Pierre Brodard

Exploring liquid–liquid interfaces with transient evanescent grating techniques

A transient grating setup with evanescent wave probing has been developed to investigate ultrafast processes at liquid–liquid interfaces. In order to evaluate the selectivity of this method to the interface, the speed of sound in the low refractive index medium has been measured as a function of the penetration depth of the probe pulse. Our preliminary results indicate an increase of the speed of sound in methanol with decreasing the probe depth from 100 to 70 nm. However, no correlation was found in acetonitrile in the same range. Modifications of the experiment for improving the selectivity to the interface are proposed.

Mechanism of Exciplex Decay: The Quantum Yields and the Rate Constants of Radical Ion Formation from Exciplexes with Partial Charge Transfer

The dynamics of exciplex and radical ion formation was studied in donor–acceptor systems with G*et > –0.1 eV. It was shown that the quenching of excited singlet states of aromatic molecules by electron donors in polar solvents led to the formation of radical ions via exciplex dissociation resulting to complete charge separation. Intersystem crossing and internal conversion into the ground state (back electron transfer) compete with this process. The quantum yields and the rate constants of the radical ion formation were measured.

Transient Grating Investigations at Liquid-Liquid Interfaces

A new four-wave-mixing technique with evanescent optical fields generated by total internal reflection at a liquid-liquid interface is described. Several applications of this method to measure thermoacoustic and dynamic properties near liquid-liquid interfaces are presented.

Surface chemistry at Swiss Universities of Applied Sciences

In the Swiss Universities of Applied Sciences, a number of research groups are involved in surface science, with different methodological approaches and a broad range of sophisticated characterization techniques. A snapshot of the current research going on in different groups from the University of Applied Sciences and Arts Western Switzerland (HES-SO), the Zurich University of Applied Sciences (ZHAW) and the University of Applied Sciences and Arts Northwestern Switzerland (FHNW) is given.

Non-destructive localization and identification of active pharmaceutical compounds by Raman chemical imaging.

Raman spectroscopy is a powerful and non-destructive technique for chemical and structural identification. Based on inelastic scattering of laser light by molecular vibrations, the analysis can be localized on a microscopic area when combined with a microscope. Thus, by moving the sample under the microscope objective and recording a Raman spectrum at each point, a map of the intensity of specific Raman bands can be generated, effectively creating a chemical image of the sample at the microscale. Here, we present an application of this technique for identifying and localizing active pharmaceutical ingredients in a polymer matrix.