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Using electrochemical deposition, Ni–P nanorod arrays with a series of aspect ratios have been successfully fabricated in the pores of anodic aluminum oxide (AAO) membranes. The aspect ratio of Ni–P nanorods was controlled by the deposition time. The morphologies were analyzed by scanning electron microscopy and transmission electron microscopy. The dependence of the optical absorbance upon the aspect ratio was studied by UV–vis spectra. The results show that the absorbance increases in visible region and decreases rapidly in ultraviolet region as the aspect ratio of nanorods increases, which qualitatively agree with the prediction of Maxwell–Garnett (MG) theory and the simulation based on the Mie scattering theory, respectively. The dependence of photoluminescence emission (PL) spectra upon the aspect ratio is also obtained. These investigations show that the optical properties of nano-array composite structure can be modified by changing the aspect ratio of nanorods. [ABSTRACT FROM AUTHOR]

Ni–P/AAO nano-array composite structure assemblies with Ni and P grown in the pores of anodic aluminum oxide (AAO) membranes were prepared by electroless deposition. The results of SEM, TEM and SAED show that as-deposited Ni–P nanowires have an amorphous structure and a few nanocrystallites form after annealing. The optical absorption spectra reveal that, as the annealing temperature increases, the absorption band edge of the Ni–P/AAO composite structure is obviously blue shifted, which is attributed to a decrease of the internal pressure after heat treatment. Meanwhile, the annealed Ni–P/AAO nano-array composite structure exhibits the absorption behavior of a direct band gap semiconductor. Details of this behavior are discussed together with the implications for potential device applications. [ABSTRACT FROM AUTHOR]

Porous anodic alumina membranes (AAMs) were prepared in oxalic acid and then carried on an etch-treatment in phosphoric acid. Using the etch-treatment the photoluminescence (PL) intensity of AAMs increases by a factor of 1/3. The effect of etch-treatment upon the intensity and peak position of photoluminescence (PL) spectra was investigated. It was found that the intensity of the photoluminescence (PL) spectra increased with the etching time increasing. A PL spectrum can be divided into two subbands with the peak at 434 and 460 nm, respectively. As the etching time prolongs, the intensity of the peak of 434 nm subband increases and that of the 460 nm subband rises firstly and then decreases. It can be explained by that two luminescence centers (F and F+ centers) coexist in AAMs. F centers are concentrated in the surface layer and F+ centers are enriched in the depth of pore wall. The increment of the PL intensity comes from the contribution of F+ photoluminescence centers concentrated in the depth of pore wall in AAMs. This work will be beneficial to improving the photoluminescence intensity and understanding the light-emitting mechanisms for related materials. [ABSTRACT FROM AUTHOR]