Research

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14 pages, 3143 KiB

Open AccessArticle

Synchrotron Characterization of Hexagonal and Cubic Lipidic Phases Loaded with Azolate/Phosphane Gold(I) Compounds: A New Approach to the Uploading of Gold(I)-Based Drugs

by Paola Astolfi, Michela Pisani, Elisabetta Giorgini, Barbara Rossi, Alessandro Damin, Francesco Vita, Oriano Francescangeli, Lorenzo Luciani and Rossana Galassi

Nanomaterials 2020, 10(9), 1851; https://doi.org/10.3390/nano10091851 - 16 Sep 2020

Cited by 7 | Viewed by 2549

Abstract

Gold(I) phosphane compounds have recently attracted a renewed interest as potential new protagonists in cancer therapy. A class of phosphane gold(I) complexes containing azolate ligands has been successfully tested against several cancer cell lines and, in particular, against basal-like breast (BLB) cancer, a [...] Read more.

Gold(I) phosphane compounds have recently attracted a renewed interest as potential new protagonists in cancer therapy. A class of phosphane gold(I) complexes containing azolate ligands has been successfully tested against several cancer cell lines and, in particular, against basal-like breast (BLB) cancer, a form characterized by strongly severe diagnosis and short life lapse after classic chemotherapy. Even though the anticancer activity of gold(I) phosphane compounds is thoroughly ascertained, no study has been devoted to the possibility of their delivery in nanovectors. Herein, nonlamellar lyotropic liquid crystalline lipid nanosystems, a promising class of smart materials, have been used to encapsulate gold(I) azolate/phosphane complexes. In particular, ((triphenylphosphine)-gold(I)-(4,5-dichloroimidazolyl-1H-1yl)) (C-I) and ((triphenylphosphine)-gold(I)-(4,5-dicyanoimidazolyl-1H-1yl)) (C-II) have been encapsulated in three different lipid matrices: monoolein (GMO), phytantriol (PHYT) and dioleoyl-phosphatidylethanolamine (DOPE). An integrated experimental approach involving X-ray diffraction and UV resonant Raman (UVRR) spectroscopy, based on synchrotron light and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, has been employed to establish the effects of drug encapsulation on the structure and phase behavior of the host mesophases. The results indicate that gold(I) complexes C-I and C-II are successfully encapsulated in the three lipid matrices as evidenced by the drug-induced phase transitions or by the changes in the mesophase lattice parameters observed in X-ray diffraction experiments and by the spectral changes occurring in UV resonant Raman spectra upon loading the lipid matrices with C-I and C-II. Full article

(This article belongs to the Special Issue Synchrotron Radiation Techniques for the Investigation of Nanomaterials)

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13 pages, 3197 KiB

Open AccessArticle

Scattering of Ultrashort X-ray Pulses by Various Nanosystems

by Marat Eseev, Andrey Goshev and Dmitry Makarov

Nanomaterials 2020, 10(7), 1355; https://doi.org/10.3390/nano10071355 - 10 Jul 2020

Cited by 9 | Viewed by 1995

Abstract

Currently, the study of the scattering of ultrashort X-ray pulses (USPs) by various objects is an urgent task, in connection with the creation of powerful sources of USP generation. In this paper, the theory of the scattering of attosecond pulses by polyatomic structures [...] Read more.

Currently, the study of the scattering of ultrashort X-ray pulses (USPs) by various objects is an urgent task, in connection with the creation of powerful sources of USP generation. In this paper, the theory of the scattering of attosecond pulses by polyatomic structures is developed taking into account the magnetic component of USPs. It is shown that the scattering spectra depend not only on the structure of the target, but also on other characteristics of USPs. Results are presented of the calculation of the scattering spectra on various nanosystems, such as rings, groups of rings, carbon nanotubes (CNTs), and groups of co-directed CNTs (forest CNTs). The calculation results are presented in an analytical form, which allows a general analysis of the expressions. It was found that taking the magnetic component of the momentum into the scattering spectra into account leads to the generation of the second harmonic. In this case, the spectra have characteristic features and differ from the scattering spectra at the carrier frequency, which can complement ultra-high-resolution X-ray analysis. It is shown that the scattering spectra of some structures, for example, forest CNTs, have a strictly specified radiation direction and such material in the field of such USPs is non-reflective (completely black). Full article

(This article belongs to the Special Issue Synchrotron Radiation Techniques for the Investigation of Nanomaterials)

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15 pages, 5352 KiB

Open AccessArticle

Role of Synthetic Parameters on the Structural and Optical Properties of N,Sn-Copromoted Nanostructured TiO₂: A Combined Ti K-Edge and Sn L_2,3-Edges X-ray Absorption Investigation

by Martina Fracchia, Paolo Ghigna, Alessandro Minguzzi, Alberto Vertova, Francesca Turco, Giuseppina Cerrato and Daniela Meroni

Nanomaterials 2020, 10(6), 1224; https://doi.org/10.3390/nano10061224 - 23 Jun 2020

Cited by 4 | Viewed by 2740

Abstract

Sn-modification of TiO₂ photocatalysts has been recently proposed as a suitable strategy to improve pollutant degradation as well as hydrogen production. In particular, visible light activity could be promoted by doping with Sn²⁺ species, which are, however, thermally unstable. Co-promotion with [...] Read more.

Sn-modification of TiO₂ photocatalysts has been recently proposed as a suitable strategy to improve pollutant degradation as well as hydrogen production. In particular, visible light activity could be promoted by doping with Sn²⁺ species, which are, however, thermally unstable. Co-promotion with N and Sn has been shown to lead to synergistic effects in terms of visible light activity, but the underlying mechanism has, so far, been poorly understood due to the system complexity. Here, the structural, optical, and electronic properties of N,Sn-copromoted, nanostructured TiO₂ from sol-gel synthesis were investigated: the Sn/Ti molar content was varied in the 0–20% range and different post-treatments (calcination and low temperature hydrothermal treatment) were adopted in order to promote the sample crystallinity. Depending on the adopted post-treatment, the optical properties present notable differences, which supports a combined role of Sn dopants and N-induced defects in visible light absorption. X-ray absorption spectroscopy at the Ti K-edge and Sn L_2,3-edges shed light onto the electronic properties and structure of both Ti and Sn species, evidencing a marked difference at the Sn L_2,3-edges between the samples with 20% and 5% Sn/Ti ratio, showing, in the latter case, the presence of tin in a partially reduced state. Full article

(This article belongs to the Special Issue Synchrotron Radiation Techniques for the Investigation of Nanomaterials)

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28 pages, 6115 KiB

Open AccessArticle

Local Structure and Magnetism of Fe₂O₃ Maghemite Nanocrystals: The Role of Crystal Dimension

by Mauro Coduri, Paolo Masala, Lucia Del Bianco, Federico Spizzo, Davide Ceresoli, Carlo Castellano, Serena Cappelli, Cesare Oliva, Stefano Checchia, Mattia Allieta, Dorothee-Vinga Szabo, Sabine Schlabach, Michael Hagelstein, Claudio Ferrero and Marco Scavini

Nanomaterials 2020, 10(5), 867; https://doi.org/10.3390/nano10050867 - 30 Apr 2020

Cited by 39 | Viewed by 4108

Abstract

Here we report on the impact of reducing the crystalline size on the structural and magnetic properties of γ-Fe₂O₃ maghemite nanoparticles. A set of polycrystalline specimens with crystallite size ranging from ~2 to ~50 nm was obtained combining microwave plasma [...] Read more.

Here we report on the impact of reducing the crystalline size on the structural and magnetic properties of γ-Fe₂O₃ maghemite nanoparticles. A set of polycrystalline specimens with crystallite size ranging from ~2 to ~50 nm was obtained combining microwave plasma synthesis and commercial samples. Crystallite size was derived by electron microscopy and synchrotron powder diffraction, which was used also to investigate the crystallographic structure. The local atomic structure was inquired combining pair distribution function (PDF) and X-ray absorption spectroscopy (XAS). PDF revealed that reducing the crystal dimension induces the depletion of the amount of Fe tetrahedral sites. XAS confirmed significant bond distance expansion and a loose Fe-Fe connectivity between octahedral and tetrahedral sites. Molecular dynamics revealed important surface effects, whose implementation in PDF reproduces the first shells of experimental curves. The structural disorder affects the magnetic properties more and more with decreasing the nanoparticle size. In particular, the saturation magnetization reduces, revealing a spin canting effect. Moreover, a large effective magnetic anisotropy is measured at low temperature together with an exchange bias effect, a behavior that we related to the existence of a highly disordered glassy magnetic phase. Full article

(This article belongs to the Special Issue Synchrotron Radiation Techniques for the Investigation of Nanomaterials)

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13 pages, 973 KiB

Open AccessArticle

The Terahertz Dynamics of an Aqueous Nanoparticle Suspension: An Inelastic X-ray Scattering Study

by Alessio De Francesco, Luisa Scaccia, Ferdinando Formisano, Eleonora Guarini, Ubaldo Bafile, Marco Maccarini, Ahmet Alatas, Yong Q. Cai and Alessandro Cunsolo

Nanomaterials 2020, 10(5), 860; https://doi.org/10.3390/nano10050860 - 29 Apr 2020

Cited by 7 | Viewed by 2179

Abstract

We used the high-resolution Inelastic X-ray Scattering beamline of the Advanced Photon Source at Argonne National Laboratory to measure the terahertz spectrum of pure water and a dilute aqueous suspension of 15 nm diameter spherical Au nanoparticles (Au-NPs). We observe that, despite their [...] Read more.

We used the high-resolution Inelastic X-ray Scattering beamline of the Advanced Photon Source at Argonne National Laboratory to measure the terahertz spectrum of pure water and a dilute aqueous suspension of 15 nm diameter spherical Au nanoparticles (Au-NPs). We observe that, despite their sparse volume concentration of about 0.5%, the immersed NPs strongly influence the collective molecular dynamics of the hosting liquid. We investigate this effect through a Bayesian inference analysis of the spectral lineshape, which elucidates how terahertz transport properties of water change upon Au-NP immersion. In particular, we observe a nearly complete disappearance of the longitudinal acoustic mode and a mildly decreased ability to support shear wave propagation. Full article

(This article belongs to the Special Issue Synchrotron Radiation Techniques for the Investigation of Nanomaterials)

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11 pages, 2784 KiB

Open AccessArticle

Structural Study of Nano-Sized Gahnite (ZnAl₂O₄): From the Average to the Local Scale

by Giorgia Confalonieri, Nicola Rotiroti, Andrea Bernasconi and Monica Dapiaggi

Nanomaterials 2020, 10(5), 824; https://doi.org/10.3390/nano10050824 - 26 Apr 2020

Cited by 7 | Viewed by 2157

Abstract

Spinel gahnite (ZnAl₂O₄) has been obtained through a hydrothermal synthesis method with a grain size of about 2 nm. The sample was calcined for a few hours at two different temperatures (800 and 900 °C) in order to obtain [...] Read more.

Spinel gahnite (ZnAl₂O₄) has been obtained through a hydrothermal synthesis method with a grain size of about 2 nm. The sample was calcined for a few hours at two different temperatures (800 and 900 °C) in order to obtain larger grain sizes to be analyzed by means of powder diffraction with the Rietveld method, and by means of total scattering with the Pair Distribution Function (PDF) method. The idea is to compare the average to the local structure, as a function of increasing grain size. The total scattering data were collected at the European Synchrotron Radiation Facility (ESRF), Grenoble. The samples have been also characterised by means of high resolution Transmission Electron Microscopy (TEM), showing an increasing grain size up to about 9 nm. The average structure presented variations in the inversion degree and an increase in grain size. TEM observations demonstrated that the small crystals are well crystallised: the high resolution images neatly showed the atomic planes, even in the smallest particles. However, the average structure did not properly fit the PDF data in the local region, owing to a slightly different coordination among the octahedra. A new structural model is proposed for the local region of the PDF, that helped our understanding of the differences between a real nanostructured sample and that of a microcrystalline one. The oxygen disorder, due to the inversion grade of the spinel, is demonstrates to be at the basis of the local deviation. No signals of interstitial Zn atoms were detected. Full article

(This article belongs to the Special Issue Synchrotron Radiation Techniques for the Investigation of Nanomaterials)

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9 pages, 1458 KiB

Open AccessArticle

Structural, Electronic and Magnetic Properties of a Few Nanometer-Thick Superconducting NdBa₂Cu₃O₇ Films

by Marco Moretti Sala, Marco Salluzzo, Matteo Minola, Gabriella Maria De Luca, Greta Dellea, Vesna Srot, Yi Wang, Peter A. van Aken, Matthieu Le Tacon, Bernhard Keimer, Claudia Dallera, Lucio Braicovich and Giacomo Ghiringhelli

Nanomaterials 2020, 10(4), 817; https://doi.org/10.3390/nano10040817 - 24 Apr 2020

Cited by 1 | Viewed by 3581

Abstract

Epitaxial films of high critical temperature (

T_{c}

) cuprate superconductors preserve their transport properties even when their thickness is reduced to a few nanometers. However, when approaching the single crystalline unit cell (u.c.) of thickness,

T_{c}

decreases and eventually, superconductivity [...] Read more.

Epitaxial films of high critical temperature (

T_{c}

) cuprate superconductors preserve their transport properties even when their thickness is reduced to a few nanometers. However, when approaching the single crystalline unit cell (u.c.) of thickness,

T_{c}

decreases and eventually, superconductivity is lost. Strain originating from the mismatch with the substrate, electronic reconstruction at the interface and alteration of the chemical composition and of doping can be the cause of such changes. Here, we use resonant inelastic x-ray scattering at the Cu

L_{3}

edge to study the crystal field and spin excitations of NdBa

_{2}

Cu

_{3}

O

_{7 - x}

ultrathin films grown on SrTiO

_{3}

, comparing 1, 2 and 80 u.c.-thick samples. We find that even at extremely low thicknesses, the strength of the in-plane superexchange interaction is mostly preserved, with just a slight decrease in the 1 u.c. with respect to the 80 u.c.-thick sample. We also observe spectroscopic signatures for a decrease of the hole-doping at low thickness, consistent with the expansion of the c-axis lattice parameter and oxygen deficiency in the chains of the first unit cell, determined by high-resolution transmission microscopy and x-ray diffraction. Full article

(This article belongs to the Special Issue Synchrotron Radiation Techniques for the Investigation of Nanomaterials)

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10 pages, 2020 KiB

Open AccessArticle

Effects of Nanodomains on Local and Long-Range Phase Transitions in Perovskite-Type Eu_0.8Ca_0.2TiO_3–δ

by Marc Widenmeyer, Stefano Checchia, Xingxing Xiao, Marco Scavini and Anke Weidenkaff

Nanomaterials 2020, 10(4), 769; https://doi.org/10.3390/nano10040769 - 16 Apr 2020

Cited by 4 | Viewed by 2338

Abstract

The determination of reversible phase transitions in the perovskite-type thermoelectric oxide Eu_0.8Ca_0.2TiO_3–δ is fundamental, since structural changes largely affect the thermal and electrical transport properties. The phase transitions were characterized by heat capacity measurements, Rietveld refinements, and [...] Read more.

The determination of reversible phase transitions in the perovskite-type thermoelectric oxide Eu_0.8Ca_0.2TiO_3–δ is fundamental, since structural changes largely affect the thermal and electrical transport properties. The phase transitions were characterized by heat capacity measurements, Rietveld refinements, and pair distribution function (PDF) analysis of the diffraction data to achieve information on the phase transition temperatures and order as well as structural changes on the local level and the long range. On the long-range scale, Eu_0.8Ca_0.2TiO_3–δ showed a phase transition sequence during heating from cubic at 100 < T < 592 K to tetragonal and finally back to cubic at T > 846 K. The phase transition at T = 592 K (diffraction)/606 K (thermal analysis) was reversible with a very small thermal hysteresis of about 2 K. The local structure at 100 K was composed of a complex nanodomain arrangement of Amm2- and Pbnm-like local structures with different coherence lengths. Since in Eu_0.8Ca_0.2TiO_3–δ the amount of Pbnm domains was too small to percolate, the competition of ferroelectrically distorted octahedra (Amm2 as in BaTiO₃) and rigid, tilted octahedra (Pbnm as in CaTiO₃) resulted in a cubic long-range structure at low temperatures. Full article

(This article belongs to the Special Issue Synchrotron Radiation Techniques for the Investigation of Nanomaterials)

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16 pages, 3744 KiB

Open AccessArticle

Structure, Morphology, and Faceting of TiO₂ Photocatalysts by the Debye Scattering Equation Method. The P25 and P90 Cases of Study

by Federica Bertolotti, Anna Vivani, Daniele Moscheni, Fabio Ferri, Antonio Cervellino, Norberto Masciocchi and Antonietta Guagliardi

Nanomaterials 2020, 10(4), 743; https://doi.org/10.3390/nano10040743 - 13 Apr 2020

Cited by 17 | Viewed by 4141

Abstract

Characterization of functional nanocrystalline materials in terms of quantitative determination of size, size dispersion, type, and extension of exposed facets still remains a challenging task. This is particularly the case of anisotropically shaped nanocrystals (NCs) like the TiO₂ photocatalysts. Here, commercially available [...] Read more.

Characterization of functional nanocrystalline materials in terms of quantitative determination of size, size dispersion, type, and extension of exposed facets still remains a challenging task. This is particularly the case of anisotropically shaped nanocrystals (NCs) like the TiO₂ photocatalysts. Here, commercially available P25 and P90 titania nanopowders have been characterized by wide-angle X-ray total scattering techniques. Synchrotron data were modelled by the reciprocal space-based Debye scattering equation (DSE) method using atomistic models of NC populations (simultaneously carrying atomic and nanoscale structural features) for both anatase and rutile phases. Statistically robust descriptors are provided of size, morphology, and {101} vs. {001} facet area of truncated tetragonal bipyramids for anatase, jointly to polymorph quantification. The effects of using the proper NC shape on the X-ray diffraction pattern are analyzed in depth through DSE simulations by considering variable bipyramid aspect ratios (resulting in different {101} vs. {001} surface) and relative dispersion in a bivariate manner. We demonstrate that using prismatic NCs having equal volume and aspect ratio as bipyramids provides reasonably accurate sizes and {101} and {001} surface areas of the parent morphology. Full article

(This article belongs to the Special Issue Synchrotron Radiation Techniques for the Investigation of Nanomaterials)

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9 pages, 1457 KiB

Open AccessArticle

Pressure Induced Stability Enhancement of Cubic Nanostructured CeO₂ †

by Mariano Andrés Paulin, Gaston Garbarino, Ana Gabriela Leyva, Mohamed Mezouar and Joaquin Sacanell

Nanomaterials 2020, 10(4), 650; https://doi.org/10.3390/nano10040650 - 31 Mar 2020

Cited by 3 | Viewed by 2197

Abstract

Ceria (CeO₂)-based materials are widely used in applications such as catalysis, fuel cells and oxygen sensors. Its cubic fluorite structure with a cell parameter similar to that of silicon makes it a candidate for implementation in electronic devices. This structure is [...] Read more.

Ceria (CeO₂)-based materials are widely used in applications such as catalysis, fuel cells and oxygen sensors. Its cubic fluorite structure with a cell parameter similar to that of silicon makes it a candidate for implementation in electronic devices. This structure is stable in a wide temperature and pressure range, with a reported structural phase transition to an orthorhombic phase. In this work, we study the structure of CeO₂ under hydrostatic pressures up to 110 GPa simultaneously for the nanometer- and micrometer-sized powders as well as for a single crystal, using He as the pressure-transmitting medium. The first-order transition is clearly present for the micrometer-sized and single-crystal samples, while, for the nanometer grain size powder, it is suppressed up to at least 110 GPa. We show that the stacking fault density increases by two orders of magnitude in the studied pressure range and could act as an internal constraint, avoiding the nucleation of the high-pressure phase. Full article

(This article belongs to the Special Issue Synchrotron Radiation Techniques for the Investigation of Nanomaterials)

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20 pages, 36319 KiB

Open AccessArticle

K⁺ vs. Na⁺ Effects on the Self-Assembly of Guanosine 5′-Monophosphate: A Solution SAXS Structural Study

by Enrico Junior Baldassarri, Maria Grazia Ortore, Francesco Spinozzi, Adam Round, Claudio Ferrero and Paolo Mariani

Nanomaterials 2020, 10(4), 629; https://doi.org/10.3390/nano10040629 - 28 Mar 2020

Cited by 4 | Viewed by 2860

Abstract

The hierarchical process of guanosine (G) self-assembly, leading in aqueous solution and in the presence of metal cations to the formation of G-quadruplexes, represents an intriguing topic both for the biological correlation with telomerase activity and for the nano-technological applications, as demonstrated by [...] Read more.

The hierarchical process of guanosine (G) self-assembly, leading in aqueous solution and in the presence of metal cations to the formation of G-quadruplexes, represents an intriguing topic both for the biological correlation with telomerase activity and for the nano-technological applications, as demonstrated by the current measured in a quadruplex wire 100 nm long. Similar to G-rich DNA sequences and G-oligonucleotides, the guanosine 5′-monophosphate (GMP) self-aggregates in water to form quadruplexes. However, due to the absence of a covalent axial backbone, this system can be very useful to understand the chemical-physical conditions that govern the guanosine supramolecular aggregation. We have then investigated by in-solution Synchrotron Small Angle X-ray Scattering technique the role of different cations in promoting the quadruplex formation as a function of concentration and temperature. Results show how potassium, with its peculiar biological traits, favours the G-quadruplex elongation process in respect to other cations (Na

^{+}

, but also NH

_{4}^{+}

and Li

^{+}

), determining the longest particles in solution. Moreover, the formation and the elongation of G-quadruplexes have been demonstrated to be controlled by both GMP concentration and excess cation content, even if they specifically contribute to these processes in different ways. The occurrence of condensed liquid crystalline phases was also detected, proving that excess cations play also unspecific effects on the effective charges on the G-quadruplex surface. Full article

(This article belongs to the Special Issue Synchrotron Radiation Techniques for the Investigation of Nanomaterials)

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22 pages, 3903 KiB

Open AccessArticle

The Structure and Chemical Composition of the Cr and Fe Pyrolytic Coatings on the MWCNTs’ Surface According to NEXAFS and XPS Spectroscopy

by Danil Sivkov, Olga Petrova, Alena Mingaleva, Anatoly Ob’edkov, Boris Kaverin, Sergey Gusev, Ilya Vilkov, Sergey Isaenko, Dmitriy Bogachuk, Roman Skandakov, Viktor Sivkov and Sergey Nekipelov

Nanomaterials 2020, 10(2), 374; https://doi.org/10.3390/nano10020374 - 21 Feb 2020

Cited by 25 | Viewed by 4016

Abstract

The paper is devoted to the structure and properties of the composite material based on multi-walled carbon nanotubes (MWCNTs) covered with pyrolytic iron and chromium. Fe/MWCNTs and Cr/MWCNTs nanocomposites have been prepared by the metal organic chemical vapor deposition (MOCVD) growth technique using [...] Read more.

The paper is devoted to the structure and properties of the composite material based on multi-walled carbon nanotubes (MWCNTs) covered with pyrolytic iron and chromium. Fe/MWCNTs and Cr/MWCNTs nanocomposites have been prepared by the metal organic chemical vapor deposition (MOCVD) growth technique using iron pentacarbonyl and bis(arene)chromium compounds, respectively. Composites structures and morphologies preliminary study were performed using X-ray diffraction, scanning and transmission electron microscopy and Raman scattering. The atomic and chemical composition of the MWCNTs’ surface, Fe-coating and Cr-coating and interface—(MWCNTs surface)/(metal coating) were studied by total electron yield method in the region of near-edge X-ray absorption fine structure (NEXAFS) C1s, Fe2p and Cr2p absorption edges using synchrotron radiation of the Russian-German dipole beamline (RGBL) at BESSY-II and the X-ray photoelectron spectroscopy (XPS) method using the ESCALAB 250 Xi spectrometer and charge compensation system. The absorption cross sections in the NEXAFS C1s edge of the nanocomposites and MWCNTs were measured using the developed approach of suppressing and estimating the contributions of the non-monochromatic background and multiple reflection orders radiation from the diffraction grating. The efficiency of the method was demonstrated by the example of the Cr/MWCNT nanocomposite, since its Cr2p NEXAFS spectra contain additional C1s NEXAFS in the second diffraction order. The study has shown that the MWCNTs’ top layers in composite have no significant destruction; the MWCNTs’ metal coatings are continuous and consist of Fe₃O₄ and Cr₂O₃. It is shown that the interface between the MWCNTs and pyrolytic Fe and Cr coatings has a multilayer structure: a layer in which carbon atoms along with epoxy –C–O–C– bonds form bonds with oxygen and metal atoms from the coating layer is formed on the outer surface of the MWCNT, a monolayer of metal carbide above it and an oxide layer on top. The iron oxide and chromium oxide adhesion is provided by single, double and epoxy chemical binding formation between carbon atoms of the MWCNT top layer and the oxygen atoms of the coating, as well as the formation of bonds with metal atoms. Full article

(This article belongs to the Special Issue Synchrotron Radiation Techniques for the Investigation of Nanomaterials)

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Review

Jump to: Research

24 pages, 16647 KiB

Open AccessReview

Contribution of Ex-Situ and In-Situ X-ray Grazing Incidence Scattering Techniques to the Understanding of Quantum Dot Self-Assembly: A Review

by Vishesh Saxena and Giuseppe Portale

Nanomaterials 2020, 10(11), 2240; https://doi.org/10.3390/nano10112240 - 12 Nov 2020

Cited by 8 | Viewed by 5387

Abstract

Quantum dots are under intense research, given their amazing properties which favor their use in electronics, optoelectronics, energy, medicine and other important applications. For many of these technological applications, quantum dots are used in their ordered self-assembled form, called superlattice. Understanding the mechanism [...] Read more.

Quantum dots are under intense research, given their amazing properties which favor their use in electronics, optoelectronics, energy, medicine and other important applications. For many of these technological applications, quantum dots are used in their ordered self-assembled form, called superlattice. Understanding the mechanism of formation of the superlattices is crucial to designing quantum dots devices with desired properties. Here we review some of the most important findings about the formation of such superlattices that have been derived using grazing incidence scattering techniques (grazing incidence small and wide angle X-ray scattering (GISAXS/GIWAXS)). Acquisition of these structural information is essential to developing some of the most important underlying theories in the field. Full article

(This article belongs to the Special Issue Synchrotron Radiation Techniques for the Investigation of Nanomaterials)

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29 pages, 12796 KiB

Open AccessReview

Nanostructure of Unconventional Liquid Crystals Investigated by Synchrotron Radiation

by Francesco Vita, Fabrizio Corrado Adamo, Michela Pisani and Oriano Francescangeli

Nanomaterials 2020, 10(9), 1679; https://doi.org/10.3390/nano10091679 - 26 Aug 2020

Cited by 4 | Viewed by 3129

Abstract

The macroscopic properties of novel liquid crystal (LC) systems—LCs with unconventional molecular structure as well as conventional LCs in unconventional geometries—directly descend from their mesoscopic structural organization. While X-ray diffraction (XRD) is an obvious choice to investigate their nanoscale structure, conventional diffractometry is [...] Read more.

The macroscopic properties of novel liquid crystal (LC) systems—LCs with unconventional molecular structure as well as conventional LCs in unconventional geometries—directly descend from their mesoscopic structural organization. While X-ray diffraction (XRD) is an obvious choice to investigate their nanoscale structure, conventional diffractometry is often hampered by experimental difficulties: the low scattering power and short-range positional order of the materials, resulting in weak and diffuse diffraction features; the need to perform measurements in challenging conditions, e.g., under magnetic and/or electric fields, on thin films, or at high temperatures; and the necessity to probe micron-sized volumes to tell the local structural properties from their macroscopic average. Synchrotron XRD allows these problems to be circumvented thanks to the superior diffraction capabilities (brilliance, q-range, energy and space resolution) and advanced sample environment available at synchrotron beamlines. Here, we highlight the potentiality of synchrotron XRD in the field of LCs by reviewing a selection of experiments on three unconventional LC systems: the potentially biaxial and polar nematic phase of bent-core mesogens; the very high-temperature nematic phase of all-aromatic LCs; and polymer-dispersed liquid crystals. In all these cases, synchrotron XRD unveils subtle nanostructural features that are reflected into macroscopic properties of great interest from both fundamental and technological points of view. Full article

(This article belongs to the Special Issue Synchrotron Radiation Techniques for the Investigation of Nanomaterials)

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