Fluorescence spectra of a solution containing Dy3+ ions have been measured at room temperature. The excitation spectrum features show a great peak at 350nm when the detection wavelength is fixed at 483 nm. Meanwhile another weaker peak takes place at 630nm, which is owing to two-photon absorption. Therefore, as the excitation wavelength is fixed at 320nm and 630 nm, respectively, both single-photon and two-photon absorption induced fluorescence emission peaks are observed. Furthermore, the emission excited by 630nm is more intense. When silver colloids are added to the solution containing Dy3+, the enhancements of two-photon absorption induced fluorescence are more intensive. We believe that these enhanced fluorescence are due to the local field enhancement around Dy3+ ions owing to the induced surface plasmon resonance of silver nanoparticles.

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.

Aqueous solutions containing a high yield of suspended gold nanorods with mean aspect ratio 2.5 have been synthesizeed via an electrochemical method. The fluoresconco emission peaks fixed at 37Onm and 67Onm are due to the local field enhancement via coupling to the transverse and longitudinal urface plasmon resonarce. The qUasi-static calculation results indicate that with the increasing aspect ratio of the nanorods, the longer wavelength emission peak decreases and red shifts, wheresas the shorter wavelenth emission peak blue shifts slightly.

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.