Regensburg 2007 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 20: POSTER: Biological Systems + New Materials
CPP 20.24: Poster
Mittwoch, 28. März 2007, 16:00–18:30, Poster B
Growth of metal nanoparticles on tubular J-aggregates by photo-induced electron transfer processes — Dörthe Melitta Eisele1, •Omar Al-Khatib1, Anna Burmistrova1, Hans von Berlepsch2, Christoph Böttcher2, and Stefan Kirstein1 — 1Humboldt-Universität zu Berlin — 2Freie Universität Berlin
In this contribution it is shown that an electron transfer reaction from cyanine dyes to noble metal ions can be utilized to grow metallic nanoparticles at the surface of respective molecular aggregates. Therefore tubular J-aggregates with typical diameters of 20 nm and length exceeding 10 µm are formed in aqueous solutions using amphiphilic tetrachloro-benzimida carbocyanine dyes. The aggregates are characterized by means of cryogenic electron transmission microscopy (cryo-TEM) and by scanning force microscopy (AFM). Upon addition of noble metal salts (Na2PdCl4 or AgNO3) to the aggregate solution metallic nanoparticles that are rather uniform in size with a mean diameter of a few nanometers are growing on the surface of the aggregates as observed by cryo-TEM. In case of Pd salt the aggregates are destroyed upon particle formation, while in case of Ag salt the aggregates are unaffected by the formation of silver particles. The growth of the metal nanoparticles is explained by a photoexcited electron transfer process from the J-aggregates to the metal ions. A systematic study of optical spectra with varying silver ion concentration allows to investigate the influence of the particle growth on aggregate structure and morphology.