Research

MULTIMAN: multifunctional-magnetic-nanoparticles

Research project selected under the 2012 call for proposals

Principal Investigator :

Katerina Soulantika (ksoulant@insa-toulouse.fr)
LPCNO (Nanostructures et Chimie Organométallique)

Type of project : Collaborative Project

Partner team(s) :

CEMES (MC2)

Date (start/end) : 2013 - 2015

          

A reaction of cobalt nanorods with another metal (M), depending on the reaction conditions, can result either in Co@M core@shell or in heterostructured nanocrystals. The two metals are segregated into different domains but belong to the same nano-object. The different interfaces formed depend on the nature of the materials but also on the reaction conditions. Different applications are envisaged for each kind of hybrid nanostructure.

Résumé

MultiMan aims at studying in detail the structure of multifunctional magnetic nanoparticles synthesized by chemical routes at the LPCNO lab. These nano-objects comprise a magnetic metal and a noble metal on the same nano-structure. The detailed structural analysis will contribute to improve and accelerate the development of the multimetallic nanoparticles and will be principally based on transmission electron microscopy performed at the TEMSCAN service and at the CEMES.

Anisotropic cobalt nanorods are a main target of MultiMan. An increased reactivity of certain facets of anisotropic nanocrystals is responsible for the tendency towards formation of heterostructured nano-objects in which the different metals connected through a limited interface. However a modulation of the reaction conditions can induce the formation of a complete shell around the cobalt nanorods. We are interested in controlling the growth location by a fine control of the chemical synthesis parameters, towards asymmetric heterodimers as well as core@shell structures.

Core@shell magnetic metal@noble-metal nano-objects especially interesting. While the metallic magnetic materials offer several advantages over their oxide counterparts, they are easily oxidized by traces of oxygen, losing their advantageous magnetic properties. Therefore, there is a great need to protect them from air and/or water. This protection is mandatory for applications in biomedicine for which aqueous solutions of the nanorods have to be handled in the presence of water and oxygen. A noble metal is an ideal shell for protecting the magnetic nanoparticles from oxidation. In parallel, depending on the noble metal, a variety of new properties can be integrated in the same nanoparticle. For instance, a magnetic nanoparticle covered by gold can be optically detected by its surface plasmon resonance and simultaneously manipulated by an externally applied magnetic field. On the other hand, a Pt shell can afford a catalytically active nanoparticle that can be easily separated from the reaction medium and recycled by using a magnet.

A full characterization by a large variety of TEM techniques, particularly by advanced methods (HRTEM, EELS, HAADF), will give information about the topological composition within each nano-object and the exact structure of interface between the metals. This knowledge will contribute to the adaptation of the reaction conditions towards the desired structure.

 

 

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