Preparation And Photoelectric Properties Of Graphene Oxide/ZnO/Ag Nanocomposites

Graphene, a new two-dimensional material composed of sp2-bonded carbon atoms with honeycomb lattice, has attracted tremendous attention because of its unique properties and potential applications since its experimental discovery in 2004. The unique structure and properties make graphene a promising building block in preparing new nanocomposites with functional materials. However, it still faces huge challenges, especially in the large-scale production, green technology and self-assembly technology. Graphene oxide (GO), as the oxidized form of graphene, is composed of a two-dimensional nanosheet with oxygen-containing functional groups, which makes the utilization of graphene oxide arguably the most easily-operated and scalable method in preparing gaphene materials-based composites.In this work, GO was prepared by a modified Hummers’method. The ZnO and Ag nanoparticles were anchored to the GO sheets through simple assembly, in-situ synthesis and step assembly, forming functional nanocomposites. The properties and application of these composites in photovoltaics were investigated and some results were made. These research results are as follows:1. Without using any surfactants or stabilizing agents, GO sheets with different sizes were prepared. ZnO quantum dots (QDs) were prepared and uniformly assembled onto the surface of the graphene oxide (GO) sheets through a simple and convenient process. The structure and optical properties of the composites were characterized by ransmission electron microscope (TEM), UV-Vis absorption spectra and photoluminescence (PL) spectra. The interaction and electron transfer that may exist between the two components were discussed. The as-fabricated devicehas large on/off currentratio and exhibits fast response and recovery speed.2. Without any capping agents or multistep process, a simple and green method for in-situ growth of Ag NPs on GO sheets via a hydrothermal reaction of a mixture of GO, AgNO3 and sodium citrate in one pot was proposed. The formation mechanism of the resulting nanocomposites was discussed. The Ag NPs were well-distributed on the surface of the GO sheets with a uniform size since the GO sheets provide nucleation sites in the growth process. The presence of Ag NPs enhanced the Raman signal of GO in the prepared nanocomposites. The resulting nanocomposites exhibited strong surface-enhanced Raman scattering (SERS) activity toward rhodamine 6G (R6G). The synergistic effects of the R6G molecules adsorbed on GO sheets and the coupled EM field caused by the Ag NPs lead to the significant SERS enhancement.3. A step assembly method of preparing GO/ZnO/Ag nanocomposites was proposed. The Ag nanopaticles were anchored to the GO sheets via a hydrothermal reaction, then ZnO QDs were mixed with the Ag-GO hybids. ZnO QDs densely distributed on the GO surface and around the Ag particles. The optical properties of the composites were characterized by UV-Vis absorption spectra and PL spectra. The PL intensity in the UV and visible range of the prepared composites significantly decreased, indicating the electron transfer from ZnO to GO and Ag under UV excitation. This result also indicates that the resulting GO/ZnO/Ag nanocomposites have potential application in photocatalytic.