Anne-Marie Galibert

AFM imaging of functionalized double-walled carbon nanotubes

We present a comparative study of several non-covalent approaches to disperse, debundle and non-covalently functionalize double-walled carbon nanotubes (DWNTs). We investigated the ability of bovine serum albumin (BSA), phospholipids grafted onto amine-terminated polyethylene glycol (PL-PEG(2000)-NH(2)), as well as a combination thereof, to coat purified DWNTs. Topographical imaging with the atomic force microscope (AFM) was used to assess the coating of individual DWNTs and the degree of debundling and dispersion. Topographical images showed that functionalized DWNTs are better separated and less aggregated than pristine DWNTs and that the different coating methods differ in their abilities to successfully debundle and disperse DWNTs. Height profiles indicated an increase in the diameter of DWNTs depending on the functionalization method and revealed adsorption of single molecules onto the nanotubes. Biofunctionalization of the DWNT surface was achieved by coating DWNTs with biotinylated BSA, providing for biospecific binding of streptavidin in a simple incubation step. Finally, biotin-BSA-functionalized DWNTs were immobilized on an avidin layer via the specific avidin-biotin interaction.

Examining the impact of multi-layer graphene using cellular and amphibian models

In the last few years, graphene has been defined as the revolutionary material showing an incredible expansion in industrial applications. Different graphene forms have been applied in several contexts, spreading from energy technologies and electronics to food and agriculture technologies. Graphene showed promises also in the biomedical field. Hopeful results have been already obtained in diagnostic, drug delivery, tissue regeneration and photothermal cancer ablation. In view of the enormous development of graphene-based technologies, a careful assessment of its impact on health and environment is demanded. It is evident how investigating the graphene toxicity is of fundamental importance in the context of medical purposes. Onthe other hand, the nanomaterial present in the environment, likely to be generated all along the industrial life-cycle, may have harmful effects on living organisms. In the present work, an important contribution on the impact of multi-layer graphene (MLG) on health and environment is given by using a multifaceted approach. For the first purpose, the effect of the material on two mammalian cell models was assessed. Key cytotoxicity parameters were considered such as cell viability and inflammatory response induction. This was combined with an evaluation ofMLGtoxicity towards Xenopus laevis, used as both in vivo and environmental model organism.

Filling of Carbon Nanotubes with Compounds in Solution or Melted Phase

Since their discovery, carbon nanotubes (CNT) have been found to exhibit remarkable structural, mechanical and electronic properties. One such property is the ability to encapsulate foreign materials inside their cylindrical cavity, for application in different fields. The procedures to fill CNT may be classified into two main groups: (a) filling in solution, using the wet chemistry route and (b) filling with a melted phase. In both cases, the filling is induced by the capillary forces. It is also possible to fill CNT in the vapour phase, although there are only few very specific examples available in the literature to date. After filling, oxides and metallic particles can be obtained by a subsequent thermal annealing in the required atmosphere. In the wet chemistry route, the nanotubes are usually treated by an oxidizing agent in order to open their tips. The filling is then performed by placing the opened tubes in a solution of the selected compound (or a precursor). When the compound is dissolved in an oxidizing acid such as nitric acid (HNO3), it is possible to combine opening and filling in a single step. Although this method allows the introduction of heat-sensitive species inside carbon nanotubes, the yield varies strongly with the diameter of the carbon nanotubes and is generally rather low in the case of CNT with a small inner diameter. This filling route mainly leads to isolated nanoparticles or short nanowires. Filling with melted compounds is a solvent-free route. The CNT are directly immersed in the melted material and capillary forces drive the compound into the CNT. Although this route is more restrictive in terms of materials, it allows for the continuous filling of CNT with long nanocrystals (up to a few micrometers), with a higher filling yield in the available CNT (up to ca. 70%). This chapter will describe these two different methods for filling CNT and illustrate them with a few selected examples.

The Unexpected Complexity of Filling Double-Wall Carbon Nanotubes With Nickel (and Iodine) 1-D Nanocrystals

A variety of iodine-based one-dimensional (1-D) nanocrystals were introduced into double-wall carbon nanotubes (DWCNTs) using the molten phase method, as an intermediate step for ultimately obtaining encapsulated metal nanowires. Based on high-resolution transmission electron microscopy (HRTEM) observations using different imaging modes (bright field, dark field, and scanning TEM) and associated analytical tools (electron energy loss spectroscopy), it is revealed that the reality of nanotube filling is much more complex than expected. For some iodides (typically NiI 2), earlier decomposition during the filling step was observed, which could not be anticipated from the known data on the bulk material. Other filling materials (e.g., iodine) show a variety of atomic structuration inside and outside the CNTs, which is driven by the available space being filled. Most of the encapsulated structures were confirmed by modeling.

The unexpected complexity of filling double-wall carbon nanotubes with iodine-based 1D nanocrystals

A variety of iodine-based 1D nanocrystals were introduced into double-wall carbon nanotubes using the molten phase method, as an intermediate step for ultimately obtaining encapsulated metal nanowires. Based on HRTEM observations using different imaging modes (bright field, dark field, STEM) and associated analytical tools (EELS), it is revealed that the reality of nanotube filling is much more complex than expected. For some halides (typically Nih), earlier decomposition during the filling step was observed, which could not be anticipated from the known data on the bulk material. Others (e.g., iodine) show a variety of atomic structuration inside and outside the CNTs which is driven by the available space being filled, and was ascertained by modelling. Overall, the whole study reveals a variety of filling efficiencies, the reason of which is discussed.