Studies On Fabrication And Functionalization Of In-plane Uniaxial Thin Films Composed Of One-Dimensional Nanomaterials

Controllable assembly of one-dimensional(1D)nanomaterials is of great importance in basic scientific research and practical applications.The 1D functional nanomaterials,especially single crystalline ones,exhibit excellent properties such as mechanical,electrical,and magnetic ones along their long axes.Their oriented assemblies taking advantage of each 1D nanocrystal can therefore exhibit specific collective properties[1-3].Numerous assembly methods have been explored to achieve uniform architectures composed of ordered nanocrystalline constituents across the macroscopic scale with adjustable particle density.Existing assembly methods rely on the presence of electric fIeld[4],magnetic fteld[5,6],Langmuir-Blodgett films[7-9],shear force[10-12]However,all methods meet the difficulty in achieving continuous uniaxial thin coatings composed of 1D nanocrystals uniform across the macroscopic distance.Consequently,devices integrated with these thin coatings exhibit unsatisfactory performance due to the presence of structural defects.More importantly,the success of these assembly methods depends on expensive tools,and often proceeds in strict conditions,which deteriorates their applicational opportunities.Therefore,it is of great theoretical and practical significance to explore a controllable method to assembly lD nanomaterials[13].In this thesis,a dip-coating method is established for continuous fabrication of 1D nanomaterials.The research system is divided into four parts:first,we fabricated a uniaxial thin film comprising cellulose nanocrystals(CNCs).After that,by taking of advantage of the synergistic assembly effect of CNCs and hydrated vanadium pentaoxide nanowires(V2O5 · nH2O NWs)under shear force,we realized the large-scale uniaxial assembly of nanowires with high aspect ratios,and the corresponding assembly mechanism was put forward.Afterward,we used an intercalation polymerization method to prepare polyaniline(PANI)-CNC hybrid film with a high degree of in-plane orientation.This hybrid film with structural anisotropic information can be employed further as a gas sensor to distinguish various gases effectively.In particular,methanol and ethanol,two normally indistinguishable gases in gas sensors,can be identified feasibly.Finally,on the basis of the unitary and binary assembly systems,we have further developed the ternary system to effectively assemble single-walled carbon nanotubes(SWNTs),which is notorious for its poor assembly behavior.In this paper,the in-plane uniaxial assembly method is proposed,and this method can assemble 1D nanomaterials on hydrophobic/hydrophilic planar and fibrous substrates.With this approach,we expect that assemblies comprising uniaxial 1D nanomaterials can be fabricated,which exhibit remarkable anisotropic properties.