Title: Upconversion mid-infrared (UCIR) spectroscopy and spectromicroscopy of heterogeneous catalysts
Supervisors:
Principal supervisor: Assoc. professor Peter Tidemand-Lichtenberg
Co-supervisor: Pablo Beato, Haldor Topsøe A/S
Evaluation Board:
Chairman: Senior researcher Ole Bjarlin Jensen, DTU Fotonik
ICREA professor Majid Ebrahim-Zadeh, ICFO-The Institute of Photonic Sciences, Spain
Assoc. professor Juha Toivonen, Laboratory of Photonics, Tempere University of Technology
Master of the Ceremony
Senior Researcher Peter John Rodrigo, DTU Fotonik
Abstract
This thesis describes an investigation of upconversion based detection for use in catalysis research. The project is focused on experimental work with the specific goal of measuring on catalytic samples. The method of infrared upconversion detection and spectroscopy is based on sum frequency generation. The infrared light is converted to the near-infrared frequency range by mixing with an intense intra-cavity laser field. The near-infrared signal can then be detected by conventional silicon-based detectors. This presents several advantages in terms of noise, cooling, and detection speed. The main results of the project comprise two significant experimental parts.
The first is a demonstration of hyperspectral imaging using the spectral imaging capabilities of the upconversion based detector system. This method relies on spatial translation of the object in order to cover each position for a range of wavelengths.
The second experimental part of this thesis deals with a method for obtaining infrared spectra using the non-collinear phasematching properties of the upconversion. The second part pertains to IR spectroscopy using upconversion and a custom grating setup. Two distinct types of experiments are performed with this system. The first is a transmission measurement using an operando sample cell to enable spectral acquisition while the catalytic sample is subjected to gas flow and heat. The results were found to correspond nicely to similar experiments using conventional FTIR instruments. The second is, to our knowledge, the first demonstration of diffuse reflectance infrared spectroscopy on a capillary reactor. Here three different catalytic samples are exposed to the same experimental conditions in terms of pre-treatment, temperature, and gas flow while infrared spectra are captured along with gas chromatography of the outlet.
Finally, the thesis concludes with a general summary of the achieved results and presents an outlook of the potential applications of upconversion based detection technology and avenues for further research within infrared detection and spectroscopy.