Molecular adsorption-desorption reactions of ammonia on alkali halide clusters and nanocrystals

Margie L. Homer, Frank E. Livingston, Robert L. Whetten

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


The initial adsorption of ammonia molecules (NH3) on larger alkali halide clusters and small nanocrystals (mainly NaF) has been investigated by flow-reactor methods as a function of cluster size and temperature. An analysis of the strong size-dependent reactivity of positively-charged NaF clusters, along with their computed structures, indicates that a particular type of defect in the nanocrystal structure facilitates adsorption. This defect is formed by removing an ion-pair from adjoining face and internal sites of a perfect crystallite, creating a basket-like opening. KF nanocrystals show very similar reactivity patterns, reflecting their corresponding structures, but LiF clusters follow a different pattern. It was established that NH3 adsorption on preformed NaF nanocrystals takes place under equilibrium conditions. The equilibrium constant for initial adsorption-desorption increases with decreasing temperature (250-340 K) and allows one to derive heats of NH3 adsorption near 0.2 eV for the more reactive (defective) nanocrystals. The much lower reactivity of negatively-charged clusters is ascribed to an additional kinetic-dynamic barrier to adsorption.

Original languageEnglish (US)
Pages (from-to)7604-7612
Number of pages9
JournalJournal of physical chemistry
Issue number19
StatePublished - 1995
Externally publishedYes

ASJC Scopus subject areas

  • General Engineering
  • Physical and Theoretical Chemistry


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