CE09 - Nanomatériaux et nanotechnologies pour les produits du futur

Induced Magnetochiral Dichroism in Helical Nanocomposites – MaChiNaCo

Submission summary

In MaChiNaCo, new nanocomposites based on magnetic objects organized on silica nanohelices will be designed, synthesized and characterized for the study and optimization of induced magnetochiral dichroism (MChD). MChD is a cross-effect between natural circular dichroism (NCD) and magnetic circular dichroism (MCD), and manifests as a differential absorption of non-polarized light by a chiral medium according to the direction of an external magnetic field. MChD was experimentally validated in 1997, and has been used to preferentially enrich one of the two enantiomers of a racemic mixture, without the use of circularly-polarized light, providing a possible mechanism for the homochirality of life.

While the existence of MChD is indisputable, only a handful of examples of this phenomenon are known in the literature. These examples encompass widely disparate systems, from small molecules in solution, complexes in the solid state, to metal-organic frameworks (MOFs), and it is still difficult to successfully predict which chiral compounds will show a strong magnetochiral response. Moreover, it is believed that the chirality and the magnetism must be present simultaneously on the same molecule or particle. Here we wish to tackle simultaneously these two statements by proposing a thorough study of MChD using a composite approach where achiral objects with a strong magneto-optical response are grafted onto chiral silica nanohelices with controllable handedness and pitch. This bottom-up strategy takes advantage of induced circular dichroism (ICD), a phenomenon observed for achiral chromophores strongly interacting with a chiral component, which must transform into induced MChD under the influence of a magnetic field.

The indisputable novelty of MaChiNaCo is to avoid the often complex synthesis of chiral magnetic objects by exploiting ICD based on chiral inorganic templates at the nanoscale. This strategy considerably increases the number of magnetic objects that can be studied, as they no longer require intrinsic chirality. The original exploitation of the induced MChD effect will allow us to envisage a wide range of nanocomposites based on different magnetic objects and helix shapes, thus significantly broadening the field of MChD research. A better understanding of this effect and the factors that govern it will clearly benefit from the proposed study. MaChiNaCo is a 48 month project proposed by a consortium uniting French expertise in magnetism (CRPP), nanotechnology (CBMN, IPCMS) and magneto-optical phenomena (LNCMI). Our work program will tackle the following challenges:

WP1) Optimize the grafting of model magnetic complexes onto silica nanohelices.
WP2) Evaluate the influence of the template (silica helices) morphology on the ICD (and eventually, the MChD) signals.
WP3) Study the influence of the nature of metal center of the magnetic complexes on the MCD and MChD signals.
WP4) Amplify the magneto-optical component with superparamagnetic clusters and nanoparticles.
WP5) Amplify the magneto-optical component by the organization of the magnetic objects to induce magnetic or magnetoplasmonic coupling.

Project coordination

Elizabeth HILLARD (Institut de Chimie de la Matière Condensée de Bordeaux)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

CBMN INSTITUT DE CHIMIE ET DE BIOLOGIE DES MEMBRANES ET DES NANOOBJETS
LNCMI LABORATOIRE NATIONAL DES CHAMPS MAGNETIQUES INTENSES
IPCMS Institut de physique et chimie des matériaux de Strasbourg (UMR 7504)
ICMCB Institut de Chimie de la Matière Condensée de Bordeaux

Help of the ANR 463,719 euros
Beginning and duration of the scientific project: January 2020 - 48 Months

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