A. Dazzi, A.Deniset-Besseau, R.Prazeres, J.M. Ortega
Laboratoire de Chimie Physique, UMR8000, Université Paris-Sud, 91405 Orsay
For 25 years, near-field techniques have quickly progressed and have taken a large place in Nanoscience microscopy. Whatever, in the infrared range, the near-field microscopes have been not so numerous to work properly. We can count up only two different way to make infrared studies : the optical technique measuring the transmitted signal coming from the nano-object and the photothermal approach using a tiny thermometer to link temperature to absorption measurements. Considering these previous methods limitations, we have developed an innovative infrared spectromicroscopy technique, called AFMIR, based on the coupling between a tunable infrared laser and an AFM (Atomic Force Microscope). This coupling allows us to perform ultra-local infrared spectroscopy and chemical mapping at the nanometric scale. The principle  is based on detecting the local thermal expansion of the sample, irradiated at the wavelength of its absorption bands. This expansion is detected by the AFM tip in contact mode. We have validated this technique by comparing the infrared spectrum of a single E.coli bacterium and the corresponding FTIR spectrum, and showing the possibility to perform chemical mapping with sub-wavelength spatial resolution (50 nm)2. Later, similar outcomes have been obtained in nanophotonics (20 nm resolution) . Our work is now mainly focused on microbiology systems [4,5,6]. The strong constraint of the biologist is often to study living samples in their common environment. To fill this condition, we have developed our technique to work in liquid  (AFM liquid scanner). The next step is to perform series of measurements on one bacterium Rhodobacter capsulatus to follow the growth of PolyHydroxyButyrate vesicle in real time by mapping the sample on its specific band. The succeed of such experiments led us to propose to biologist users a technique suited to their thematic mixing infrared studies and “in vivo” experiments.
For four years, the AFMIR technique associated to the CLIO infrared FEL facility (http://clio.lcp.u-psud.fr/clio_eng/...) is proposed to users as a standard beam line (also called AFMIR).
-  A.Dazzi, R.Prazeres, F.Glotin, J.M.Ortega, Opt. Lett. 30, Issue 18, 2388-2390 (2005).
-  A.Dazzi, R.Prazeres, F.Glotin, J.M.Ortega, Ultramicroscopy 107, Issue 12, 1194-1200 (2007).
-  J.Houel, S.Sauvage, P.Boucaud, A.Dazzi, R.Prazeres, F.Glotin, J.M.Ortega, A.Miard, A.Lemaitre Phys. Rev. Lett. 99, 217404 (2007).
-  A.Dazzi, R.Prazeres, F.Glotin, J.M.Ortega, M.Alsawaftah, M.De Frutos, Ultramicroscopy 108, 635-641(2008).
-  C.Mayet, A.Dazzi, R.Prazeres, J.M.Ortega , D.Jaillard, Analyst 135, 2540-2545 (2010).
-  C.Policar, J. B.Waern, M.A.Plamont, S.Clède, C.Mayet, R.Prazeres, J.-M.Ortega, A.Vessières, and A.Dazzi, Angewandte Chemie, Volume 123, Issue 4, 890–894, (2011).
-  C.Mayet, A.Dazzi, R.Prazeres, F.Allot, F.Glotin, J.M.Ortega, Opt. Lett. 33, 1611-1613 (2008).