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Dispersion of metal nanoparticles on flat surfaces has attracted considerable interest in many technological applications. Numerous advantages of functionalized patterned nanostructures especially in medical physics, chemistry, biology, and semiconductor quantum dot applications have rapidly driven the growth of this field in the last two decades. In particular, for applications involving biomedical imaging, the nanoparticles have attracted perhaps the greatest attention as these materials provide a direct interface at the subcellular length scale. Reliable characterization methods are thus often needed to infer their detailed structural properties such as average particle size, particle shape, internal structure, surface morphology, distribution of particles, and their chemical composition. As a nondestructive probe, X-ray fluorescence measurements at grazing incidence provide sensitive information about the physical and chemical nature of the nanoparticles over the large surface area of a substrate. Herein, we demonstrate the potential capabilities of the X-ray fluorescence technique for reliable and precise determination of surface morphology of metal nanoparticles, dispersed on a flat surface. Our results show that X-ray standing wave assisted fluorescence measurements are markedly sensitive to the nature of dispersion of nanoparticles on a substrate surface. We have analyzed different types of nanostructured materials; e.g. a W thin film structure and Au nanoparticles deposited on a Si surface. The average size of the Au nanoparticles estimated, using X-ray standing wave fluorescence analysis, was found to closely agree with the atomic force microscopy measurements. The inherent features of the X-ray fluorescence technique permit us to analyze distribution of all kinds of metal and metalloid nanoparticles on a flat surface. Copyright © 2017 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Long-term durability of a thin film device is strongly correlated with the nature of interface structure associated between different constituent layers. Synthetic periodic multilayer structures are primarily employed as artificial X-ray Bragg reflectors in many applications, and their reflection efficiency is predominantly dictated by the nature of the buried interfaces between the different layers. Herein, we demonstrate the applicability of the combined analysis approach of the X-ray reflectivity and grazing incidence X-ray fluorescence measurements for the reliable and precise determination of a buried interface structure inside periodic X-ray multilayer structures. X-ray standing wave field (XSW) generated under Bragg reflection condition is used to probe the different constituent layers of the W-B4C multilayer structure at 10 keV and 12 keV incident X-ray energies. Our results show that the XSW assisted fluorescence measurements are markedly sensitive to the location and interface morphology of a buried layer structure inside a periodic multilayer structure. The cross sectional transmission electron microscopy results obtained on the W-B4C multilayer structure provide a deeper look on the overall reliability and accuracy of the XSW method. The method described here would also be applicable for nondestructive characterization of a wide range of thin film based semiconductor and optical devices. [ABSTRACT FROM AUTHOR]

We report results of simultaneous x-ray reflectivity and grazing incidence x-ray fluorescence measurements in combination with x-ray standing-wave-assisted depth-resolved near-edge x-ray absorption measurements to reveal new insights on chemical speciation of W in a W-B4C multilayer structure. Interestingly, our results show the existence of various unusual electronic states for the W atoms especially those near to the surface and interface boundary of a thin film medium as compared to those of the bulk. These observations are found to be consistent with the results obtained using first-principles calculations. Unlike the conventional x-ray absorption measurements the present approach has an advantage that it permits the determination of the depth-resolved chemical nature of an element in the thin-layered materials at atomic length scale resolution. [ABSTRACT FROM AUTHOR]

Total reflection X-ray fluorescence (TXRF)-based X-ray absorption near-edge spectroscopy has been used to determine the oxidation state of uranium in mixed-valent U3O8 and U3O7 uranium oxides. The TXRF spectra of the compounds were measured using variable X-ray energies in the vicinity of the U L3 edge in the TXRF excitation mode at the microfocus beamline of the Indus-2 synchrotron facility. The TXRF-based X-ray absorption near-edge spectroscopy (TXRF-XANES) spectra were deduced from the emission spectra measured using the energies below and above the U L3 edge in the XANES region. The data processing using TXRF-XANES spectra of U(IV), U(V), and U(VI) standard compounds revealed that U present in U3O8 is a mixture of U(V) and U(VI), whereas U in U3O7 is mixture of U(IV) and U(VI). The results obtained in this study are similar to that reported in literature using the U M edge. The present study has demonstrated the possibility of application of TXRF for the oxidation state determination and elemental speciation of radioactive substances in a nondestructive manner with very small amount of sample requirement. [ABSTRACT FROM AUTHOR]