Study On Preparation Of Graphene Oxide/Nano-Oxide Hybrid Materials And Applications Of Their Polymer Composites

Nano-materials have been widely applied in diverse fields, such as sensors, catalysis, photoelectric device, etc. due to their remarkable properties. And nano-hybrid materials composed of different nano-materials not only have excellent properties, but also can compensate disadvantages of single nanoparticle. Therefore, the presence of the nano-hybrid materials broadens the applications of nano-materials, and provides an effective way to acquire functional materials with high performance.As a derivative of graphene, graphene oxide (GO) exhibits different but also exciting physical and chemical properties compared with the graphene. This can be attributed to the presence of a large number of oxygen-containing groups on the GO platelets, including hydroxyl, carboxyl and carbonyl groups. The existence of these groups endows GO with better controllability, hydrophilicity and chemical activity. As a consequence, GO can be used as a support material and/or substrate to prepare nano-hybrid materials through hydrogen bonding or electrostatic interactions between GO and other metals or inorganic nanoparticles.In order to explore the synthesis of the GO-based hybrid materials and the effects of these materials on macroscopic properties of the composites, in this work, GO@SiO2 and GO@Cu2O hybrid materials were firstly prepared through the interaction between GO and SiO2 or Cu2O. And then, the GO@SiO2 hybrid materials were introduced into polyvinyl alcohol (PVA) and polyvinylidene fluoride (PVDF) to research the influences of the hybrid fillers on the mechanical properties of PVA and the dielectric properties of PVDF, respectively. At the same time, the effects of GO on morphologies of GO@Cu2O obtained under different experimental conditions and the resultant photocatalytic performances were comparatively investigated. The main results obtained in this work are listed as follows:(1) Considering the interaction between the oxygen-containing functional groups on GO surface and the hydroxyl groups on the SiO2 surface, the hybrid GO@SiO2 nanocomposites were successfully prepared through a simple solution blending method. The characterization of microstructures and morphologies of the GO@SiO2 nanocomposites indicated that SiO2 was located on the surface of GO or intercalated into the layers of GO. Therefore, SiO2 nanoparticles promoted the exfoliation of GO and impeded the agglomeration of GO. Either for GO or for SiO2 particles, the PVA/GO@SiO2 composites exhibit better dispersion of particles compared with the PVA/GO and PVA/SiO2 composites. Furthermore, due to the synergistic effect between GO and SiO2, the hybrid GO@SiO2 nanofillers exhibited the strengthening and toughening effects on PVA/GO@SiO2 composites simultaneously.(2) PVDF/GO@SiO2 composites were prepared through combining the solution blending and subsequent melt blending methods. The characterization of the microstructures of composites demonstrated that GO was partially reduced in the melt compounding process. And there were strong interaction between GO and PVDF, which induced the crystal transformation of PVDF matrix from a-form to β-form. As a result, the PVDF/GO composites exhibited higher dielectric constant. Interestingly, when the hybrid GO@SiO2 nanofillers were introduced into PVDF, SiO2 promoted the exfoliation and dispersion of GO due to the strong interaction between GO and SiO2 and consequently, more β-form PVDF were induced. What’s more, insulative SiO2 could also inhibit the formation of conductive path through increasing the distance between adjacent GO. So, although the dielectric constant of the PVDF/GO@SiO2 composites was smaller than that of the PVDF/GO composites, they exhibited much lower dielectric loss.(3) Negatively charged GO absorbs metal cations. So the hybrid GO@Cu2O nanocomposites were successfully prepared through the in-situ reduction method. The characterization of the morphologies and crystal structures demonstrated that the addition of GO would affect the nucleation and growth mechanisms of Cu2O. The morphology of Cu2O transformed from the polygon single crystal to spherical polycrystal with the incorporation of GO. Also, reaction time, Cu2+ concentration and the number of functional groups also influenced the amount and size of Cu2O nanoparticles. In addition, GO@Cu2O hybrid materials had better photocatalytic degradation properties for methylene blue (MB). This was attributed to the large aspect ratio and excellent carrier mobility of GO, which resulted in the easier adsorption of organic dyes on GO@Cu2O, quick transition of the electron from Cu2O to the GO surface under light through preventing the recombination of electrons and holes, and life extension of the photo-producing electronic. As a consequence, GO@Cu2O hybrid materials had better photocatalytic performance.