<i>In Situ</i> Formation of Carbon Nanotubes Encapsulated within Boron Nitride Nanotubes <i>via</i> Electron Irradiation

We report experimental evidence of the formation by <i>in situ</i> electron-irradiation of single-walled carbon nanotubes (C-NT) confined within boron nitride nanotubes (BN-NT). The electron radiation stemming from the microscope supplies the energy required by the amorphous carbonaceous structures to crystallize in a tubular form in a catalyst-free procedure, at room temperature and high vacuum. The structural defects resulting from the interaction of the shapeless carbon with the BN nanotube are corrected in a self-healing process throughout the crystallinization. Structural changes developed during the irradiation process such as defects formation and evolution, shrinkage, and shortness of the BN-NT were <i>in situ</i> monitored. The outer BN wall provides a protective and insulating shell against environmental perturbations to the inner C-NT without affecting their electronic properties, as demonstrated by first-principles calculations

Dynamic HAADF-STEM Observation of a Single-Atom Chain as the Transient State of Gold Ultrathin Nanowire Breakdown

Ultrathin chemically grown gold nanowires undergo irremediable structural modification under external stimuli. Thanks to dynamic high-angle annular dark-field imaging, electron-beam-induced damage was followed, revealing the formation of linear chains of gold atoms as well as reactive clusters on the side, opening fascinating prospects for applications in both catalysis and electronic transport

Dynamic HAADF-STEM Observation of a Single-Atom Chain as the Transient State of Gold Ultrathin Nanowire Breakdown

Ultrathin chemically grown gold nanowires undergo irremediable structural modification under external stimuli. Thanks to dynamic high-angle annular dark-field imaging, electron-beam-induced damage was followed, revealing the formation of linear chains of gold atoms as well as reactive clusters on the side, opening fascinating prospects for applications in both catalysis and electronic transport

Dynamic HAADF-STEM Observation of a Single-Atom Chain as the Transient State of Gold Ultrathin Nanowire Breakdown

Ultrathin chemically grown gold nanowires undergo irremediable structural modification under external stimuli. Thanks to dynamic high-angle annular dark-field imaging, electron-beam-induced damage was followed, revealing the formation of linear chains of gold atoms as well as reactive clusters on the side, opening fascinating prospects for applications in both catalysis and electronic transport

Dynamic HAADF-STEM Observation of a Single-Atom Chain as the Transient State of Gold Ultrathin Nanowire Breakdown

Ultrathin chemically grown gold nanowires undergo irremediable structural modification under external stimuli. Thanks to dynamic high-angle annular dark-field imaging, electron-beam-induced damage was followed, revealing the formation of linear chains of gold atoms as well as reactive clusters on the side, opening fascinating prospects for applications in both catalysis and electronic transport

Quaternary Chalcogenide-Based Misfit Nanotubes LnS(Se)-TaS(Se)₂ (Ln = La, Ce, Nd, and Ho): Synthesis and Atomic Structural Studies

We have synthesized quaternary chalcogenide-based misfit nanotubes LnS­(Se)-TaS₂(Se) (Ln = La, Ce, Nd, and Ho). None of the compounds described here were reported in the literature as a bulk compound. The characterization of these nanotubes, at the atomic level, has been developed via different transmission electron microscopy techniques, including high-resolution scanning transmission electron microscopy, electron diffraction, and electron energy-loss spectroscopy. In particular, quantification at sub-nanometer scale was achieved by acquiring high-quality electron energy-loss spectra at high energy (∼between 1000 and 2500 eV). Remarkably, the sulfur was found to reside primarily in the distorted rocksalt LnS lattice, while the Se is associated with the hexagonal TaSe₂ site. Consequently, these quaternary misfit layered compounds in the form of nanostructures possess a double superstructure of La/Ta and S/Se with the same periodicity. In addition, the interlayer spacing between the layers and the interatomic distances within the layer vary systematically in the nanotubes, showing clear reduction when going from the lightest (La atom) to the heaviest (Ho) atom. Amorphous layers, of different nature, were observed at the surface of the nanotubes. For La-based NTs, the thin external amorphous layer (inferior to 10 nm) can be ascribed to a Se deficiency. Contrarily, for Ho-based NTs, the thick amorphous layer (between 10 and 20 nm) is clearly ascribed to oxidation. All of these findings helped us to understand the atomic structure of these new compounds and nanotubes thereof

Atomic Structural Studies on Thin Single-Crystalline Misfit-Layered Nanotubes of TbS-CrS₂

Various nanotubes from ternary misfit compounds have been reported in recent years. In the present work, the detailed atomic structure and chemical configuration of misfit-layered nanotubes based on the TbS-CrS₂ are reported. These analyses have been developed via different transmission electron microscopy techniques, including high-resolution scanning transmission electron microscopy, electron diffraction, and electron energy loss spectroscopy. These structural analyses show that two different kinds of nanotubes can be produced: a “regular” nanotube and a “wavy” one. Both kinds of nanotubes show the alternating arrangements of the TbS and CrS₂ subsystems; however, the wavy ones present a nearly periodically deficiency in terbium. In addition to the structural investigation, the chemical analyses have proved that the outer layer of both kinds of nanotubes is composed of the elements Cr and S. All these findings helped to understand the growth mechanism during the sulfurization reaction taking place in the synthesis process

Strontium Cobalt Oxide Misfit Nanotubes

Low-dimensional misfit layered compounds have been found to have ultralow thermal conductivity, which is attributed to their unique structure and the low dimensionality. There are a few studies reporting the preparation of sulfide-based misfit nanotubes but only one study on oxide-based analogs. In this investigation, we report a new oxide-based misfit nanotube derived from misfit layered strontium cobaltite. Thorough structural investigation by electron microscopy techniques, including electron diffraction, aberration corrected high-resolution (scanning) transmission electron microscopy, and electron energy-loss spectroscopy along with density functional theory calculations show that these nanotubes consist of alternating layers of SrCoO₂ and CoO₂. We have studied systematically the effect of base concentration on the structure and composition of the nanotubes, which reveals the importance of misfit stress to tightly roll the structure into tubular form and thus control the synthesis. Electronic structure calculations find that the structures are semiconducting with a ferrimagnetic ground state. Our studies further extend the family of bulk misfit layered oxides into the 1D realm with potential applications in thermoelectric and electronic devices

Nanotubes from Oxide-Based Misfit Family: The Case of Calcium Cobalt Oxide

Misfit layered compounds (MLCs) have generated significant interest in recent years as potential thermoelectric materials. MLC nanotubes could reveal behavior that is entirely different from the bulk material. Recently, new chemical strategies were exploited for the synthesis of nanotubular forms of chalcogenide-based MLCs, which are promising candidates for thermoelectric materials. However, analogous synthesis of oxide-based MLC nanotubes has not been demonstrated until now. Here, we report a chemical strategy for synthesis of cobalt-oxide-based misfit nanotubes. A combination of high-resolution (scanning) transmission electron microscopy (including image simulations), spatially resolved electron energy-loss spectroscopy, electron diffraction, and density functional theory (DFT) calculations is used to discover the formation of a phase within these nanotubes that differs significantly from bulk calcium cobaltite MLCs. Furthermore, DFT calculations show that this phase is semiconducting with a band gap in excess of 1 eV, unlike bulk calcium cobaltite MLCs, which are known to be metallic. Through systematic experiments, we propose a formation mechanism for these nanotubes that could also apply more generally to realizing other oxide-based MLC nanotubes

Synthesis and Optical Properties of Homogeneous Nanoshurikens

During the last years the controlled synthesis of Au nanoparticles (NPs) has almost become a reality, and structures such as spheres, cubes, rods, decahedra, or octahedra can be prepared with <i>a la carte</i> dimensions in a very homogeneous manner. However, the fabrication of spiked particles, the most efficient plasmonic NPs, with controllable geometric parameters remains elusive. Here we show how to prepare highly homogeneous spiked nanoparticles composed of a penta-twinned core and five tips. These nanoparticles, reminiscent of ninja nanoshurikens (throwing stars), exhibit the ability to concentrate large electromagnetic fields at the apexes of the tips upon illumination. The apexes also present high affinity for analytes, giving rise to an unprecedented capacity for quantitative optical ultradetection with SERS