| Fluorescence spectroscopy has been widely used in fingerprint identification,chemical detection and biological imaging,due to its high sensitivity,convenience and stability.However,only a few fluorescent molecules can meet the requirements of high quantum efficiency and large scattering cross section.Therefore,how to effectively enhance the fluorescence intensity has become the research goal of many researchers.Under the excitation of external electromagnetic field,the electron motion and electromagnetic field excitation on the surface of metal nanoparticles can produce a common harmonic oscillation,which can change the local electromagnetic field near the surface,so as to achieve the enhancement of fluorescence intensity of nearby fluorescent molecules.At present,gold nanorods are one of the important substrates materials for the enhancement fluorescence and many composite structures have been derived.The presence of hot spots in the gold-silver core-shell nanorods,enhanced the local electromagnetic field,are widely used in the surface enhancement.The traditional measurement method collects fluorescence signal from a large number of particles,which interaction between particles will have an impact on the observation results.Therefore,we use nano-positioning technology to collect the fluorescence signal of single Au@Ag@SiO2-dye nanostructures particle.The quantitative of fluorescence enhancement and the polarization dependence of anisotropic nanostructures on incident light are analysised.The main contents of the paper are as follows:1.Gold nanorods were synthesized.The ratio of silver nitrate and ascorbic acid is changed to control the aspect ratio of gold nanorods,which can adjust the position of the LSPR peaks;Base on this,wet chemical method was used to prepare Au@Ag core-shell nanorods by formatting a silver shell on the surface of gold nanorods;Finally,the improved Stober method and one step embedding method were used to successfully synthesis the Au@Ag@SiO2-dye nanostructures.2.Using in-situ single particle collection technology,the influence of the coupling degree of excitation wavelength,LSPR and emission wavelength on the enhancement effect of Au@Ag@SiO2-dye single particles was investigated.By adjusting the thickness of SiO2-dye layer in Au@Ag@SiO2-dye structure,we studied the effect of molecular distribution on fluorescence enhancement.It was found that the fluorescence enhancement effect is best and the enhancement factor can reach 127 folds,when the shell thickness is 5 nm.3.The dependence of single particle nanoscale Au@Ag@SiO2-dye on the polarization properties of incident light was also investigated.It is found that,with the change of incident light angle,the different surface plasmon modes of the anisotropic metal substrate are excited.Then,corresponding local electromagnetic field also changes,which results in difference fluorescence intensity.When the incident light is perpendicular to the long axis of the rod-like nanostructure,the effect of fluorescence enhancement is the strongest.Conversely,the weakest.Simultaneously,the polarization dependence of incident light of Au@Ag@SiO2-dye enhanced fluorescence was further studied by finite element simulation. |
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