Radical generation on hydroxyapatite by UV irradiation

The radical species generated on hydroxyapatite (HAp) samples by UV irradiation were investigated and compared by electron spin resonance (ESR) with spin trapping reagent. It was recognized that OH and O-2(-) species were produced on HAp after heat treatment at 200 degreesC (HAp200) by UV irradiation. It was assumed that OH radical was generated from H2O on HAp200 by photo-induced excitation with UV irradiation as well as O-2(-) from O-2 in air. These radicals were very active. On the other hand, few radical species were produced on HAp after heat treatment at 1150 degreesC by UV irradiation. The difference of generation of active radical species on HAp by UV irradiation must influence the activity for the photocatalytic decomposition of organic compounds. (C) 2003 Elsevier B.V. All rights reserved.