Preparation And Optical Properties Of Au Core-ag Shell Composite Nanoparticles

With the development of science and technology, there are many different preparation methods of nanoparticlas. As we know,vapor phase synthetic method,sputtering method,chemical reduction method,laser compositing method and so on are all usual methods to prepare metal nanoparticles. However,because the laser compositing method can well control nanoparticles'uniformity and the scale in the preparing process,it is well used widespread in many fields.In this paper,we use the laser ablation method to prepare noble metal (Ag/Au) nanoparticles in redistilled deionized water and weak aqua ammonia,especially the Au core/Ag shell nanoparticles with tunable surface plasma resonance absorption frequency. With the measuring tools of transmission electron microscope (TEM) and scanning eletron microscope (SEM),we analyzed the influences of redistilled deionized water and weak aqua ammonia to the metal nanoparticles'scaled-size,dispersibility and uniformity.Plasmon hybridization theory provides a conceptually enlightening method for calculating the plasmon resonance of complex nanostructures.This method is a mesoscale electromagnetic analog of how atomic orbitals interact to form molecular orbitals in electronic structure theory. Plasmon hybridization theory deconstructs a nanoparticle or composite structure into more elementary shapes, and then calculates how the plasmon resonances of the composite particles interact or hybridize with each other. This theory enables scientists to draw on decades of intuition from molecular orbital theory to predict the plasmonic response of complicated nanostructures.In this paper,we use the Au core/ Ag shell nanoparticles as theory model to simulate the SPR by Mie theory, which indicate that the two SPR peaks are the characteristic of the Au Core/Ag shell formed. Meanwhile the surface Plasmon hybridization model interpreted the result of the experiment and the Mie theory.