Study On The Preparation Of Metal Nanoparticles And Optical Enhancement Effects

In recent years, nanoparticles in many fields such as electronics, optoelectronics, biomedical, catalytic chemistry, materials synthesis has shown considerable applications. Much emphasis has been put on azo materials for many advantages in large nonlinear optical coefficient, wide response wave band, high damage threshold, low cost, and easy modification, because of which they have prospective applications in all-optical switching and optical storage. In this thesis, we systematically investigate the nonlinear optical, photoinduced anisotropy and photoluminescence enhancement effects of azo composite system in the presence of nanoparticles.Firstly, the detailed preparation process of the sodium citrate reduction of chloroauric acid, laser ablation and electrochemical reduction based on micro-plasma have been studied. In the process of preparation, the shape, size and distribution of the nanoparticles were characterized by UV-visible absorption spectroscopy and transmission electron microscopy.Secondly, we investigated enhancement effects of two-photon absorption, photoinduced birefringence and photoluminescence. Experimental results show that enhancement factors of photoinduced birefringence and two-photon absorption coefficient can be up to 2.6 and 42 times, respectively. Surface enhanced fluorescence spectrum of methyl orange doped Au nanoparticles was observed, which further confirms that the enhancement of nonlinear refraction and two-photon absorption is induced by surface plasmon resonant enhancement. Finally,we have experimentally studied the luminescence properties of pure colloidal gold solution. The results demonstrate that colloidal Au solution have a good photoluminescence(PL) characteristics, the mechanism of luminescence is attributed to the combination of sp electrons and d band hole with the external excitation light.