37 research outputs found
Ultrafast Structural Dynamics of Photo-Reactions Revealed by Model-Independent X-ray Cross-Correlation Analysis
We applied angular X-ray Cross-Correlation analysis (XCCA) to scattering
images from a femtosecond resolution LCLS X-ray free-electron laser (XFEL)
pump-probe experiment with solvated PtPOP
([Pt(POH)]) metal complex molecules. The molecules
were pumped with linear polarized laser pulses creating an excited state
population with a preferred orientational (alignment) direction. Two time
scales of ps and ps were revealed by model-independent
XCCA, associated with an internal structural changes and rotational dephasing,
respectively. Our studies illustrate the potential of XCCA to reveal hidden
structural information in a model independent analysis of time evolution of
solvated metal complex molecules.Comment: 8 pages, 5 figures, 50 reference
Local structure of semicrystalline P3HT films probed by nanofocused coherent x-rays
We present results of an x-ray study of structural properties of
semicrystalline polymer films using nanofocused x-ray beam. We applied the
x-ray cross-correlation analysis (XCCA) to scattering data from blends of
poly(3-hexylthiophene) (P3HT) embedded with gold nanoparticles (AuNPs).
Spatially resolved maps of orientational distribution of crystalline domains
allow us to distinguish sample regions of predominant face-on morphology,with a
continuous transition to edge-on morphology. The average size of crystalline
domains was determined to be of the order of 10 nm. As compared to pristine
P3HT film, the P3HT/AuNPs blend is characterized by substantial ordering of
crystalline domains, which can be induced by Au nanoparticles. The
inhomogeneous structure of the polymer film is clearly visualized on the
spatially resolved nanoscale 2D maps obtained using XCCA. Our results suggest
that the observed changes of the polymer matrix within crystalline regions can
be attributed to nanoconfinement in the presence of gold nanoparticles.Comment: 10 pages, 6 figures, 53 reference
Coherent soft X-ray diffraction imaging of coliphage PR772 at the Linac coherent light source
Single-particle diffraction from X-ray Free Electron Lasers offers the potential for molecular structure determination without the need for crystallization. In an effort to further develop the technique, we present a dataset of coherent soft X-ray diffraction images of Coliphage PR772 virus, collected at the Atomic Molecular Optics (AMO) beamline with pnCCD detectors in the LAMP instrument at the Linac Coherent Light Source. The diameter of PR772 ranges from 65–70 nm, which is considerably smaller than the previously reported ~600 nm diameter Mimivirus. This reflects continued progress in XFEL-based single-particle imaging towards the single molecular imaging regime. The data set contains significantly more single particle hits than collected in previous experiments, enabling the development of improved statistical analysis, reconstruction algorithms, and quantitative metrics to determine resolution and self-consistency
Correlations in Scattered X-Ray Laser Pulses Reveal Nanoscale Structural Features of Viruses
Diffraction based Hanbury Brown and Twiss interferometry at a hard x-ray free-electron laser
X-ray free-electron lasers (XFELs) provide extremely bright and highly spatially coherent x-ray radiation with femtosecond pulse duration. Currently, they are widely used in biology and material science. Knowledge of the XFEL statistical properties during an experiment may be vitally important for the accurate interpretation of the results. Here, for the first time, we demonstrate Hanbury Brown and Twiss (HBT) interferometry performed in diffraction mode at an XFEL source. It allowed us to determine the XFEL statistical properties directly from the Bragg peaks originating from colloidal crystals. This approach is different from the traditional one when HBT interferometry is performed in the direct beam without a sample. Our analysis has demonstrated nearly full (80%) global spatial coherence of the XFEL pulses and an average pulse duration on the order of ten femtoseconds for the monochromatized beam, which is significantly shorter than expected from the electron bunch measurements.publishe
Unravelling the structural rearrangement of polymer colloidal crystals under dry sintering conditions
\u3cp\u3eThe structural rearrangement of polystyrene colloidal crystals under dry sintering conditions has been revealed by in situ grazing incidence X-ray scattering. The measured diffraction patterns were analysed using distorted wave Born approximation (DWBA) theory and the structural parameters of the as-grown colloidal crystals of three different particle sizes were determined for the in-plane and out-of-plane directions in a film. By analysing the temperature evolution of the diffraction peak positions, integrated intensities, and widths, the detailed scenario of the structural rearrangement of crystalline domains at the nanoscale has been revealed, including thermal expansion, particle shape transformation and crystal amorphisation. Based on DWBA analysis, we demonstrate that in the process of dry sintering, the shape of colloidal particles in a crystal transforms from a sphere to a polyhedron. Our results deepen the understanding of the thermal annealing of polymer colloidal crystals as an efficient route for the design of new nano-materials.\u3c/p\u3
Evidence of a first-order smectic-hexatic transition and its proximity to a tricritical point in smectic films
Revealing Grain Boundaries and Defect Formation in Nanocrystal Superlattices by Nanodiffraction
X-ray nanodiffraction is applied to study the formation and correlation ofdomain boundaries in mesocrystalline superlattices of PbS nanocrystalswith face-centered cubic structure. Each domain of the superlattice can bedescribed with one of two mesocrystalline polymorphs with different orientationalorders. Close to a grain boundary, the lattice constant decreases andthe superlattice undergoes an out-of-plane rotation, while the orientation ofthe nanocrystals with respect to the superlattice remains unchanged. Thesefindings are explained with the release of stress on the expense of specificnanocrystal–substrate interactions. The fact that correlations between adjacentnanocrystals are found to survive the structural changes at most grainboundaries implies that the key to nanocrystal superlattices with macroscopicdomain sizes are strengthened interactions with the substrate