Ultraviolet stimulated photocatalytic activity on polycrystalline diamond film surfaces

A photocatalytic reaction produced on polycrystalline diamond film surfaces by ultraviolet (UV) light was studied by micro-Raman spectroscopy. The diamond films were specially prepared for this study by the rf-assisted chemical vapor deposition technique. The photocatalytic activity was analyzed in terms of the sharpness of the typical diamond Raman band at 1332 cm−1 and by the weak nondiamond carbon (NDC) features around 1550 cm−1. The micro-Raman spectra show a decrease of the NDC content originally codeposited on diamond film surfaces during the synthesis. This decreasing is proportional to the UV irradiation time, suggesting that the photocatalytic reaction can be controlled by the UV irradiation dose. Since a selective reduction of the NDC phase was achieved on diamond surfaces. The UV irradiation was applied continuously during 1, 2, and 3 days in open atmosphere at room temperature. The role of oxygen radicals, such as ozone (O3) and atomic oxygen (O*) on the photocatalytic reaction is discussed, a...