NANOCAT(R) Superfine Fe2O3 nanoparticles were evaluated both as a catalyst and as an oxidant for carbon monoxide oxidation. It was found that the nanoparticles are much more effective as carbon monoxide catalysts than the non-nano oxide powder. For the Fe2O3 nanoparticles, the reaction order is first-order with respect to the partial pressure of carbon monoxide, and zero-order with respect to the partial pressure of oxygen. The apparent activation energy was 14.5 kcal mol(-1) and the normalized reaction rate was 19 s(-1) m(-2) at 300degreesC. In the absence of oxygen, Fe2O3 nanoparticles oxidize carbon monoxide directly as an oxidant. The resulting reduced forms of Fe2O3 also catalyze a disproportionation reaction for a considerable amount of carbon monoxide. The significant amount of carbon monoxide it can remove through the catalytic oxidation, direct oxidation, and the disproportionation reaction make it a very promising material in certain special applications, such as removing the carbon monoxide from a burning cigarette, where the potential toxicity of other, more conventional catalysts would be undesirable. The higher activity of Fe2O3 nanoparticles over non-nano Fe2O3 powders was attributed to a small particle size (3 nm), the presence of an hydroxylated phase of iron oxide (FeOOH), as revealed by both high resolution transmission electron microscopy (HRTEM) and a comparable study of FeOOH (goethite) powder. (C) 2002 Published by Elsevier Science B.V.