UTFacultiesEEMCSEventsPhD Defence Koen Jorissen | Instrumentation Development for Spectroscopy at the Micro- and Nanoscale

PhD Defence Koen Jorissen | Instrumentation Development for Spectroscopy at the Micro- and Nanoscale

Instrumentation Development for Spectroscopy at the Micro- and Nanoscale

The PhD defence of Koen Jorissen will take place in the Waaier building of the University of Twente and can be followed by a live stream.
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Koen Jorissen is a PhD student in the Department of Biomedical and Environmental Sensorsystems. Promotors are prof.dr.ir. M. Odijk from the Faculty of Electrical Engineering, Mathematics and Computer Science and prof.dr. R.P.H. Bischoff from the University of Groningen.

In the pharmaceutical industry, research and development costs for a single drug vary from hundreds of millions to billions of dollars. A significant component of these costs lies in developing drugs that do not reach the market. Drug viability goes through various phases of assessment before it makes it to market. One way of assessing drug behaviour in the body before in-vivo testing (human or animal) is by mimicking the drug metabolism and looking at its metabolites, for example through electrochemistry. By studying reactions with spectroscopy, information on reaction products and potential metabolism of the reaction precursors can be achieved. This thesis covers several spectroscopic techniques and reports on the development of instrumentation for spectroscopic applications.

Chapter 2 describes the design and building of a quantum cascade laser-based discrete frequency infrared spectrometer. The spectrometer is built on an optical breadboard table. It is based on a commercially available external cavity quantum cascade laser, mercury cadmium telluride detectors and a field programmable gate array-based data acquisition system. This setup is capable of writing the signal of a single wavelength at a 2 MHz frequency, or the signal from two detectors up to 1 MHz. The signal-to-noise performance is evaluated for different timescales using the Allan variance for gated integration and lock-in amplification approaches for the processing of the pulsed laser signal. Chapter 2 also describes the application of the spectrometer in infrared reflection-absorption spectroscopy mode (PM-IRRAS). To enable this study, the spectrometer beam path is configured to measure the P- and S-polarized signals simultaneously. The light-induced cis-trans isomerization of a azobenzene-containing self assembled monolayer on a gold surface is studied as a proof-of-principle. The data is insufficient to draw conclusions with respect to the self-assembled structure.

Chapter 3 describes the application of the infrared spectrometer to the time-resolved study of solvent-induced swelling of poly(SPMA) brushes grafted onto an attenuated total reflection crystal. Using a microfluidic flow cell built around the crystal, we can rapidly cycle the humidity of a nitrogen stream running over the brush. Due to the high reproducibility of the swelling dynamics, this rapid switching enables the sequential acquisition of the time-resolved infrared absorption at different wavelengths. Thus, we can show the infrared absorption of the brush after swelling at millisecond time resolution after averaging for noise. The timescale of the infrared absorbance change is compared to a study of the thickness of an identical brush using spectroscopic ellipsometry, which is found to be slower.

Chapter 4 describes the design of a custom electrochemical thin-layer flow cell for online conversion in high-pressure liquid chromatography-mass spectroscopy workflows. The cell features a titanium counter electrode, a boron-doped diamond working electrode, and a silver-silverchloride pseudo-reference electrode. Although the pseudo-reference electrode is not capable of withstanding pressures over 20 bar, the cell is shown to be usable up to at least 230 bar in a two-electrode setup. This enables online conversion upstream of the column. The cell is used to study two red pigments, PR5 and PR53. For both PR5 and PR53, redox reaction products are identified.
Chapter 5 describes the integration of a visible light waveguide in a microfluidic flow cell featuring a boron-doped diamond electrode. To optimize conversion in flow, the flow cell is designed to be as thin as feasible using the available techniques. The microfluidic flow cell is assembled using a chip with boron-doped diamond electrodes, the chip featuring the visible light waveguide, and a patterned piece of tape. Different types of tape of varying thicknesses are used to form flow cells.