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The optical behaviour of nanostructured nanoporous alumina anodic oxide thin film (AAOF) on sapphires was investigated. The AAOF was intentionally nanostructured by varying the nanopore diameters, as a result, the distance between neighbour pores decreased. The resultant nanostructured nanoporous patterns cause super-paramagnetism and the excited photoluminescence splits into two wavelengths of near blue and green peaks. This light modulation could be related to the super-paramagnetic magnetisation of the patterns upon in nanoscale. With increasing the nanopore size by the reaming method, the super-paramagnetic susceptibility first decreases and then increases. Once the super-paramagnetic susceptibility deviates from that of the as-received AAOF, the green peak would be excited. On the other hand, strong super-paramagnetism facilitates excitation of the blue peak.
Date of Publication: July 2011