Total reflection X-ray fluorescence study of Langmuir monolayers on water surface

Abstract

X-ray total external reflection fluorescence has been applied to detect an angular dependence of fluorescence yield modulated by evanescent/X-ray standing wave pattern from metal-rich organic monolayer alone on water surface. Theoretical consideration reveals that electric field intensity in a molecular monolayer is completely determined by an area per one molecule value that can be obtained from pressure-area isotherm. This allows getting an ion position inside a monolayer from the corresponding fluorescence angular dependence. The possibilities of the technique have been used at the SR beamline ID10B (ESRF) to characterize Langmuir monolayers of phthalocyanines and cyclolinear polyorganosiloxanes formed on air/water interface.

Quantitative determination of ion distributions in bacterial lipopolysaccharide membranes by grazing-incidence X-ray fluorescence

“…In the vicinity of the critical edge of total reflection (q c ¼ 0.022 Å −1 ) the shape of the curve depends on the imaginary part β of the refractive index (n ¼ 1 − δ þ iβ) of the bulk medium for the incident X-ray beam. In our experimental system a maximum near the critical edge (13) was not observed due to the strong X-ray absorption by water at 8 keV. Instead, we observed a monotonic increase in the signal with increasing q z .…”

“…1B), which permits determination of the distribution of chemical elements, identified from their emission spectra. Although this method was used to resolve the weak depletion of ions in the vicinity of the water surface (11), applications of GIXF have been limited to studies with little relevance to biological systems, such as the adsorption of proteins stabilized with lead acetates to the solid/liquid interface (12) and ion adsorption to synthetic surfactant monolayers at the air/water interface (13,14). Our intent is to utilize GIXF to establish the distributions of monovalent and divalent cations in a realistic model of bacterial surfaces and compare the results with the predictions of our MC simulations.…”

Amorphous iron-(hydr) oxide networks at liquid/vapor interfaces: In situ X-ray scattering and spectroscopy studies

“…To determine the amount and structure of iron aggregates at Langmuir monolayers on molecular length scales, we employed X-ray reflectivity [18][19][20][21][22][23], fluorescence spectroscopy [24][25][26][27][28][29] and grazing incidence X-ray diffraction (GIXD) techniques, using synchrotron radiation. In this study we used dihexadecyl-phosphate (DHDP) and arachidic acid (AA) to form two-dimensional (2D) charged templates.…”

Arrangement of trace metal contaminations in thin films of liquid crystals studied by X-ray standing wave technique

“…XRSW measurements are based on recording along with angular dependence of reflected X-ray beam the yield of characteristic X-ray fluorescence. This technique has been demonstrated to be very precise in determining the position of impurity atoms in the organic films deposited on solid substrates and directly on the surface of the water subphase [11,13,14].…”

“…The great potential have spectral Xray techniques such as X-ray standing wave method (XRSW method) that combines the advantages of high-resolution X-ray experiments with spectroscopic selectivity of obtained data [9][10][11][12][13][14]. XRSW measurements are based on recording along with angular dependence of reflected X-ray beam the yield of characteristic X-ray fluorescence.…”