High-resolution X-ray techniques were applied to examine the effects of gold nanoparticles (size <5 nm) on natural pulmonary surfactant and pure DPPC monolayers preliminarily formed on water subphase ...in a Langmuir trough. Hydrophobic and hydrophilic nanoparticles were delivered from nanoaerosol using electrodeposition method. Grazing incidence diffraction, X-ray reflectivity, and X-ray standing wave measurements allow to monitor the changes in molecular organization of lipid monolayer and to locate the position of gold nanoparticles. X-ray experiments were performed over a period of 9–14 h. The obtained results evidenced that, on a long time scale, the deposition of nanoparticles, even at low doses, can induce pronounced alterations in lipid monolayer. The presented data can help to elucidate the mechanism of pulmonary translocation of inhaled nanoparticles that is of special interest for biomedical investigations of potential risk of nanoaerosols for human health.
X-ray studies revealed the considerable enhancement of metal-binding properties in human hemoglobin under exposure to mild damaging factors (in the presence of 0.09 M urea or upon heating for 30 min ...at 50 °C). Changes in the element composition of the hemoglobin monolayer, formed on the water subphase in the Langmuir trough, have been monitored in real time by the total external reflection X-ray fluorescence measurements. X-ray absorption spectroscopy has been applied to study the local environment of zinc ions bound on hemoglobin molecules. According to these data, each zinc ion is coordinated by four ligands, two of which are cysteine and histidine. The oxidative stress has been found to accelerate extensively the enhancement of metal-binding ability in protein. A two-stage mechanism has been proposed as a possible explanation of the observed phenomenon: First, in the presence of the mild damaging agents, protein molecules can undergo a transition from the native conformation to a more labile intermediate state that increases the accessibility of amino acid residues (in particular cysteine). At the second stage, oxidation of cysteine and the subsequent activation of cysteine SH groups can affect markedly the protein–metal interaction. The presented investigations provide a deeper insight into the pathogenesis of metabolic disorders that excessive concentrations of the endogenic toxicants might trigger in an organism.
We present a way to analyze the chemical composition of periodical multilayer structures using the simultaneous analysis of grazing incidence hard X-Ray reflectivity (GIXR) and normal incidence ...extreme ultraviolet reflectance (EUVR). This allows to combine the high sensitivity of GIXR data to layer and interface thicknesses with the sensitivity of EUVR to the layer densities and atomic compositions. This method was applied to the reconstruction of the layered structure of a LaN/B multilayer mirror with 3.5 nm periodicity. We have compared profiles obtained by simultaneous EUVR and GIXR and GIXR-only data analysis, both reconstructed profiles result in a similar description of the layered structure. However, the simultaneous analysis of both EUVR and GIXR by a single algorithm lead to a ∼ 2x increased accuracy of the reconstructed layered model, or a more narrow range of solutions, as compared to the GIXR analysis only. It also explains the inherent difficulty of accurately predicting EUV reflectivity from a GIXR-only analysis.
The structural inhomogeneities of silicon films embedded within W/Si multilayer mirrors were studied by X‐ray reflection, grazing‐incidence small‐angle X‐ray scattering (GISAXS) and X‐ray ...photoelectron spectroscopy (XPS). In the diffuse scattering spectra, evidence of laterally and vertically ordered in‐layer inhomogeneities was consistently observed. In particular, specific substructures resonant in nature (named here `ridges') were detected. The properties of the ridges were similar to the roughness determined by quasi‐Bragg peaks of scattering, which required a high interlayer correlation of particles. The XPS showed the nanocrystalline nature of the Si particles in the amorphous matrix. The geometric characteristics and in‐layer and inter‐layer correlations of the nanoparticles were determined. In GISAXS imaging, the unusual splitting of the waists between the Bragg sheets into filament structures was observed, whose physical nature cannot yet be explained.
The nature of the observed bulk inhomogeneities in the silicon layers in W/Si multilayers is established. In the diffuse scattering spectra, specific substructures, which are clearly resonant in nature, are observed. The physical nature of some of them is not established.
Recent research has demonstrated the high potential of grazing-emission X-ray fluorescence as a nanometrology tool for structures with complex 3D architecture. The technique now allows separate ...reconstruction of the spatial atomic distributions of different chemical elements both vertically and laterally, which opens up new and interesting applications in the nanofabrication industry. This study compares grazing-emission fluorescence with the well established grazing-incidence X-ray fluorescence method. The comparison uses a simple 1D thin-film structure. Reconstruction of the structure by both methods is performed and the statistical uncertainties of these reconstructions are compared by means of Monte Carlo Markov-chain simulations. For the forward model a semi-analytic approach is derived which allows simulation of the fluorescence intensity. This approach takes into account both grazing-incidence and grazing-emission cases. It also accounts for an even more complex physical phenomenon, the anomalous Kossel effect. Finally, using this semi-analytic approach, an experimental scheme combining grazing-incidence and grazing-emission X-ray fluorescence is studied theoretically.
A detailed theoretical review of phase retrieval algorithms, including the generalized Gerchberg–Saxton algorithm and some of its modifications, is presented. The possibility of applying phase ...retrieval algorithms to study the magnetic domain structure by dichroic coherent diffractive imaging is investigated on numerical examples. An optimal strategy for analyzing experimental data, stable to their nonidealities, is developed.
Abstract
The article describes the behaviour of the Zn ions in aqueous subphase in presence of arachidic acid films at the air/liquid interface first studied by XANES spectroscopy in the fluorescent ...mode under total external reflection conditions. Fingerprint analysis of experimental spectra was carried out to determine the local structure of zinc ions in arachidic acid. It showed that zinc is surrounded by oxygen atoms, which may correspond to the interaction of zinc ions with polar groups of arachidic acid.
The molecular mechanisms of the interaction of anticancer antibiotic doxorubicin with lipid cell membrane models have been investigated using grazing incidence X-ray diffraction (XRD) and X-ray ...reflectivity (XRR). The model systems were monolayers of four types of phospholipids, related to the main components of animal cell membranes. New information on the processes of damage of phospholipid monolayer lattice caused by doxorubicin is obtained. It is established that the action of doxorubicin on anionic phospholipid monolayers is determined by the electrostatic interaction: positively charged doxorubicin molecules are incorporated between negatively charged phospholipid functional groups. In the case of neutral phospholipids the key role belongs to the hydrophobic interaction: doxorubicin molecules are coordinated with phospholipid hydrocarbon tails in disordered regions.
Photoinduced pulsed heating of a suspension of silicon nanoparticles (NPs) excited by continuous-wave (CW) and pulsed nanosecond laser radiation was studied using Raman spectroscopy (RS). Based on ...the intensity ratio of the Stokes and anti-Stokes components of Raman scattering, the temperatures of the NPs and the liquid (alcohol) in the suspension were determined. It was found that silicon NPs heat up more than the surrounding liquid, which is due to their higher absorption coefficient at the excitation wavelength. Under heating by nanosecond laser pulses, the Raman method reveals strong short-term overheating of both the NPs and the surrounding liquid, but the time-average temperature of the suspension remains low. The results show that Raman spectroscopy is a convenient noncontact method for simultaneous temperature monitoring of both nanoparticles and the surrounding liquid, which is important for biomedical applications of nanoparticles, in particular in photothermal cancer therapy.
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