Matjaz Licen1 Lucija Čoga3 Stefano Masiero4 Irena Drevenšek Olenik1 2

1, Jozef Stefan Institute, Ljubljana, , Slovenia
3, Faculty of Mechanical Engineering, University of Ljubljana, Ljubljana, , Slovenia
4, Alma Mater Studiorum – Università di Bologna, Bologna, , Italy
2, Faculty of Mathemathics and Physics, University of Ljubljana, Ljubljana, , Slovenia

Basic blocks of DNA are very interesting constituents for designing supramolecular single-layer and multilayer surface architectures. Our recent studies of self-assembly of nucleoside derivatives in monolayer films at the air-water interface (Langmuir films) reveal that guanosine derivatives exhibit very different behaviour from analogous derivatives containing other nucleobases [1]. We also demonstrated that the number of lipophilic chains attached to the sugar hydroxyl groups and the type/concentration of ions present in the water subphase strongly affected molecular organization of guanosine derivatives in Langmuir monolayers as well as in Langmuir-Blodgett (LB) films deposited on various solid substrates [2,3,4]. Modifications of these parameters hence provide a possibility of tuning intermolecular organization in thin film configurations.
An appealing strategy for control and manipulation of intermolecular organization is to use optical irradiation. To test the applicability of this method in case of guanosine derivatives we investigated Langmuir films of azo-functionalised guanosine molecules in which the isomerisation can be switched from trans to cis and vice versa by irradiation with UV and visible light. Photoinduced modifications within Langmuir films were studied by film balance experiments and by Brewster angle microscopy (BAM). We were able to revesibly induce changes in the surface pressure of the film by alternatingly irradiating with UV and blue light, indicating a light-induced change in the film structure. We also investigated effect of optical irradiation on binding properties of the film for different compounds added either to the water subphase or to the air-water interface.

[1] L. Čoga, T. Ilc, M. Devetak, S. Masiero, L. Gramigna, G. P. Spada, and I. Drevenšek Olenik, Colloid. Surface B 103, 45 – 51 (2013).
[2] M. Devetak, S. Masiero, S. Pieraccini, G. P. Spada, M. Čopič, and I. Drevenšek Olenik, Appl. Surf. Sci. 256, 2038 – 2043 (2010)
[3] L. Čoga, S. Masiero, and I. Drevenšek Olenik, Colloid. Surface B 121, 114 – 121 (2014)
[4] L. Čoga, S. Masiero, and I. Drevenšek Olenik, Langmuir 31, 4837 – 4843 (2015)