Characteristics and Mechanism of Atomic Fluorine Anions Emission from Nanoporous Crystal [Ca24Al28O64]4+ • (F-)3.36(O2-)0.32 Surface

Atomic fluorine anion (F-) emission from the nanoporous crystal [Ca24Al28O64](4+) center dot (F-)(3.36)(O2-)(0.32) (C12A7-F-) surface, was observed via a time-of-flight mass spectrometry (TOF-MS). C12A7-F- is a nanoporous crystal material with a BET surface area of 1.1 +/- 0.1 ml/g. The storage characteristics of C12A7-F-, its emission features (including branching ratios, temperature effect, field effect, apparent activation energy, and emission stability), and its structural alteration after the emission, have been investigated in detail. The anionic species emitted from the C12A7-F- surface were dominant by the F- anions (maximal purity: 96%). A small amount of O- anions and electrons emission were also observed. The emission intensity of F- was significantly enhanced by temperature and the extraction field. The apparent activation energies for the F- emission ranged from 190 to 121 kJ/mol, depending on the extraction field applied. The binding energy between the F- anion and the C12A7-F- surface was about 237 kJ/mol. The anionic species stored in C12A7-F- was dominant by the F- anions ((1.96 +/- 0.25) x 10(21) cm(23)) based on ion chromatography, electron paramagnetic resonance. The formation and emission mechanism for the F- anion was discussed based on the above investigations.