||Metallic nanoparticles due to surface plasmon effects are used to fabricate devices with particular electro-optic properties, so that, they have been widely studied in many fields. With progressive developments of interesting phenomena and applications, metallic nanoparticles have become an important role in different kinds of the studies. One interesting application is the surface enhanced Raman scattering associated with metallic nanoparticles. It is worthy to investigate the relationship between the surface plasmon effects of metallic nanoparticles and the enhancement mechanism of the Raman scattering. Besides, the shape effects of metallic nanoparticles in an array are interesting for a combination with optical circuits. On the basis of these properties of metallic nanoparticles, two studies will be introduced in this dissertation:|
First, the intensity of surface-enhanced Raman scattering (SERS) light of crystal violet (CV) molecules are probed as the molecules adsorbs on silver nanoparticles with SiO2 coating. We find that the intensity of the SERS light from CV molecules varies with the thickness of the SiO2 coating. Hence, this experiment investigates the enhancement mechanism of surface enhanced Raman scattering by modulating the thickness of the SiO2 coating. In addition, the SiO2 coating can work as a preventer to remain the activity of the silver nanoparticles. This makes the silver nanoparticles with SiO2 coating as a reusable substrate, which can provide a possibility to increase the precession of SERS measurements.
Second, a gold nanoparticle grating is fabricated by lithographic method. The shape effect of gold nanoparticles in the grating is investigated by probing the diffraction light intensity of the array. A variation of the diffraction light intensity of the grating is revealed as rotating the polarization of the probe light. And, the peak of the diffraction spectra shifts with the increasing of the polarization angle of the probe light. Under observation of the SEM, gold nanoparticles of an ellipsoid-like shape are shown and the major axis of gold nanoparticles are parallel a direction with an averaged angle of 57.8o respect to grating direction. We thus considerably thought that this the varying of the diffraction spectra are attributed to the shifts of localized surface plasmon resonance. In addition, the boundary effect on the shape of gold nanoparticles in the grating is explored.