. . . . . . . . . .    ANM 2010     3rd International Conference on Advanced Nano Materials     12-15 September 2010 - Agadir, Morocco Back    Abstract ANMM151 ORDERED MONO AND MULTILAYER NANOPARTICLE ARRAYS RE-ASSEMBLED BY UV PHOTOLYSIS E. Majkova(1), L. Chitu(1), P. Siffalovic(1), M. Jergel(1), S. Luby(1), A. Satka(2), S. V. Roth(3), and G. Maier(4) (1) Institute of Physics, Slovak Academy of Sciences, 84511 Bratislava, Slovakia (2) International Laser Center and FEEI SUT, 81219 Bratislava, Slovakia (3) HASYLAB /DESY, Notkestr. 86, 22603 Hamburg, Germany (4) Materials Center Leoben Forschung GmbH, Roseggerstraße 12, A-8700 Leoben, Austria . Ordered nanoparticle mono-and multilayers are interesting for various applications including photodetectors, light emitting devices and solar cells. The nanoparticles prepared by chemical synthesis are covered with an organic surfactant which suppresses the agglomeration of nanoparticles and affects the final array formation. On the other hand, its presence limits the applicability of the ordered nanoparticle arrays in many cases. Methods often applied for the surfactant removal like vacuum annealing, chemical and/or plasma etching could result in changes of the nanoparticle composition and destroy the ordering. An alternative technique could be the UV photolysis of surfactant in ambient air atmosphere. We report on a real-time observation of the nanoparticle re-assembly accompanying the UV surfactant photolysis of ordered nanoparticle mono- and multilayers. The time-resolved grazing-incidence small-angle X-ray scattering (GISAXS) was employed to extract changes in the nanoparticle pair correlation function within an ordered array while the sample was processed with a UV reactor (4.9 eV photon energy). We used iron oxide nanoparticles with the mean size of 6.2±0.7 nm and a surfactant shell composed of oleic acid and oleylamine. The presence of layering in the nanoparticle multilayer was proved by the X-ray reflectivity measurements. For the nanoparticle monolayer the time resolved GISAXS measurements revealed continuous reduction of the interparticle spacing and formation of agglomerates of nanoparticles. The process can be well described by a simple exponential decay function. From the analysis it follows that the nanoparticles agglomerate with a diffusion-like kinetics. The nanoparticle agglomerates were confirmed also by scanning electron microscopy. The process of the UV induced surfactant removal is more complex for the nanoparticle multilayers. Again a continuous reduction of the interparticle spacing is observed. The GISAXS data indicate formation of a thick uniform layer of dense packed nanoparticles. Neither lateral nor vertical nanoparticle ordering were observed in the resulting structure. . © nanoAC . . . . . . . . . .

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