X-Ray Fluorescence Correlation Spectroscopy: A Method for Studying Particle Dynamics in Condensed Matter (original) (raw)
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X-ray fluorescence correlation spectroscopy for studying particle dynamics in condensed matter
1997
Photon correlation spectroscopy probing fluctuations in scattered or fluorescent intensity to study particle dynamics in fluids is by now well established in the visible light regime. With the advent of high-brilliance synchrotron radiation sources, correlation spectroscopy utilizing scattered radiation has recently been extended to the x-ray wavelength regime by using spatially coherent x-rays to study the time fluctuations of the corresponding speckle patterns. In this presentation, we report the development of a new technique, x-ray fluorescence correlation spectroscopy (XFCS) for elucidating the dynamics of particles. This technique does not require coherent beams but relies on intense microfocused x-ray beams. Further, it is element specific. As a demonstration of this method, the dynamics of gold colloidal particles and aggregates undergoing diffusion and sedimentation in water was studied by measuring the time autocorrelation of the gold fluorescence intensity from a small illuminated volume. The values of the translational diffusion constants and sedimentation velocities obtained are in excellent agreement with theoretical estimates and other measurements. Further potential applications of the technique are discussed.
The European Physical Journal E, 2001
We have studied the static and dynamic behaviour of magnetic colloidal systems (ferrofluids) by Small-Angle X-ray Scattering (SAXS) and X-ray Photon Correlation Spectroscopy (XPCS). The main features of the novel XPCS technique will be illustrated by data taken on a model system, colloidal silica spheres. We will then present the results obtained on an optically opaque suspension of magnetic colloids (maghemite) in the wave vector range from 10 −3 to 10 −2Å−1. Translational diffusion in zero field and anisotropic diffusion under external magnetic fields will be discussed.
X-ray photon correlation spectroscopy under flow
Journal of Synchrotron Radiation, 2008
X-ray photon correlation spectroscopy was used to probe the diffusive dynamics of colloidal particles in a shear flow. Combining X-ray techniques with microfluidics is an experimental strategy that reduces the risk of x-ray induced beam damage and also allows time-resolved studies of processes taking place in flowcells. The experimental results and theoretical predictions presented here, show that in the low shear limit, for a "transverse flow" scattering geometry (scattering wave vector q perpendicular to the direction of flow) the measured relaxation times are independent of the flow rate and determined only by the diffusive motion of the particles. This is not generally valid and in particular, for a "longitudinal flow" (q flow) scattering geometry, the relaxation times are strongly affected by the flow-induced motion of the particles. Our results show that the Brownian diffusion of colloidal particles can be measured in a flowing sample and that, up to flux limitations, the experimental conditions under which this is possible are easier to achieve at higher values of q.
Journal of Applied Crystallography, 2000
The dynamics of concentrated, charge-stabilized colloidal silica suspensions was studied over a wide range of wave-vectors. The short-time diffusion coefficient, D(Q), was measured for concentrated suspensions up to their solidification points by photon correlation spectroscopy with coherent X-rays and compared to free particle diffusion D 0 , studied by Dynamic Light Scattering (DLS) in the dilute case. Small angle X-ray scattering (SAXS) was used to determine the static structure factor S(Q). D 0 /D(Q) peaks for Q values corresponding to the maximum of the static structure factor showing that the mostly likely density fluctuations decay the slowest. The data allow one to estimate the diffusion coefficient D(Q) in the Q → 0 and Q → ∞ limits. Thus, hydrodynamic functions can be derived free from any modeling of the static or dynamic properties. The effects of hydrodynamic interactions on the diffusion coefficient in charge-stabilized suspensions are presented for volume fractions 0.075 < Φ < 0.28.
X-Ray Photon Correlation Spectroscopy Study of Brownian Motion of Gold Colloids in Glycerol
Physical Review Letters, 1995
We report x-ray photon correlation spectroscopy studies of the static structure factor and dynamic correlation function of a gold colloid dispersed in the viscous liquid glycerol. We find a diffusion coefficient for Brownian motion of the gold colloid which agrees well with that extrapolated from measurements made with visible light, but which was determined on an optically opaque sample and in a wave-vector range inaccessible to visible light.
Microsecond hydrodynamic interactions in dense colloidal dispersions probed at the European XFEL
IUCrJ
Many soft-matter systems are composed of macromolecules or nanoparticles suspended in water. The characteristic times at intrinsic length scales of a few nanometres fall therefore in the microsecond and sub-microsecond time regimes. With the development of free-electron lasers (FELs) and fourth-generation synchrotron light-sources, time-resolved experiments in such time and length ranges will become routinely accessible in the near future. In the present work we report our findings on prototypical soft-matter systems, composed of charge-stabilized silica nanoparticles dispersed in water, with radii between 12 and 15 nm and volume fractions between 0.005 and 0.2. The sample dynamics were probed by means of X-ray photon correlation spectroscopy, employing the megahertz pulse repetition rate of the European XFEL and the Adaptive Gain Integrating Pixel Detector. We show that it is possible to correctly identify the dynamical properties that determine the diffusion constant, both for sta...
Structure and dynamics of colloidal suspensions studied by means of XPCS
Structure and dynamics of suspensions of charged colloidal spheres in water were studied by means of small-angle X-ray scattering and X-ray photon correlation spectroscopy using synchrotron radiation. Experimentally obtained dependences on the scattering vector q of the structure factor S(q), short-time collective diffusion coefficient D(q) and hydrodynamic function H(q) were in good agreement with theoretical predictions. No effect of screening of the hydrodynamic interactions, suggested in the literature, was found. The conditions are discussed at which the maximum of the hydrodynamic function peak value H(qm) can be obtained experimentally.
In situ measurements of colloid transport and retention using synchrotron X-ray fluorescence
2006
1] The physics regarding the retention and mobilization of colloids in saturated and unsaturated conditions remains poorly understood, partially because of the inability to measure colloid concentrations in situ. In this study, we attached Cd +2 ions to clay colloids and used synchrotron X rays to cause the Cd to fluoresce. By measuring the fluorescence and attenuation of the X rays we obtained simultaneous in situ water saturations and colloid concentrations on timescales of tens of seconds. We used this technique to study the transport of colloids consisting of Na and Ca Montmorillonite clays through a preferential flow path in uniform well-sorted sand. This flow path had both saturated and unsaturated zones that travel downward with time. We found that the Na colloids showed little retention in the sand, while the Ca colloids were retarded with respect to the wetting front. By comparing the results to those obtained by infiltrations with a Cd solute we find that the retention of the colloids seen in the unsaturated portion of the column was no greater than that seen in the saturated portion. We discussed the advantages and limitations of this X-ray fluorescence technique and the implications for colloid transport.
Polymer Journal, 2012
The effects of a thermal gradient on the dynamical behavior of nanoparticles dispersed in a polymer matrix were studied using X-ray photon correlation spectroscopy. Polystyrene (PS)-grafted silica nanoparticles (SiNPs-PS), which are nanoparticles dispersed in a PS matrix controlled at temperatures above the glass transition temperature, were used in this study. Anisotropic motions of the SiNPs-PS were observed when the sample was kept in a conventional capillary tube, whereas isotropic motion was observed when the sample was kept in a newly designed cell with a low thermal flow, demonstrating the importance of the thermal gradient on the dynamical behavior of the SiNPs-PS.