Ordered self-assembly of molecules on gold substrates, for activated organic monolayers – Prof. Emmanuelle Lacaze

Date: Wed. July 17th, 2013, 12:30 pm-1:30 pm
Location: Rockefeller 221

Photochromic molecules are characterized by a functional group whose configuration is modified by absorption of light, in a reversible manner. They could be at the basis of new electronic displays which would be activated by light irradiation. For the formation of ultra-thin electronic displays, researchers now try to adsorb them on metallic substrates. Two main questions are thus asked : Firstly, is it possible to self-assemble this type of molecule on a substrate. Second, when self-assembled in monolayer, do the molecules remain active under irradiation, and most importantly, can they be locally switched under STM tip Ordered self-assemblies have been successfully obtained with azo-benzene based photochromes, the switching phenomenon being in majority studied under UHV and with a low efficiency, partly due to the desexcitation induced by the proximity of the metal substrate [1]. We now show that using diarylethene molecules, we can self-organize the photoactive group away from a gold substrate in an ordered network. We have identified the closed form as well as the open form of the molecule by STM [2]. We show that efficient switching can occur in ambiant conditions using light irradiation but also in presence of the electric field of the STM tip. In parallel, we have introduced an azobenzene group in a molecule with symmetry 6 [3]. We show that on gold substrate, azo-benzene groups are responsible for the formation of extremely stable self-assemblies of original high period. The dynamics of single molecules shows that interactions between azo-benzene very finely depend on the respective orientations of two neighboring molecules. 1. van der Molen, S. J.; Liljeroth, P. J. Phys.: Condens. Matter.2010, 22, 133001 2. Snegir, S.V.; Marchenko, A.A.; Yu, P.; Maurel, F.; Kapitanchuk, O.L.; Mazerat, S.; Lepeltier, M.; Leaustic, A.; Lacaze, E. J. Phys. Chem. Lett. 2011, 2, 2433-2436. 3. Y. Shimizu, A. Kurobe, H. Monobe, N, Terasawa,, K. Kiyohara and K. Uchida, , Chem. Commun. 2003, 14, 1676..