Research Of Cyanine Dyes-coated Core-shell Nanoparticles Based On Silica

Core-shell nanoparticles based on silica has been developing rapidly and opening up a promising area in new bioassay development. Among them, nanoparticles of various shapes, sizes, and compositions have been successfully used in bioimaging, labeling and sensing because of their unique properties. Most of the core-shell nanoparticles were doped with Rubpy, magnetic materials, fluorescein, rhodamine, thulium chelate etc. Unfortunately, there are few reports on Cyanine dyes doped nanoparticles, This work was concentrated on the preparation and study of the Cyanine dyes doped nanoparticles.Difference in the preparation of four soluable cyanines, Rubpy, methlyene blue and Cy2 dyes doped into silica nanoparticles by reverse microemulsion method were studied, TEM of Rubpy, methlyene blue and Cy2, as-well as leakage experiment, spectra properties were detected. The results demonstrated that the solubility and the cation numbers containing in the Cyanine dyes are very important for those can be successfully doped into silica nanoparticles to form stable core-shell nanoparticles.Cy3 and Cy5 with three cations in their molecules were synthesized respectively. They were characterized by NMR, MS. Both of them were successfully doped into silica nanoparticles by reverse microemulsion method, the nanoparticles were uniform and monodispersed with an average diameter of 55nm (Cy3) and 60 nm( Cy5 ). Spectra of both dyes and nanoparticles were measured, leakage experiment was also conducted by immerging the nanoparticles in water, the nanoparticles remained about 82% and 64% of fluorescence intensity, respectively. Photostability was studied by illuminating the Cy3 and Cy3-doped nanoparticles for 90 min, the fluorescence intensity of the dye decreased to 15%, while the nanoparticle remained about 78%.Cy7 with APS in structure was synthesized, and the dye was characterized by NMR, MS. Cy7 dye has a large stokes shift about 140nm. The Cy7 doped nanoparticles were uniform and monodisperse with an average diameter of 65 nm, the stokes shift was 120nm. After immerged in water for 72h, the fluorescence intensity of the nanoparticles remained about 96%, by illuminating the Cy7doped nanoparticles for 20min, the fluorescence intensity of dye decreased to 33%, and the nanoparticles remained high intensity of about 53%, the photostablity was increased 20%.