| Abstract |
The THz frequency range is one of the most interesting regions of the electromagnetic spectrum. THz radiation lies between the far-infrared and the microwave region, in a frequency interval from 0.1 THz to 30 THz. Historically, it is known as the ‘’THz gap’’ due to the lack of coherent sources in this frequency range. Nevertheless since the last two decades numerous works have been done on coherent sources and it is now possible to access the THz frequency region of the electromagnetic spectrum.
Many non-metallic and non-polar materials are transparent to THz radiation, due to the vibrational and rotational transitions of many molecules that lie in the THz frequency range. Furthermore, THz radiation is non-ionizing (~ meV) and is absorbed highly by water. These unique properties of this radiation have been revealed, suggesting the development of promising applications either spectroscopic or imaging. In this work which is divided into two parts, we present the application of THz Time-Domain Spectroscopy (THz-TDS) in two different scientific fields.
In the first part of the thesis, applications of THz-TDS in food inspection are presented. Specifically studies have been performed in distinguishing different antibiotics and acaricides residues in honey. The antibiotics and acaricides have been optically characterized in the THz frequency range between 0.3 THz and 8 THz and most of them showing specific fingerprints in this frequency range. The main spectral features of two antibiotics were still detectable when they were mixed with pure honey. These residues in honey can be detectable in concentrations up to 0.1%. These results indicate that THz-TDS can be used in the production line in the near future.
In the second part of the thesis, a number of different excipients constituting a pharmaceutical tablet have been characterized in the THz frequency range. These preliminary studies aim to use THz-TDS as an efficient tool for detecting the dosages of the excipients in the production line. This work is still in progress and is conducted in cooperation with a pharmaceutical industry.
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Terahertz spectroscopy of macromolecular systems
