Planting of bis(1,5‐cyclooctadiene) nickel upon silica to harvest NiO (<5 nm) nanoparticles in a silica matrix

Bis(1,5‐cyclooctadiene) nickel [Ni(COD)₂] was employed as a nickel precursor to prepare nickel oxide nanoparticles upon high‐surface‐area mesoporous silica. Under protection of argon, Ni(COD)₂ was dissolved in tetrahydrofuran (THF) to react with surface silanols of mesoporous silica SBA‐15, which formed a black powder after completion of the surface reaction. Calcination of the powder produced ultrafine NiO inside the mesoporous silica matrix, which was evidenced by X‐ray diffraction, N₂ adsorption–desorption, transmission electron microscopy and thermogravimetric analysis. The thermogravimetric analysis suggests that NiO formation is a result of surface nickel species calcination, whereas structural characterization clearly show that NiO nanoparticles of <5 nm are evenly distributed inside the silica SBA‐15 matrix and mesoporosity is well preserved upon calcinations and NiO formation. The surface reaction between Ni(COD)₂ and surface silanols was found for the first time, and the method used here may be extended conveniently to prepare other metal oxide nanoparticles upon high‐surface‐area supports as well. Copyright © 2005 John Wiley & Sons, Ltd.