The Preparation And Investigation Of Graphene-based Inorganic Nanostructures Hybrid Materials

Graphene, a monolayer of two-dimensional atomic carbon sheet arranged in a hexagonal honeycomb lattice, possesses many excellent properties such as good photoelectric and mechanical properties, extremely large specific surface area, high chemical stability and regular two-dimensional structure. Due to these unique propertites, graphene can be used as an ideal substrate to load various types of inorganic compound for the fabrication of high-performance graphene-based inorganic nanostructures hybrid heterostructure, opening up an important direction in practical application for grapheme.The graphene with a variety of semiconductor nanomaterials, At present, many inorganic nanostructures such as metal（Au, Ag, Cu, Pt, Pd）, semiconductor materials（TiO2, SnO2, MnO2, ZnO, ZnS, CdS and CdSe）, topological insulators（Bi₂Se₃, Bi2Te3 and Sb2Te3） has been successful grown on the grapheme layers, obtaining grapheme-based inorganic nanostructures hybrid hterostructure, and show great application value in multiple areas. In all kinds of inorganic semiconductor materials, ZnO is direct band gap wide bandgap semiconductor, which not only has the unique catalytic, electronic, optoelectronics and photochemical properties, but also easy to grow vertically. So ZnO become the preferred material in the study of graphene based hybrid nanostructures.In addition, in order to further develop the application of graphene based materials, grapheme-topological insulator hybrid materials have attracted more and more people attention. Graphene and topological insulators are all typical Dirac materials, research have proved grapheme or topological insulators as saturable absorber have lots of advanges, such as high thermal damage threshold, great modulation depth, wide wavelength tuning range and short recovery time. But there are also a lot of problems, such as large lattice mismatch, easily oxidized, small size, layers uncontrollable, easily damaged during transfer process. Hybrid Dirac saturated absorber is made with topological insulators growing on grapheme substrates, which can overcome drawback of topological insulators or grapheme alone as saturable absorbers and further improve optical absorption properties.In this study, large-area single-layer or tilayer graphene films were fabricated on copper foils and high-quality graphene were synthesized directly on taper quartz fiber using chemical vapor deposition（CVD） method. Based on these grown graphene, graphene-based inorganic nanostructures hybrid heterostructure, composed of inorganic nanostrctures（ZnO, Bi₂Se₃） grown on directly on grapheme layers, were fabricated simply and low cost using the CVD methods. The main works was as follows:（1） Aligned grapheme-ZnO nanorods hybrid heterostructure with high optical quality is synthesized on the Si substrate with the assist of Au predeposition layer via chemical vapor deposition（CVD） method. The individual and combined effects of graphene and Au layer are analyzed in our experiment. The results show that only randomly oriented ZnO nanorods or nanowires with a broad green emission band are obtained with individual Au layer or individual graphene layer as nucleation sites. Aligned ZnO nanorods with high UV emission peaks were obtained with the assist of Au-graphene hybrid layer. The results verify that the Au-graphene hybrid layer can provide favorable nucleation sites for the fabrication of aligned ZnO nanorods. The graphene layer in the Au-graphene hybrid layer plays a crucial role for the alignment of ZnO growth and the Au layer in the Au-graphene hybrid layer can limit the graphene oxidation and catalyze synthesis of rods-like ZnO nanostructures.（2） How to limit graphene oxidized in the formation of the graphene-ZnO Hybrid nanostructures using chemical vapor deposition（CVD） method are studied here. In the CVD-ZnO nanostructure synthesis process, graphene are easily oxidized using the ZnO and graphite power mixture as source. The Zn powder was added in the ZnO and graphite power mixture and Zn predeposition layer were formed on the graphene, the results demonstrate the graphene oxidation can be limited. The growth mechanism and the change of morphology are analyzed by changing the growth time from 15 min to 45 min,the results vertify the Zn-graphene aggregates were formed through Zn atoms diffusing into graphene layer, and provide some favorable nucleation sites for ZnO.（3） High-quality grapheme-Bi₂Se₃ nanoplates hybrid materials were synthesized with the assist of Se seed layer via chemical vapor deposition（CVD） method. To illuminate the individual and combined effect of Se predeposition layer and grapheme layer, the Bi₂Se₃ nanoplates were grown on different substrates such as SiO2, Se/SiO2, graphene/SiO2 and Se/graphene/SiO2. The results certify the Se layer can provides effective nucleation layer for Bi₂Se₃ nanoplates, and can reduce the lattice mismatch of Bi₂Se₃ and substrate. The results also verify that the Se seed layer on the graphene surface can effectively saturate the surface dangling bonds of the graphene, which not only impel the uniform Bi₂Se₃ nanoplates growing along the horizontal direction but also can supply enough Se atoms to fill the Se vacancies. We also demonstrate the Se seed layer can effectively avoid the interaction of Bi₂Se₃ and the graphene. Bi₂Se₃ thin films were synthesized on different size and density Se/graphene/SiO2 substrates and experiments testify the different Se seed layer on the graphene surface can be used to control the density of the Bi₂Se₃ nanoplates. In addition, the Graphene-Bi₂Se₃ nanoplates hybrid materials were applied to solid-state laser and obtained stable Q-switched laser output.（4） Graphene film were first synthesized on the single mode fiber taper using a Cu-vapor-assisted chemical vapor deposition system, and then grapheme-Bi₂Se₃ nanoplates hybrid materials were successful synthesized on the fiber taper using chemical vapor deposition method. We compare the different morphology and structure of the Bi₂Se₃ thin film deposited on the taper of pure fiber and graphene/fiber. At the same time, in order to find the best growth conditions, the taper of pure fiber and graphene/fiber were placed different area for growth of Bi₂Se₃ thin film. The results demonstrated that the higher quality Bi₂Se₃ nanoplates were obtained when the substrate and the source distance was 5.5 cm. Bi₂Se₃ nanoplates stand on the pure fiber taper, while, with the assist of graphene, the Bi₂Se₃ nanoplates were tightly coated on the fiber taper. The Graphene-Bi₂Se₃ nanoplates hybrid materials as saturable absorber was applied to fiber laser and stable mode-locked fiber laser was generated. In addition, Graphene-Bi2Te3 nanoplates hybrid materials also were successful synthesized on the fiber taper, and the higher quality Bi2Te3 nanoplates were obtained when the substrate and the source distance is 13 cm.