Carbon nanotubes as nanoreators for Magnetic applications – CarMa

During this project we aim to:
a) develop new chemical synthesis routes effective and innovative way to manage and secure exclusively inside nanotubes magnetic metal nano-objects with significant magnetization and controlled anisotropy. Depending on the concentration of metal magnetic nano-objects, the size of nano-objects, their shape and composition, various hybrid materials will be prepared.
b) to study and quantify, in collaboration with physicists, the confinement effect resulting from the interaction between the metal magnetic nano-objects and the inner cavity of nanotubes multiwall carbon (an article in preparation)
c) the use of nanotubes as nanoreactors for phase transformations, and to ensure the chemical stability of magnetic metal nano-objects using an original in situ polymerization reaction. This essential step will also:
d) allow to to evaluate the potential of these new hybrid systems for important applications such as the treatment of cancer by hyperthermia and preparation of composite materials based on carbon nanotubes

In this project, we studied the magnetic confinement of metal nanoparticles (MMNPs) in carbon nanotubes, multi-wall (CNTs) of different diameters. The project was divided into two main themes:
- Selective containment NPMMs defined monometallic (Fe, Co) in functionalized CNTs and their protection against oxidative polymerization; and
- The study of bimetallic (CoPt and FePt) MMNPs inside CNTs and phase transformation by thermal annealing.
MMNPs of Co and Fe of controlled size and shape were synthesized with new aromatic ligands as stabilizers. These NPMMs were then selectively introduced into the cavity due to attractive/repulsive interactions between functionalized CNTs and MMNPs. We were then involved in the protection of these nanoparticles of the oxidation by air. Thus, confined MMNPs of iron were coated by polyisoprene. To do this, the surface of the nanoparticles of iron has been modified with a polymerization catalyst by ligand exchange. Then, the polymerization of isoprene was conducted inside the channel of CNTs. The protection from oxidation by the polyisoprene was evaluated by magnetic measurements after exposure to air. Finally, bimetallic magnetic nanostructures (particles or son) combining Pt and cobalt or iron were obtained and confined in the CNTs. Their levels of chemical structure have also been studied by thermal annealing studies.

Although most of the objectives of CARMA project were achieved, further work on the first part of the project should focus on: 1) the development of the method of filling to confine more MMNPs in carbon nanotubes; 2) improving the polymerization to achieve better protection of the air; and 3) a comprehensive study of the air protection of MMNPs by the iron complex grafted. The outlook for the second part of the project, additional efforts should be focused on: 1) the effects of confinement on the morphology and composition of bimetallic MMNPs; 2) the increase in Fe or Co composition nanostructures confined to a stoichiometry of 50% compared to Pt; 3) the search for species that are responsible for the formation of the nanowires; and 4) searching for a suitable method for the phase transformation anneal.

To date an article on the preparation of magnetic nanoparticles of cobalt and iron was published [N. Liakakos, B. Cormary, X. Li, P. Lecante Mr. Respaud, L. Maron, A. Falqui, A. Genovese, L. Vendier, S. Koinis, B. Chaudret, K. Soulantica The Big Impact of a Small Detail: Cobalt Nanocrystal Polymorphism as a Result of Precursor Addition Rate DURING Stock Solution preparation, J. Am Chem.. Soc. 2012, 134, 17922-17931]

Carbon nanotubes (CNTs) are one of the most intensively studied class of nanomaterials due to their outstanding properties and potential use in a number of high value applications. Today, the main application concerns the field of composite materials, where the use of CNTs may allow the production of conductive and highly resistant composites. Recently, confinement effects coming from specific interactions of nanoparticles with the walls of CNTs have become the object of a hot research domain that makes use of the CNTs as nanoreactors. On the other hand, metallic magnetic nanoparticles of the 3d series and their alloys (MMNPs) are some of the most important targets in nanoscience research, as very promising candidates for applications ranging from magnetic storage to magnetic manipulation and biomedicine. Their unique properties which may significantly deviate from those of their bulk counterparts can be further tailored by interaction of CNTs in order to meet the demand of novel versatile hybrid materials.
Taking advantage of the LCC’s expertise in CNTs synthesis and functionalization as well as of the expertise of the LPCNO in MMNPs synthesis and study of the magnetic properties, we propose CarMa.
The CarMa project constitutes an important step through the control of the complexity linked to the use of chemistry to organized nano-objects in hybrid systems presenting a complex architecture.
In CarMa we intend to (i) develop efficient and innovative chemical routes to direct and immobilize exclusively in the interior of CNT well defined pre-synthesised metallic magnetic nanoparticles (MMNPs) displaying a large magnetization and a controlled anisotropy. Depending on the MMNPs concentration, particle size, shape and composition, “superparamagnetic” or “ferromagnetic” CNT will be targeted; (ii) study the confinement effect arising from the interaction between metallic magnetic nanoparticles (MMNPs) and the inner cavities of multiwall carbon nanotubes (CNTs); (iii) exploit CNTs as nanoreactors to make phase transformations and to assure the chemical stability MMNPs by an original in situ polymerisation reaction. This step will permit to (iv) evaluate the potential of these hybrid systems in key applications such as, hyperthermia treatment of cancer, and CNT nanocomposites.