Exfoliation On Two Dimentional Nanosheets And Ocomposites Synthesis

Graphene (G) and hexagonal boron nitride (h-BN) have been received enormousattention due to their outstanding physical and mechanical properties. Owing to theirsimilar structures and distinct electronic properties, h-BN as the isoelectric analog ofgraphene that is considered as good candidate for fabricating h-BN/G composites withstackings structures, which could be a complete new compound and offer newfunctionalities, such as electron field, itinerant ferromagnetism, and half metallicity.So if h-BN hybridizes with graphene, it could be used in microelectronic applications,which may be a post-silicon solution. To further develop the layered h-BN as a carrierto fabricate nanoparticles/h-BN bio-composite material. We prepared the silver nano-particles depositing on the h-BN nanosheets by using chemical reduction method.This novel composite possesses excellent antibacterial effect and durability.Here we demonstrate this concept for solids consisting of randomly stacked layers ofgraphene and hexagonal boron nitride (h-BN). Exfoliated h-BN and graphene weremixed, in various concentrations, to create artificially stacked h-BN/G solids. Thesevan der Waals stacked hybrid solid materials show interesting electrical, mechanicaland optical properties distinctly different from their starting parent layers. Theapproach could be used to create artificial materials, made from the van der Waalsstacking of robust atomic layers of different layered solids with vastly differentproperties.(1) Dispersions of exfoliated h-BN layers and graphene have been prepared by liquidphase exfoliation method. Several organic solvents were selected to exfoliate boronnitride and graphite into2-D layered h-BN and graphene nanosheets. The resultsshow that the surface tension has a significant effect on exfoliation these twomaterials. The optimal solvent for exfoliation on h-BN is isopropanol (IPA) and forgraphene is dimethyl formamide (DMF). The crystal structures of exfoliated h-BNand graphene nanosheets are improved and satisfied. In addition, single-layer, double-layer and multi-layered h-BN and graphene were obtained by controllingcentrifugation speed. The diameter of h-BN nanosheets is about500~800nm, andgraphene nanosheets is around600~900nm. It is easier to be scable and high yield by using liquid phase exfoliation comparing to other methods, such as chemical vapordeposition (CVD).(2) Layered hexagonal boron nitride and graphene dissovled in DMF, h-BN/graphenehybrid nanosheets was obtained after sonication and centrifugation. As the surfacetension and mechanical ultrasonication, the atomic van der Waals forces betweenlayered h-BN and graphene re-arranged which fabricate stacking sturctures of h-BNand graphene hybrid layer by layer. The physical, chemical and electrical propertieswere characterized. The resistivity, magnetoresistance and Hall Effect results showthat h-BN/graphene hybrid composites exhibit resistivity and Hall-effect phenomenon.(3) The band gaps investigation of h-BN/G hybrid composites was conducted usingVASP (Vienna Ab-initio Simulation Package), a software package which relaxes alattice to its minimum energy configuration by means of density functional theory(DFT). The following two and three layer systems were studied: G/h-BN, G/h-BN/G,h-BN/G/h-BN, h-BN/h-BN/G, and G/G/h-BN. Ultimately, the minimum energystacking arrangements, inter-layer separations, and intra-layer lattice parameters werefound for each system. These maximally stable configurations were then analyzed fortheir structural and electronic properties. For the two-layer system, an AB stackingarrangement with boron, nitride overtop of carbon was found to be the most stable.Similarly, three-layer systems were found to be most stable with boron overtop ofcarbon (h-BN/G/h-BN system). In addition, the results suggest that h-BN layersadjacent to graphene do not significantly increase the band gap of the overall structure;we predict that the further addition of h-BN layers to h-BN/G/h-BN or h-BN/h-BN/G system would not significantly increase the band gaps of either.(4) Layered hexagonal boron nitride nanosheets as substrate, the silver nano-particles(SNPs) was synthesized by using chemical reaction with microwave-assisted.From the TEM results show that the uniform silver nano-particles were deposited onthe surface of hexagonal boron nitride nanosheets to fabricate SNPs/h-BN composites.The size of silver nano-particles is about5~10nm, and no agglomeration phenomenon.The antimicrobial and bactericidal properties of SNPs/h-BN composite material wereinvestigated by inhibition zone. The results indicate that the SNPs/h-BN compositesexhibit strong antibacterial fuction, and the sterilization rate up to99%.In this paper, layered h-BN/G hybrid composites were fabricated by liquid phaseexfoliation method. It is expected that the novel material would replace siliconmaterials which is used in microelectronic divices; chemical reduction with microwave-assisted to synthesize nano-silver/h-Bncomposite. It is expected that thiscomposite material would be used for bio-medicine, marine engineering anti-corrosion and anti-fouling coating fields.