UMR 5182

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Solid State Fluorescence

Y. Bretonnière, C. Andraud

Publications En lien

Design of Small Organic Fluorophores Emitting in the Solid State

Organic molecules emitting in the solid state are much sought after for their applications in bio-imaging, in which they represent an interesting alternative to soluble fluorophores. In that perspective, red emitting compounds are the most promising.

We are particularly interested in small push-pull dipolar molecules, in which the terminal functional groups on the donor and on the acceptor end can easily be changed to tune the emission properties in the solid state. We undertook a systematic molecular engineering around this structure in order to identify the most promising groups. We are also trying to understand the role of the self-assembly and of the interactions between molecules in the solid state fluorescence with the aim of rationalizing the excitonic origin of the phenomenon. To that end, we used X-ray diffraction coupled with theoretical calculation in addition to fluorescence spectroscopy.

Systematic end group variation on small push-pull dipolar structures

Functional group variation on push-pull dipolar structure

Crystal packing showing the difference between fluorescent J- and nonfluorescent H-aggregate

Crystal paking showing different types of aggregates in the solid state

For all the compound studied, the X-ray crystal structure show the presence of long chain of specific aggregates in the form of J-aggregates, whereas the crystal packing of the non-emitting compounds reveal tighly packed dimer.

With the aim of pushing the emission in the far red / near-infrared region, we used strong electron-accepting moeities such as dicyanoisophorone and 2-dicyanomethylene-3-cyano-4,5,5-trimethyl-2,5-dihydrofurane (also called TCF). Emission above 700 nm could be obtained with quantum yield (ΦF) as high as 5% and over 25% for emission at λem=680 nm. For a given electron-accepting group, subtle variation in the donor end, such as changing the alkyl groups on the N,N-dialkylamino moiety (Chem. Mater. 2011, 23, 862-873), ) or varying the number and the position of methoxy group on TCF dipole (J. Mater. Chem. C 2016, 4, 766-779), induced considerable change on the solid-state fluorescence.

Further modification around the push-pull structure have been realized, with the aim of improving the quantum yield while shifting the emission to the near-infrared (> 800 nm), J. Org. Chem. 2019, 84(16), 9965-9974.

In parallel to the design of new fluorophores emitting in the solid-state, we are also trying to develop stable, ultrabright and biodegrable tracers based on these organic fluorophores embedded in polymer nanocapsules (ACS Appl. Mater. Interfaces 2018, 10(30), 25154-25165) or in mix polymer/silica nanoparticles (RSC Adv. 2016, 6, 94200-94205). Beside obtaining high quantum yield on the nano-aggregates, the main challenge here is to control and decrease the size of the nanoparticles as well as increasing the stability.

The NP probes were successfully tested in vivo on mice bearing tumours without diffusion across the tumour vascular endothelium. The two photon excitation wavelength at 1000 nm is optimum for deep tissue excitation.


  • F. Ganachaud, J. Bernard, S. Chambert (INSA Lyon) for the nanoparticles design.
  • B. van der Sanden (Clinatec Grenoble) for imaging study.