The Synthesis Of Visible Surface-Enhanced Raman Spectroscopy(SERS) Substrates Used In Aqueous Solution

As NaYF4:Yb3+/Er3+one of the most efficient NIR-to-visible UCL materials,NaYF4:Yb3+/Er3+has been Widely used as fluorescent labels for bioimaging in living cells.In this thesis,novel core-shell nanocrystals were designed and synthesized based on a 'from core to shell' method.In brief,two kinds of NaYF4:Yb3+/Er3+cystals with different shapes,which were rod and hexagonal prism type,respectively,were synthesized firstly.Then,based on the in-situ reduction reaction in aqueous solution,silver nanoparticles(NPs)were successfully attached onto the NaYF4:Yb3+/Er3+UCNPs with variable density to forms a non-continous shell.Based on SEM,XRD and UV-vis spectrum,the morphology and structure of the as prepared core-shell nanocrystal NaYF4:Yb3+/Er3+@Ag were investigated.Moreover,it has also been found that the upconversion fluorescence in NaYF4:Yb3+/Er3+UCNPs can be modulated by silver NPs.A strong upconversion fluorescence emission from the core can be observed when NaYF4:Yb3+/Er3+UCNPs were excited with a 980 nm laser.However,the core emission can also be greatly suppressed by silver NPs under visible light excitation,meaning that the SERS measurement could not be intervened under such experimental condition.