Johnson Grant E, Tyo Eric C, Castleman A W
Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
J Phys Chem A. 2008 May 29;112(21):4732-5. doi: 10.1021/jp7118313. Epub 2008 May 2.
Small aluminum oxide cluster cations and anions, produced by laser vaporization, were investigated regarding their reactivity toward CO and N2O employing guided-ion-beam mass spectrometry. Clusters with the same stoichiometry as bulk alumina, Al2O3, exhibited atomic oxygen transfer products when reacted with CO, suggesting the formation of CO2. Anionic clusters were less reactive than cations but showed higher selectivity towards the transfer of only a single oxygen atom. Cationic clusters, in contrast, exhibited additional products corresponding to the sequential transfer of two oxygen atoms and the loss of an aluminum atom. To determine if these stoichiometric clusters could be generated from oxygen-deficient species, clusters having a stoichiometry with one less oxygen atom than bulk alumina, Al2O2, were reacted with N2O. Cationic clusters were found to be selectively oxidized to Al2O3(+), while anionic clusters added both one and two oxygen atoms forming Al2O3(-) and Al2O4(-). The oxygen-rich Al2O4(-) cluster exhibited comparable reactivity to Al2O3(-) when reacted with CO.
通过激光蒸发产生的小尺寸氧化铝团簇阳离子和阴离子，利用导向离子束质谱法研究了它们与一氧化碳和一氧化二氮的反应活性。与块状氧化铝Al2O3具有相同化学计量比的团簇，在与一氧化碳反应时表现出原子氧转移产物，表明形成了二氧化碳。阴离子团簇的反应活性低于阳离子团簇，但对仅单个氧原子的转移表现出更高的选择性。相比之下，阳离子团簇表现出对应于两个氧原子顺序转移和一个铝原子损失的额外产物。为了确定这些化学计量团簇是否可以由缺氧物种产生，将化学计量比比块状氧化铝少一个氧原子的Al2O2团簇与一氧化二氮反应。发现阳离子团簇被选择性氧化为Al2O3(+)，而阴离子团簇添加了一个和两个氧原子，形成Al2O3(-)和Al2O4(-)。富氧的Al2O4(-)团簇在与一氧化碳反应时表现出与Al2O3(-)相当的反应活性。
