Metal Nanoparticles Modified with Molecular Receptors

The central goal of this research project is the preparation and characterization of metal nanoparticles with molecular receptors covalently attached to their surfaces. Ideally, these novel systems maintain the electronic, magnetic and or catalytic properties characteristic of the metal cores. However, these unique and often size-dependent properties may be modulated by the molecular recognition ability of their organic 'skins'.1 We have successfully demonstrated this idea and developed gold and palladium nanoparticles (~3 nm in diameter) capped with thiolated cyclodextrin hosts.2 Recent reports from our group in this area deal with the reversible aggregation of g-cyclodextrin-capped gold nanoparticles driven by minute concentrations of fullerene C60,3 binding of ferrocene-containing amphiphiles onto b-cyclodextrin-capped gold nanoparticles4 and inhibition of the catalytic activity of b-cyclodextrin-capped palladium nano- particles in alkene hydrogenation reactions.5 Our current efforts focus on the development of new types of capped Pd nanoparticle catalysts that will exhibit selectivity properties derived from host-guest phenomena on their surfaces.

References: 1Liu, J.; Alvarez, J.; Kaifer, A. E. "Metal Nanoparticles Modified with Cyclodextrin Hosts: Making Metal Nanoparticles with a Knack for Molecular Recognition", Adv. Mat. 2000, 12, 1381-1383. 2For Spanish-language readers, see: Kaifer, A. E.; "Nanopartículas Metálicas Modificadas con Monocapas Orgánicas", Anales de la Real Sociedad Española de Química 2001, 97, 3-9. 3Liu, J.; Alvarez, J.; Ong, W.; Kaifer, A. E. "Network Aggregates Formed by C60 and Gold Nanoparticles Capped with g-Cyclodextrin Hosts", Nano Letters 2001, 1, 57-60. 4Liu, J.; Alvarez, J.; Ong, W.; Roman, E.; Kaifer, A. E.; "Phase Transfer of Hydrophilic, Cyclodextrin- Modified Gold Nanoparticles to Chloroform Solution", J. Am. Chem. Soc 2001, 123,11148-11154. 5Liu, J.; Alvarez, J.; Ong, W.; Román, E.; Kaifer, A. E.; "Tuning the Catalytic Activity of Cyclodextrin -Modified Palldium Nanoparticles through Host-Guest Binding Interactions", Langmuir 2001, 17, 6762-6764.

Electroactive and Fluorescent Dendrimers Syntheses and Characterization of New Hosts