Dendrimer-Encapsulated Metal Nanoparticles:  Synthesis, Characterization, and Applications to Catalysis

Abstract

This Account reports the synthesis and characterization of dendrimer-encapsulated metal nanoparticles and their applications to catalysis. These materials are prepared by sequestering metal ions within dendrimers followed by chemical reduction to yield the corresponding zerovalent metal nanoparticle. The size of such particles depends on the number of metal ions initially loaded into the dendrimer. Intradendrimer hydrogenation and carbon-carbon coupling reactions in water, organic solvents, biphasic fluorous/ organic solvents, and supercritical CO 2 are also described.

Alkanethiolate-Protected Copper Nanoparticles: Spectroscopy, Electrochemistry, and Solid-State Morphological Evolution

“…12 Proton NMR spectroscopy (Varian 300) was used to examine the purity of the nanoparticles where a concentrated solution of particles was prepared in benzene-d 6 . The resulting spectrum showed only a pair of broad peaks at 0.95 and 1.4 ppm corresponding to the methyl and methylene protons, similar to those observed with other alkanethiolate-protected (transitionmetal) particles.…”

“…4 Using reverse micelles as microreactors and protecting shells, Pileni et al 5 reported the synthesis of copper nanoparticles of varied shapes, whereas in dendrimer nanoreactors, typically only spherical copper nanoparticles were found. 6 More recently, Alivisatos et al reported the synthesis of spherical and rodshaped cobalt particles using a wet-chemistry approach at elevated temperatures. 7 Also, electrolytic techniques have been utilized to synthesize a variety of transition-metal colloids (e.g., gold, silver, palladium, nickel, and copper) of decahedral or icosahedral shapes by controlling the electrode potentials.…”

Extraction of Monodisperse Palladium Nanoparticles from Dendrimer Templates

“…Third, it demonstrates that multiple, fairly complex operations, including formation of covalent bonds, electron-transfer, molecular transport, heterogeneous self-assembly, and nanoparticle transport, can all be executed within the interior of a 4.5-nm dendrimer. These points are demonstrated here by templating the formation of ∼1.7-nm Pd nanoparticles within poly(amidoamine) (PAMAM) dendrimers, [4][5][6][7][8] and then extracting the Pd into a toluene phase while leaving the dendrimer in the aqueous phase (Scheme 1).Dendrimer-encapsulated nanoparticles (DENs) 4-7 are prepared in a two-step process. First, metal ions are sequestered within the dendrimer, and then the ions are chemically reduced.…”

Cobalt–poly(amido amine) superparamagnetic nanocomposites

“…Colloidal metallic cobalt -dendrimer nanocomposites in the filtrate were separated by ultrafiltration. Samples were dissolved in HNO 3 and Co was determined by AAS. Cobalt:dendrimer ratios were calculated based on the assumption of 100% recovery of the original dendrimer concentration on the ultrafiltration membrane.…”

“…Several research groups have prepared dendrimer-metal nanocomposites [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. The internal tertiary nitrogens of poly(amido amine) (PAMAM) dendrimers are well suited to the formation of complexes with transition metal and noble metal ions at the appropriate pH.…”