Synthesis And Properties Of Surface Functionalized Carbon Nanotubers And CdSe Quantum Dots/Epoxy Composites

Facile approaches of surface functionalizing carbon nanotubes (CNTs) and CdSe quantum dots (QDs) were designed respectively in order to synthesis epoxy matrix nanocomposites with improved properties. The functionalization should introduce effective modified groups, such as epoxy, carboxyl or amido on the surface of nano-material for the aim of epoxy matrix. These groups could adjust the polarity of nano-material and form covalent bond with epoxy backbone. Thereby, the homogenous dispersion of nano-material and stronger interface could be achieved. And mechanical, thermal and optical properties will be also enhanced.In the first part of manuscript, a facile approach of magnifying the functional groups on the multi-walled carbon nanotubes was developed by introducing the bridge of poly (acryloyl chloride). Special functional groups could be further generated by the reaction of acyl chloride groups. Accordingly, the CNTs with magnified epoxy groups (CNTs-epoxy) were prepared, and its reinforcement for epoxy composites was studied. The structural destruction of acid treated CNTs was testified by Raman spectra. The CNTs-epoxy was characterized by Fourier Transform Infrared (FT-IR), Differential Scanning Calorimetry (DSC), Transmission Electron Microscopy (TEM), and Thermo-Gravimetric Analysis (TGA). The properties of nanocomposites were measured by Dynamical Mechanical Analysis (DMA), tensile testing and Scanning Electron Microscopy (SEM). Because of the magnification of functional groups and the higher interfacial adhesion between CNTs-epoxy and epoxy matrix, the composites exhibited the enhancement of mechanical properties at lower content. Tensile strength and tensile modulus were increased nearly 45% and 90%, respectively.In the second part of manuscript, a facile approach to introduce carboxyl groups onto the surface of CdSe QDs was achieved via oleic acid ligands self-assembly, and then QDs/epoxy fluorescence nanocomposites were successfully fabricated. The surface constitution of QDs, the better dispersibility of QDs in epoxy matrix, and the reactivity with epoxy of carboxyl groups functionalized QDs were characterized by FT-IR, TEM, and DSC, respectively. As the result of surface modification, the carboxyl groups functionalized QDs could be stably and homogenously dispersed in chloroform and acid anhydride cured epoxy matrix. The fresh fluorescence as well as the toughening behavior of the QDs/epoxy nanocomposites was presented.In the third part of manuscript, high transparent and high luminescent QDs/epoxy nanocomposite was prepared by introducing the QDs with amido functionalized ligand into epoxy matrix. The original oleic acid ligand was replaced by thioglycolic acid, and then primary amine group was introduced via the reaction between carboxyl group of thioglycolic acid and Schiff's base. The QDs with amido functionalized ligand showed higher luminescent intensity and better dispersibility in epoxy matrix. It could be found that the transparence of the nanocomposite was equal to neat epoxy, and almost achieved double luminescent intensity than the nanocomposite filled QDs with original ligand. Moreover, the QDs/epoxy nanocomposite which could express clear white light by combining un-absorbed blue excitation light and re-emit yellow light was successfully fabricated following the same strategy. Such nanocomposites could be used as encapsulant for light emitting diode.In the fourth part of manuscript, a facile approach to fabricate the surface-modified QDs with compatibility to versatile media and better dispersibility by self-assembling the functionalizable comb polymer was proposed. The comb polymer was prepared by the reaction between the acyl chloride groups in poly (acryloyl chloride) and the hydroxyl group in 1-octadecanol. Under the action of the entanglement and the compatibility of aliphatic chain in 1-octadecanol and similar aliphatic chain in oleic acid ligand of QDs, the comb polymer could cap on the QDs and bring the functional groups onto QDs. The structure of such polymer was tested by FT-IR. According to the reactivity of remaining acyl chloride groups in the comb polymer, the polymer ligands could be tailored to be different structures, and then the lipophilic, hydrophilic, and functional QDs were prepared, respectively. The fluorescence properties of surface-modified QDs were testified by fluorescence spectrophotometer. And the morphologies and dispersity of different kinds of surface-modified QDs were characterized by TEM. Thereby, the homogeneous and stable dispersibility of QDs in different media could be realized by adjusting the structure of comb polymer.In the fifth part of manuscript, a facile approach to synthesis CNTs and QDs self-assembled nano-hybrid in aqueous phase was developed by design functional organic layer onto each surface. Both of CNTs and QDs were transferred from hydrophobic into hydrophilic respectively:Firstly, hydroxyl group was introduced onto the surface of CNTs by controlled acid treatment. And carboxyl group was magnified (CNTs-COOH) via esterify between hydroxyl group and polyacrylic acid. At the same time, the surface of oleic acid ligand stabilized QDs was modified from chemically inert into carboxyl group functionalized, which could be carried out because of exchange original ligand by thioglycolic acid. And then ethylenediamine was employed to modify functional group into amido (QDs-NH2). Thereby, the well dispersed CNTs-COOH and QDs-NH2 could be self-assembled in aqueous phase easily. Such QDs-CNTs nano-hybrid will be applied as photovoltaic solar cells material.