Immobilization copper nanoparticles

Immobilizing DENs within a sol-gel matrix is another potential method for preparing new supported catalysts. PAMAM and PPI dendrimers can be added to sol-gel preparations of silicas " and zinc arsenates to template mesopores. In one early report, the dendrimer bound Cu + ions were added to sol-gel silica and calcined to yield supported copper oxide nanoparticles. Sol-gel chemistry can also be used to prepare titania supported Pd, Au, and Pd-Au nanoparticle catalysts. Aqueous solutions of Pd and Au DENs were added to titanium isopropoxide to coprecipitate the DENs with Ti02. Activation at 500°C resulted in particles approximately 4 nm in diameter. In this preparation, the PAMAM dendrimers served two roles, templating both nanoparticles and the pores of the titania support. 

Originally, the effect of charge state of nanostructures on their catalytic activity was recognized from analysis of the experimental data on the catalytic properties of metallic nanoparticles immobilized in the matrix of a poly-paraxylylene polymer [13-15,24]. It was found that the dependence of the catalytic activity (and, in some cases, of the selectivity) of copper, palladium, and iron nanoparticles on the metal content of these structures has a maximum. This maximum exists not only for the specific (related to unit weight) activity, but also for the absolute activity. More specifically, for copper and... 

Silver, gold and copper are the most commonly used metals for SERS and the variety of substrates include, among others, roughened surfaces, nanoparticle colloidal suspensions, island films and nanostmctured surfaces (4). Current trends in SERS and Raman spectroscopy include the development of new substrates which includes immobilized particles, functionalized nanoparticles and nanolayered films. These recent development have created new opportunities for chemical and biological sensing. 

The synthesis of metal-complexing nanoparticles with an average size ranging from 15 to 25 nm was recently described (Larpent et al, 2003). It consists of a two-step procedure starting first with the microemulsion polymerization of a mixture of styrene and vinylbenzylchloride in the presence of a cationic surfactant, then followed by the postfunctionalization with a selective macrocyclic ligand, tetrazacyclotetradecane (cyclam). The authors showed the ability of these cyclam-functionalized nanoparticles to complex copper and in addition they observed that they exhibited a solution-hke complexation behavior, demonstrating the accessibility of the immobilized ligand. 

A class of perfluorinated bis(dihydrooxazole) copper(ll) (PBDC) complexes immobilized on FSG was developed as catalysts for the enantioselective Diels-TUder reaction (Scheme 7.13) [23]. The perfluorinated bis(dihydrooxazole) copper(II) complexes were synthesized from enantiomericaUy pure 2-aminoethanols, which were then immobilized on FSG to give FSG-PBDG. This catalyst promoted the Diels-Alder reaction with reasonable conversions and enantioselectivities in water or dichloromethane. The fluorous nanoparticle catalysts can be recovered and... 

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