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FULLY DIGITAL - NO PUBLIC : PhD Defence Jasper Lozeman | Surface enhanced vibrational spectroscopy: Implementations in lab-on-a-chip

Surface enhanced vibrational spectroscopy: Implementations in lab-on-a-chip

Due to the COVID-19 crisis measures the PhD defence of Jasper Lozeman will take place online.

The PhD defence can be followed by a live stream.

Jasper Lozeman is a PhD student in the research group Biomedical and Environmental Sensorsystems (BIOS). His supervisors are prof.dr.ir. M. Odijk and prof.dr.ir. A. van den Berg from the Faculty of Electrical Engineering, Mathematics and Computer Science (EEMCS).

The goal of this thesis was to develop a lab-on-a-chip device for online reaction monitoring using vibrational spectroscopy. Vibrational spectroscopy covers techniques of infrared (IR) spectroscopy and Raman spectroscopy. Both techniques provide vibrational information, although in fundamentally different ways. One of the shortcomings of IR spectroscopy – and to a lesser extend – Raman spectroscopy is that they suffer from a weak signal to noise. This is especially a problem for IR spectroscopy when measuring in an aqueous environment. Nanofabricated antennas for surface enhanced spectroscopy could be used to address this problem, with literature claiming enhancement factors of up to 103 for IR and 1010 for Raman spectroscopy.

As a platform for these antennas, we present a modular, microfluidic microreactor platform. This microreactor has an integrated internal reflection element for attenuated total reflection (ATR)-IR spectroscopy. A Paal-Knorr reaction is performed as proof-of-concept. To highlight the strength of IR spectroscopy as a tool for reaction monitoring, the peaks are identified and different reaction orders of various steps of the Paal-Knorr reaction are calculated.

The antennas for surface enhanced infrared spectroscopy (SEIRS) are fabricated according to a half-dipole configuration. We discuss several different fabrication techniques to fabricate both nano-rod and nano-slit Au nanoantennas. Furthermore we present FTDT simulations that were used in order to predict the resonant wavelength of the antennas. The results of these simulations showed correlation between the antenna length and the resonance frequency. We also showed that the simulations can be used to determine at which periodicity between the antennas the strongest enhancement is obtained. This additional enhancement is based on the far-field coupling between the antennas. Finally, we show the correlation between simulations and experimental results.

For the surface enhanced Raman spectroscopy (SERS) – already a more established technique than SEIRS – we discuss a novel, high-yield fabrication method for wafer-scale patterning of high-quality arrays of dense gold nanogaps. We achieve this using displacement Talbot lithography and shrink-etching of the resist. Additionally, we prove that the Au nanogaps show a significant enhancement of the signal of benzenethiol molecules chemisorbed on the structure surface, with an average enhancement factor up to 1.5 × 106.