Preparation And Application Of Gold Nanoparticles And Silica Core-shell Structure

Metal nanoparticles with core-shell structures attracted more and more researchers' interest because of their versatility,stability and modulated physicochemical properties.Metal nanoparticles exist strong surface plasmon resonance and thus can produce a strong surface plasmon absorption in a certain range of light wavelength via an interaction between metal nanoparticle and light wave.The plasmon absorption and scattering effects of metal nanoparticles based on the surface plasmon resonance can bring many special properties,such as the strong local electromagnetic fields generated plasmon enhanced Ramon spectroscopy and enhanced fluorescence spectroscopy,as well as plasmonic nonlinear absorption and scattering induced optical limiting.In this thesis,the core-shell nanostructures of gold nanoparticles and silica with different morphologies were prepared.Then,the composite materials of gold nanoparticle-doped silicone rubber were obtained as optical limiting materials which showed typical optical limiting property under several light wavelength.Finally,plasmon resonance enhancement of carbon qutanum dots by this core-shell structure surface.The main research work and conclusions include:1.Firstly,gold nanospheres and gold nanorods were prepared by seed-mediated method.The effects of the concentration of silver nitrate,ascorbic acid,CTAB,and the amount of seeds on the morphology of gold nanospheres and gold nanorods were investigated.The results show that highly dispersed gold nanospheres of uniform size and gold nanorods with uniform aspect ratios between 1 and 4 can be prepared by optimizing the concentration of CTAB and the amount of seeds,silver nitrate,and ascorbic acid.Then,various gold nanoparticles coated with a series of silica shells were prepared by hydrolysis of ethyl orthosilicate under alkaline conditions,and the obtained silica coated gold nanoparticles showed an improved stability.The effect of reaction factors on the thickness of the silica shell were explored,such as the amount of ethyl orthosilicate,reaction time and so on.Finally,the thickness of the silica shell can be controlled by controlling the rate of hydrolysis of ethyl orthosilicate,the amount of ethyl orthosilicate,and the reaction time.2.The morphology of gold nanoparticles doped in silicone rubber can modulate the plasmon resonance peak position of the composite materials.The nanocomposites with a certain absorbance in the visible range of 350-850 nm were obtained by mixing gold nanospheres and gold nanorods with different shapes,and the obtained composite rubber material showed several surface plasmon resonance pekas.The results show that gold-silicone rubber composite material with broad wavelength absorption properties has optical limiting effect at several laser wavelengths.When the transmittance of the composite silicone rubber sheet is lower,the optical limiting effect is better,and the sooner the optical limiting effect occurs.The closer the laser wavelength is to the plasmon formant position,the earlier the optical limiting effect occurs.3.The surface of silica shell of the core-shell structures were endow with contary charge to the surface charge of carbon quantum dots,then the electrostatic adsorption was used to fix carbon quantum dots onto the surface of silica shell.The thickness of silica shells and the length of gold nanorods were studied.The effect of factors such as rod length on plasmon resonance-enhanced fluorescence.It is found that the fluorescence of carbon quantum dots is enhanced in the range of 7 to 24 nm of silicon dioxide thickness,and the largest fluorescence enhancement factor corresponds the silica thickness of 20 nm.Meanwhile,the aspect ratio of gold nanorods has little influence on the fluorescence enhancement of carbon quantum,and the short gold nanorod shows a better result.