Size dependence of CH stretchign features on diamond nanocrystal surfaces:Infrared spectroscopy and density functional theory calculation.

摘要

Surface CH stretchign features on diamond nanocrystals of differetn origins and sizes have been characterized by fourier transform infrared spectroscopy and density functional calculations.Independent of the origins of the samples,a single sharp transition,corresponding to the CH stretch on C(111)-1X1,is observed at 2834 cm~-1 for particles of sizes(d) larger than 100 nm.the feature,however,gradually diminishes as the particle size decreases and disappears nearly completely at d=5nm.We interpretd the observation in terms of domain size effect,namely,the domains of the {111}-type facets on the 5 nm diamonds are too small to yield the characteristic CH stretching feature[Chen et al.,J.Chem.Phys.116,1211(2002)].The interpretation is supported by the present density functional calculations performed at the B3LYP/6-31G~* level for three H-truncated of the C-H stretching features on the {111}-type facets of these clusters are calculated and the results agree satisfactorily with the values obtained form the mixed isotope measurements conducted on diamond C(111)-1X1 single crystal surfaces[Cheng et al.,J.Chem.Phys.106,7411(1997)].