Preparation Of Core-shell Structure Of Gold Nanoparticles Coated With SiO₂ And Study Of Dye Loaded

Core-shell composite nanomaterials integrates the properties of inorganic,organic and nano-particles,it can adjust the properties of core and shell to obtain excellent performance.It is widely applied in imaging research,disease diagnosis,fluorescence labeling and other fields which becomes a research focus gradually.Cyanine dyes of water solubility have many advantages such as long wavelength,large molar absorption coefficient and large Stokes shift.They are often used in photothermal?photodynamic therapy and fundus angiography.It can maintain good stability in light and fluorescence due to its special structure,which is unique in biomedicine.At present,fluorescence imaging has been widely used in biomedical targeting,proteomics and other biological fields.Functionalized nanoparticles can not only realize fluorescence imaging,but also carry drugs in their shells,which is conducive to further research and exploration of drug loading and release rate of substances.Limited by the laser confocal optical resolution,the way and morphology of particles in the cell is not clear in detail.Gold nanoparticles can be used as models for the interaction of particles with cells,biological media,organism and ecosystem.In this thesis,the layered preparation of mesoporous silica on solid gold nanoparticles was realized.Two kinds of composite nanomaterials of Au@mSiO2 and Au@SiO2@mSiO2 were facilely synthesized.We also studied the coating mechanism of secondary core-shell structure.Functionalized nanoparticles with different potentials and hydrophilic interface properties were prepared,the results showed that the surface potential of the modified particles transformed from negative potential to positive potential.Based on the charge properties of the shell surface,the loading process of dyes was simplified by the strong electrostatic adsorption between the particle surface and the heterogeneously negatively charged dyes.The fluorescence intensity and fluorescence lifetimes of the load fluorescent dyes showed the dyes could not produce effective tunneling in the mesoporous materials under the action of alkyl chain barrier,and was limited to the surface of the particles,the longer the charged alkyl chain,the stronger the fluorescence intensity.The data showed that functionalized groups have binding effect on the active molecules,and the positively charged alkyl chain will prevent the guest molecules from entering shell structure.After loading,the nanoparticles still exhibit high fluorescence intensity,achieving dual-mode microscopic imaging(TEM and fluorescence).At the same time,the removal methods of cationic surfactants on nanoparticles were studied and the mechanism was discussed,then a new idea of removing surfactants was proposed.In addition,the nanoparticles can be covalently coupled with the dye.The result showed that the fluorescence quenching effect occurs when the dye is loaded on the mSiO2.However,the fluorescence intensity of the double-layer silica shell is no different from that of the free dye.The interaction between gold nanoparticles and nearby fluorophores is electromagnetic coupling under light excitation,the surface plasmon resonance(SPR)effect of gold nanoparticles is fully reflected in this process.and the effect intensity is related to distance of fluorescence chromophore.It provides a way to explore the energy transfer of nanoparticles.The study of the quenching effect of gold core on dye also shows the importance of surface functionalization of nanoparticles.It may be of great enlightenment to the research on the loading or release control of other guest molecules in nanostructures.