Controlled Synthesis And Properties Investigations Of Carbon-Based Mesoporous Functional Nanomaterials

Carbon nanotubes(CNTs)and graphene(G)are one-dimensional and two-dimensional carbon nanomaterials which are composed of sp2 hybridized carbon atoms arranged with honeycomb crystal lattice.Owing to their prominent properties such as high carrier mobility,superior mechanical strength and fast thermal transport,CNTs and G have found their wide applications in touch screen,energy storage and conversion,catalysis,sensor,transparent conductive film,adsorption,separation and flexible bioelectronics.By controlling the synthesis condition,CNTs and G can be assembled into various macro-nanostructures like one-dimensional fibers,two-dimensional films and three-dimensional(3D)foams.CNT sponge and G foam are 3D conductive networks which are assembled by individual CNTs and G sheets.With high mechanical performance and structural stability,CNT sponges and G foams have attracted considerable attention in the areas of oil absorption,separation,and electrocatalysis.However,the limited porosity impedes the molecular transport,and the low surface area significantly reduces the contact sites between the solute molecules and material surface,thus hindering the realization of high performance adsorbents and electrocatalyst.Single-layer G films have the advantages of excellent electrical performance,ultrathin,transparent and ease to large-scale fabrication,and they have shown promising applications in the field of flexible electronics,transparent conductive electrode,separation,sensor,corrosion resistant coating,supercapacitor and battery.Among which,the characteristics of fast electrons transport,flexible and ease to surface modification made G very suitable for constructing flexible biosensor for early diagnosis.However,the intrinsic zero bandgap nature has limited the on/off ratio of field-effect transistors(FETs)and the sensitivity of biosensors based on G.Mesoporous materials are a type of porous materials with pore size in the range of 2?50 nm.Mesoporous materials have been applied in adsorption,separation,catalysis,battery,and biosensor due to the high surface area,large pore volume,chemical and thermal stability,as well as biocompatibility.Also,the flexibility in tuning the structure,components and properties in a large-scale range make mesoporous materials to be able to fulfill the realistic demands for multifunctional materials.In this dissertation,by combining the CNT and G macroscopic structure with the high surface area and structure tunable mesoporous materials,we constructed a series of mesoporous materials functionalized CNT and G hybrid nanostructures.In addition,the applications of these carbon-based mesoporous functional nanomaterials in the areas of adsorption,catalysis and biosensor were comprehensively investigated.The specific contents of this dissertation are described as follows:(1)A 3D hierarchical porous CNT/mesoporous SiO2(CNT/meso-SiO2)hybrid structure was constructed by directly casting a uniform meso-SiO2 layer onto the surface of CNTs.In this CNT/meso-SiO2 structure,the hierarchical porous structure can accelerate molecular transport,and the high surface area facilitates the efficient adsorption.A "pump”was designed based on this compressible CNT/meso-SiO2 sponge and demonstrated highly efficient dye removal from water.In addition,after converting meso-SiO2 layer into meso-Si covered by carbon,a freestanding and highly porous CNT/meso-Si composite sponge consisting of three-dimensionally interconnected sandwiched carbon-Si-CNT skeletons was obtained.The embedding of CNT sponge into meso-Si enhances the mechanical stability of meso-Si and avoids the structural collapse.(2)A hierarchical porous flexible G/meso-LaSrMnO hybrid architecture was obtained by coating thin mesoporous yet crystalline LaSrMnO layers throughout a 3D graphene foam to form graphene/meso-LaSrMnO sandwich-like nanosheets.The formation mechanism of uniform meso-LaSrMnO type oxides was investigated.In this well designed system,the macropore between nanosheets facilitates ions diffusion,and the mesopore provides large surface area for electrolyte and material contact.Meanwhile,the graphene serves as conductive network for electrons transport.In this regard,a highly efficient electrocatalyst was obtained based on this hierarchical porous G/meso-LaSrMnO hybrid foam.(3)By exploring a directly grown meso-SiO2 template,an ultrafine graphene nanomeshs(GNMs)with considerably narrower neck width(<3 nm)and strong quantum confinement to enable flexible FETs with greatly improved on/off ratio was fabricated.After functionalization of specific receptors,the GNM FETs can be readily used to construct highly sensitive biosensors for selective detection of cancer biomarkers.Additionally,an ultrathin and high mechanical strength single-walled CNT/GNM(SWNT/GNM)hybrid film was designed based on porous SWNT network and GNM.