Quantitative investigation in the influence of oxalic impurities on photoluminescence properties of porous AAOs

Anodic alumina oxides (AAOs) prepared in oxalic acid (H2C2O4) solution at a constant voltage of 40 V were investigated by the techniques of temperature programmed desorption combined mass spectrograph (TPD-MS), thermogravimetric analysis (TGA), differential thermal analysis (DTA) and photoluminescence (PL). The results indicate that the desorption of H2O, CO and CO2 and the decomposition of H2C2O4 which led to the weight loss of AAOs samples occurred below 400 °C, while the water desorption was the main reason for weight loss. In the temperature range of 400–900 °C, a small quantity of aluminum oxalate (Al2(C2O4)3) decomposed and gave birth to CO and CO2, during this process CO became the major product. The drastic decompositions of aluminum carbonate (Al2(CO3)3) and Al2(C2O4)3 took place near 930 °C, which produced a large amount of CO2. The amount of (C2O4)2− embedded in bulk AAOs was calculated versus the total weight of AAOs film, and the PL intensity of AAOs was correlated to the doping of oxalic acid radical. The above results may have great significance in the better application of AAOs as matrix of photonic crystals.