Preparation of Pt nanoparticles templated by poly(amidoamine) dendrimers

The complexation of Pt²⁺ ions with G5.5-COOCH₃ PAMAM dendrimers was investigated by UV-VIS and FT-IR spectral methods, showing that Pt²⁺ ions are coordinated with the interior amino groups of dendrimers. It needs more time for the complexation reaction to come to balance with the increase of molar ratios of Pt²⁺ ions to dendrimers. The maximum loadings of 50~55 Pt²⁺ ions within the G5.5-COOCH₃ dendrimers were also obtained. Following reduction with NaBH4 resulted in spherical and well-dispersed Pt nanoparticles (average size<2 nm) encapsulated in the dendrimers as shown in HRTEM images. When the ratio of Pt²⁺ ions to dendrimers was 10, the yielded Pt nanoparticles with smaller sizes and a narrow distribution were intradendrimer templated. When the ratio of Pt²⁺ ions to dendrimers was 50, new partially formed Pt nanoparticles with larger sizes and a broad distribution were interdendrimer templated.