Photocatalysis by Calcium Hydroxyapatite Modified with Ti(IV): Albumin Decomposition and Bactericidal Effect

Colloidal calcium hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2; HAP) particles doped with Ti(IV) ions in different atomic ratios, Ti/(Ca + Ti) = X Ti, by a coprecipitation method were characterized by TEM, UV, FTIR, XPS, and ICP−AES. The photocatalytic activity of the modified HAP particles was examined by decomposition of acetaldehyde and albumin and a bactericidal test by colon bacillus. Ca(II) of HAP was one-to-one substituted by Ti(IV) at X Ti ≤ 0.1. When doped at X Ti > 0.1, irregular particles of amorphous titanium phosphate were formed besides long rectangular particles of HAP. X Ti of the surface phase of the particles was much less than that of the whole particle; Ti(IV) is less contained in the surface phase than in the bulk one. A UV beam was absorbed by Ti(IV)-modified HAP particles but not by the unmodified particles. The decomposition of acetaldehyde and albumin by Ti(IV)-doped particles was found under UV irradiation, while the unmodified HAP particles were inactive for the decomposition of both materials. Further, different from TiO 2, Ti(IV)-doped HAP showed a bactericidal function in the dark.