This dissertation consists of four chapters detailing terahertz time-domain spectroscopy (THz-TDS) and the application thereof to the investigation of biological samples and related analytes.
Chapter 1 provides a background of the evolution of THz-TDS from a historical and physics/engineering perspective followed by an extensive section from a chemistry perspective dedicated to the interaction of THz radiation with matter. A variety of measurement techniques are discussed, culminating in a literature review.
Chapter 2 focuses on the investigation of the 20 essential amino acids as crystalline solids using THz spectroscopy, in which absorbance of THz frequencies by crystal lattice phonon propagation is documented. A study dedicated to qualitative analysis of L-alanine introduces a novel approach for the spectral assignment of the observed THz absorbance frequencies to the crystal structure of the analyte.
Chapter 3 presents the study of five types of excised human breast tissue – normal, benign, lobular carcinoma, ductal carcinoma in situ and invasive ductal carcinoma – using THz pulsed imaging, which consists of successive THz-TDS measurements over a two-dimensional space. The presentation and evaluation of the tissue images are supplemented with the examination of frequency-domain reflectance spectra of selected tissue areas. The results of the studies presented herein are followed by detailed guidelines for the maximization of the efficiency and benefit of continued pursuits in this field.
Chapter 4 investigates the potential of reflectance-mode THz-TDS as a method for the non-destructive determination of the gel-point of sol-gel monoliths. Results are used to compare the gel point properties of sol-gels with and without a stabilizing dendrimer. The conclusions are found to support a particular theory concerning the stabilization mechanism of the dendrimer in the sol-gel process.