Preparation And Research On Optical Properties Of Ag/Fluorescent Molecules With Core-Shell Nanostructure

Fluorescent nanomaterials have attracted tremendous interest in variousareas，they have great applied potential in optoelectronics, biology, diagnosticsand other aspects. Core-shell nanoparticles combining noble metals withfluorescent can exhibit excellent optical properties and high stability. Althoughit has been extensively studied on the species and synthetic methods forfluorescent nanoparticles， there are still many problems on the opticalapplication based on noble metal enhanced fluorescence，especially that thefluorescence enhancement depends on the fluorescent species combining withthe noble metal. In our work, we prepared the Ag@organic fluorescentmolecule nanocomposites with core-shell nanostructure by an in-situdeposition chemical method， the optical properties of the core-shellnanostructures have been investigated, including other core-shellnanostructures based on Ag nanoparticles. The details are summarized asfollows：1. The synthesis and separation of monodispersed Ag nanoparticles with different shapes.Monodispersed and uniform Ag nanospheres， Ag nanorods， Agnanocubes were obtained by polyol process and density gradientcentrifugation separation. A novel and simple chelation-reduction method tosynthesize a series of hexagonal Ag nanoplates with controlled aspect ratio.The synthesis of nanoplates with controlled size endowed the nanostructureswith well-defined SPR absorption features that can be systematically tunedfrom the visible to the near-infrared （NIR） spectral range. Besides, the SPRabsorption shows linear relationship with the amount of EDTA.2. Synthesis and study of optical performance of Ag@organic fluorescentmolecule （hereinafter called as R） core-shell nanostructures.Monodispersed Ag@R （R=ZnTPP, Perylene, Rubrene） core-shellnanostructures were obtained by an in-situ chemical deposition method. Weinvestigated the effects of Ag nanoparticle on the fluorescent properties ofR， Ag nanoparticles could largely enhance the fluorescence intensity of R.The Ag nanorod@ZnTPP core-shell nanostructures showed dual optical signaloutput: fluorescence and SERS signal. However，it is unexpected that thefluorescence in visible range is tunable from blue to red by tailoring thethickness of the organic molecule shell, and the SERS signal is strong enoughfor individual nanorod imaging. Quantum yield of these core-shellnanostructure is higher than ZnTPP neutral molecule.3. Synthesis of uniform core-shell Ag@mesoporous silica nanosphere Ag@mSiO₂are prepared by two different methods： one-pot andtwo-steps method. The size of the core and shell could be tuned by adjustingthe concentration of precursor and reaction time. We primarily realized thesynthesis of water-soluble nanomaterials with metal-enhanced fluorescence,providing a new opportunity for related biological applications.