Research On Synthesis And Plasmonic Properties Of Gold Nanorod-Based Nanostructures

Noble metal nanomaterial(especially, gold and silver) become a hot topic in nanoscience, due to their stable physical properties and unique optical properties—local surface plasmon resonance(LSPR). Among the different metal nanoparticles, gold nanorods(GNRs) attract much attention in biomedical science, photoelectric technology, et al., for their unique anisotropy and tunable SPR characteristics depending strongly on their morphology. This dissertation bases on experimental synthesis and theoretical analysis on the GNRs, self-assembly and core-shell structures. FDTD calculations are also ultilized to analysis all the factors which affects the SPR. The results lay the foundation for the GNRs-based research and applications.The main work and some results included in this dissertation are as follows:1. Monodispersed GNRs colloids with different aspect ratio are synthesized by the seed-mediated growth method, and corresponding SPRL absorption spectrum can be tuned in near infrared region. The effects of the incident light and temperature on the growth of the GNRs are investigated. The relationships between the SPRL peak and aspect ratio and media refractive index are both theoretically discussed by Gan theory and FDTD method. Effects of polarization of the light source and the morphology of the ends on SPRL peak are also studied by FDTD simulation. The calculated results show that SPRL intensity is mainly influenced by the polarization of the light, and fitting cosine relationship. And the end morphology of GNRs can not only cause the change of intensity, but also cause SPRL peak shifts.2. HS-PEG-SH, CYS and MPA are respectively utilized as the linking molecules to induce the well-controlled self-assembly of GNRs. Linear assemblies of the end-to-end(EE) and side-by-side(SS) modes are obtained, and the self-assembled mechanism are analyzed in detail. The FDTD calculations show that SPR coupling can be influenced by the number of the GNRs in the self-assembled chains, the gap and the angle between the neighbouring GNRs. With the increasing of the number of GNRs, SPRL peak will appear redshift or blueshift for EE or SS structure, respectively. SPRL peak shifts show exponential relationship between the number of GNRs.With the increasing gap distance between neighbouring NRs, coupling effect becomes weak, SPRL peak of assembly is similar to that of the single GNR finally. And the angle only affects the intensity of high-energy peak and low-energy peak, arising from symmetry broken, and does not affect the position of SPR peak. As the angle is increased, the ratio between those two SPR peak intensities is found to decay exponentially.3. The sol-gel mothod is introduced to synthesize the GNR@SiO2 core-shell structure with different shell thickness, and the hydrolysis mechanism of the TEOS under alkaline condition is discussed. Additionally, 808 nm continuous laser is ultilized to study the thermal stability of the GNRs and GNR@SiO2, showing that stability of GNR@SiO2 is higher with the protection of the shell. With the laser power increasing, CTAB molecules begin to fall off from the GNRs surface, the exposed surface occurs melting, and eventually form the spherical structure. For GNR@SiO2 structure, as the the laser power increasing, SiO2 shell around the GNRs will break, resulting in the destroyed core-shell structure.4. Solube and stable GNRs-based assembly of core-shell composite nanostructure is synthesized experimentally through a simple and effective way, in which the core structures have both EE and SS assembled GNRs. FDTD calculations indicated that SiO2 shell well keep the optical response of the core, and the SPRL peak shows exponentially increasing or decreasing as increasing the number of GNRs in core. Moreover, the GNRs assembly core-SiO2 shell composite nanostructures are facilitating for further quantitative study of the SPR between the assembled GNRs.