Simon Pascal

Two-photon absorption in the near-infrared region: towards bio-imaging applications.
Simon Pascal


In 1931, Maria Göppert-Mayer[1] theoretically predicted the two-photon absorption (TPA), a nonlinear optical phenomenon observed under strong laser irradiation. The development of the first Ruby laser (694 nm) in 1960 enabled the observation of TPA in the visible range[2]. In the 90’s, the democratisation of Ti:sapphire lasers (600-1000 nm) has enhanced the research around TPA dyes with emission in the near-infrared for applications in biological imaging by two-photon excitation. Indeed, this absorption mechanism provides important advantages such as the reduction of photo-damages, 3D resolution and a better penetration in biological media[3]. More recently, OPO lasers operating at telecommunications wavelengths (1100-1700 nm) have paved the way toward bio-imaging with excitation and emission localized in the near-infrared (NIR) region.

In this context, our group focuses on the development of heptamethine cyanines (scheme 1) and the understanding of their optical properties which are in close relation with their electronic structure[4]. These dyes exhibit intense linear absorption and emission centered in the nearinfrared region, corresponding to the transparency window of biological media (600-1100 nm) and are, as a consequence, very interesting for the development of luminescent probes for bio-imaging applications by TPA.

 
Scheme 1. Ketocyanine candidate for bio-imaging in the NIR and its internalisation in a living cancerous cell observed by two-photon excited fluorescence.


(1) Göppert-Mayer, M. Annalen der Physik 1931, 9, 273.
(2) Kaiser, W.; Garrett, C. G. B. Phys. Rev. Lett. 1961, 7, 229.
(3) (a) Denk, W.; Strickler, J.; Webb, W. Science 1990, 248, 73. (b) Yao, S.; Belfield, K.
D. Eur. J. Org. Chem. 2012, 2012, 3199. (c) Pawlicki, M.; Collins, H. A.; Denning, R.
G.; Anderson, H. L. Angew. Chem. Int. Ed. 2009, 48, 3244.
(4) (a) Bouit, P.-A.; Wetzel, G.; Berginc, G.; Loiseaux, B.; Toupet, L.; Feneyrou, P.;
Bretonnière, Y.; Kamada, K.; Maury, O.; Andraud, C. Chem. Mater. 2007, 19, 5325.
(b) Bouit, P.-A.; Di Piazza, E.; Rigaut, S. p.; Le Guennic, B.; Aronica, C.; Toupet, L.;
Andraud, C.; Maury, O. Org. Lett. 2008, 10, 4159. (c) Bouit, P.-A.; Aronica, C.;
Toupet, L.; Le Guennic, B.; Andraud, C.; Maury, O. J. Am. Chem. Soc. 2010, 132,
4328. (d) Pascal, S.; Bouit, P.-A.; Le Guennic, B.; Parola, S.; Maury, O.; Andraud, C.
Proc. SPIE 2013, 86220F.