Activity of Atomically Precise Titania Nanoparticles in CO Oxidation.

Understanding the property evolution of atomically precise nanoparticles atom by atom along the size continuum is critical for selecting potential candidates to assemble nanomaterials with desired functionality, but it is very challenging experimentally especially for systems having mixtures of elements such as metal oxides. In this work, the capability to oxidize carbon monoxide has been measured experimentally for titania nanocluster anions of (TiO2)(n)O-m(-) (-3 <= m <= 3) across a broad size range in the gas phase. Stoichiometric (TiO2)(n)O- exhibits superior oxidative activity over other clusters of (TiO2)(n)O-m(-) (m not equal 1) even when the cluster dimensions are scaled up to n=60, indicating that each atom still influences the chemical behavior of titania nanoparticles composed of approximate to 180 atoms. The fascinating result not only identifies a promising building block of TinO2n+1 for devising new nanoscale titania materials with desirable oxidative activity, but also provides compelling molecular-level evidence for the Mars-van Krevelen mechanism of CO oxidation over titania supports.