Structure Transition of CuOX Nanoparticles in Copper−Silica Nanocomposites

Two series of CuO X /SiO 2 nanocomposites with various Cu/Si molar ratios have been synthesized by sol−gel technique from two different copper metal precursors, cupric nitrate hydrate (Cu(NO 3 ) 2 ·3H 2 O) and cupric acetylacetonate (Cu(acac) 2 ), respectively. The influence of various chemical precursors and Cu content on the morphological evolution of CuO X nanoparticles in CuO X /SiO 2 nanocomposites has been characterized by XRD, TEM, TG, FTIR, and XPS. For the first time, we demonstrated that, with the increase of Cu content, CuO X nanoparticles in CuO X /SiO 2 nanocomposites performed two different morphology transitions, that is, from nanospherical aggregates to uniform nanorods using Cu(NO 3 ) 2 ·3H 2 O as chemical precursor and to squarelike frames starting from Cu(acac) 2 . The effects of reducing agents on these different morphology transformations of CuO X nanoparticles between the SCuN and SCuC series were also discussed.