Aluminiumorganisch stabilisierte Übergangsmetallkolloide : Synthese, Bildungsmechanismus und Aufbau von organisierten Strukturen

Subject of the dissertation is the synthesis and characterization of novel, nanoscopic transition metal colloids having reactive aluminumorganic protecting shells, and the formation of 3-D nanoparticle networks. The synthesis of aluminumorganic stabilized platinum colloids was investigated using the reaction of Pt(II)-acetylacetonate with aluminumtrimethyl. A novel di-platinum complex was identified as the key intermediate of the colloid formation. This complex decomposes in solution under formation of nanoscopic platinum particles with a mean diameter of 1.2 nm. The formation of these particles in solution was studied with Anomalous Small Angle X-ray Scattering (ASAXS). The isolated platinum colloids were characterized further with several analytic methods like Electron Microscopy (TEM) and X-ray Absorption Spectroscopy (XANES, EXAFS). The investigations showed, that the particles consist of zero-valent platinum with an aluminumorganic protecting shell containing reactive aluminum-methyl-groups. These reactive aluminum-methyl-groups are the prerequisite for the interconnection of the particles to form a 3-D nanoparticle network. For that purpose, the colloids are reacted with proton-active bifunctional "spacer-molecules". Suitable spacer molecules are diols or dicarboxylic acids which react with the aluminum-alkyl groups in the protecting shell under cleavage of methane. The structure and the electronic- and catalytic properties of the resulting Pt-nanoparticle-networks were intensively characterized. The investigations revealed, that the structure of the networks is strongly depending on the "spacer-molecule" chosen. The mean interparticle distance in the network increases with increasing length of the "spacer molecule". Variation of the "spacer molecule" also allows the pore-sizes and the specific surface areas to be tailored. Furthermore catalytic tests showed, that the Pt-nanoparticle networks are very efficient heterogeneous catalysts for the hydrogenation of alkenes.

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2002

Author dc:creator

• Waldöfner, Norbert

Contributors dc:contributor

• Bönnemann, Helmut

• info:eu-repo/classification/ddc/540
• Chemie

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

ger

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-121826%22

OAI identifier oai:identifier

oai:publications.rwth-aachen.de:60099