Research On Synthesis Of Nanogold/Organosilicon Composite Materials And Optical Limiting Application

With the rapid development of laser technology,lasers have been widely used in various fields,and at the same time,the threat of laser to human eyes and optical instruments is also growing.Therefore,nanomaterials represented by gold nanoparticles have attracted extensive attention due to their excellent optical limiting performance.As the gold nanoparticles are easy to agglomerate in the colloid and can not be processed and formed,it is not suitable for practical applications.Thus,researching on gold nanoparticle-polymer composite materials is good for the application.Silicone materials are very suitable as a matrix for optical materials because of its excellent resistance to high and low temperature,weather resistance,and high transmittance.Therefore,the purpose of this paper is to develop new methods for the preparation of gold nanoparticle-silicone composites and to study the application of nonlinear optics,and to explore the feasibility of the preparation of gold nanoparticle colloids with new organosilicon reducing agents and organosilicon protective agents.At the same time,gold nanoparticles-silicone composites were prepared by direct dispersion method and in-situ generation method,and their nonlinear optical limiting properties were studied.The gold nanoparticle-silicone composite material prepared by the two composite methods realizes uniform distribution of the gold nanoparticles in the organosilicon matrix without additional synthesizing of the protective agent.These methods also simplify the preparation steps while saving energy and protecting the environment,which have a wide application prospect in the field of nonlinear optical limiting.The main research content is as follows:(1)Preparation of Gold Nanoparticle Colloids and Their Nonlinear Optical Properties:A series of gold nanoparticle colloids were prepared by wet chemical method using sodium borohydride,triphenylsilane,poly(methylhydrogensiloxane)as reducing agent,polyvinylpyrrolidone,aminopropyltriethoxysilane,and self-produced carboxyl silane as protective agent.The morphology of colloidal gold nanoparticles was characterized by infrared spectroscopy,ultraviolet-visible absorption spectroscopy and transmission electron microscopy.The results show that both triphenylsilane and poly(methylhydrogensiloxane)containing Si-H bonds can reduce chloroauric acid to form gold nanoparticles,which can be used as a reducing agent instead of traditional sodium borohydride.As for the protective agent,the self-produced carbamido silane has a good protective effect on the gold nanoparticles,which limits the particle size of the gold nanoparticles on the nanoscale;while the gold nanoparticles prepared using the aminopropyltriethoxysilane as a protective agent show a non-uniform particle size and the particle size is too large.Gold nanoparticles prepared with triphenylsilane as a reducing agent and carboxyl silane as a protective agent were used as seed,and gold nanoparticles colloids with different particle sizes were prepared by a seed growth method.The results show that the surface plasmon resonance absorption peak are red-shifted with the increase of the particle sizes.However,the nonlinear absorption of the sample under the irradiation of 532 nm nanosecond laser is first enhanced and then decreased with the red shift of the surface plasmon resonance absorption peak.The red shift increases first and then weakens.This provides an important reference for the preparation of gold nanoparticles with strong nonlinear absorption properties.(2)Preparation of gold nanoparticle-aminosilane gel glass composite by direct dispersion method and its optical limiting performance:Poly(methylhydrogensiloxane)was used as the reducing agent and polyvinylpyrrolidone as the protective agent to prepare colloidal gold nanoparticles with the average particle size of 4.04 nm.Then it is directly dispersed into the aminopropylsilane prepolymer,and the uniform distribution of the gold nanoparticles in the matrix is achieved by utilizing the interaction between the amino group and the gold nanoparticle surface.After further hydrolysis and condensation,gold nanoparticle-aminosilane gel glass composites were obtained.The experimental results show that the gold nanoparticles are uniformly distributed in the matrix,no obvious agglomeration is observed,and a good transmittance is maintained.The sample has a nonlinear optical response to 532 nm nanosecond laser.Its third-order nonlinear absorption coefficient increases gradually with increasing doping concentration.Aminopropyl silane prepolymer is not only a surface modifier of gold nanoparticles,but also a precursor of the matrix.This method eliminates the need for additional synthesis of gold nanoparticle surface modifier,greatly reduced the preparation process and preparation difficulties,which is efficiently energy-saving.(3)Preparation of Gold nanoparticle-carbamido silane gel glass composites by in-situ generation method and their optical limiting properties:triphenylsilane was used as a reducing agent to generate gold nanoparticles in situ in the matrix of carboxysilane prepolymers.The gold nanoparticle-carbamido silane gel glass composites were obtained by further condensation and the structure and properties of the samples were studied using infrared spectroscopy,ultraviolet-visible absorption spectroscopy,transmission electron microscopy,X-ray photoelectron spectroscopy,and Z-scanning techniques.The experimental results show that the gold nanoparticles uniformly grow in the carboxyl silane prepolymer without agglomeration.The dehydration-condensed bulk material maintains good transparency and has a nonlinear optical response to 532 nm and 1064 nm nanosecond lasers.As the doping concentration of gold nanoparticles increases,its nonlinear absorption coefficient gradually increases.