Core-shell Plasmonic Nanostructures Fabricated Via Layer-by-layer Method To Fine-tune "Au Nanoparticle-fluorophore"Distance And Energy Transfer Thereof

Upon excitation of electromagnetic radiation with appropriate frequency, the free electrons surrounding the surface of noble metal nanoparticles (NPs) such as silver and gold nanoparticles would oscillate coherently and exhibit as Localized Surface Plasmon Resonance (LSPR) peaks in the Uv-vis extinction spectra. In the previous research on interactions between Au NPs and fluorescent dyes, it was frequently discovered that the fluorescence intensity of the dyes could be either quenched or enhanced, dependent on influencing factors such as the specific distance between the two parts, the local environment dielectric strength, etc, which is closely related to the possible occurrence of electron/energy transfer process thereof. However, so far the role played by LSPR during the process remains unclear. Therefore, herein we designed and constructed core-shell plasmonic nanostructures via layer-by-layer method to investigate LSPR involved energy transfer process. The thesis is mainly divided into five sections:1. Background introduction.2. The synthesis and characterizations of the Au NPs with diameter-14nm.3. Fabrication of core-shell plasmonic nanostructure in the solution by Layer-by-Layer assembly method (LbL).4. Investigation of energy transfer process as a function of separation distance between the gold core and the Rhodamine B (RhB) dyes via spectroscopic measurement.The observed fluorescence quenching showed that, the energy transfer between the gold core and the RhB dyes was distance dependent. However, neither Fluorescence resonance energy transfer (FRET) nor Nanometal surface energy transfer (NSET) model is suitable for describing the fluorescence quenching efficiency as a function of separation distance reported in this thesis.5. Transferring the plasmonic nanostructure on the glass slide to investigate the LSPR involved energy transfer process in solid phase. Similar fluorescence quenching to solution phase was observed in solid phase.