Fabrication of Plasmonics Platform for the Chemical and Environmental Sensors

Abstract

In the various field of nanotechnology and nanoscience, such as biomedical and environmental science, the design and synthesis of certain nanostructure for a desired purpose is important. Metallic nanostructures have attracted significant attention in the research area of chemical and environmental sensor due to the superior physic-chemical properties and, especially, applicability to the utilization of surface plasmon resonance phenomena. This thesis mainly deals with the application of novel metallic nanostructures to the surface plasmon resonance phenomena for the realization of effective chemical and environmental sensor. And more detailed strategies and results related with these topics, as follows

Firstly, highly selective detection system for Cu2+ ions by exploiting specific interactions between the Cu-demetallated form (E,Zn-SOD1) of Cu/Zn-superoxide dismutase (SOD1) and Cu2+ ions using surface plasmon resonance spectroscopy (SPRS) was suggested. I demonstrated that Cu2+ ions have a high affinity for vacant metal-binding sites in the E,Zn-SOD1 protein, compared to other divalent metal ions. On the basis of these measurements, it can be concluded that small amounts of Cu2+ ions can be readily detected as the result of the selective binding between the E,Zn-SOD1 protein and Cu2+ ions. It appears that metalloproteins have considerable potential for use as a novel sensing actuator, as evidenced by the selective binding of E,Zn-SOD1 proteins with Cu2+ ion. This approach can be used in conjunction with other fully or partially demetallated metalloproteins, hence it could be potentially useful in the determination of specific metal ions in aqueous media or demetallated proteins in biological fluids. Additionally, the applicability of gold nanoparticles as a ratiometric sensor was suggested. From the theoretical study using discrete dipole approximation method, it is investigated that dimer structure of gold nanoparticles has unique optical properties compared to separated single gold nanoparticle. It can be appeared new plasmon band with longer wavelength due to the electron oscillations along the longitudinal interparticle axis, and this band can be distinguished clearly with the inherent plasmon band. The intensity ratio of inherent and additional plasmon band could be utilized as the value for the ratiometric sensor. Finally, simple method to fabricate highly branched gold nanostructures with abundant petal-shaped tips by direct growth on the substrate was suggested. A lot of experiments and theoretical calculations have shown highly enhancement of the electromagnetic field in complex gold nanostructures due to the abundant hot spots in the individual nanostructures. Among them, multi-branched nanostructure has attracted much attention because of their stronger SERS enhancement factor than other gold nanostructures. In this work, I synthesized and characterized the multi-branched gold nanoparticles, which are applicable to the surface-enhanced Raman detection. It was directly grown on the substrate with simple seed-mediated method, and the optical properties as growth procedure was investigated for the better understanding on the growth process. The multi-branched gold nanoparticles show the very high enhancement factor, thus it can be promising materials for the effective SERS substrate.