Edge Doped Graphite Nanosheets And The Preparation Of Conducting Polymer Composites

Graphite is a natural resource widely existed in nature.Since the single-layer graphene was exfoliated by Geim and Novoselov from graphite,the excellent properties of graphene which resulted by the reduction of the layer number of graphite had attracted enormous attention.Graphite nanosheets(GNS)is a kind of graphene-like material,which has many excellent properties,and can be used as an ideal substrate material for metal nanoparticles and high-performance reinforced particles for polymer matrix.The current preparation methods of GNS were high-cost,time-consuming and the prepared GNS had low quality.In this paper,we prepared the GNS through a high-pressure homogenization method(HPH)which was low-cost and high-efficiency.We doped the Ag nanoparticles on GNS substrate(Ag-GNS composite)which utilized the naturally produced defects on GNS during the HPH progress.Finally,we fabricated the PVA/graphite composite,PVA/GNS composite and PVA/Ag-GNS composite through a solution blending method and studied the electrical conductivity properties of the composites.This doping method for the preparation of Ag-GNS composite provided a guide for convenient,efficient and green doping method for metal-nanoparticle-doped-GNS.The GNS and Ag-GNS composite could act as a low-cost and high electrical conductivity filler particles for preparation of the conducting polymer composite.1)The GNS was prepared through a high pressure homogenizer in water.The thickness,morphology and defects of GNS was characterized by AFM,FT-IR,Raman and XPS.The results showed that the HPH method can efficiently exfoliate the graphite in the aqueous phase,and the GNS has more defects than the graphite,but far less than graphene oxide(GO)or reduced graphene oxide(rGO).The defects on GNS provided an active site for silver nanoparticles to anchor which made the preparation of Ag-GNS composite is feasible.2)The Ag-GNS composite was fabricated through an edge doping method which took advantage of the defects on GNS produced by HPH process.The silver ions were first complexed with the defect sites of GNS,then the reducing agent was added and the Ag-GNS composite was finally formed.Because the defects of the GNS prepared by the HPH method were mostly at the edge,the doping method was called edge doping.The morphology,crystalline form and the nanoparticle size distribution of Ag nanoparticles of Ag/GNS composite and the morphology,defects and element composition of the Ag-GNS composite were characterized by XRD,FESEM,XPS,FT-IR and Raman.The results showed that the silver nanoparticles were effectively doped on the GNS and distributed mainly on the edge of the GNS.The composite has high stability and less defects.The silver nanoparticles were hexahedral,the average nanoparticle size was 52.6nm.The UV-vis spectra showed the presence of the surface plasmon resonance(SPR)of silver nanoparticle,so the Ag-GNS composite could be used as a surface enhanced Raman scattering(SERS)substrate to enhance the Raman signals of the adsorbed molecules.We used the rhodamine 6G and rhodamine B as the probe molecule to examine the SERS of the Ag-GNS composite.The results showed that the Raman signals of rhodamine 6G and rhodamine B could be enhanced and the fluorescence interference of them were eliminated,The Raman enhancement factor was 2.33×10~4.3)The different particle content of PVA/Graphite composite,PVA/GNS composite and PVA/Ag-GNS composite were fabricated through a solution blending method.The section morphology,particle distribution,crystallinity,thermal stability and electrical conductivity were characterized by FESEM,DSC,TG,DMA,insulation resistance meter and high speed programmable microohmmeter.The results showed that the particles of PVA/GNS composite and PVA/Ag-GNS composite were smaller and better dispersed than that of PVA/graphite comosite.The thermal stability of PVA/GNS composite and the PVA/Ag-GNS composite were better than that of PVA/Graphite.The addition of filler particles reduced the crystallinity of PVA slightly.The percolation thresholds of PVA/Graphite composite,PVA/GNS composite and PVA/Ag-GNS composite was 6.88,3.36 and 3.98 vol%,respectively.The electrical conductivity relationship of the three composites after the formation of conducting network was PVA/Ag-GNS composite > PVA/GNS composite > PVA/Graphite composite,which indicated that the GNS and the Ag-GNS have better conductivity and lower percolation threshold than graphite as electrical conducting filler particles of polymer matrix.Besides,the preparation methods of GNS and Ag-GNS in this paper were green and efficient which could be used as high electrical conductive filler for the conducting polymer composite.