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

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 H-1 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.