title: Seedless polyol synthesis and CO oxidation activity of monodisperse (111)- and (100)-oriented rhodium nanocrystals in sub-10 nm sizes.
abstract: Monodisperse sub-10 nm (6.5 nm) sized Rh nanocrystals with (111) and (100) surface structures were synthesized by a seedless polyol reduction in ethylene glycol, with poly(vinylpyrrolidone) as a capping ligand. When using [Rh(Ac)(2)](2) as the metal precursor, (111)-oriented Rh nanopolyhedra containing 76% (111)-twinned hexagons (in 2D projection) were obtained; whereas, when employing RhCl(3) as the metal precursor in the presence of alkylammonium bromide, such as tetramethylammonium bromide and trimethyl(tetradecyl)ammonium bromide, (100)-oriented Rh nanocubes were obtained with 85% selectivity. The {100} faces of the Rh nanocrystals are stabilized by chemically adsorbed Br(-) ions from alkylammonium bromides, which led to (100)-oriented nanocubes. Monolayer films of the (111)-oriented Rh nanopolyhedra and (100)-oriented Rh nanocubes were deposited on silicon wafers in a Langmuir-Blodgett trough to make model 2D nanoarray catalysts. These nanocatalysts were active for CO oxidation by O(2), and the turnover frequency was independent of nanoparticle shape, consistent with that previously observed for Rh(111) and Rh(100) single crystals.
authors.affiliation: College of Chemistry and Molecular Engineering, and the State Key Lab of Rare Earth Materials Chemistry and Applications, Peking University, Beijing 100871, China. ywzhang@pku.edu.cn
authors.forename: Yawen
authors.initials: Y
authors.lastname: Zhang
authors.forename: Michael E
authors.initials: ME
authors.lastname: Grass
authors.forename: Wenyu
authors.initials: W
authors.lastname: Huang
authors.forename: Gabor A
authors.initials: GA
authors.lastname: Somorjai
mesh_terms: D000327:Adsorption; D002248:Carbon Monoxide / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry*; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D010084:Oxidation-Reduction; D010316:Particle Size; D011108:Polymers / Q000138:chemical synthesis* / Q000737:chemistry; D012238:Rhodium / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D009942:Organometallic Compounds; D011108:Polymers; C024617:polyol; D002248:Carbon Monoxide; D012238:Rhodium