Claudia Manuela Müller

Ordered arrays of faceted gold nanoparticles obtained by dewetting and nanosphere lithography

Nanoparticle arrays have potential applications in many areas, such as optics and electronics. Earlier work is mostly concentrated on the synthesis of such arrays, whereas we would like to focus on the control of particle size and shape, which has a great influence on the particle properties. In this study three different types of arrays of faceted nanoparticles were synthesized; it is shown that the particle size and shape in such arrays can be modified by the annealing treatment. By taking advantage of this, a novel method for the production of lines of faceted particles was demonstrated. These structures have potential applications as plasmon waveguides.

Isomerization of Alkoxy Radicals under Atmospheric Conditions.

The reactions of the 2-hexoxy radical and the 3-hexoxy radical have been studied in a collapsible Teflon bag reactor under conditions relevant to the atmosphere. The alkoxy radicals were generated either by the photolysis of the corresponding hexyl nitrite or by the OH radical initiated photooxidation of hexane. The hexoxy radicals were chosen as model species to examine the importance of alkoxy radical isomerization versus unimolecular decomposition or reaction with oxygen. The fraction of 2-hexoxy radicals undergoing isomerization was determined directly from the analysis of the 5-hydroxyhexan-2-one product. The fraction of 3-hexoxy radicals undergoing isomerization could only be determined indirectly

Dewetting of Au and AuPt alloy films: A dewetting zone model

When thin metal films are annealed they can degrade into particles. This happens even at annealing temperatures below the melting point and is known as solid-state dewetting or agglomeration. The solid-state dewetting behaviour of 15–35 nm thick Au and 20 nm thick AuPt films on SiNx/SiO2/Si substrates was investigated in the temperature range of 500–900 °C in air. Morphology maps were created based on which a dewetting zone model is proposed. The morphology maps can be divided into three zones: a zone where the film remains continuous, a zone where dewetting takes place, and a zone where dewetting is complete. Coverage measurements can be used to determine zone boundaries and the activation energy for void growth, which was 1.05 ± 0.1 eV in the case of Au. The influence of film thickness and alloying on the dewetting behaviour was studied; both factors had only an influence at low annealing temperatures, with the influence of alloying being more pronounced than the influence of film thickness.

The Rates and Mechanisms for VOC Photo-oxidation Reactions under Simulated Tropospheric Conditions

Laboratory kinetic studies of gas-phase elementary reactions of importance to tropospheric chemistry were initiated as part of the LACTOZ programme at the Swiss Federal Institute of Environmental Science and Technology (EAWAG) in October 1989. Two types of experiments have been carried out: (i) studies of the kinetics of competitive OH radical reactions with VOC in an atmospheric flow reactor and (ii) detailed end-product analyses of the OH radical initiated photooxidations of VOCs carried out in a static Teflon bag reactor.