Methylene blue is a standard aqueous impurity used to determine the photocatalytic potential of various materials, including ZnO. The spectra of the MB solutions before degradation and after 240 minute degradation for all samples along with the trends of degradation as a function of time for all samples are shown in Figure . Generally, the higher the oxidation temperature, the better the conversion efficiency (Table ). The annealing at 400 °C shows similar MB degradation for samples B, C and D, while for the sample A it shows almost no degradation. The low percentage of methylene blue degradation for sample A annealed at 400 °C may be attributed to incomplete oxidation of the zinc layer, making oxidation under such conditions insufficient to obtain a homogeneous ZnO layer, as shown in the XRD patterns in image 6. Increasing the oxidation temperature to 600 °C increases the degradation percentage of MB for all samples, however the increase is the smallest for the sample B. It is worth noting, that samples C and D start to show some degree of ripening while sample A shows agglomeration, with larger crystallites. This does not seem to influence the degradation. Furthermore, heating at a temperature of 800 °C causes a more pronounced ripening of the samples C and D and substan- tial agglomeration and calcination of the sample A, as shown in SEM images, leading to a reduction in the active surface area of porous layers in the case of the sample A to almost no porosity. This leads to a drop in the degradation efficiency for sample A Sample B, shows other behavior, with no morphology changes visible and an increase in the percentage of degradation. The photodegradation of organic dyes in solution is a complex process, depending on a number of factors, such as the available surface area and availability of active sites at the surface of the catalyst. Trying to understand the photodegradation behavior, we analyzed the areas of all photoluminescence lines, fitted using Gaussian profiles, and their combinations, to find correlations with the degradation percentage. Since the luminescence of the samples annealed at 400 °C is very low, we will present the discussion for samples annealed at 600 and 800 °C. Figure presents the trends for the individual lines from the N BE region, the V O and the SS lines along with the trend for percent of MB degraded. Looking at the data for 800 °C, it seems that the V O profile well correlates with the degradation profile, which would be argued by some, as the V O profile intensity has been shown to correlate positively with the photodegradation efficiency.(42) However, taking into account the system we identified in our samples, including N BE, V O and SS it is evident, that the V O is not only an acceptor, which would kill any free electron but is also below the energy level of the SS, which would therefore intercept any surface electrons before it got the chance to get to the V O . This is further supported by the fact that there is no correlation between the V O and the degradation for the samples annealed at 600 °C. There, the SS line looks as correlated in a very good way. The SS trend is not well correlated for the samples annealed at 800 °C. However, taking account that the surface effects are responsible for the photocatalytic degradation we notice, that for the 800 °C samples another surface-bound feature is visible in the luminescence spectra -the SBX. If we now combine the SBX and SS lines, we get a very good correlation with the degradation trend, except for the sample A. In the case of this sample, we can assume that the much lower degradation efficiency is related to the calcination and loss of porosity, resulting in a significant loss of surface area. In order to get more qualitative results, enabling comparison with other approaches, we recalculated the degradation from percent to actuall mass. The typical photocatalytic procedure utilized a 50 mL solution of methylene blue with 50mg/L, which gives 7.82 • 10 -8 moles MB in the volume used, V = 50 ml. Analyses of the deposited ZnO material indicated that 1 µm of it weighs in the range of 2-77 mg depending on the annealing temperature and deposition parameters. The recalculated values in moles of degraded MB per mass of the ZnO used are shown in Table . Since the obtained efficiencies are competitive to the nanoparticle material efficiencies at much less mass required, we can conclude that ZnO thin films obtained by magnetron sputtering act as highly efficient photocatalysts for the degradation of aqueous pollutants.