Advantages of immobilization of Pt nanoparticles protected by dendrimers on multiwalled carbon nanotubes

Pt nanoparticles (PtNPs) were synthesized in the presence of a NH2-terminated fourth generation poly(amido amine) (PAMAM) dendrimer as a stabilizer at different molar ratios (M : D) of metal precursor to amine terminal group of dendrimer. Subsequently, PtNPs protected by dendrimers (DENPtNPs) were covalently immobilized on multiwalled carbon nanotubes (MWCNTs) by using a condensing agent for amide bond formation between acid-treated MWCNTs and DENPtNPs and the product CNT/DENPtNPs were characterized. PtNPs on MWCNTs increased quantitatively in content with M: D and dispersed with same aspect as the dispersion of DENPtNPs in water: PtNPs homogeneously dispersed at low M : D ratio and slightly aggregated at high ratio. The decomposition of CNT/DENPtNPs occurred at the lower temperature owing to the catalytic effect of PtNPs. A near-infrared absorption band around 2083 nm, which is extremely weak for MWCNTs, was intensified and D, D' and G Raman bands were slightly downshifted when DENPtNPs were attached. These phenomena can be attributed to the electron transfer from DENPtNPs to MWCNTs. Remarkable advantage is apparent from the enhanced electrochemical behavior of CNT/DENPtNPs loaded on gold electrode. PtNPs promoted the electron transfer of MWCNTs and dendrimers contributed to uptake of redox materials.