Reversible optical induced change between two states with distinct absorption spectra, referred to as photochromism, can be used to photoswitch reversibly different physical properties (magnetism, emission,…), thereby conducting to the modulation of absorption spectra, dipole moments, fluorescence, magnetism, chirality to name but a few. Photochromic molecules are involved in the development of disruptive and innovative photofunctional materials amenable for instance to change shape, trigger the electronic conductivity in electronic devices or the fluorescence properties for high-resolution microscopy. Besides, this project is expected to develop research for photochromic materials from another view point than the one classically explored by linear and additive schemes. Assembling large collections of molecules into well-defined nano-arrangements represents an approach of great interest, in order to develop novel advanced materials with specific features that cannot be achieved by means of the simple sum of isolated molecules, showing individual physical and chemical molecular properties. In recent years, research on photoactive and electroactive materials based on organic molecular assemblies (such as organic crystals or supramolecules) has attracted much attention and is being actively developed, to take advantage of cooperative effects and produce cascade effects. In addition, smart multifunctional hybrid nanomaterials for applications in optical data storage, multimodal bioimaging and “on-demand” drug delivery can be foreseen using new photochromic molecules. In this context, high-load nanoassemblies are fabricated and comprise a photoactive organic component (photochromic and/or fluorescent) combined with inorganic nanoparticles displaying plasmonic or 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 self-assembled units will represent considerable advances in the bottom-up construction of molecular edifices and contribute towards the general concern of sustained development targeting strong reduction of the consumption of chemicals/materials and energy.
This project thus aims at designing and studying novel complex photochromic molecular nanomaterials (organic and hybrid) based on nonlinear cooperative effects, multi-photon processes, and multifunctionality thanks to the crossexpertise of several researchers in French and Japanese laboratories having already demonstrated intensive collaborative work programs. Two main axes will be targeted:
(1) the design and fabrication of molecular systems and functional photoactive nano-assemblies.
(2) the structural characterizations and photophysical investigations of the photoreaction dynamics (especially under multiphoton excitation) based on advanced spectroscopies: NMR, EPR, ultrafast femtosecond spectroscopy and timeresolved fluorescence microscopy combined with detailed analyses and theoretical computations.
In the Nano-Synergetics LIA project, we propose a smart and efficient combination of systems, technical tools and scientific findings of the research fields described above to cover the whole value chain of photostimulable materials. As a general perspective, we intend to create novel photoresponsive molecular nano-materials that can be controlled by light and based on molecular cooperativity. Another target of Nano-Synergetics is to combine the strength of both countries to understand unexpected results, synthesis and materials. Indeed, due to the complexity inherent to such nano-photofunctional systems based on photochromic molecular assemblies with nonlinear behaviors, the associated research field still remains unexplored. Unexpected results, may they be in physical chemistry or in synthesis, need to be deeply discussed to better understand their origin and address the system complexity. The Nano-Synergetics project is thus expected to contribute largely to the development of this field from both the fundamental point of view and the design of novel photofunctional nano-materials. It will also fully respond to the strategic imperatives of sustainable economy, impacted by all sectors of science, and materials science in priority.
Five research axes are planned in Nano-Synergetics. For each axes there are one responsible of Japan and France.
Axis 1: New photoswitchable organic fluorescent nanoparticles: Dr. M. Sliwa, Pr. J. Abe
Axis 2: Charge transfer (CT) and aggregation-induced emission (AIE) photochromic nanoparticles: Dr. R. Métivier, Pr. K. Matsuda
Axis 3: Photomechanical effects: Dr. R. Métivier, Pr. T. Kawai
Axis 4: Multiphoton, upconversion in nanoparticles: Dr. M. Sliwa, Pr. H. Miyasaka
Axis 5: Hybrid nanoparticles for magnetism and plasmonics: Dr. G. Laurent, Pr. J. Abe