The Study Of Preparation Carbon Nanotubes-and Graphene-Based Nanohybrids Via A SC CO2-Assisted Process

As typical one-dimensional and two-dimensional carbon nanomaterials, carbon nanotubes (CNTs) and graphene, have attracted considerable interest due to their specific structure, and extraordinary mechanical, electrical, thermal and optic properties. CNTs and graphene based nanohybrids especially polymer nanohybrids not only endow good functionalization and dispersion of CNTs and graphene, but broaden their application in nanocomposite, sensor, electronic device and biomedical fields. Therefore, this work is aim at exploring a facile and efficient method to fabricate functional CNTs and graphene based nanohybrids, and studying the effect of experimental conditions on the functionalization degree of CNTs and graphene. Meanwhile the varing morphologies of the nanohybrids will also be discussed. This work will open up new opportunities for nanoscience and nano techno logy and accelerate their applicationThe main work in this paper contains:(1) Fabrication of polyethylene (PE) and poly(ethylene oxide)(PEO)/CNTs nanohybrids via supercritical CO2, and comparison study of varing morphologies of PE and PEO on CNTs.CNTs were decorated by PE lamellar crystals, forming "nanohybrid shish-kebab" structure, whereas PEO only wrapped on CNTs and formed thin amorphous polymer coating on the surface of CNTs. The results showed that the varing morphologies of PE/CNTs and PEO/CNTs nanohybrids depend on the molecular conformantin and the interaction between polymer chains and CNTs. CNTs provided heterogeneous nucleation sites for PE and the fromed shish-kebab structure hindered PE chains diffusion and crystal growth, whereas CNTs played antinucleation effect on PEO chains. This work provided theoretical understanding of fabricating multifunctional CNTs based nanohybrids. (2) Fabrication of pyrene-PEG/CNTs nanohybrids based on supercritical CO2and study of their stability in different solvents.The results showed that pyrene-PEG can form strong noncovalent π-π interaction with CNTs, and PEG chains endow good dispersion of CNTs in aqueous solution. There exists fluorescence quenching of pyrene-PEG/CNTs solution as a result of strong photoinduced electron/energy transfer between pyrene-and CNTs. In addition, pyrene-PEG/CNTs nanohybrids showed good stability in0.1M HCl and strong ionic solution, which paved way for CNTs in the field of biological application.(3) Fabrication of PE-b-PEO/graphite oxide (GO) nanohybrids via supercritical CO2and its further functionalizationIn this section, we succefully fabricated amphiphilic double-crystalline block copolymer PE-b-PEO/GO nanohybrids via supercritical CO2-The results showed that the solvent system and supercritical CO2play remarkable influence on the crystallization,aggregation and assembly of PE-b-PEO chains on the surface of GO. Furthermore, the PE-b-PEO/GO nanohybrid was used as template to immobilize Au nanoparticles (Au NPs) and CdTe nanoparticles (CdTe NPs), which succefully produced multifunctional GO based nanohybrids.(4) Direct exfoliation of graphite to graphene based on supercritical CO2and pyrene-polymerIn this section, we used pyrene-polymers and supercrital CO2, that the large-scale direct exfoliation of graphite into defect-free graphene sheets has been achieved, leading to stable graphene dispersions in solutions. This novel exfoliation process involves with multiple interactions among graphite, solvent, pyrene-derivatives and SC CO2, where SC CO2acts as penetrant, expanding agent and antisolvent, and pyrene-derivatives act as molecular wedges and modifier to obtain high-yield and stable graphene solutions. The method of combining high-throughput production and functionalization of graphene in one step, which might pave the way for developing multifunctional high-performance applications of graphene and graphene-based materials in various fields.