| 1. |
- Berkowicz, Sharon, 1994-, et al.
(författare)
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Resolving nanoscale dynamics during a liquid-liquid transition in supercooled glycerol-water solutions
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- It is proposed that a liquid-liquid transition (LLT), related to the hypothesized transition between high- and low-density liquids (HDL, LDL) in pure water, also exists in supercooled aqueous mixtures. However, experimental observations of the LLT in the supercooled solution is often complicated by the overlap with freezing. Here, we conducted an experiment probing the hypothesized LLT in deeply supercooled 16.5 mol% glycerol-water solution, combining X-ray photon correlation spectroscopy (XPCS), ultra small-angle X-ray scattering (USAXS) and wide-angle X-ray scattering (WAXS). This approach allows us to capture simultaneous, discontinuous structural and dynamic changes within the supercooled liquid following quenching to cryogenic temperatures (172-182 K). We observe changes in the inter-atomic liquid structure (from WAXS) as well as in the nanoscale structure and dynamics (from USAXS/XPCS), resembling a first-order LLT between HDL-like to LDL-like liquid. Importantly, we find that the LLT precedes the onset of ice crystalliization, which we can distinguish based on the advent of ice bragg peaks in WAXS. In addition, analysis of the two-time correlation (TTC) function from XPCS enables us to follow the dynamics during the LLT, which indicates super-diffusive ballistic-like motion and a gradual slowdown towards an arrested state upon freezing, consistent with an LLT via spinodal decomposition. We conclude that these results indicate the existence of a first-order LLT in supercooled glycerol-water solutions at intermediate glycerol concentrations, similar to that hypothesized for pure water at elevated pressures.
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| 2. |
- Bin, Maddalena, et al.
(författare)
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Coherent X-ray Scattering Reveals Nanoscale Fluctuations in Hydrated Proteins
- 2023
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 127:21, s. 4922-4930
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Tidskriftsartikel (refereegranskat)abstract
- Hydrated proteins undergo a transition in the deeply supercooled regime, which is attributed to rapid changes in hydration water and protein structural dynamics. Here, we investigate the nanoscale stress-relaxation in hydrated lysozyme proteins stimulated and probed by X-ray Photon Correlation Spectroscopy (XPCS). This approach allows us to access the nanoscale dynamics in the deeply supercooled regime (T = 180 K), which is typically not accessible through equilibrium methods. The observed stimulated dynamic response is attributed to collective stress-relaxation as the system transitions from a jammed granular state to an elastically driven regime. The relaxation time constants exhibit Arrhenius temperature dependence upon cooling with a minimum in the Kohlrausch-Williams-Watts exponent at T = 227 K. The observed minimum is attributed to an increase in dynamical heterogeneity, which coincides with enhanced fluctuations observed in the two-time correlation functions and a maximum in the dynamic susceptibility quantified by the normalized variance χT. The amplification of fluctuations is consistent with previous studies of hydrated proteins, which indicate the key role of density and enthalpy fluctuations in hydration water. Our study provides new insights into X-ray stimulated stress-relaxation and the underlying mechanisms behind spatiotemporal fluctuations in biological granular materials.
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| 3. |
- Dallari, Francesco, et al.
(författare)
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Analysis Strategies for MHz XPCS at the European XFEL
- 2021
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Ingår i: Applied Sciences. - : MDPI AG. - 2076-3417. ; 11:17
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Tidskriftsartikel (refereegranskat)abstract
- The nanometer length-scale holds precious information on several dynamical processes that develop from picoseconds to seconds. In the past decades, X-ray scattering techniques have been developed to probe the dynamics at such length-scales on either ultrafast (sub-nanosecond) or slow ((milli-)second) time scales. With the start of operation of the European XFEL, thanks to the MHz repetition rate of its X-ray pulses, even the intermediate mu s range have become accessible. Measuring dynamics on such fast timescales requires the development of new technologies such as the Adaptive Gain Integrating Pixel Detector (AGIPD). mu s-XPCS is a promising technique to answer many scientific questions regarding microscopic structural dynamics, especially for soft condensed matter systems. However, obtaining reliable results with complex detectors at free-electron laser facilities is challenging and requires more sophisticated analysis methods compared to experiments at storage rings. Here, we discuss challenges and possible solutions to perform XPCS experiments with the AGIPD at European XFEL; in particular, at the Materials Imaging and Dynamics (MID) instrument. We present our data analysis pipeline and benchmark the results obtained at the MID instrument with a well-known sample composed by silica nanoparticles dispersed in water.
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| 4. |
- Ladd-Parada, Marjorie, et al.
(författare)
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Using coherent X-rays to follow dynamics in amorphous ices
- 2022
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Ingår i: Environmental Science. - : Royal Society of Chemistry (RSC). - 2634-3606. ; 2:6, s. 1314-1323
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Tidskriftsartikel (refereegranskat)abstract
- Amorphous solid water plays an important role in our overall understanding of water's phase diagram. X-ray scattering is an important tool for characterising the different states of water, and modern storage ring and XFEL facilities have opened up new pathways to simultaneously study structure and dynamics. Here, X-ray photon correlation spectroscopy (XPCS) was used to study the dynamics of high-density amorphous (HDA) ice upon heating. We follow the structural transition from HDA to low-density amorphous (LDA) ice, by using wide-angle X-ray scattering (WAXS), for different heating rates. We used a new type of sample preparation, which allowed us to study μm-sized ice layers rather than powdered bulk samples. The study focuses on the non-equilibrium dynamics during fast heating, spontaneous transformation and crystallization. Performing the XPCS study at ultra-small angle (USAXS) geometry allows us to characterize the transition dynamics at length scales ranging from 60 nm–800 nm. For the HDA-LDA transition we observe a clear separation in three dynamical regimes, which show different dynamical crossovers at different length scales. The crystallization from LDA, instead, is observed to appear homogenously throughout the studied length scales.
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| 5. |
- Perakis, Fivos, et al.
(författare)
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Coherent X-rays reveal the influence of cage effects on ultrafast water dynamics
- 2018
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- The dynamics of liquid water feature a variety of time scales, ranging from extremely fast ballistic-like thermal motion, to slower molecular diffusion and hydrogen-bond rearrangements. Here, we utilize coherent X-ray pulses to investigate the sub-100 fs equilibrium dynamics of water from ambient conditions down to supercooled temperatures. This novel approach utilizes the inherent capability of X-ray speckle visibility spectroscopy to measure equilibrium intermolecular dynamics with lengthscale selectivity, by measuring oxygen motion in momentum space. The observed decay of the speckle contrast at the first diffraction peak, which reflects tetrahedral coordination, is attributed to motion on a molecular scale within the first 120 fs. Through comparison with molecular dynamics simulations, we conclude that the slowing down upon cooling from 328 K down to 253 K is not due to simple thermal ballistic-like motion, but that cage effects play an important role even on timescales over 25 fs due to hydrogen-bonding.
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| 6. |
- Perakis, Fivos, et al.
(författare)
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Diffusive dynamics during the high-to-low density transition in amorphous ice
- 2017
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 114:31, s. 8193-8198
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Tidskriftsartikel (refereegranskat)abstract
- Water exists in high- and low-density amorphous ice forms (HDA and LDA), which could correspond to the glassy states of high(HDL) and low-density liquid (LDL) in the metastable part of the phase diagram. However, the nature of both the glass transition and the high-to-low-density transition are debated and new experimental evidence is needed. Here we combine wide-angle X-ray scattering (WAXS) with X-ray photon-correlation spectroscopy (XPCS) in the small-angle X-ray scattering (SAXS) geometry to probe both the structural and dynamical properties during the high-to-low-density transition in amorphous ice at 1 bar. By analyzing the structure factor and the radial distribution function, the coexistence of two structurally distinct domains is observed at T = 125 K. XPCS probes the dynamics in momentum space, which in the SAXS geometry reflects structural relaxation on the nanometer length scale. The dynamics of HDA are characterized by a slow component with a large time constant, arising from viscoelastic relaxation and stress release from nanometer-sized heterogeneities. Above 110 K a faster, strongly temperature-dependent component appears, with momentum transfer dependence pointing toward nanoscale diffusion. This dynamical component slows down after transition into the low-density form at 130 K, but remains diffusive. The diffusive character of both the high- and low-density forms is discussed among different interpretations and the results are most consistent with the hypothesis of a liquid-liquid transition in the ultraviscous regime.
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