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Gold Colloids (gold + colloid)

Distribution by Scientific Domains
Chemistry100%

Selected Abstracts

Cooperative Catalysis in the Hydrolytic Kinetic Resolution of Epoxides by Chiral [(salen)Co(III)] Complexes Immobilized on Gold Colloids

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 7-8 2008
Thomas Belser
Abstract Chiral salen ligands were incorporated into self-assembled thiolate monolayers (SAMs) on gold colloids. Treatment of the immobilized ligand with Co(OAc)2,4,H2O yielded the corresponding [(salen)Co(II)] complex, and aerobic oxidation in the presence of triflic acid afforded the catalytically active [(salen)Co(III)] complex. Functionalized gold colloids with a diameter of 3.4,nm, coated with a mixed monolayer of n -octanethiolates and thiolates with chiral [(salen)Co(III)] end groups were studied as catalysts in the hydrolytic kinetic resolution (HKR) of hexene-1-oxide. Extremely high selectivitiy and significant rate acceleration relative to homogeneous monomeric catalysts were observed. Recovery of the immobilized catalyst was accomplished by simple filtration, and catalyst reoxidation and repeated recycling (seven times) was possible with no loss of reactivity or enantioselectivity. [source]

Aggregation and surface-enhanced Raman activity study of dye-coated mixed silver,gold colloids

JOURNAL OF RAMAN SPECTROSCOPY, Issue 11 2004
Jinghuai Fang
Abstract The aggregate morphologies of silver, gold, and mixed silver,gold nanoparticles coated with fuchsine basic were directly investigated by means of transmission electron microscopy. It was found that the aggregation of silver and gold colloids induced by the adsorption of fuchsine basic displayed different aggregate characteristics. The adsorption of fuchsine basic in mixed silver and gold colloidal systems led to altered aggregation and surface-enhanced Raman scattering (SERS) enhancement behavior. A suitable ratio of mixed silver and gold colloids could form a favorable state of aggregation and significantly increase the SERS activity of mixed colloids compared with single silver and gold colloids. This is the first report of the SERS of fuchsine basic on mixed silver and gold colloids. Copyright © 2004 John Wiley & Sons, Ltd. [source]