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Article

Copper Oxide Nanocrystals

Supporting Info

Ming Yin,^† Chun-Kwei Wu,^‡ Yongbing Lou,^§ Clemens Burda,^§ Jeffrey T. Koberstein,^‡ Yimei Zhu, and Stephen O'Brien*^†

Contribution from the Department of Applied Physics and Applied Mathematics and Department of Chemical Engineering, Materials Research Science and Engineering Center, Columbia University, New York, New York 10027, Department of Chemistry, Center for Chemical Dynamics and Nanomaterials Research, Case Western Reserve University, Cleveland, Ohio 44106, and Department of Materials Science, Brookhaven National Lab, Upton, New York 11973

J. Am. Chem. Soc., 2005, 127 (26), pp 9506–9511

DOI: 10.1021/ja050006u

Publication Date (Web): June 10, 2005

†

Department of Applied Physics and Applied Mathematics.

‡

Department of Chemical Engineering, Materials Research Science and Engineering Center, Columbia University.

Case Western Reserve University.

⊥

Brookhaven National Lab.

In papers with more than one author, the asterisk indicates the name of the author to whom inquiries about the paper should be addressed.

so188@columbia.edu

Abstract

It is well-known that inorganic nanocrystals are a benchmark model for nanotechnology, given that the tunability of optical properties and the stabilization of specific phases are uniquely possible at the nanoscale. Copper (I) oxide (Cu₂O) is a metal oxide semiconductor with promising applications in solar energy conversion and catalysis. To understand the Cu/Cu₂O/CuO system at the nanoscale, we have developed a method for preparing highly uniform monodisperse nanocrystals of Cu₂O. The procedure also serves to demonstrate our development of a generalized method for the synthesis of transition metal oxide nanocrystals. Cu nanocrystals are initially formed and subsequently oxidized to form highly crystalline Cu₂O. The volume change during phase transformation can induce crystal twinning. Absorption in the visible region of the spectrum gave evidence for the presence of a thin, epitaxial layer of CuO, which is blue-shifted, and appears to increase in energy as a function of decreasing particle size. XPS confirmed the thin layer of CuO, calculated to have a thickness of 5 Å. We note that the copper (I) oxide phase is surprisingly well-stabilized at this length scale.