Edge-induced active sites enhance the reactivity of large aluminum cluster anions with alcohols.

Understanding the emergence of properties from the size-selective cluster regime to larger nanoparticles is one of the principal goals of nanoscience. We have measured the size-selective reactivity of aluminum cluster anions with alcohols. All clusters with more than 20 atoms are found to be reactive, while Al11–, Al13–, and Al20– show enhanced resistance to oxidation at smaller sizes. The reactivity of aluminum cluster anions with water, methanol, and tert-butyl alcohol all exhibit patterns that require complementary active sites (Lewis acid, Lewis base) on adjacent atoms. Theoretical investigations reveal that at small sizes, the location of reactive pairs occurs on specific active sites, but at larger sizes the reactive pairs begin to accumulate on the edges between facets, marking the transition from the nonscalable size-dependent regime to the scalable regime where the nanoparticles are universally reactive.