| Fluorescence spectroscopy has been widely used in the fields of medical diagnostics, biological imaging and substances analysis. The detection limit is determined by the ratio of signal to background emission caused from the sample autofluorescence. An effective way to increase the fluorescence signal, and thus improve the detection sensitivity is by locating the fluorophores near metallic nanoparticles which can support localized surface plasmon (LSP). The interactions among the incident electromagnetic field, metallic nanoparticles and fluorophores may bring about a modification in the fluorophores’ excitation and decay rates.By employing gold and gold/silver core-shell nanorods (NRs) solutions as enhancement substrates, the influence of spectral correlation between LSP resonance mode of metallic nanoparticles and emission band of fluorophore on surface enhanced fluorescence (SEF) effect is investigated in current thesis. Also, a preliminary attempt to enhance the two-photon excited fluorescence (TPEF) of anthracene is conducted. This thesis consists of four parts as follows:1. The generation and properties of LSP, as well as an important LSP-based application, that is SEF, are introduced systematically in this part.2. Gold NRs solution was synthesised by a seed mediated growth method, and gold/silver core-shell NRs were fabricated by using gold NRs as the seeds. By changing the quantity of reagents, metallic NRs with different LSP resonance modes can be obtained.3. Surface enhanced fluorescence of Oxazine720 fluorophore with gold and gold/silver core-shell NRs is investigated experimentally in aqueous solution system. Metallic NRs with different LSP resonance modes are employed for providing necessary spectral overlap with the emission band of Oxazine720. The experimental observation shows that the fluorescence enhancement increases firstly and then decreases with the increasing metallic NRs concentration in fluorophore-nanorods suspension, which can be explained by the competition between enhanced emission and inner-filtering effect. Further investigation with different metallic NRs shows that the relationship between SEF and spectral correlation strongly depends on the concentration of metallic NRs. At a low metallic NRs concentration, the maximum enhancement factor is exhibited by metallic NRs with largest spectral overlap. While when the concentration increases to a certain degree, metallic NRs with largest spectral overlap may produce the weakest enhancement effect.4. The effect of gold NRs on TPEF of anthracene is studied. A mixture of anthracene and gold NRs is prepared by utilizing phase transfer technique and slow-evaporating solvent method. The experimental result shows that the introduction of gold NRs can obviously increase the TPEF intensity of anthracene, which can be attributed to the modification of excitation and decay rates. |
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