Enhanced stabilization and deposition of Pt nanocrystals on carbon by dumbbell-like polyethyleniminated poly(oxypropylene)diamine.

Pseudo-dendritic polyethyleniminated poly(oxypropylene)diamine (D400(EI)(20)) was used as a stabilizer and promoter to prepare Pt nanoparticles in aqueous solution, which was then deposited on carbon surface followed by calcination. After being deposited on carbon surface, no Pt(0) could be detected in the solution phase. In all steps, the increasing molar ratio of the amino groups of D400(EI)(20) to H(2)PtCl(6) ([N]/[Pt]) drastically reduced the size and the polydispersity and kept a constant low value after [N]/[Pt] = 20.

Stabilizing effect of pseudo-dendritic polyethylenimine on platinum nanoparticles supported on carbon.

A new type of surfactant with a hydrophile of dendritic polyethylenimine (C(12)(EI)(7)) was synthesized by a cationic polymerization of dodecylamine with aziridine and was used as a stabilizer to prepare Pt colloid, which is then used in situ to prepare carbon-supported Pt nanoparticles. The effects of supporting carbon, surfactant concentration, and calcination time on the nanoparticle size and catalytic performance were determined from the transmission electron microscopic analyses and cyclic voltammograms. In the presence of carbon, the Pt particle size increased slightly with lower C(12)(EI)(7) content, while those with higher C(12)(EI)(7) concentrations remained unchanged.

Self-assembly of gold nanoparticles induced by poly(oxypropylene)diamines.

A series of poly(oxypropylene)diamines D230, D400, D2000, and D4000, having molecular weights of hydrophobic segments of 230, 400, 2000, and 4000, were used as ligands to synthesize self-organized gold nanocrystals. Ligand exchange significantly reduced the average particle size and the polydispersity of nanocrystals, and this effect was more remarkable as the molar ratio of amine groups to Au3+ ions ([N]/[Au3+] ratio) was increased. Under the same [N]/[Au3+] ratio of 100, D2000 generated an ordered 2D-monolayer; however, D230 and D400 colloids formed mainly a densely packed 3D structure with minor 2-D layers, and D4000 presented disordered 3D and 2D structures.