Photocatalytic effects of reactively sputtered N-doped anatase upon irradiation at UV-A and UV-A/VIS threshold wavelengths

Abstract

In biomedicine, light induced photocatalysis at implant surfaces has been gaining increasing interest during the last years. In the fields of biofilm attack at dental implant sites, photocatalytic decomposition of proteinaceous conditioning films could be shown recently on polycrystalline anatase coatings. However, for clinical treatments directly at the patient, the commonly applied UV-A is unwanted due to possible cell damage at host tissues. Therefore, in this study, anatase thin films were N-doped during reactive pulse magnetron sputtering, and the respective modifications were investigated for red-shifting, hydrophilization, and efficiency of photocatalytic organic decomposition upon UV-A compared to irradiation at the UV-A/VIS threshold around 400nm wavelengths. Generally, with increasing nitrogen flow during anatase sputtering, the ability of gaining superhydrophilicity or decomposing methylene blue decreased. Anatase sputtered under lowest nitrogen flow rates≤1sccm decomposed human serum albumin films more efficiently upon 405nm irradiation than anatase variants sputtered under higher nitrogen flow rates. Furthermore, undoped anatase could be activated similarly to low-doped variants even upon irradiation at 405nm peak wavelength enabling significant protein decomposition. These findings open the way for clinical applications of undoped and low-doped anatase modifications in cases where biocompatibility requires longer wavelengths than UV-A. Further research is still needed to clarify possible functional advantages of undoped and low-doped anatase modifications for specific biomedical applications at the UV-A/VIS threshold region around 400nm.