| The synthesis, characterization, and applications of nanoparticles are among the most important sections of the wide range of nanotechnology areas falling under the general "nanotechnology" umbrella. In recent years, nanoparticles have been the center of attention of researchers in the field as the transition from zero dimensional to one-dimensional nanorods, from single material nanrods extended to make composite nanorods of two or more than two kinds of material. Researchers found that heterogeneous, composite or colloidal particles have better efficiency than their corresponding single particles, and in some cases they even develop some new properties.In this thesis, gold nanorods colloids were prepared by chemical synthesis method. We prepared gold nanorods in single-component surfactant (1-Hexadecyl)trimethylammonium bromide (CTAB) solution and use of a binary surfactant mixture containing CTAB and benzyldimethylammonium chloride hydrate (BDAC). By controlling the growth conditions, gold nanorods with different aspect ratio were prepared. We use ultraviolet-visible spectrophotometer on the optical absorption properties of surface plasmon resonance of gold nanorods. Gold nanorods show two obvious peaks at520nm and780nm, which are attributed to the gold nanorods in transverse and longitudinal surface plasmon resonance absorption. The study indicates that the transverse band is insensitive to the size of the nanorods, while the longitudinal band is red-shifted largely from the visible to near-infrared region with increasing aspect ratio. In addition, based on the size and morphology were characterized by transmission electron microscopy, the growth mechanism of gold nanorods and explore.In the preparation of gold nanorods, we employed it as seed to deposition a layer of silver on the outer surface, forming the core-shell nanorods materials. Au@Ag core-shell nanorods with different shell thickness were synthesized in aqueous solution by chemically depositing silver on gold nanorods surface. With the silver coating, obvious change were happened to the SPR spectra of the core-shell nanorods. Along with the increase of silver shell, appearance of a new peak position at around420nm, the peak had slight red shift. Simply by varying the composition of the nanorods, strongly color changed solution can be obtained, the spectra will cover a wide range.Here we prepare gold nanoros and Au@Ag nanorods for sensitive SERS substrates and study the function of local field enhancement with the SERS enhancement. First, different aspect ratio gold nanorods as SERS substrates excited at532nm and785nm. Study the same gold nanorods as substrates at an excitation wavelength of325nm,532nm and785nm. In addition, the systematic study on the Au@Ag nanorods as SERS substrates, under different excitation wavelengths. The excitation wavelength is only limited in some specific values, by changing the nanorod aspect ratio and the silver shell thickness will range of the plasmon resonance peak modulation to the Raman excitation wavelength, have strong resonance enhanced SERS signal, can further improve the strengthening effect of SERS substrate. This has great significance to research on SERS.The finite difference time domain method (FDTD) is a kind of simulation method is in common use, we use FDTD theory to extinction spectra of gold nanorods and Au@Ag nanorods is simulated. The relationship between surface plasma system analysis of gold nanorods and silver coated gold nanorods in the putamen structure resonance absorption peak position moves with the nanorod aspect ratio dependence between silver coated gold nanorods and resonance absorption peak position and the coated silver shell thickness. The theoretical results are compared with the experimental results, obtained very good consistency between the two. |
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