Synthesis of nano-AgI arrays and their optical properties
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Lide Zhang Institute of Solid State Physics, Chinese Academy of Science, Hefei 230031, People’s Republic of China (Received 1 December 2000; accepted 15 January 2001)
Nano-AgI arrays were synthesized by electrochemical double liquor deposition in ordered porous alumina membrane. On the basis of the analysis of x-ray diffraction patterns, the assembly of nano-AgI/Al2O3 is a mixture of a cubic zinc blende type ␥–AgI and a hexagonal wurtzite type –AgI. The visible–ultraviolet optical absorption measuring showed that the assembly only had an absorption edge at 2.82 eV and exhibited the optical features of a semiconductor with a direct band gap. The absorption edge of the assembly was shifted to a shorter wavelength compared with pure ␥–AgI and a longer wavelength compared with pure –AgI. We believed that the change of the absorption edge of the assembly is due to the mixture of ␥–AgI and –AgI.
Ordered nanostructure materials have been attracting more and more interest recently, because of both their fundamental importance and the wide range of potential applications in nanodevices. However, it is still a challenge to synthesize aligned and well-distributed nanoparticle arrays. Anodic alumina possesses uniform and parallel porous structures and hence has been used as an ideal template to prepare ordered nanoparticles arrays.1 Electrochemical synthesis using a porous alumina template is one of the most efficient methods for the growth of nanoparticles because the growth occurs almost exclusively normal to the substrate surface.2 In this paper, we prepared assemblies of nano-AgI particles with porous alumina, for which nano-AgI particles are located in the ordered channels of alumina by electrochemical double liquor deposition (EDLD),3 and their optical features were investigated. The porous alumina membrane with ordered channels arrays was prepared from high-purity (99.999%) aluminum foil in 0.3 M H2SO4 by anodization.4 The anodizing voltage was 20 V, and the temperature of the electrolyte was kept constant at 5 °C. After the 12 h anodization, the specimen was immersed in a mixture of 6 wt% H3PO4 and 1.8% H2CrO4 at 60 °C for 12 h to remove the
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J. Mater. Res., Vol. 16, No. 4, Apr 2001 Downloaded: 14 Mar 2015
alumina layers. Then, the aluminum foil was anodized again for 12 h under the same anodization conditions. At the bottom of the alumina membrane existed the remaining aluminum layer, and a barrier layer of alumina existed between porous alumina and the aluminum layer. The aluminum layer was removed in 1 M CuCl2 solution, and the barrier layer was removed by floating the alumina membrane on the surface of 5% H3PO4. A porous alumina membrane with ordered holes array was prepared. The resulting porous alumina membrane was adhered to a hole (with diameter approximately 1 cm) located between two solution containers.3 One container was filled with 0.1 M AgNO3 solution, while the other was filled with 0.1 M KI so
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