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11 pages, 1638 KiB

Open AccessFeature PaperArticle

Diffracted X-Ray Tracking for Analysis of Heterogeneity of Hydrogels

by Hiroshi Sekiguchi, Taiga Shinohara and Isamu Akiba

Quantum Beam Sci. 2025, 9(2), 19; https://doi.org/10.3390/qubs9020019 - 3 Jun 2025

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Diffracted X-ray tracking (DXT) was applied to evaluate spatial heterogeneities in polyacrylamide gel networks. Diffraction spots from the (111) planes of gold nanocrystals (GNPs) encapsulated in the gels exhibited temporal motion during time-resolved X-ray diffraction measurements using a quasi-monochromatic X-ray beam. This observation indicates that the GNPs undergo rotational motion within the gel matrix. An analysis of the diffraction spot trajectories revealed that the rotational diffusion coefficient of GNPs in homogeneous gels follows a single Gaussian distribution, whereas that of heterogeneous PAAm gels, with regions of varying cross-linking density, is described by a bimodal distribution. These findings demonstrate that DXT is a powerful technique for analyzing polymer network heterogeneity. Full article

(This article belongs to the Section Structure and Dynamics of Functional Materials)

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13 pages, 1699 KiB

Open AccessArticle

Metallic Ca Aggregates Formed Along Ion Tracks and Optical Anisotropy in CaF₂ Crystals Irradiated with Swift Heavy Ions

by Hiroshi Amekura, Norito Ishikawa, Nariaki Okubo, Feng Chen, Kazumasa Narumi, Atsuya Chiba, Yoshimi Hirano, Keisuke Yamada, Shunya Yamamoto and Yuichi Saitoh

Quantum Beam Sci. 2024, 8(4), 29; https://doi.org/10.3390/qubs8040029 - 7 Nov 2024

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Abstract

It is known that swift heavy ion (SHI) irradiation induces the shape elongation of metal nanoparticles (NPs) embedded in transparent insulators, which results in anisotropic optical absorption. Here, we report another type of the optical anisotropy induced in CaF₂ crystals without including intentionally embedded metal NPs. The CaF₂ samples were irradiated with 200 MeV Xe¹⁴⁺ ions with an incident angle of 45° from the surface normal. With the increasing fluence, an absorption band at ~550 nm, which is ascribed to Ca aggregates, increases both the intensity and the anisotropy. XTEM observation clarified the formation of the continuous line structures and the discontinuous NP chains parallel to the SHI beam. Numerical simulations of the optical absorption spectra suggested the NP chains but not the continuous line structures as the origin of the anisotropy. The optical anisotropy in CaF₂ irradiated with SHIs is different from the shape elongation of NPs. Full article

(This article belongs to the Special Issue Modification of Materials by Using Energetic Ion/Electron Beams)

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13 pages, 3547 KiB

Open AccessArticle

The Structure of Liquid and Glassy Carbamazepine

by Chris J. Benmore, Angela Edwards, Oliver L. G. Alderman, Brian R. Cherry, Pamela Smith, Daniel Smith, Stephen Byrn, Richard Weber and Jeffery L. Yarger

Quantum Beam Sci. 2022, 6(4), 31; https://doi.org/10.3390/qubs6040031 - 15 Nov 2022

Cited by 5 | Viewed by 3365

Abstract

To enhance the solubility of orally administered pharmaceuticals, liquid capsules or amorphous tablets are often preferred over crystalline drug products. However, little is known regarding the variation in bonding mechanisms between pharmaceutical molecules in their different disordered forms. In this study, liquid and melt-quenched glassy carbamazepine have been studied using high energy X-ray diffraction and modeled using Empirical Potential Structure Refinement. The results show significant structural differences between the liquid and glassy states. The liquid shows a wide range of structures; from isolated molecules, to aromatic ring correlations and NH-O hydrogen bonding. Upon quenching from the liquid to the glass the number of hydrogen bonds per molecule increases by ~50% at the expense of a ~30% decrease in the close contact (non-bonded) carbon-carbon interactions between aromatic rings. During the cooling process, there is an increase in both singly and doubly hydrogen-bonded adjacent molecules. Although hydrogen-bonded dimers found in the crystalline states persist in the glassy state, the absence of a crystalline lattice also allows small, hydrogen-bonded NH-O trimers and tetramers to form. This proposed model for the structure of glassy carbamazepine is consistent with the results from vibrational spectroscopy and nuclear magnetic resonance. Full article

(This article belongs to the Special Issue Quantum Beam Diffraction on Glasses and Liquids: Advanced Instrumentation, Data Analysis, and Applications)

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8 pages, 5204 KiB

Open AccessArticle

Virtual Angstrom-Beam Electron Diffraction Analysis for Zr₈₀Pt₂₀ Metallic Glasses

by Akihiko Hirata

Quantum Beam Sci. 2022, 6(4), 28; https://doi.org/10.3390/qubs6040028 - 22 Sep 2022

Cited by 2 | Viewed by 2491

Abstract

To analyze amorphous structure models obtained by a molecular dynamics (or reverse Monte Carlo) simulation, we propose a virtual angstrom-beam electron diffraction analysis. In this analysis, local electron diffraction patterns are calculated for the amorphous models at equal intervals as performed in the experiment, and the local structures that generate paired diffraction spots in the diffraction patterns are further analyzed by combining them with a Fourier transform and a Voronoi polyhedral analysis. For an example of Zr₈₀Pt₂₀, an aggregate of coordination polyhedra is formed which generates similar diffraction patterns from most parts within the aggregate. Furthermore, the coordination polyhedra are connected in certain orientational relationships which could enhance the intensity of the diffraction spots. Full article

(This article belongs to the Special Issue Quantum Beam Diffraction on Glasses and Liquids: Advanced Instrumentation, Data Analysis, and Applications)

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