Green Synthesis, Characterizations, And Biosensor Application Of Self-Assembled Reduced Graphene Oxide/Metal Nanoparticles Hybrid Membranes

This work is divided into three parts. The first part is to report a facile one-pot green synthesis method to prepare a self-assembled membrane of reduced graphene oxide/gold nanoparticle (RGO/AuNP) nanohybrids at a liquid/air interface. The obtained sandwich-like multilayer RGO/AuNP hybrid membranes were characterized by atomic force microscope, scanning electron microscope, transmission electron microscope, UV-vis spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and Raman spectroscopy, and the obtained results prove that GO and chloroauric acid (HAuCl4) were synchronously reduced by glucose successfully. In addition, the experimental data indicate that the self-assembly and formation of RGO/AuNP hybrid membranes is mainly governed by the Brownian motion and electrostatic interaction between RGO and AuNPs, and the encapsulation of AuNPs in the hybrid membrane can be easily adjusted by changing the concentration of HAuCl4. The created functional semi-transparent RGO/AuNP hybrid membranes are very stable in various organic and inorganic solvents, and can be used to fabricate a novel nonenzymatic amperometric biosensor of hydrogen peroxide (H2O2). The fabricated H2O2 biosensor reveals wide linear range from 0.25 to 22.5 mM, low detection limitation of 6.2μM (S/N=3), high selectivity, and long-term stability. It is expected that this one-pot green method for fabricating sandwich-like multilayer hybrid functional membranes have broaden applications in biosensing, catalysis, and energy storage.The following part is to demonstrate a facile one-step synthesis strategy for the preparation of a large-scale reduced graphene oxide multi-layered film doped with gold nanoparticles (RGO/AuNP film) and applied this film as functional nanomaterials for electrochemistry and Raman detection applications. The related applications of the fabricated RGO/AuNP film in electrochemical nonenzymatic H2O2 biosensor, electrochemical oxygen reduction reaction (ORR), and surface-enhanced Raman scattering (SERS) detection were investigated. Electrochemical data indicate that the H2O2 biosensor fabricated by RGO/AuNP film shows a wide linear range, low limitation of detection, high selectivity, and long-term stability. In addition, it was proved that the created RGO/AuNP film also exhibits excellent ORR electrochemical catalysis performance. The created RGO/AuNP film, when serving as SERS biodetection platform, presents outstanding performances in detecting 4-aminothiophenol with an enhancement factor of approximately 5.6×105 as well as 2-thiouracil sensing with a low concentration to 1μM. It is expected that this facile strategy for fabricating large-scale graphene film doped with metallic nanoparticles will spark inspirations in preparing functional nanomaterials and further extend their applications in drug delivery, wastewater purification, and bioenergy.The final part is that graphene and silver nanoparticles (AgNPs) are the importance building blocks for the synthesis of functional nanomaterials for bio-related applications. Here, we report a facile strategy to decorate AgNPs onto reduced graphene oxide (RGO) by the simultaneous reduction of silver ions and graphene oxide nanosheets within one system, and further to fabricate a dimension-adjustable RGO/AgNP multi-layered membrane by a thermal-driven self-assembly process. The structures of the fabricated RGO/AgNP hybrid membranes were identified by UV-visible spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and transmission electron microscopy. The thickness of the fabricated RGO/AgNP membrane was further measured by scanning electron microscopy. The hydrophilicity of the RGO/AgNP membranes was tested by contact angle measurement. Antibacterial and cell culture experiments based on the fabricated RGO/AgNP membranes indicate that this kind of hybrid membrane exhibits excellent antibacterial activity and high biocompatibility. A potential antibacterial mechanism of the fabricated RGO/AgNP hybrid membrane was proposed.