Doctor of Philosophy
Dr. François Lagugné-Labarthet
The knowledge on the chemical and the structural properties of substances benefits strongly from characterization methods that can provide access to the sample’s nanoscale building blocks. Not only should the sensitivity of these methods approach a high detection limit up to single molecule, but also the accessible spatial resolution must enable chemical imaging of individual nanoscale features of the substances. High resolution imaging is often provided by electron microscopes through methods such as transmission electron microscopy (TEM) and scanning electron microscopy (STM), nevertheless, these methods lack offering chemical information. Surface-enhanced spectroscopy was developed to improve the sensitivity of the chemical measurements through placing the sample onto rough metallic surfaces. However, in SERS, spatially resolved measurements are not possible since an ensemble of nanoscale features give birth to the SERS effect. The challenge of the simultaneous improvement of the spatial resolution and sensitivity was addressed indeed through combining high resolution optical microscopy with high sensitivity of surface-enhanced spectroscopy and was termed as tip-enhanced Raman spectroscopy.
In this thesis, the confined electric field in proximity of the nanoscale apex of the metallic TERS tip is first investigated theoretically through conducting finite-difference time-domain calculations. The results were employed in optimization of the experimental TERS setup which is utilized in this thesis. The power of TERS in high resolution detection of nanoscale substances is then evaluated through TERS study of isolated single walled carbon nanotubes. The accessible high resolution is also used to acquire insight into the impact of structural strains on the molecular vibrations in silicon nanowires. The large surface sensitivity and specificity of TERS is also evaluated through TERS mapping of the adsorption sites of osteopontin phosphoprpteins on the surface of calcium oxalate microcrystal which are responsible for the formation of kidney stones in human body.
Kazemi Zanjani, Nastaran, "Tip-Enhances Raman Spectroscopy, Enabling Spectroscopy at the Nanoscale" (2014). Electronic Thesis and Dissertation Repository. 2079.