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Subject: small-angle X-ray scattering (SAXS) ×

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    Protein-Assisted Assembly of Modular 3D Plasmonic Raspberry-like Core/Satellite Nanoclusters: Correlation of Structure and Optical Properties
    (Washington, DC : Soc., 2016) Höller, Roland P. M.; Dulle, Martin; Thomä, Sabrina; Mayer, Martin; Steiner, Anja Maria; Förster, Stephan; Fery, Andreas; Kuttner, Christian; Chanana, Munish
    We present a bottom-up assembly route for a large-scale organization of plasmonic nanoparticles (NPs) into three-dimensional (3D) modular assemblies with core/satellite structure. The protein-assisted assembly of small spherical gold or silver NPs with a hydrophilic protein shell (as satellites) onto larger metal NPs (as cores) offers high modularity in sizes and composition at high satellite coverage (close to the jamming limit). The resulting dispersions of metal/metal nanoclusters exhibit high colloidal stability and therefore allow for high concentrations and a precise characterization of the nanocluster architecture in dispersion by small-angle X-ray scattering (SAXS). Strong near-field coupling between the building blocks results in distinct regimes of dominant satellite-to-satellite and core-to-satellite coupling. High robustness against satellite disorder was proved by UV/vis diffuse reflectance (integrating sphere) measurements. Generalized multiparticle Mie theory (GMMT) simulations were employed to describe the electromagnetic coupling within the nanoclusters. The close correlation of structure and optical property allows for the rational design of core/satellite nanoclusters with tailored plasmonics and well-defined near-field enhancement, with perspectives for applications such as surface-enhanced spectroscopies.
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    Short-Term Morphology Relaxation of Thermoplastic Polyurethane Elastomers after Fast Strain Steps
    (New York, NY [u.a.] : Wiley InterScience, 2020) Stribeck, Almut; Schneider, Konrad; Eling, Berend; Pöselt, Elmar
    Strain steps are applied to elastomers in a pneumatic relaxometer and monitored by small-angle X-ray scattering (SAXS). The relaxometer provides a rise time of 13 ms for strain pulses of step height ?e = ±1 in strain. The basic character of the 2D SAXS frames is examined and corresponding invariants Q(t) are analyzed. Three thermoplastic polyurethanes (TPU) of hardness 85 Shore A with different soft segments are studied both unannealed and annealed. The first response of all materials is a fast morphology conversion which finishes within tmc =250 ms. Because it has been untraceable, it is characterized by a settling stroke Q(tmc) - Q(0). The second response is a slow morphology adjustment process which complies with logarithmic relaxation. It is characterized by a relaxation rate DQ = Q(10 t)/Q(t) - 1. Comparison indicates that the nanoscopic morphology relaxation processes appear to have little direct relation to the macroscopic stress relaxation curves. The materials differ with respect to hard-domain morphology stability and morphology recovery. Most unstable is the morphology of the annealed polyether-based material. It forms nanofibrillary entities when strained. © 2020 The Authors. Published by Wiley-VCH GmbH