Multiamino-functionalized carbon nanotubes and their applications in loading quantum dots and magnetic nanoparticles

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Abstract
Two strategies were employed to synthesize amino-functionalized multiwalled carbon nanotubes (MWNTs). In the first strategy, we grew poly(2-dimethylaminoethyl methacrylate) (PDMAEMA) from the surfaces of MWNTs by in situ atom transfer radical polymerization (ATRP), then allowed the polymer chains to react with methyl iodide to acquire cationic polyamine coated-carbon nanotubes (MWNT-PAmMeI). Three samples with different amounts of grafted polyamine were obtained. TGA measurements showed that the content of PDMAEMA was ca. 25, 60 and 80% by mass. The chemical structure, morphology and nanostructures of the polyamine-grafted MWNTs were confirmed by 1H NMR spectroscopy, SEM and TEM. In the second strategy, we prepared amino-functionalized MWNTs (MWNT-NH2) by reacting acyl chloride-containing MWNTs with para-phenylenediamine in the presence of pyridine. The resulting polyamine- and amino-functionalized MWNTs were then used as templates to load CdTe quantum dots (QDs) and Fe3O4 magnetic nanoparticles by the electrostatic self-assembly approach, affording MWNT/CdTe and MWNT/Fe3O4 nanohybrids. TEM, EDS and XRD showed the structure and components of the obtained nanohybrids. Luminescence measurements indicated that the MWNT/CdTe complexes based on MWNT-PAmMeI could retain the luminescent properties of the QDs, which showed an emission peak at a wavelength of 550 nm, while the photoluminescence (PL) of the MWNT-NH2/CdTe composites can be hardly detected.