Morphology-Dependent Ullmann C-O Arylation Using Cu2O Nanocrystals

Abstract

Five different copper-oxide nanocrystals were prepared by colloidal synthesis to form either cubic, octahedral, rhombic dodecahedral, truncated cubic, or fluffy sphere structures. These Cu-oxide nanocrystals were characterised using scanning electron microscopy, X-ray photoelectron spectroscopy, and UV-vis. The SEM images show that the Cu2O nanocrystals are relatively uniform and all the crystals have a particle mean diameter below 1000 nm. The smallest particle mean diameter is 411 nm for the rhombic dodecahedral crystals, while the octahedral crystal displays the largest particle mean diameter of 864 nm. The XPS results indicate that the copper is primarily CuI in Cu2O, but some as CuII are also present. The apparent optical band gap energies could be determined from the optical properties of the five Cu-oxide nanocrystals, using the classical Tauc equation. The apparent optical band gap energies ranged between 2.04 and 2.14 eV. The Ullmann C-O coupling reaction was used to investigate the catalytic performance of the Cu-oxide nanocrystals. The fluffy sphere gave the highest % conversion, while the rhombic dodecahedral showed the lowest conversion.