Stepwise current-driven release of attogram quantities of copper iodide encapsulated in carbon nanotubes

Current-induced restructuring in bent silver nanowires

A number of metallic one-dimensional nanostructures have been proposed as interconnects for next-generation electronic devices. Generally, reports on charge transport properties consider low current density regimes in nanowires (or nanotubes) with intrinsically straight configurations. In these circumstances, direct observations of the interconnecting nanofilament electrical failure are scarce, particularly for initially crooked structures. Here, the electrical and structural responses of suspended silver nanowires exposed to increasing current densities were analysed using in situ transmission electron microscopy. At low rates of bias application, initially straight nanowires showed trivial behaviour up to their breakdown, with electromigration and gradual necking taking place. By contrast, these nanowires with an initially crooked configuration exhibit a mixed set of responses which included string-like resonance and structural rearrangements. Remarkably, it was observed that restructuring does not necessarily compromise the transport function of these interconnectors. Hence, initially crooked nanowires could import higher resilience to future nanoelectronic devices by delaying catastrophic breakdown of interconnectors subjected to unexpected current surges.

In situepitaxial growth of GdF3on NaGdF4:Yb,Er nanoparticles

By electron-beam irradiation of TEM, GdF₃(020) was epitaxially grown on the interface of NaGdF₄(111).

Structural and chemical analysis of gadolinium halides encapsulated within WS2 nanotubes

The hollow cavities of nanotubes serve as templates for the growth of size- and shape-confined functional nanostructures, giving rise to novel materials and properties. In this work, considering their potential application as MRI contrast agents, gadolinium halides are encapsulated within the hollow cavities of WS2 nanotubes by capillary filling to obtain GdX3@WS2 nanotubes (where X = Cl, Br or I and @ means encapsulated in). Aberration corrected scanning/transmission electron microscopy (S/TEM) and spectroscopy is employed to understand the morphology and composition of the GdI3@WS2 nanotubes. The three dimensional morphology is studied with STEM tomography but understanding the compositional information is non-trivial due to the presence of multiple high atomic number elements. Therefore, energy dispersive X-ray spectroscopy (EDS) tomography was employed revealing the three dimensional chemical composition. Molecular dynamics simulations of the filling procedure shed light into the mechanics behind the formation of the confined gadolinium halide crystals. The quasi-1D system employed here serves as an example of a TEM-based chemical nanotomography method that could be extended to other materials, including beam-sensitive soft materials.

Spontaneous Migration of Polyethylene Molecule Sheathed inside Single-Walled Carbon Nanotube for Nano-Heat Pipe

Development of nanoscale thermal exchanging devices is critical to thermal management in nanoscale. The spontaneous migration of polyethylene molecule sheathed inside single-walled carbon nanotube (SWCNT) are observed. And the multi-factor analysis of spontaneous migration about temperature, mass and potential barrier shows new features about motion mechanisms, and enriches the existing mass transport theory greatly. Here, based on this finding, we report a nano-heat pipe (NHP) composing of a SWCNT and a polyethylene molecule. Using molecular dynamics simulations, the heat exchanging coefficient can reach 450 WK(-1) cm(-2) at 500 K by NHP arrays with a quantity density of 7 × 10(13) cm(-2). This study will benefit the designs of NHP and other nanoscale mass transport devices.

Dynamic In-Situ Experimentation on Nanomaterials at the Atomic Scale

With the development of in situ techniques inside transmission electron microscopes (TEMs), external fields and probes can be applied to the specimen. This development transforms the TEM specimen chamber into a nanolab, in which reactions, structures, and properties can be activated or altered at the nanoscale, and all processes can be simultaneously recorded in real time with atomic resolution. Consequently, the capabilities of TEM are extended beyond static structural characterization to the dynamic observation of the changes in specimen structures or properties in response to environmental stimuli. This extension introduces new possibilities for understanding the relationships between structures, unique properties, and functions of nanomaterials at the atomic scale. Based on the idea of setting up a nanolab inside a TEM, tactics for design of in situ experiments inside the machine, as well as corresponding examples in nanomaterial research, including in situ growth, nanofabrication with atomic precision, in situ property characterization, and nanodevice construction are presented.

Synthesis of PbI(2) single-layered inorganic nanotubes encapsulated within carbon nanotubes

The template assisted growth of single-layered inorganic nanotubes is reported. Single-crystalline lead iodide single-layered nanotubes have been prepared using the inner cavities of carbon nanotubes as hosting templates. The diameter of the resulting inorganic nanotubes is merely dependent on the diameter of the host. This facile method is highly versatile opening up new horizons in the preparation of single-layered nanostructures.

Melting of metallic electrodes and their flowing through a carbon nanotube channel within a device

Evidence is presented of a new cause of Joule heating within a simple electronic device involving a multiwalled carbon nanotube (CNT) mounted on two metal electrodes forming an electrical circuit. This time-resolved, high-resolution in situ observation of metal electrode material melting and its flow driven by the thermomigration and electromigration forces through the CNT channel sheds an additional light on the effects affecting the real electrical performance of the CNT-based devices.

High-Pressure Phase Favored by a Symmetry-Recognized Nanoconfinement Effect

Recently, a high-pressure phase (B2) of KI has been experimentally observed in the inner space of single-walled carbon nanotubes. Our first-principles calculations indicate that in a confined nanospace, relative stabilities of the high-pressure B2 phase and the low-pressure B1 phase of KI are not necessarily determined by their external pressures. As a result of crystal symmetry differences, different phases are preferred at different K/I ratios. Such a symmetry-recognized confinement effect opens a new avenue for nanomaterials synthesis.

Electrically driven gallium movement in carbon nanotubes

Electrically driven gallium movement in carbon nanotubes is discussed. A higher current (~15 mA) makes the gallium migrate sharply toward the anode, which increases its mass transport speed with time in the range of 0 to more than 10.345 fg s(-1). In contrast, a lower current (~2 mA) only drives gallium to contact the anode, which decreases the resistance of the nanocomposite sharply, from 2.564 kΩ to 0.4 Ω. These results are valuable for designing electrically driven nanomass delivery and nanoswitches, respectively.

Nanomaterial engineering and property studies in a transmission electron microscope

Modern methods of in situ transmission electron microscopy (TEM) allow one to not only manipulate with a nanoscale object at the nanometer-range precision but also to get deep insights into its physical and chemical statuses. Dedicated TEM holders combining the capabilities of a conventional high-resolution TEM instrument and atomic force -, and/or scanning tunneling microscopy probes become the powerful tools in nanomaterials analysis. This progress report highlights the past, present and future of these exciting methods based on the extensive authors endeavors over the last five years. The objects of interest are diverse. They include carbon, boron nitride and other inorganic one- and two-dimensional nanoscale materials, e.g., nanotubes, nanowires and nanosheets. The key point of all experiments discussed is that the mechanical and electrical transport data are acquired on an individual nanostructure level under ultimately high spatial, temporal and energy resolution achievable in TEM, and thus can directly be linked to morphological, structural and chemical peculiarities of a given nanomaterial.

Electronic interactions between "pea" and "pod": the case of oligothiophenes encapsulated in carbon nanotubes

One of the most challenging strategies to achieve tunable nanophotonic devices is to build robust nanohybrids with variable emission in the visible spectral range, while keeping the merits of pristine single-walled carbon nanotubes (SWNTs). This goal is realized by filling SWNTs ("pods") with a series of oligothiophene molecules ("peas"). The physical properties of these peapods are depicted by using aberration-corrected high-resolution transmission electron microscopy, Raman spectroscopy, and other optical methods including steady-state and time-resolved measurements. Visible photoluminescence with quantum yields up to 30% is observed for all the hybrids. The underlying electronic structure is investigated by density functional theory calculations for a series of peapods with different molecular lengths and tube diameters, which demonstrate that van der Waals interactions are the bonding mechanism between the encapsulated molecule and the tube.

Encapsulated inorganic nanostructures: a route to sizable modulated, noncovalent, on-tube potentials in carbon nanotubes

The large variety of hybrid carbon nanotube systems synthesized to date (e.g., by encapsulation, wrapping, or stacking) has provided a body of interactions with which to modify the host nanotubes to produce new functionalities and control their behavior. Each, however, has limitations: hybridization can strongly degrade desirable nanotube properties; noncovalent interactions with molecular systems are generally weak; and interlayer interactions in layered nanotubes are strongly dependent upon the precise stacking sequence. Here we show that the electrostatic/polarization interaction provides a generic route to designing unprecedented, sizable and highly modulated (1 eV range), noncovalent on-tube potentials via encapsulation of inorganic partially ionic phases where charge anisotropy is maximized. Focusing on silver iodide (AgI) nanowires inside single-walled carbon nanotubes, we exploit the polymorphism of AgI, which creates a variety of different charge distributions and, consequently, interactions of varying strength and symmetry. Combined ab initio calculations, high-resolution transmission electron microscopy, and scanning tunneling microscopy and spectroscopy are used to demonstrate symmetry breaking of the nanotube wave functions and novel electronic superstructure formation, which we then correlate with the modulated, noncovalent electrostatic/polarization potentials from the AgI filling. These on-tube potentials are markedly stronger than those due to other noncovalent interactions known in carbon nanotube systems and lead to significant redistribution of the wave function around the nanotube, with implications for conceptually new single-nanotube electronic devices and molecular assembly. Principles derived can translate more broadly to relating graphene systems, for designing/controlling potentials and superstructures.

Mass transportation mechanism in electric-biased carbon nanotubes

The mass transportation mechanism in electric-biased carbon nanotubes (CNTs) is investigated experimentally. Except for the widely accepted electromigration mechanism, we find out the thermal effect can also induce the mass transportation in the form of thermomigration or thermal evaporation. Moreover, the convincing in situ transmission electron microscope experiment results show the thermal gradient force overrides the electromigration force in most conditions, according to specific parameters of the CNTs and "cargos". A full analysis on the thermal gradient force and electromigration force imposed on the cargos is given, thus our experimental results are well explained and understood.

The mechanical response of turbostratic carbon nanotubes filled with Ga-doped ZnS: II. Slenderness ratio and crystalline filling effects

Using a sample holder with an integrated force sensor, a collection of carbon nanotubes filled with Ga-doped ZnS, and spanning a broad window of lengths and diameters, has been mechanically studied inside a transmission electron microscope. The successful evaluation of the filled nanostructures was seen to depend on their slenderness ratio. Upon controlled removal of the encapsulated sulfide, the system considerably changed its response to uniaxial compressive stress. This report follows part 1 of the study which was instrument-focused and laid the ground to achieve consistent results with a novel type of nanomechanics setup for one-dimensional nanostructures (Costa et al, 2009 Nanotechnology. 40:405706).