RESUMO
In this work, porous anodic aluminium oxide (AAO) films were fabricated by anodization in an electrolyte mixture with various concentration ratios of malonic acid and oxalic acid at room temperature. The photoluminescence (PL) properties of the AAO films before and after annealing from 300°C to 650°C in air or vacuum conditions were investigated, showing a strong PL band in the range 300-550 nm. We observed a weak PL in the AAO film formed in the malonic acid electrolyte, whereas the films fabricated using an electrolyte mixture showed strong PL emissions, exhibiting a maximum. The broad PL band was decomposed into three Gaussian sub-bands, in which the first two sub-bands could be attributed to the luminescence centre oxygen vacancies (F+ and F defect centres), whereas the latter transformed from malonic impurities and oxalic impurities. More interestingly, the redshift of the PL bands occurred with increasing oxalic acid concentration, and the PL wavelength and intensity could be modulated by varying the concentration ratios in the malonic acid and oxalic acid electrolyte mixture.
RESUMO
Ordered Co/AAO nano-array structures were fabricated by alternating current (AC) electrodeposition method within the cylindrical pores of anodic aluminum oxide (AAO) template prepared in oxalic acid electrolyte. The photoluminescence (PL) emission and photoabsorption of AAO templates and Co/AAO nano-array structures were investigated respectively. The results show that a marked photoluminescence band of AAO membranes occurs in the wavelength range of 350-550 nm and their PL peak position is at 395 nm. And with the increase in the deposition amount of Co nanoparticles, the PL intensity of Co/AAO nano-array structures decreases gradually, and their peak positions of the PL are invariable (395 nm). Meanwhile the absorption edges of Co/AAO show a larger redshift, and the largest shift from the near ultraviolet to the infrared exceeds 380 nm. The above phenomena caused by Co nano-particles in Co/AAO composite were analyzed.
