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A vacuum-compatible photon-counting hybrid pixel detector has been installed in the ultra-high vacuum (UHV) reflectometer of the four-crystal monochromator (FCM) beamline of the Physikalisch-Technische Bundesanstalt (PTB) at the electron storage ring BESSY II in Berlin, Germany. The setup is based on the PILATUS3 100K module. The detector can be used in the entire photon energy range accessible at the beamline from 1.75 to 10 keV. Complementing the already installed vacuum-compatible PILATUS 1M detector used for small-angle scattering (SAXS) and grazing incidence SAXS (GISAXS), it is possible to access larger scattering angles. The water-cooled module is located on the goniometer arm and can be positioned from -90{\deg} to 90{\deg} with respect to the incoming beam at a distance of about 200 mm from the sample. To perform absolute scattering experiments the linearity, homogeneity and the angular dependence of the quantum efficiency, including their relative uncertainties, have been investigated. In addition, first results of the performance in wide-angle X-ray scattering (WAXS), X-ray diffraction (XRD) and X-ray reflectometry (XRR) are presented., Comment: The following article has been accepted by Review of Scientific Instruments. After it is published, it will be found at https://aip.scitation.org/journal/rsi

We investigated the growth of β-phase NaYF4:Yb3+,Er3+ upconversion nanoparticles synthesized by the thermal decomposition method using a combination of in situ and offline analytical methods for determining the application-relevant optical properties, size, crystal phase, and chemical composition. This included in situ steady state luminescence in combination with offline time-resolved luminescence spectroscopy as well as small-angle X-ray scattering (SAXS) transmission electron microscopy (TEM), X-ray diffraction analysis (XRD), and inductively coupled plasma optical emission spectrometry (ICP-OES). For assessing the suitability of our optical monitoring approach, the in situ-collected spectroscopic data, which reveal the luminescence evolution during nanocrystal synthesis, were compared to measurements done after cooling of the reaction mixture of the as-synthesized particles. The excellent correlation of the in situ and time-resolved upconversion luminescence with the nanoparticle sizes determined duri...

The industrial exploitation of high value nanoparticles is in need of robust measurement methods to increase the control over product manufacturing and to implement quality assurance. InNanoPart, a European metrology project responded to these needs by developing methods for the measurement of particle size, concentration, agglomeration, surface chemistry and shell thickness. This paper illustrates the advancements this project produced for the traceable measurement of nanoparticle number concentration in liquids through small angle X-ray scattering (SAXS) and single particle inductively coupled plasma mass spectrometry (spICPMS). It also details the validation of a range of laboratory methods, including particle tracking analysis (PTA), dynamic light scattering (DLS), differential centrifugal sedimentation (DCS), ultraviolet visible spectroscopy (UV-vis) and electrospray-differential mobility analysis with a condensation particle counter (ES-DMA-CPC). We used a set of spherical gold nanoparticles with nominal diameters between 10 nm and 100 nm and discuss the results from the various techniques along with the associated uncertainty budgets.

The industrial exploitation of high value nanoparticles is in need of robust measurement methods to increase the control over product manufacturing and to implement quality assurance. InNanoPart, a European metrology project responded to these needs by developing methods for the measurement of particle size, concentration, agglomeration, surface chemistry and shell thickness. This paper illustrates the advancements this project produced for the traceable measurement of nanoparticle number concentration in liquids through small angle X-ray scattering (SAXS) and single particle inductively coupled plasma mass spectrometry (spICPMS). It also details the validation of a range of laboratory methods, including particle tracking analysis (PTA), dynamic light scattering (DLS), differential centrifugal sedimentation (DCS), ultraviolet visible spectroscopy (UV-vis) and electrospray-differential mobility analysis with a condensation particle counter (ES-DMA-CPC). We used a set of spherical gold nanoparticles with nominal diameters between 10 nm and 100 nm and discuss the results from the various techniques along with the associated uncertainty budgets.

This thesis investigates structural properties and the underlying microscopic dynamicsof suspensions of $\alpha$-FeOOH goethite platelets in water under the influence of magneticfields. Goethite particles show unusual physical properties and a rich phase diagram,which makes their suspensions an object of high interest for research in the area of”smart nanoparticles”. Five nanoparticle concentrations were chosen such that differentliquid crystal phases could be studied. The suspensions of platelets of these chosenconcentrations were exposed to magnetic fields of varying strength. Small angle X-rayscattering and X-ray photon correlation spectroscopy data were taken and evaluated.The appearing phases and phase transitions were studied as a function of concentrationand applied magnetic field. For this purpose, order parameters, ellipticity, radial andazimuthal peak positions and widths of scattering features were investigated to clarifythe structural properties in detail. For the analysis of the underlying dynamics, therelaxation rates and the shape of measured time correlation functions were evaluated.The results show that with increasing magnetic field a partial realignment of the plateletsoccurs. This realignment is connected to the magnetic properties of the particles. Thedynamics of the corresponding phases revealed a dependence on the concentration ofnanoparticles in the suspension. At a concentration ofc= 20 vol%the transition from thenematic to the anti-nematic phase traverses a mixed state. The nematic and anti-nematicphases show ballistic motion and very similar properties, even though a realignment ofthe particles from an orientation with the long axis parallel to the applied magnetic fieldin the nematic phase to an orientation with the long axis perpendicular to the magneticfield in the anti-nematic phase occurs. The mixed state of20 vol%-suspension exhibits adiffusive motion of the particles and different characteristics. A significant differencewas observed forc= 16 vol%, where the original nematic state has a transition into theanti-nematic phase via an intermediate state of the mixed phase, too. In contrast to thebehaviour atc= 20 vol%the underlying motion atc= 16 vol%shows ballistic dynamicsonly for the nematic state. At this concentration the mixed state and the anti-nematicphase show both diffusive motions. The formation of different phases and underlyingmicroscopic dynamics are explained through the establishment of qualitative modelbased on dipole-dipole interactions. The results obtained in this thesis describe thestructural properties of goethite suspensions and try to our knowledge for first time tolink the microscopic dynamics of the platelets in the suspensions to their structural andunusual physical properties.

Universität Hamburg, Diss., 2017; DESY-THESIS 187 p.(2017). doi:10.3204/PUBDB-2017-02077, This thesis investigates structural properties and the underlying microscopic dynamicsof suspensions of $\alpha$-FeOOH goethite platelets in water under the influence of magneticfields. Goethite particles show unusual physical properties and a rich phase diagram,which makes their suspensions an object of high interest for research in the area of”smart nanoparticles”. Five nanoparticle concentrations were chosen such that differentliquid crystal phases could be studied. The suspensions of platelets of these chosenconcentrations were exposed to magnetic fields of varying strength. Small angle X-rayscattering and X-ray photon correlation spectroscopy data were taken and evaluated.The appearing phases and phase transitions were studied as a function of concentrationand applied magnetic field. For this purpose, order parameters, ellipticity, radial andazimuthal peak positions and widths of scattering features were investigated to clarifythe structural properties in detail. For the analysis of the underlying dynamics, therelaxation rates and the shape of measured time correlation functions were evaluated.The results show that with increasing magnetic field a partial realignment of the plateletsoccurs. This realignment is connected to the magnetic properties of the particles. Thedynamics of the corresponding phases revealed a dependence on the concentration ofnanoparticles in the suspension. At a concentration ofc= 20 vol%the transition from thenematic to the anti-nematic phase traverses a mixed state. The nematic and anti-nematicphases show ballistic motion and very similar properties, even though a realignment ofthe particles from an orientation with the long axis parallel to the applied magnetic fieldin the nematic phase to an orientation with the long axis perpendicular to the magneticfield in the anti-nematic phase occurs. The mixed state of20 vol%-suspension exhibits adiffusive motion of the particles and different characteristics. A significant differencewas observed forc= 16 vol%, where the original nematic state has a transition into theanti-nematic phase via an intermediate state of the mixed phase, too. In contrast to thebehaviour atc= 20 vol%the underlying motion atc= 16 vol%shows ballistic dynamicsonly for the nematic state. At this concentration the mixed state and the anti-nematicphase show both diffusive motions. The formation of different phases and underlyingmicroscopic dynamics are explained through the establishment of qualitative modelbased on dipole-dipole interactions. The results obtained in this thesis describe thestructural properties of goethite suspensions and try to our knowledge for first time tolink the microscopic dynamics of the platelets in the suspensions to their structural andunusual physical properties., Published by Verlag Deutsches Elektronen-Synchrotron, Hamburg

We report on high pressure small angle x-ray scattering on suspensions of colloidal crystallites in water. The crystallites made out of charge-stabilized poly-acrylate particles exhibit a complex pressure dependence which is based on the specific pressure properties of the suspending medium water. The dominant effect is a compression of the crystallites caused by the compression of the water. In addition, we find indications that also the electrostatic properties of the system, i.e. the particle charge and the dissociation of ions, might play a role for the pressure dependence of the samples. The data further suggest that crystallites in a metastable state induced by shear-induced melting can relax to a similar structural state upon the application of pressure and dilution with water. X-ray cross correlation analysis of the two-dimensional scattering patterns indicates a pressure-dependent increase of the orientational order of the crystallites correlated with growth of these in the suspension. This study underlines the potential of pressure as a very relevant parameter to understand colloidal crystallite systems in aqueous suspension.

We have used scanning micro x-ray diffraction to characterize different phases in superconducting KxFe2-ySe2 as a function of temperature, unveiling the thermal evolution across the superconducting transition temperature (T-c similar to 32 K), phase separation temperature (T-ps similar to 520 K), and iron-vacancy order temperature (T-vo similar to 580 K). In addition to the iron-vacancy ordered tetragonalmagnetic phase and orthorhombicmetallic minority filamentary phase, we have found clear evidence of the interface phase with tetragonal symmetry. The metallic phase is surrounded by this interface phase below similar to 300 K, and is embedded in the insulating texture. The spatial distribution of coexisting phases as a function of temperature provides clear evidence of the formation of protected metallic percolative paths in themajority texturewith largemagnetic moment, required for the electronic coherence for the superconductivity. Furthermore, a clear reorganization of iron-vacancy order around the T-ps and T-c is found with the interface phase being mostly associated with a different iron-vacancy configuration, that may be important for protecting the percolative superconductivity in KxFe2-ySe2.

We have used scanning micro x-ray diffraction to characterize different phases in superconducting K$_{x}$Fe$_{2−y}$Se$_{2}$ as a function of temperature, unveiling the thermal evolution across the superconducting transition temperature (T$_{c}$∼32 K), phase separation temperature (T$_{ps}$∼520 K), and iron-vacancy order temperature (T$_{vo}$∼580 K). In addition to the iron-vacancy ordered tetragonal magnetic phase and orthorhombic metallic minority filamentary phase, we have found clear evidence of the interface phase with tetragonal symmetry. The metallic phase is surrounded by this interface phase below ∼ 300 K, and is embedded in the insulating texture. The spatial distribution of coexisting phases as a function of temperature provides clear evidence of the formation of protected metallic percolative paths in the majority texture with large magnetic moment, required for the electronic coherence for the superconductivity. Furthermore, a clear reorganization of iron-vacancy order around the T$_{ps}$ and T$_{c}$ is found with the interface phase being mostly associated with a different iron-vacancy configuration, that may be important for protecting the percolative superconductivity in K$_{x}$Fe$_{2−y}$Se$_{2}$.

16th International Conference on Small Angle Scattering, SAS2015, Berlin, Germany, 13 Sep 2015 - 18 Sep 2015

11th International Conference on Synchrotron Radiation Instrumentation, SRI 2012, Lyon, France, 9 Jul 2012 - 13 Jul 2012; Journal of physics / Conference Series 425, 202004 (2013). doi:10.1088/1742-6596/425/20/202004, Published by IOP Publ., Bristol

X-ray Photon Correlation Spectroscopy (XPCS) is an experimental technique to measure the dynamics of materials on nano- and microscales. Often, the maximum frame rate of the detector limits which dynamical processes can be investigated. This study examines the applicability of the Mythen 1D detector for coherent scattering applications with special focus on XPCS experiments.

An x-ray transfocator design for the combined use of 1D and 2D compound refractive lenses is described. The device includes stacks of beryllium parabolic lenses with different radii of curvature and provides microfocused x-ray beams in the 4-20 keV photon energy range. The transfocator has been implemented at the P10 Coherence Beamline of the PETRA III synchrotron at DESY, Hamburg. Results of transfocator performance and applications for coherent x-ray scattering experiments are presented.