Nanometallurgy of colloidal aluminides: Soft chemical synthesis of CuAl 2 and α/β-CuAl colloids by co-hydrogenolysis of (AICp*) 4 with [CpCu(PMe 3)]

Mirza Cokoja, Harish Parala, Marie Katrin Schröter, Alexander Birkner, Maurits W.E. Van Den Berg, Wolfgang Grünert, Roland A. Fischer

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Abstract

In this work, we present a novel soft chemical synthesis to aluminum nanoparticles based on the hydrogenolysis of the metastable organoaluminum (1) compound (AlCp*) 4 (1) in mesitylene at 150°C and 3 bar H 2. Aiming at the development of a general wet-chemical, nonaqueous route to M/E intermetallic nanophases (E = Al, Ga, In), we studied the co-hydrogenolysis of 1 with [CpCu(PMe 3)] (2) as the model case aiming at Cu/Al alloyed nanoparticles. One equivalent of 1 combined with 2 equiv of 2 yields the nanocrystalline intermetallic θ-CuAl 2 phase (Cu 0.33Al 0.67), as revealed by elemental analysis, powder X-ray diffraction, transmission electron microscopy (TEM), and energy-dispersive X-ray analysis. The obtained Cu 0.33Al 0.67 material was also characterized by the 27A1 Knight Shift resonance. Alloy particles Cu -xAl x (0.10 ≤ x ≤ 0.50), typically 15 ± 5 nm (TEM) in size, are accessible as colloidal solutions by variation of the molar ratio of 1 and 2 and by the addition of poly(2,6-dimethyl-1,4- phenylene oxide) during hydrogenolysis. The 27A1 NMR Knight Shift resonance moves to high field starting form the value of 1639 ppm for pure nano-aluminum particles to 1486 ppm of Cu 0.33Al 0.67, reaching 1446 ppm for Cu 0.50Al 0.50, and was not detectable for Al contents below 50%. Upon oxidation (controlled exposure to the ambient), a selective oxidation of the Al component, presumably forming core-shell structured Al 2O 3@Cu 1-yAl y (0.10 ≤ y ≤ 0.50) particles, was studied by UV-vis spectroscopy, 27Al magic-angle spinning NMR, and X-ray photoelectron spectroscopy. The Al content can be freely adjusted and lowered down to about 15 atom % (Cu 0.85Al 0.15) without oxidizing the Cu(0) core.

Original languageEnglish
Pages (from-to)1634-1642
Number of pages9
JournalChemistry of Materials
Volume18
Issue number6
DOIs
StatePublished - 21 Mar 2006
Externally publishedYes

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