass spectrometry, support our claims. The EELS analyses showed that the C bonding near the Ge1-xCx/Si substrate interface presented a higher sp3 character than in the central region or at the surface. Two interpretations are given for this observation; one is that structural relaxation occurs when C atoms occupy substitutional sites in the Ge crystal closer to the Ge1-xCx/Si substrate interface; the other is that the higher sp3 character of the C atoms might be an indication that C-containing tetrahedral interstitial complexes form at the interface (chemical relaxation). [ABSTRACT FROM AUTHOR]

The microstructure of Si/Ti/Al/Ni/Au was investigated using transmission electron microscopy and energy dispersive x-ray spectroscopy. The dependence of the contact resistance on the silicon layer thickness and the temperature was correlated to the microstructure of the alloyed contacts. The enhancement of the contact resistance by inserting a 30 Å thick Si layer under the Ti/Al/Ni/Au metallization was attributed to diffusion of the contact into the AlGaN layer. Increasing the Si thickness and or the temperature resulted in the formation of Gold (Au)-based silicides, which prevent the formation of low interfacial TiN or AlN layers. [ABSTRACT FROM AUTHOR]

The effect of gold on keV x-ray emission from gold-copper (Au–Cu) mix-Z plasma has been experimentally studied. The intensity of the copper L-shell line radiation (λ∼7.8–10.9 Å) as well as the integrated keV x-ray yield were observed to decrease sharply with increasing atomic fraction of gold in the mix-Z target. The decrease was observed to be by a factor of ∼2.1 for 0.12 atomic fraction of gold in the Au–Cu mix-Z target with respect to the pure copper target. The results can be explained from physical consideration of the high value of free-bound opacity of gold in the spectral region of the L-shell emission of copper ions and downconversion of the absorbed keV line radiation. [ABSTRACT FROM AUTHOR]

The bleaching relaxation characteristics of PbS quantum dots with diameters in the range of 3.8–4.3 nm synthesized in silicate and phosphate glasses have been studied under the conditions of femtosecond excitation. It has been observed that increase of pump fluence from 0.1 to 2.2 mJ/cm2 leads to the appearance of a second (slow) component in the bleaching relaxation kinetics and to the shortening of both the fast (from several tens of picoseconds to several picoseconds) and slow relaxation times. An absorption saturation fluence of ≈15 μJ/cm2 with a nonsaturable absorption coefficient of 2.5–3 cm-1 at 1.05 μm has been evaluated for the PbS quantum-dot-doped glasses studied. The nature of the nonsaturable absorption and the mechanism of the bleaching relaxation in PbS quantum dots have been discussed. [ABSTRACT FROM AUTHOR]

Lanthanum oxide thin films were deposited at deposition temperatures ranging from 170 to 370 °C using alternate injection of tris(isopropyl-cyclopentadienyl)lanthanum and various reactants (H2O, O2, and NH3). It was possible to deposit films containing a carbon impurity concentration <1 at. %. The residual carbon could be further reduced by postdeposition annealing. X-ray photoelectron spectroscopy (XPS) showed that after rapid thermal annealing (RTA) at 870 °C the films transformed to silicate which increased the band gap of the films (7.0±0.15 eV). With changing the RTA ambient from O2 to N2, a binding energy shift of the substrate’s Si peaks by 0.9 eV was observed in the XPS spectra relative to the signals from the oxide layer. The shift was attributed to the electric field in the oxide film caused by the fixed charge distribution. A flat band voltage shift indicating the change of the fixed charge was also observed according to the RTA ambient. From Pt/La-oxide/p-Si(100) structures, the dielectric constant and the interface trap density were estimated to be ∼16 and ∼4×1011 eV-1 cm-2, respectively. An equivalent oxide thickness of 0.9 nm was obtained after RTA. [ABSTRACT FROM AUTHOR]

In this paper we present structural and electrical investigations on high temperature Fe-implanted InP. The aim of the work is to relate the lattice position of the implanted atoms after annealing treatments (from 300 to 600 °C) with their electrical activation as compensating deep traps and to draw a comprehensive picture of the activation mechanisms. The overall results demonstrate that the electrical behavior and the Fe2+ deep trap activation properties are strictly connected to the annealing evolution of the implant-induced damage and to the escape process of the Fe atoms from substitutional sites, which in turn is controlled by the background doping density in the substrates. [ABSTRACT FROM AUTHOR]

We studied the electronic states and magnetic moments of a bcc-Co(001) monatomic layer facing an amorphous Al–O tunneling barrier using x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) at the L2,3 core edges of Co. Both the XAS and XMCD measurements revealed that 1 monolayer (ML) Co is not oxidized. The magnetic moment of 1 ML bcc Co(001) facing the amorphous Al–O was observed to be almost the same as that of bulk Co. In contrast, the total magnetic moment of 1 ML bcc Co(001) facing a metallic Al layer was reduced by the effect of the proximity to Al atoms. [ABSTRACT FROM AUTHOR]

Rotationally resolved fluorescence excitation spectra of the S1←S0 origin bands and higher vibronic bands of fluorene (FLU), carbazole (CAR), and dibenzofuran (DBF) have been observed and assigned. Analyses of these data show that replacement of the CH2 group in FLU with a NH group in CAR and an O atom in DBF produces only localized changes in structure, in the ground state. But the three molecules exhibit different changes in geometry when they are excited by light. The S1 states of the three molecules also are electronically very different. The S1←S0 transition moments of CAR and DBF are parallel to the C2 symmetry axis whereas the corresponding transition moment in FLU is perpendicular to this axis. Herzberg-Teller coupling involving the S2 state also has been observed in the spectra of higher vibronic bands of CAR and DBF. Possible reasons for these behaviors are discussed. [ABSTRACT FROM AUTHOR]

The Cu(In,Ga)(S,Se)2/Mo interface in thin-film solar cells has been investigated by surface-sensitive photoelectron spectroscopy, bulk-sensitive x-ray emission spectroscopy, and atomic force microscopy. It is possible to access this deeply buried interface by using a suitable lift-off technique, which allows us to investigate the back side of the absorber layer as well as the front side of the Mo back contact. We find a layer of Mo(S,Se)2 on the surface of the Mo back contact and a copper-poor stoichiometry at the back side of the Cu(In,Ga)(S,Se)2 absorber. Furthermore, we observe that the Na content at the Cu(In,Ga)(S,Se)2/Mo interface as well as at the inner grain boundaries in the back contact region is significantly lower than at the absorber front surface. [ABSTRACT FROM AUTHOR]

The measurement of the electron mean kinetic energy by identifying the electron temperature and the excitation temperature obtained by optical emission spectroscopy is theoretically studied for two temperature argon plasmas at atmospheric pressure. Using a 32-level collisional radiative model in which both electron impact and argon-impact inelastic collisions are taken into account, it has been found that under certain conditions the argon inelastic collisions may cause a decrease of the argon excitation temperature so that the relation Te>Texc>T0 is satisfied. This inequality also appears when electron losses due to diffusion are important and the electron density is lower than its equilibrium value. [ABSTRACT FROM AUTHOR]

The electronic structure of the single molecule magnet system {M[Fe(L1)2]3}·4CHCl3 [M=Fe,Cr;L1=CH3N(CH2CH2O)22-] has been studied using x-ray photoelectron spectroscopy, x-ray-absorption spectroscopy, soft-x-ray emission spectroscopy, as well as theoretical density-functional-based methods. There is a good agreement between theoretical calculations and experimental data. The valence band mainly consists of three bands between 2 and 30 eV. Both theory and experiments show that the top of the valence band is dominated by the hybridization between Fe 3d and O 2p bands. From the shape of the Fe 2p spectra it is argued that Fe in the molecule is most likely in the 2+ charge state. Its neighboring atoms (O,N) exhibit a magnetic polarization yielding effective spin S=5/2 per iron atom, giving a high-spin state molecule with a total S=5 effective spin for the case of M=Fe. [ABSTRACT FROM AUTHOR]

The structure of porous silicon layers was accurately investigated by diverse x-ray methods. A series of samples with etching times varying from 1 to 10 min was produced by chemical etch using a HF/HNO3-based solution assisted with NaNO2. The porosity determined from low-angle x-ray reflectivity spectra was found to fluctuate from 35% to 55% as the etch proceeds. Reciprocal space mapping around the (004) Si lattice point revealed that the Si crystallites are deformed due to a distribution of in-plane compressive strain caused by the neighboring pores, which leads to an expansion of the perpendicular lattice parameter. No signature of mosaicity was found. The perpendicular strain could be precisely determined by fitting the x-ray-diffraction spectra, measured in the triple-axis configuration, to a set of Voigt and Gaussian distributions. These strain distributions are certainly associated with the different population of crystallite sizes formed during the stain etching process. We were able here to determine the temporal evolution of the strain inside the nanostructured porous silicon. [ABSTRACT FROM AUTHOR]