Photocatalytic hydroxyapatite/titanium dioxide multilayer thin film deposited onto glass using an rf magnetron sputtering technique

Hydroxyapatite (HA)/titanium dioxide (TiO2) thin film was deposited on glass using a radio frequency magnetron sputtering. X-ray diffraction (XRD), Fourier-transform infrared spectrometry, ultraviolet–visible spectroscopy and measurement of its photocatalytic activity by the decomposition of formaldehyde gas and the bacterial survival test of Escherichia coli (E. coli) cells were applied to characterize the film. After heat treatment (at 500 8C), XRD analysis of the HA/TiO2 film showed a crystalline TiO2 crystal structure with anatase phase. The transmittance of the HA/TiO2 film decreased after the heat treatment, however, the average transmittance remained at 87% in the visible light range. In the decomposition of formaldehyde gas, the HA/TiO2 film showed a higher decomposition rate than either the TiO2 or the HA film alone. However, in the bacterial survival test, survival of cells on the HA/TiO2 film was higher than that on the TiO2 film, which indicates the HA/TiO2 film has a lower bactericidal effect than the TiO2 film alone.