The Study On The Optical Properties Of Au@Ag Coreshell Nanorod

Noble metal nanoparticles can display extraordinary electronic, magnetic and optical properties comparing to bulk materials owing to the size effect. When it is excited by incident light with specific wavelength, the free electrons on the surface of the metal nanoparticle will participate a collective oscillation with the incident light, which is called the surface plasmon resonance (SPR). The size, shape and the material of the metal nanoparticles have great effect on the position of the SPR peaks. For gold nanorod, the longitudinal surface plasmon resonance (LSPR) mode has a strong dependence on the aspect ratio of the gold nanorod and can be tuned continuously from visible range (-600nm) to the near infrared region (-1800nm). Nanostrctures based on gold nanorod has become a hot research area.We can tailor the plasmon properties of gold nanorod effectively by modification and coating.In this paper we first introduced the general theory of surface plasma and reviewed the development of gold nanorod research. Then, we synthesized gold nanorods with tunable aspect ratio by seed-mediated growth method. We took Us-Vis sspectra and Transmission electron microscopy pictures of the goldnanorods and analyzed the surface plasmon resonance as well as the lattice structure of gold nanorods. We also introduced the SERS effect of grapheme with gold nanorod deposition briefly.Secondly, we achieved the micromodification at the ends of gold nanorod by adding proper amount of acid or alkaline solution to the goldnanorod colloid and changed the gold nanorod into nanodumbbells with arrow-like ends and spherical ends along with the shift of the surface plasmon resonance peaks. And we give the growth mechanism of nanodumbbell with some theoretical analysis.Lastly, we do a systematically research on Au@Ag coreshell nanorod, characterization methods including synthesis,Uv-Vis spectra, Transmission electron microscopy were used to get some useful information about this nanostructure. And we obtained the single particle dark-field spectra of the coreshell nanostructure, allowing us to have a new understanding of the surface plasmon resonance properties of the Au@Ag coreshell nanorod at single pariticle scale.