Pedro M. F. J. Costa

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

Encapsulated nanograins of copper iodide have been sequentially discharged from individual carbon nanotubes. Using a high resolution electron microscope equipped with a two-terminal electrical measurements unit, it was possible to manipulate the filling contents with precisions of a few attograms at a time. Changes in electrical resistance and filling ratio were followed in tandem and in real-time. It is shown that the pulsed release of the halide is directly related to the overall conductance of the filled nanotube.

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.

Single-walled carbon nanotubes filled with M OH (M = K, Cs) and then washed and refilled with clusters and molecules

Heating single-walled carbon nanotubes (SWNTs) with molten hydroxides MOH (M = K, Cs) gave MOH@SWNT in good yield; high resolution transmission electron microscopy (HRTEM) indicated that CsOH in CsOH@SWNT often adopts twisted 1D crystal structures inside SWNTs; treating MOH@SWNT with water at room temperature removes the soluble hydroxide filling and the resulting SWNTs may then be filled using aqueous solutions of uranyl acetate or uranyl nitrate at rt giving SWNTs filled with UO(2) clusters and uranyl acetate molecules.

Light-induced instability of PbO-filled single-wall carbon nanotubes

We investigated single-wall carbon nanotubes filled with lead oxide, PbO, by transmission electron microscopy and Raman spectroscopy. It is concluded that PbO crystallizes in the orthorombic phase forming nanowires inside the nanotubes. The positions of the PbO Raman lines are downshifted as compared to the bulk material as a result of the reduced dimensionality. As a consequence of the filling, nanotubes become sensitive to the laser irradiation. At higher laser power densities, they oxidize and the free PbO nanowires are left in the sample.

Influence of catalyst metal particles on the hydrogen sorption of single-walled carbon nanotube materials

The hydrogen sorption capacity of arc-synthesized single-walled carbon nanotubes (SWNTs) was studied using a specially built high-pressure rig coupled to a Toepler pump capable of directly measuring the desorbed volumes of gas. The samples studied were prepared using the arc-evaporation method and were as-produced SWNT material formed at the cathode (collar), as-produced SWNTs deposited in the soot and a purified sample of SWNTs. The three samples had similar diameter ranges, the major difference between them being the concentration of remaining metal particles from the Ni/Y/C catalyst used in the arc-synthesis. The effect of the presence of these residual catalyst metal particles has been analysed and seen to strongly influence the hydrogen storage capacity of the samples.

Nitrogen-doped carbon nanotube structure tailoring and time-resolved transport measurements in a transmission electron microscope

A dynamical response of the current-voltage characteristics of ropes and individual structures of multiwalled nitrogen-doped carbon nanotubes has been observed inside a transmission electron microscope. The drastic change of the current transport properties is thought to be due to purging of contaminating gaseous surface adsorbed species. In addition, an in situ methodology was developed to obtain individually pure and length-tailored nanotubes. By carefully controlling the current flow across the nanotubes, residual surface-decorating and encapsulated catalyst particles were eliminated, and short sections of the nanotubes (200to500nm) were cut.

Encapsulation of quaternary 1D pentlandite-type alloy crystals within conical multi-layer carbon nanotubes

Ordered 1D crystals of a complex pentlandite-type alloy with the general composition (Fe,Ni,Co)9S8 have been synthesised inside conical Multi Walled Carbon Nanotubes (MWNTs); the crystals are observed as a by-product of an arc-evaporation synthesis of Double Walled Carbon Nanotubes (DWNTs).

Physics and Chemistry Inside Nanotubes

Abstract The interior of single‐wall carbon nanotubes (SWCNTs) is investigated by filling it with fullerenes and PbO. In the former case, maximum filling concentrations are evaluated for various fullerenes as a function of tube diameter. For filling with C60 a calibration table is provided that allows the determination of the filling concentration from Raman experiments. Smart filling from solution, from isotope‐labeled fullerenes, and filling from nonfullerenic carbon sources is discussed. In the case of filling with PbO, an influence of lateral confinement on the phonon wave functions, an instability of the tubes versus laser irradiation, and the persistent formation of PbO nano‐wires are observed.

In Situ TEM Electrical and Mechanical Probing of Individual Multi-walled Boron Nitride Nanotubes

Measurements of electrical and mechanical properties of individual multi-walled BN nanotubes inside a high-resolution transmission electron microscope are presented.

Electrical and mechanical property studies on individual low-dimensional inorganic nanostructures in HRTEM

The present contribution demonstrates the recent advances achieved by the Group in pioneering studies of electromechanical properties of diverse low-dimensional individual inorganic nanomaterials inside a transmission electron microscope. The measurements were performed in high-resolution field-emission transmission electron microscopes operating at 300 kV, namely JEOL-3000F and JEM-3100FEF, and on freestanding individual nanoscale objects by means of specialized piezo-driven STM-TEM and AFM-TEM holders commercialized by “Nanofactory Instruments AB”.