Study On Synthesis Of Titanium Dioxide/Reduced Graphene Oxide Nanocomposites And Their Optical Limiting Performances

In the modern informational high-tech war,as the“eyes”and“ears”and“nerve center”of the commander,the satellite plays an important role in the success or failure.As the structure design of the photoelectric detection system of the satellite is relatively fragile,the damage threshold is low,thus it is easy to be attacked.Therefore,the laser protection of the satellite,especially the laser protection of the photoelectric detection system on the satellite,is very urgent in view of the great threat of laser weapons.In the existing three types of laser protective materials,the laser protective materials based on nonlinear optical principle,whose protection effect is not limited by wavelength,is the main research direction.The laser protection materials based on the principle of nonlinear optics is also known as the optical limiting materials.The property that the transmittance of the materials changes versus the change of incident energy is called the optical limiting effect,and the optical limiting property of the materials is also known as the performance of the laser protection materials.As a semiconductor material,titanium dioxide?TiO₂?has been at the forefront of application research in the fields of optical active coating,photocatalysis and energy conversion,due to its high transmittance in the visible to infrared region,good thermal and chemical stability,excellent photoelectric performance,large refractive index and other photoelectric characteristics.Graphene materials have planar geometric structures with atomic thickness,special energy band structures and high carrier mobility,which have aroused great interest of researchers in the fields of nanocomposites,energy materials and optoelectronic devices.In graphene materials,a lot of work in recent years is based on the research of reduced graphene oxide?rGO?.Compared with graphene oxide?GO?,rGO has a higher degree of?-conjugation,better electrical conductivity and electron-hole transmission performance,and better optical limiting performances.Compared with graphene,rGO has more defects and some oxygen-containing groups,which is more conducive to the composite of materials and better solubility.In this study,rGO with excellent optical limiting performances and TiO₂ with high visible light transmittance were selected to prepare namocomposite materials and investigate their optical limiting performances.The main results of this work are as following:1.A modified Hummers method was used to prepare the precursor materials GO,and the obtained precursor materials GO and the analyzed pure tetrabutyl titanate?TBT?were used to prepare TiO₂/rGO nanocomposites by a facile one-step hydrothermal method.XRD,TEM and other characterization methods were used to characterize the microstructure of the materials.The results shows that the precursor materials GO consist a mixture of monolayer GO and multilayer?8-10 layers?GO,while the interaction between TiO₂ and rGO was chemical bond.2.Determine the optimal ratio and composition of nanocomposite materials to maximize synergies.In order to discuss the influence of different particle sizes of TiO₂ on the materials,commercial TiO₂ powder?P25?and tetrabutyl titanate?TBT?were selected as precursors of TiO₂ in the composites for materials preparation.The optical limiting performances of the nanocomposite were tested by Z-scan technique to explore the optimal amount of TiO₂ to achieve the optimal optical limiting performances.Z-scan results show that,with the same amount of TiO₂,TBT as the precursor of the nanocomposites has better optical limiting performances than P25.However,among a series of composites using TBT as precursor,the composite has the best optical limiting performances when the TBT content is 0.25g.3.The nanocomposites are modified by Au nanoparticles to obtain the ternary system Au@TiO₂/rGO.Au nanoparticles can effectively capture excited electrons and redistribute free carriers,so that electrons can be transferred from TiO₂ particles with higher Fermi level to Au with lower Fermi level until they reach the same Fermi level,thus forming the schottky barrier.Z-scan test results show that the Au@TiO2/rGO composites with 0.2mL HAuCl₄ solution?0.0014mol/L?show the best light limiting performances.Compared with the composites without Au nanoparticles,the transmittance of the composites decreased by 15%and that of GO decreased by48.2%.At present,there are only a few reports about TiO₂/rGO nanocomposites in the field of optical limiting.This research innovatively focuses on optimizing the optical limiting performances of TiO₂/rGO nanocomposites in multiple perspectives.Firstly,in view of the mechanism of optical limiting,we investigated the effect of TiO₂particle size on the optical limiting properties of TiO₂/rGO nanocomposites;based on the basic properties of composite materials,we inquired into the diversity of optical limiting performances of different composition ratios of composite materials;for the sake of synergistic effect,gold nanoparticles were added into the composite system to form a ternary composite system,and the synergistic effect between the three materials can optimize the optical limiting performances of the materials.This research investigated the properties of TiO₂/rGO nanocomposites by a variety of characterations,and improved the optical limiting performances of the composites by modifying the microstructure of the composites,and provided the reasonable explanations of optical limiting mechanism analysis based on the microstructure of materials.