Research axis 5

Hybrid nanoparticles for magnetism and plasmonics: Dr. G. Laurent, Pr. J. Abe

Several developments are expected from nano-scale interactions and phenomena, combining inorganic and organic components. Indeed, the presence of metal (or metal oxide) provides the possibility to introduce magnetic or plasmonic properties. Adding photoswitching may trigger these properties, and lead to new types of storage, detection, superresolution or amplification of signals. A first task will be focusing on the development of new molecules for which spin state can be switched. Indeed Pr. J. Abe (Aoyama Gakuin Univ.) is synthesizing new HexaArylBiImidazole (HABI) (HABI) compounds that can be photo-switched in solid state from a neutral state to a bi-radical state. Moreover back reaction is in the micro to millisecond range. In some case the biradical state can be a triplet state, singlet state or a quinoidal state. To achieve new devices for magnetic data storage, a complete understanding of magnetic properties is needed. Such studies already started between DR. H. Vezin (Lille Univ.) and Pr. J. Abe within a CNRS-JSPS project (2012-2013). The relevance and the performance of single crystal and polycrystalline of new fast HABI compounds were tested by a unique imaging Electron Paramagnetic Resonance technique. Within nano-synergetics the resulting photo-and magneto-active objects based on HABI will represent innovative nanoassemblies where strong cooperative effects are expected for applications in the fields of spin quantum magnetic data storage. These organic based systems will take the advantage of electron and nuclear spin manipulation at higher temperature compared to those performed with rare earth ions in this research field area. Another task will be foreseen, getting multifunctional hybrid nanomaterials for multimodal bioimaging. In this context, high-load nanoassemblies will be fabricated and comprise a photoactive organic core (photochromic or fluorescent) and a shell of inorganic nanoparticles displaying magnetic properties. The resulting disruptive architectures offer high photostability, as well as additive and synergetic effects, which leads to high responses (relaxivity, one- and two-photon brightness, Raman scattering) under excitation by an optical or magnetic field. Understanding and mastering the cooperative effects arising from the self-assembled units represent the target of this task. In addition, mutual interplay between the photo- and magneto-active units will be investigated to explore the potentiality of magneto-optical coupling at the nanometer scale. This work involves the groups of Pr. H. Miyasaka and T. Kawai. Concerning plasmonics, the project will center on the development of new multifunctional photoactive nanomaterials based on interactions between different sub-units, which will contain fluorescent and photochromic molecules, and metal particles. The latter component will provide plasmonic properties. Depending on the sub-unit combination and interactions, new materials will be designed for optical data storage, photo-switchable nanosensors or super-resolution microscopy. In this context, hybrid nanomaterials will be developed and optimized to show a very high photoswitching control of photophysical properties like the fluorescence emission and the plasmonic enhancement. Proper combination of photoactive molecules with plasmonic nanoparticles can modify (enhance or quench) the photophysical properties. A new collaboration is planned (by exchange of PhD students) to design new materials showing a triple interaction between the photochromic, fluorescent and plasmonic units. Such sub-units interactions will be studied from collective assemblies at the micrometer scale to the single particle level by combining fluorescence, transmission, Rayleigh and Raman scattering optical spectroscopies, under confocal optical and atomic force microscopies.

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