Research On The Optical And Photoacoustic Properties Of Gold Nanoparticle Materials

In recent years,gold nanoparticles have attracted attent ion owing to its stable chemical properties and enable optical thermal manipulations.While the gold nanosystem already exhibit remarkable complexity and versatility,it is still an emerging,but rapidly evolving field,increasing energy conversion efficie ncy in optoelectronic,improving accuracy of photoacoustic imaging,reliability of medical therapy,and readiness for technological applications.In this thesis the fixation and optical properties of gold nanoparticles on glass substrate are described,in details there are preparation process of polydimethyl siloxane(PDMS)composites and fabrication of optical fiber ultrasonic generators based on PDMS,characterization of their optical and photoacoustic properties.First,gold nanoparticles colloid is prepared by sodium citrate reduction method.They are deposited and fixed on the surface of quartz glass by using concentrated gold nanoparticles colloid and polyethylene imine(PEI)solution.After several times deposition,an accumulation behavior of single nanoparticle takes place,and this phenomenon is enhanced with increasing of deposition times.The extinction spectrum shows two peaks due to coexist of two forms of gold nanoparticles.The peak shapes are influenced by the structure of nanoparticles.Wit h a size increasing,the intensity of peak at higher energy decreases,while the peaks at low energy broaden and shows a red shift.The dielectric constant of surrounding medium also influences the energy of absorption peaks.Second,gold nanoparticles are prepared in PDMS matrix by reduction method.The composites with different concentrations and thickness are rotated on quartz sheets.Ruby red and extinction spectra confirm the presence of gold nanoparticles,and particle diameter is about 20 nm.The results show that the light absorption capacity increases with the increasing of the concentration and thickness of the polymer film.Finally,the fiber optic ultrasound generator are fabricated by coating the gold nanocomposite on the tip of an optical fiber.An ultrasonic pulse generation experiment explores the relationship between the photoacoustic generation and the thickness of the film as well as the concentration.The change of photoacoustic signal is discussed when the hydrophone is moved further awa y from the fiber tip.The increment of the concentration enhances the photoacoustic generation efficiency with the same thickness.With a same particle concentration,a higher conversion efficiency of photoacoustic signal is observed with a thicker gold na nocomposite.When the conversion efficiency reaches to maximum,an optimal thickness of nanoparticles layer is defined.The above experimental results provide a good experimental reference for exploring the application of gold nanoparticles composites in optical sensing and photoacoustic conversion.