Anodized template

Figure 6.16 illustrates the correlation between the graded ITO thickness and the EL peak position. The EL peak of the device shows a clear blue shift from 586 to 547 nm as the thickness of the interposed ITO increases from 20 to 65 nm. Likewise, there is a blue shift in EL spectra from 547 to 655 nm when the ITO layer thickness increases from 65 to 175 nm. It demonstrates an easier device fabrication route for multicolor OLED displays using an anode template with a graded ITO thickness. 

Imai H, Takei Y, Shimizu K, Matsuda M, Hirashima H (1999) Direct preparation of anatase Ti02 nanotubes in porous alumina membranes. J Mater Chem 9 2971-2972 Michailowski A, A1 Mawlawi D, Cheng GS, Moskovits M (2001) Highly regular anatase nanotubule arrays fabricated in porous anodic templates. Chem Phys Lett 349 1-5 Jung JH, Kobayashi H, van Bommel KJC, Shinkai S, Shimizu T (2002) Creation of novel helical ribbon and double-layered nanotube Ti02 structures using an... 

Michailowski A, Al-Mawlwai D, Cheng GS, Moskovits M (2001). Highly regular anatase nanotubule arrays fabricated in porous anodic templates. Chem Phys Lett 349 1-5... 

A very important recent application is to use aluminized membranes as a mask for physical vapor deposition. In these cases the membrane is either attached to the substrate or a film of aluminum (typically a few microns thick) is grown on a substrate such as Si. This is followed by the anodic oxidation process to convert the aluminum film to an anodized template. The growth process is either physical... 

Routkevitch D, Bigioni T, Moskovits M, Xu JM (1996) Electrochemical fabrication of CdS nanowire arrays in porous anodic aluminum oxide templates. J Phys Chem 100 14037-14047... 

Li N.C., Martin C.R. A high-rate, high-capacity, nanostructured Sn-based anode prepared using sol-gel template synthesis. J Electrochem. Soc.2001 148(2) A164-70. 

Over the past few years, a large number of experimental approaches have been successfully used as routes to synthesize nanorods or nanowires based on titania, such as combining sol-gel processing with electrophoretic deposition,152 spin-on process,153 sol-gel template method,154-157 metalorganic chemical vapor deposition,158-159 anodic oxidative hydrolysis,160 sonochemical synthesis,161 inverse microemulsion method,162 molten salt-assisted and pyrolysis routes163 and hydrothermal synthesis.163-171 We will discuss more in detail the latter preparation, because the advantage of this technique is that nanorods can be obtained in relatively large amounts. 

The deposition of nanostructured Ti02-based material directly on glass is expected to achieve enhanced photocatalysis and mechanical strength. Sputtering and a combination of sputtering and sol-gel techniques seem to be the most adequate for such a purpose [91,97,98], In the latter case, porous alumina Trims on glass formed by anodizing sputter-deposited A1 layers were used as templates in the successive sol-gel process. 

Various nanoporous AAO membranes have been obtained by varying different parameters such as applied voltage, temperature of electrolyte, electrolytic concentration and speed of rotation of electrolyte in two step anodization process. SEM analysis performed for evaluation of results. The relationship between pore size and variation of different parameters obtained. The synthesized membranes have been used as template for the synthesis of carbon nanotubes of different nano dimensions. 

For the anodic substitution of unactivated CH-bonds, some fairly selective reactions for tertiary CH-bonds in hydrocarbons and y—CH-bonds in esters or ketones are available [85-87]. However, in some cases, a better control of follow-up oxidations remains to be developed. Chemically, a number of selective reactions are available, such as the ozone on silica gel for tertiary CH-bonds [88], the Barton or Hoffmann-LoefHer-Freytag reaction for y-CH-bonds [89], and for remote CH-bonds, Cprop)2NCl/H [90, 91], photochlorination of fatty acids adsorbed on alumina [92] or template-directed oxidations [93]. 

Anodically grown aluminum oxide (AI2O3) has also been used extensively as a template [3,32-37]. When grown on high-purity aluminum, this material has a hexagonal pattern of cylindrical pores, which extend through the thickness of the alumina (Fig. 1C and ID). These microporous alumina films can be removed from the substrate A1 metal and collected as a freestanding membrane [37,38]. 

A very early use of anodic alumina as a template involved colonization of the alumina by depositing nanometals in the pores [39]. Somewhat later, Kawai and Ueda templated cobalt and nickel in alumina by electrodeposition [40]. Other metals were deposited by Andersson et al. [41] and Patel et al. [42]. The use of anodic alumina as a template increased after Furneaux et al. developed a convenient voltage-reduction method for detaching the porous anodized alumina from the underlying aluminum [38]. 

Alumina nanotubes have been prepared by the anodic oxidation of aluminum [41] the resulting tubes have one-dimensional channels with uniform diameters of 5nm and lengths of 50-100 nm. An alumina membrane with a highly ordered nanohole array in 50-100 nm diameter has also been synthesized by long-period anodization thus these local alumina nanotubes have been tried as a template for metal nanowire formation. 

Metal oxide nanotubes have been synthesized by a diverse variety of fabrication routes. For example titania nanotubes, and nanotube arrays, have been produced by deposition into a nanoporous alumina template [48-51], sol-gel transcription using organo-gelators as templates [52,53], seeded growth [54], hydrothermal processes [55-57] and anodic oxidation [58-65]. 

It should be mentioned that alternative possibilities to prepare similar membranes include the use of a porous alumina membrane as matrix, with the titania nanotubes grown in the channels. Nanoporous alumina membranes are commercial products, also synthesized by anodic oxidation. The commercial Whatman Corporation anodic membrane has holes of about 20-nm diameter at the top of the membrane and about 200-nm diameter at the bottom of membrane. Within these pores Ti02 nanotubes fabricated by template synthesis and water vapour hydrolysis could be grown, but non-uniform membrane characteristics are obtained due to the non-uniform pores of the commercial alumina... 

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