Size-controlled in situ synthesis of metal nanoparticles on dendrimer-modified carbon nanotubes

Multiwalled carbon nanotubes (MWCNTs) were covalently modified with fourth-generation NH2-terminated poly(amido amine) (G4-PAMAM) dendrimers, named CNT/DEN. The covalent linkages between CNT and dendrimers were identified by an infrared absorption spectrometry, and the weight content of G4-PAMAM dendrimers in CNT/DEN was determined to be about 40 wt % by a thermal gravimetric analysis. By simply tuning the metal ion-to-dendrimer terminal amine ratio, Au nanoparticles (NPs) with different sizes from 3 to 11 nm were in situ synthesized and deposited on the surface of CNT/DEN, as confirmed by a transmission electron microscopy (TEM) and an ultra violet-visible (UV-vis) absorption spectrometry. Furthermore, many metal NPs other than Au NPs, such as Ag, Cu, and Pt NPs, as well as binary NPs of Ag@Au, were synthesized in situ on CNT/DEN, which were identified with TEM and UV-vis spectrometry, as well as an energy-dispersion X-ray spectroscopy, yielding the water-dispersible and stable CNT/DEN/NPs.