Suspended gold nanorods with mean aspect ratio 2.5 have been synthesized via electrochemical method. Resonance scattering properties have been studied. Two scattering peaks fixed at 400 and 640nm are due to the scattering of the gold nanorods via coupling to the transverse and longitudinal surface plasmon resonance. The quasi-static calculation results indicate that with the increasing aspect ratio of the nanorods, the longer wavelength scattering peak red shifts linearly and the shorter wavelength peak blue shifts non-linearly. When aspect ratio a/b=1.0, ellipse degenerate to sphere and the two peaks unite into one peak at 450nm.

Suspended gold nanospheres have been synthesized via electrochemical method. UV-vis spectra and fluorescence emission spectra have been studied at room temperature. Numerical calculations based on quasi-static, scattering and local field theories were developed to describe these optical properties. With the increasing dielectric constant of surrounding medium from 1.0 to 2.0, both local field enhancement factor and absorption wavelength maximum red shift in a linear way. However, the wavelength maximum of scattering cross-section depends on the surrounding medium dielectric constant in a nonlinear fashion.

Silver colloidal nanospheres have been synthesized via electrochemical method. The absorption spectrum features show two peaks at 410 and 470nm, which result from transverse and longitudinal surface plasmon resonance, respectively. Two kinds of fluorescence emission peaks are observed. The shorter wavelength peaks fixed at about 315nm are due to the local field enhancement and the longer wavelength peaks red shift with the increasing excitation wavelength, which results from the electron interband transitions.

Nanoparticles containing gold cores and silver shells have been synthesized via electrochemical method. The resonance light scattering spectrum has been studied at room temperature. Scattering features show two peaks at 370 nm and 570 nm, which result from the scattering of solid silver nanoparticles and silver coated gold nanoparticles, respectively. The calculation results based on quasi-static theory indicate that with the increasing ratio of the core radius to the total radius of the compound nanoparticles, the peak of scattering cross section decreases first then increases and reaches the minimum when the ratio is about 0.5. And meanwhile the scattering peak red shifts nonlinearly. Furthermore, with the increasing dielectric constant of surrounding medium, the scattering peak increases monotonic and red shifts.

Aqueous solutions containing a high yield of suspended pure silver, pure gold and silver-coated gold nanoshells have been synthesized via an electrochemical method. UV-vis absorption spectra and fluorescence emission spectra have been measured at room temperature. The absorption spectra show two peaks at 445 and 485 nm, which due to the plasmon resonance of silver-coated gold nanoparticles. Fluorescence emission peaks have been observed in the wavelength region of 550-700nm. The emission peak corresponding to solid silver particles is more intensive than the peaks corresponding to silver-coated gold nanoshells and solid gold particles. The relationship between relative thickness of silver shell and fluorescence intensity has been illuminated from the quasi-static and local field theory. With decreasing the thickness of silver shell, the maximum of local field enhancement factor decrease and red shifts nonlinearly.