X-ray photon correlation spectroscopy under flow.
01 Jul 2008-Journal of Synchrotron Radiation (International Union of Crystallography)-Vol. 15, Iss: 4, pp 378-384
TL;DR: The experimental results and theoretical predictions presented in this paper show that in the low shear limit for a transverse flow scattering geometry (scattering wavevector 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.
Abstract: 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 flow cells. The experimental results and theoretical predictions presented here show that in the low shear limit for a `transverse flow' scattering geometry (scattering wavevector 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. The results here 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.
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TL;DR: In this paper, the role of the filler-filler interaction in the aging mechanism of a cross-linked elastomer was investigated using X-ray photon correlation spectroscopy in homodyne and heterodyne configurations.
Abstract: The complexity of the mechanical behavior of filled elastomers can be partly attributed to the fact that the duration of an applied strain plays a crucial role. In order to bring new insights into this still incompletely solved problem, we look for relationships between the macroscopic mechanical relaxation and the relaxation of the filler particles at the nano- to mesoscale. To this end, X-ray photon correlation spectroscopy (XPCS) in homodyne and heterodyne configurations combined with tensile stress relaxation is employed. The paper is devoted to the study of the role of the filler–filler and the filler–matrix interactions in a cross-linked elastomer on the aging mechanisms under strain. The fillers investigated are carbon black, as an example of strong filler–matrix interactions, and hydroxylated silica for which the filler–filler interaction is strong (H-bonds). Homodyne XPCS correlation reveals features of jammed systems (compressed exponential and ballistic motion) for both systems. The exponents c...
50 citations
Stanford University1, University of Hamburg2, University of Michigan3, University of Melbourne4, Lawrence Berkeley National Laboratory5, University of Pennsylvania6, Shanghai Jiao Tong University7, University College Dublin8, University of Kiel9, Karolinska University Hospital10, Nanjing University11, Chinese Academy of Sciences12, Ikerbasque13, European XFEL14, La Trobe University15, Ludwig Maximilian University of Munich16, Saha Institute of Nuclear Physics17, Pennsylvania State University18, German Cancer Research Center19, University of Wisconsin–Milwaukee20, Indian Institute of Science21, University of California, Los Angeles22, Hunan University23, Armenian National Academy of Sciences24
TL;DR: X-ray-based analytics are routinely applied in many fields, including physics, chemistry, materials science, and engineering as discussed by the authors, but the full potential of such techniques in the life sciences and medicine has not yet been fully exploited.
Abstract: X-ray-based analytics are routinely applied in many fields, including physics, chemistry, materials science, and engineering. The full potential of such techniques in the life sciences and medicine, however, has not yet been fully exploited. We highlight current and upcoming advances in this direction. We describe different X-ray-based methodologies (including those performed at synchrotron light sources and X-ray free-electron lasers) and their potentials for application to investigate the nano-bio interface. The discussion is predominantly guided by asking how such methods could better help to understand and to improve nanoparticle-based drug delivery, though the concepts also apply to nano-bio interactions in general. We discuss current limitations and how they might be overcome, particularly for future use in vivo.
45 citations
TL;DR: Small-angle X-ray photon correlation spectroscopy measurements spanning delay times from 826 ns to 52.8 s were performed using a photon-counting pixel array detector with a dynamic range of 0-3 (2 bits), and it was found that in burst mode the ratio of 2-to-1 ratio is markedly smaller than predicted and that this is attributable to pixel-response dead-time.
Abstract: Small-angle X-ray photon correlation spectroscopy (XPCS) measurements spanning delay times from 826 ns to 52.8 s were performed using a photon-counting pixel array detector with a dynamic range of 0–3 (2 bits). Fine resolution and a wide dynamic range of time scales was achieved by combining two modes of operation of the detector: (i) continuous mode, where data acquisition and data readout are performed in parallel with a frame acquisition time of 19.36 µs, and (ii) burst mode, where 12 frames are acquired with frame integration times of either 2.56 µs frame−1 or 826 ns frame−1 followed by 3.49 ms or 1.16 ms, respectively, for readout. The applicability of the detector for performing multi-speckle XPCS was demonstrated by measuring the Brownian dynamics of 10 nm-radius gold and 57 nm-radius silica colloids in water at room temperature. In addition, the capability of the detector to faithfully record one- and two-photon counts was examined by comparing the statistical distribution of photon counts with expected probabilities from the negative binomial distribution. It was found that in burst mode the ratio of 2 s to 1 s is markedly smaller than predicted and that this is attributable to pixel-response dead-time.
38 citations
TL;DR: How to optimize experimental setups to make BioXPCS measurements feasible at new generation synchrotron sources is explained.
37 citations
TL;DR: In this paper, a model colloidal suspension is used to show how the macroscopic advective response to flow and the microscopic dissipative dynamics (diffusion) can be quantified from the x-ray data.
Abstract: X-ray photon correlation spectroscopy (XPCS) has emerged as a unique technique allowing the measurement of dynamics of materials on mesoscopic lengthscales. One of the most common problems associated with the use of bright x-ray beams is beam-induced radiation damage, and this is likely to become an even more limiting factor at future synchrotron and free-electron laser sources. Flowing the sample during data acquisition is one of the simplest methods allowing the radiation damage to be limited. In addition to distributing the dose over many different scatterers, the method also enables new functionalities such as time-resolved studies. Here, we further develop a recently proposed experimental technique that combines XPCS and continuously flowing samples. More specifically, we use a model colloidal suspension to show how the macroscopic advective response to flow and the microscopic dissipative dynamics (diffusion) can be quantified from the x-ray data. Our results show very good quantitative agreement with a Poisseuille-flow hydrodynamical model combined with Brownian mechanics. The method has many potential applications, e.g. in the study of dynamics of glasses and gels under continuous shear/flow, protein aggregation processes and the interplay between dynamics and rheology in complex fluids.
34 citations
References
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TL;DR: The microfabrication technologies of the semiconductor industry have made it possible to integrate increasingly complex electronic and mechanical functions, providing us with ever smaller, cheaper and smarter sensors and devices, which has revolutionized ability to precisely control fluid/fluid interfaces for use in fields ranging from materials processing and analytical chemistry to biology and medicine.
Abstract: The microfabrication technologies of the semiconductor industry have made it possible to integrate increasingly complex electronic and mechanical functions, providing us with ever smaller, cheaper and smarter sensors and devices. These technologies have also spawned microfluidics systems for containing and controlling fluid at the micrometre scale, where the increasing importance of viscosity and surface tension profoundly affects fluid behaviour. It is this confluence of available microscale engineering and scale-dependence of fluid behaviour that has revolutionized our ability to precisely control fluid/fluid interfaces for use in fields ranging from materials processing and analytical chemistry to biology and medicine.
925 citations
TL;DR: In this article, it was shown that by using a high-brilliance X-ray source it should be possible to perform this type of measurement using radiation of wavelength ∼ 0.15nm.
Abstract: REFLECTED light from a coherent light source such as a laser shows a graininess known as speckle. In general, a speckle pattern is produced whenever randomly distributed regions of a material introduce different phase shifts into the scattering of coherent incident light. If the arrangement of the regions evolves with time, the speckle pattern will also change. Observation of the intensity fluctuations at a single point in the speckle pattern provides a direct measure of the time correlation function of the inhomogeneity. This leads to a technique1,2, alternatively called light-beating spectroscopy, dynamic light scattering or intensity fluctuation spectroscopy, which has been widely used with visible light to study processes such as critical fluctuations near phase transitions in fluids and the diffusion of particles in liquids. But it is not possible to study processes involving length scales less than about 200 nm, or those in opaque materials, using visible light. If intensity fluctuation spectroscopy could be carried out using coherent X-rays, however, one could probe the dynamics of processes involving atomic length scales in a wide range of materials. Here we show that by using a high-brilliance X-ray source it should be possible to perform this type of measurement using radiation of wavelength ∼0.15nm. Specifically, we have observed a speckle pattern in the diffraction of coherent X-rays from randomly arranged antiphase domains in a single crystal of the binary alloy Cu3Au.
294 citations
TL;DR: In this article, the authors used Viscometry and dynamic light scattering (DLS) to study suspensions of colloidal particles which interact like hard spheres and found that the rate of ''structural relaxation'' of microscopic density fluctuations, indicated by the long-time diffusion coefficient measured by DLS at the peak of the static structure factor, was found to vary with particle concentration quantitatively like the inverse of the low-shear-rate viscosity.
Abstract: Viscometry and dynamic light scattering (DLS) were used to study suspensions of colloidal particles which interact like hard spheres. The rate of ``structural relaxation'' of microscopic density fluctuations, indicated by the long-time diffusion coefficient measured by DLS at the peak of the static structure factor, was found to vary with particle concentration quantitatively like the inverse of the low-shear-rate viscosity. Sample concentrations were calibrated with respect to the thermodynamic ``freezing'' transition of the suspension.
186 citations
TL;DR: This Letter describes recent work on the protein bovine beta-lactoglobulin where collapse from an expanded to a compact set of states was directly observed on the millisecond time scale.
Abstract: High-intensity, "pink" beam from an undulator was used in conjunction with microfabricated rapid-fluid mixing devices to monitor the early events in protein folding with time resolved small angle x-ray scattering This Letter describes recent work on the protein bovine beta-lactoglobulin where collapse from an expanded to a compact set of states was directly observed on the millisecond time scale The role of chain collapse, one of the initial stages of protein folding, is not currently understood The characterization of transient, compact states is vital in assessing the validity of theories and models of the folding process
151 citations