Nanowires of bismuth oxide were grown on Si substrates by unbalanced magnetron sputtering. Deposition time for the seed layer and oxygen partial pressure were varied to optimize the morphology of the resulting array of wires. A two step process involving variable oxygen flow rates was found to create the highest density of Bi2O3 nanowires in the array. Top-view and cross-sectional SEM micrographs suggested that the resulting Bi2O3 nanowires were approximately 300 nm in length with diameters of 100 nm at the base and 30 nm at the top. Investigation into the growth method suggests a self-catalytic process similar to vapor-liquid-solid growth. Band gap was determined by two different methods, using transmission spectroscopy and cyclic voltammetry which gave values of 2.53 eV and 2.61 eV respectively. Degradation experiments using rhodamine 6G display a direct relationship between nanowire density and photocatalytic results. (C) 2012 Elsevier B. V. All rights reserved.