Grafting effects of Cu2+ on the photocatalytic activity of titanium-substituted hydroxyapatite

• UV light photocatalytic activity of hydroxyapatite increased suddenly at 10 wt% Ti.
• By grafting 0.05 wt% Cu2+ the activity of Ti:HAp became about three times.
• Photoexcitation to the grafted Cu2+ was very small because valence band consists of PO4.
• Electron transfer from Ti-hybridized states to grafted Cu2+ was revealed by ESR.

We examined the grafting effect of Cu2+ on the photocatalytic activity of Ti-substituted hydroxyapatite (Ti:HAp). When 0.05 wt% Cu2+ was grafted on the 10%-Ti:HAp, the photocatalytic activity to acetaldehyde decomposition under UV light irradiation was increased by three times. ESR measurements revealed that valence band electrons transfer to the Cu2+ via hybridized band, which promotes electron–hole separation. However, visible light activity of Ti:HAp did not appear even after Cu2+ grafting although TiO2 was reported to become active by the grafting. This experimental result was explained by the difference in the electronic states of valence bands of Ti:HAp and TiO2.

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