Berlin 2012 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 8: Poster: Nanoparticles and Composite Materials

CPP 8.41: Poster

Montag, 26. März 2012, 17:30–20:00, Poster A

Photo-fluorescence spectroscopy of a novel form of ultra-stable silicon nanoparticles — Hanieh Yazdanfar, Gediminas Galinis, Gauthier Torricelli, Mark Watkins, Atea Akraiam, and •Klaus von Haeften — Department of Physics and Astronomy, University of Leicester, Leicester, LE1 7RH, United Kingdom

Silicon nanoparticles produced by a novel co-deposition technique [1] show a number of extraordinary properties: clusters smaller than 3 nm in diameter form a stable phase in water, do not agglomerate [2] and emit strong and exceptionally stable fluorescence when excited with UV light [3]. An unequivocal assignment of the fluorescence is challenging because of the breadth of possible geometric structures and cluster sizes. We found the fluorescence wavelength un-shifted irrespective of the excitation energy and concluded that the fluorescent transitions originated from localised defects presumably caused by a chemical reaction of silicon with water. In alcoholic solvents the clusters fluoresce as well but the bands exhibit a blue-shift which we found to correlate with the dipole moment of the solvent molecules and which we interpreted as evidence for a location of the defects at the cluster surface. Size effects were investigated by AFM of clusters placed on HOPG in UHV and by filtering the solutions, which revealed that the fluorescence stemmed only from the smaller clusters in the solution.

[1] K. von Haeften et al. Eur. Phys. J. D 52, 11 (2009).

[2] A. Brewer, K. von Haeften, Appl. Phys. Lett. 94, 261102 (2009).

[3] G. Torricelli, A. Akraiam, K. von Haeften, Nanotechnology 22, 315711 (2011).