Organic Materials For Sensing Applications – OUTSMART

1. Optimization of synthesis
For the synthesis of our materials, we use a synthesis strategy based on copper-catalyzed Ullmann coupling to yield the extended aromatic core followed by N-alkylation in the presence of alkyl bromide. This strategy makes it possible to obtain the desired materials in 2 or 3 steps followed by an anion exchange. The synthesis was carried out starting with 1-bromo-naphthalene. Following this, an anion exchange was carried out to study the impact of the anion on the physico-chemical properties (film-forming, hydrophobicity , Melting point, etc.) and luminescence.
In the last 18 months, four families of molecules, having different chromophores, have been synthesized with similar yields.
Finally, we began to explore the shaping of the compound containing a fluorene unit and the BF4 anion (1 mm thick, 3 cm in diameter) for the detection of low and high energy neutrons.

2) Neutron Detection
The past year was devoted mainly to highlighting the ability of our materials to detect slow neutrons. This detection takes place via the nuclear reaction 10B (nth, a) 7Li * which is exothermic (Q = 2.31 MeV). The kinetic energy transmitted to the a essentially (Ea = 1.47 MeV) will cause excitation of the scintillating medium.
The counts of the neutrons detected could be normalized to those of the detector BF3 calibrated in situ at the site. In this way, detection efficiencies could be estimated as well as presented on the distributions to the right of the figure. By extrapolating the estimated efficiency to 0.05% for energy neutrons at ~ 110 keV, along the cross section of the interaction 10B (nth, a) 7Li *, a detection efficiency of 100% is reached for a Energy of neutrons slightly higher than the thermal energy (25 meV).
3) Detection of gaseous molecules.
Films of a series of ionic materials with naphthalene and N-methyl carbazole as substituents and a series of anions were deposited on interdigital electrodes of ITO. Their insulating character has been shown and some of these materials have been incorporated into MSDI devices, with Pc2Lu as the upper semiconductor layer. The I (V) characteristics are nonlinear and symmetric, as expected for MSDIs. These devices are sensitive to ammonia in the 10-100 ppm range but show high sensitivity to moisture.

4) Detection of low-energy Neutrons
If the predicted efficiencies are confirmed, our material will exhibit detection performances equal to those of the 3He detectors which are currently the benchmark in this detection domain but whose manufacture is compromised in the future because of the 3He scarcity . If our results are confirmed, our material will be very competitive in the market for the detection of slow neutrons in many fields in radiation protection, safety, medical, nuclear industry, logging, etc ...

Publications:
1. F. Rigoni, S. Freddi, S. Pagliara, G. Drera, L. Sangaletti, J. Suisse, M. Bouvet, A. Malovichko, A. Emelianov, I. Bobrinetskiy,, Nanotechnology, 28(25), 2017
2.Alexandre Al Abbas, Benoit Heinrich, Matthieu L’Her, Emilie Couzigne, Richard Welter and Laurent Douce, New J. Chem., 2017, 41, 2604-26014.
Communications:
1. M. Mateos, R. Meunier-Prest, A. Wannebroucq, J.-M. Suisse, M. Bouvet, “Spectroscopie d’impedance d’heterojonctions moleculaires – vers une meilleure comprehension du rôle des interfaces”, Forum Impedance, Université Curie, Paris, 12 déc. 2016.
2. (Conf. Invitée) M. Bouvet, «Emerging sensing materials for air quality monitoring«, COST action TD1105 «European Network on New Sensing Technologies for Air-pollution Control and Environment Sustainability«, EuNetAir, Final meeting, Czech Academy of Sciences, Prague, Czech Republique, October 5-7, 2016.
3. (Conf. Invitée) M. Bouvet, «Solution processing of molecular materials for better chemical sensors«, JSPS workshop «Green processes«, Dijon, 22-23 septembre 2016.
4. (Conf. Invitée) M. Bouvet, «Gas sensors based on lanthanide double- and triple-decker complexes« Seventh International Conference on Porphyrins and Phthalocyanines (ICPP-9), Nanjing, China, 3-9 juillet 2016.
5.M. Bouvet, «Phthalocyanines as molecular semiconductors, from electrical properties to gas sensing«, International Symposium for Metal Porphyrins and Phthalocyanines, Beijing, China, 1-3 juillet 2016.
6.(Conf. Invitée) M. Bouvet, J.-M. Suisse, R. Meunier-Prest, «Advanced hybrid materials for environmental sensors«, E-MRS 2016 Spring Meeting, Lille, 2-6 mai 2016.
7. L. Douce, L. Stuttgé, Ionic Liquids, Gordon R. C. (Ionic Liquids for Future Technologies), « Ionic Liquid Crystals for Nanochemistry, Gene Delivery and Radiation Sensors » August 14-19, 2016, Newry, ME, USA.
8. S. Leroux, European Material Research Society fall meetingWarsaw, 2016, September 20th, an overview using first principles molecular dynamics«