Optical Properties Modulation Of Metal Nanostructures To Dye Molecules And Rare Earth Ions

In recent years, surface plasmon resonances in metallic nanoparticles are widely exploited for a variety of applications including molecular sensing, optical swich, near-field optical microscopy and focusing of light and so on. The reason of surface plasmon for these applications basically arises not only from the flexibly change of the resonances wavelength by varying the nanoparticle's size, component, shape and local dielectric environment, but also from the large electromagnetic field near the metal surface. The large electromagnetic field makes metal nanoparticles can interact with nearby molecules resonantly or nonresonantly. In this paper, we synthesized metal nanoparticles with different structures, morphologies and components, and we studied the modulation of optical properties of these nanoparticles to dye molecules and rare earth ions. The followings are the details:Firstly, we have prepared hybrids of Au nanorods strongly coupled to IR-806 molecule which is a near-infrared cyanine liquid crystal dye—AuNR@IR806 hybrid. We investigated multiple hybridized resonances of AuNR@IR-806 hybrids. We can see five hybridized resonance peaks in the extinction spectra of the AuNR@IR-806 hybrids, and then we analysis these peaks theoretically. The dependence of these five hybridized peaks on the longitudinal surface plasmon resonance wavelength of AuNRs and the dye's concentration is also demonstrated. In addition, two new extinction peaks at approximately 840 and 912 nm of IR-806 are reported for the first time. The observations presented herein provide us a plasmon-molecule coupling route for applying optical responses of near-infrared dye molecules.Secondly, we have proposed a facile aqueous-phase method to synthesized silver-coated gold nanoshells, that is Ag/Au/SiO2 nanoshell, on the surface of SiO2 nanospheres with 1,4-BDT molecules as the spacer. We tuned the surface plasmon resonance of Au/SiO2 and Ag/Au/SiO2 nanoparticles through changing the thickness of Au and Ag nanoshells. We then measured the Raman scattering and nonlinear refraction of these two samples. And we found that compared with Au/SiO2 nanoparticles Raman intensity of Ag/Au/SiO2 nanoparticles is enhanced by 17 times, while the nonlinear refractive index is enhanced by 30%. These results demonstrate that the local field in the gap of Au and Ag shell is enhanced due to the coated of Ag nanoshell. This nanostructure can be applied in the fields of electromagnetic equipment, sensor and nonlinear nanodevice and so on.Thirdly, we have synthesized AuNR/Nd2O3 nanocomposites with the yolk/shell nanostructure by hydrothermal method. We studied the growth mechanism, extinction spectra and the spectroscopic spectra of the composites. The results showed that the growth mechanism of the composites could be ascribed to Ostwald ripening process and that AuNRs core can enhance the down conversion emission property of Nd2O3 shell at 873 nm by a factor about 3.3 and at 1056 nm by a factor about 1.5.In addition, we further investigated the dependence of enhancement factor on the plasmon resonance wavelength of AuNR/Nd2O3 nanocomposites.Finally, we synthesized the AuNR/SiO2/Au core/shell nanocomposites based on the gold nanorods by changing the parameters and the growth environment during the experiment process. We studied the morphology and the plasmon resonance property of the nanocomposites. These nanoparticles can be applied in the fields of optical sensor, biological imaging and biological label and so on.