Fabrication of function-switchable surfaces in metallic biomaterials

羟基磷灰石（HAp）通过浸泡在模拟体液（SBF）中沉淀在生物活性物质上。研究了紫外光照射下TiO2和ZrO2表面HAp的形成。ZrO2表面HAp的形成对热处理和UV辐照不敏感。相反，热处理和紫外辐照对SBF中TiO2上HAp的形成有很大影响。热处理可以降低TiO2表面羟基的密度。然后通过先前的紫外线照射可以恢复密度，从而促进HAp的形成。这意味着TiO2表面生物活性的恢复。紫外光在TiO2中产生电子-空穴对，光生空穴迁移到表面排斥溶液中的正离子。因此，持续的紫外线照射抑制了HAp的形成。这些结果表明，光照射可能会改变TiO2中的几种功能。

Hydroxyapatite (HAp) is known to precipitate on bioactive materials by soaking in simulated body fluid (SBF). The formation of HAp on TiO2 and ZrO2 surfaces under ultraviolet (UV) irradiation was investigated. HAp formation on ZrO2 surface was not sensitive to heat treatment and UV irradiation. In contrast, the HAp formation on the TiO2 in SBF was strongly influenced by heat treatments and UV irradiation. Hydroxyl group density on TiO2 surface could be decreased by the heat treatment. Then the density could be recovered by previous UV irradiation, it led to promotion of HAp formation. This means recovery of bioactivity on the TiO2 surface. The UV light produced electron-hole pairs in the TiO2, and the photogenerated holes that migrated to the surface repelled the positively charged ions in the solution. As a consequence, the continuous UV irradiation suppressed the formation of HAp. These results suggest that several functions in TiO2 might be switched by light irradiation.