Catalytic Behavior of Different Sizes of Dendrimer-Encapsulated Au(n) Nanoparticles in the Oxidative Degradation of Morin with H2O2.

Different sizes of icosahedral-like dendrimer-encapsulated Au nanoparticles (Au55- and Au147-DENs) were prepared in the presence of generation 6 amine-terminated dendrimers (G6-PAMAM-NH2) as a template. The synthesis is carried out by the complexation of a Au metal precursor (AuHCI4) with the tertiary amine groups within the dendrimer framework. The addition of excess reducing agent, NaBH4, results in the formation of Au nanoparticles encapsulated within the dendrimer cavities. The as-prepared catalysts were characterized using UV-visible (UV-vis) spectroscopy, high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray analysis (EDX), and Fourier transform infrared (FTIR). The average sizes of Au55- and Au147-DENs were determined to be 1.7 ± 0.4 and 2.0 ± 0.3 nm, respectively. The catalytic activity of these Au-DEN catalysts was evaluated in the oxidative decomposition of morin by H2O2. Since morin has a maximum absorption band at λ 410 nm at pH 10, this catalyzed oxidation process was monitored by time-resolved UV-vis spectroscopy. The catalytic activities of these two catalysts were compared by fitting the kinetic data to the Langmuir-Hinshelwood model. This model allows the determination of adsorption constants of both morin (K(morin)) and H2O2 (K(H2O2)) on the catalyst surface. A full kinetic study for this Au-DEN-catalyzed oxidative degradation of morin is reported.

Synthesis and characterization of Cu, Ag and Au dendrimer-encapsulated nanoparticles and their application in the reduction of 4-nitrophenol to 4-aminophenol.

Here, we report on the synthesis, characterization and catalytic evaluation of Cu, Ag and Au dendrimer encapsulated nanoparticles (DENs). Generations 4-6 of PAMAM-OH and PAMAM-NH(2) were used as templating agents for the synthesis of Cu and Ag-DENs respectively. Generation 4 PAMAM-NH(2) dendrimers were used for the synthesis of Au-DENs. These prepared DENs were characterized using UV visible (UV-vis) spectroscopy as well as a high resolution transmission electron microscopy (HRTEM). The catalytic activity of these DENs was evaluated on the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AMP) by sodium borohydride (NaBH(4)). The reaction was monitored by UV-vis spectroscopy at λ 400 nm. These prepared DENs were found to exhibit good activity for this reduction reaction.