Aggregation Induced Emission at SIngle Particle level : characterization and nanofabrication inside microfluidic devices – SIPAIE

As stated in the National Strategy for Research report (SNR, Action Plan 2017, ANR Call), while presenting one of the five priorities of Challenge 3 "Industrial Renewal" (Orientation 14 "Design of new materials"): "The future industry will rely, in part, on multi-functional materials and on integrated measurement and detection systems. These will be all the more efficient as the integration of their functions at different scales (micro-macro) and their assembly will be thought from the nanometric scale". The SIPAIE project is precisely proposed in this context, with the ambition to contribute to a better understanding of the phenomena guiding the structuring process of self-assembled architectures.

Aggregation Induced Emission, which was discovered in 2001, is a paradigm shift for luminescence with very promising applications. In this novel photophysical phenomenon, weakly luminescent chromogens in solution become highly emissive in the aggregate or solid state. Consequently, aggregation is no more a threat for fluorophore based application. During the past decade, the AIE mechanisms have been deciphered and can now mostly be resume in one acronym: RIM i.e. Restriction of Internal Motion.

AIE is an extremely competitive field of research. Looking at the literature it appears that the AIE mechanisms have more or less come to a consensus without systematic studies at the single aggregate level. The main scientific hypothesis and innovative character of the SIPAIE project are that systematic photo-physics studies at the single particle level will bring new insights on the AIE mechanisms, in particular, the aggregation process, that could lead to even more efficient AIE materials.

The SIPAÏE project has two main goals.
- The first one, more fundamental, aims at getting a better understanding of the photophysical mechanisms inside AIE aggregates through original systematic measurements at the single aggregate level in solution inside microfluidic devices.
- The second one, more applied, aims at nanofabricating calibrated AIE aggregates.
We will use a lab-on-chip based on “T-junctions” where two reactants are mixed under a laminar flow with a precise control of the aggregation reaction (temperature, AIEgen concentration, water to AIEgen solvent ratio). An optical confocal filtering system permits to analyze only one class (i.e. size) of aggregates at a time. The evolution of the spectral properties (intensity, spectrum, lifetime, polarization) with respect to the size of the AIE aggregates will be used to assemble reproducible and efficient AIE material.

Various new AIGen molecules based on distyrylfuran have already been synthesized and will be analyzed at the single aggregate level concurrently with the two archetypal and commercially available AIEgens: HPS and TPE. We will build an automated and ultra-sensitive OptoFluidic Characterization Platform (OFCP) that will firstly be tested and calibrated with a well-characterized mock-up system : the dimerization of plasmonic nanoparticles. The OFCP will be used to understand the influence of temperature, AIEgen concentration, water to AIEgen solvent ratio, on the size and the spectral properties of AIE aggregates and also the AIEgen aggregation mechanisms at the single particle level. Then the same optofluidic device will be used to prepare AIE solid materials and AIE nanoparticled (know as AIE dots) made from calibrated AIE aggregates inside microfluidic channels. These samples will be thoroughly characterized (AFM, SNOM, NLO) with the collaboration of my teammates.