With the developments in technology, more and more materials and substances are being developed for different spheres of life, from construction works and computer industry to medicine. Many techniques and instruments are available to determine the macroscopic properties of bulk materials, such as tensiometric and rheological equipment, instruments to measure impact resistance and combustibility and many others. Currently, however, a big interest lies in nanotechnology, as different materials start to exhibit new and often very different properties with respect to the bulk state when the size of particles is much smaller than one micron. This, in turn, requires different instruments and techniques, which would be capable to reveal the properties of these nanomaterials.
Raman spectroscopy can be an effective tool for the study of nanostructures due to its high sensitivity to differences in structure, chemical functionalities and even to stresses on the nanoscale. However, there exist a number of drawbacks that hinder the use of Raman spectroscopy for nano-analysis. Among them are the low signal intensity, the diffraction-limited resolution of current instruments and difficulty in interpreting the acquired data.
The strategy for overcoming the low intensity is to induce an enhancement in the electric field in the sample by placing it next to noble metal particles. This phenomenon is called Surface Enhanced Raman Scattering (SERS). The key to successful application of SERS is the correct choice of the particles and illuminating wavelengths, which determines the strength of the enhancement. In this Dissertation, we have studied SERS substrates prepared by different techniques and with different metals (Ag and Au) and characterized their SERS effectiveness.
To optimize the lateral resolution of SERS and to simultaneously access additional information such as surface topography, a Raman spectrometer and accompanying optics have been combined with a scanning probe microscope (SPM), a technique currently known as Tip-Enhanced Raman Scattering (TERS). However, there are still a few challenges for this technique, namely the efficiency of enhancing tips, their longevity and the potential damage they can induce in the sample through heating. We present a few promising designs of tips that could give high enhancement, suggest an effective method of their protection from environmental damage and show the increase in temperature in the analyte that will be caused by the enhancing tip.
Finally, we apply Raman scattering to the studies of carbon nanotubes separations and show how to interpret the data to get an understanding of the real changes in the sample after various treatments of the nanotubes.