Controlled growth of branched channels by a factor of 1/√n anodizing voltage?

Shuoshuo, Chen; Ling, Zhiyuan; Hu, Xing; Li, Yi

doi:10.1039/b908815f

Cited by 32 publications

(15 citation statements)

References 25 publications

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“…Notice that conventional nanofabrication approaches cannot produce INAAFs with well-dened cylindrical nanopores from top to bottom due to the pore branching effect, which takes place when the anodisation voltage is switched as a result of the dependence between anodisation voltage and interpore distance. [36][37][38][39] Our approach, however, overcomes these limitations and enables the generation of multi-strati-ed INAAFs featuring well-dened cylindrical nanopores from top to bottom. Furthermore, taking advantage of the optical properties of NAA, we demonstrate that the formation process of INAAFs can be monitored in real-time and in situ by RIfS.…”

Section: Introductionmentioning

confidence: 99%

In situ monitored engineering of inverted nanoporous anodic alumina funnels: on the precise generation of 3D optical nanostructures

et al. 2014

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Herein, we present an innovative approach to generate a novel type of 3D optical nanostructures based on nanoporous anodic alumina (NAA), the so-called inverted nanoporous anodic alumina funnels (INAAFs). This electrochemical approach takes advantage of the differential dissolution rate of NAA with the annealing temperature, which enables the in-depth engineering of nanopores. The structural engineering of these 3D nanostructures is monitored in situ by reflectometric interference spectroscopy through changes in the effective optical thickness of NAA, making it possible to precisely control the formation of INAAFs in real-time. The resulting INAAFs are optical nanostructures featuring a stratified structure of well-defined cylindrical nanopores with increasing pore diameter from top to bottom. As a result of their geometric characteristics and optical properties, INAAFs are envisaged for replicating novel nanostructures and developing optical and photonic devices.

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Section: Introductionmentioning

confidence: 99%

In situ monitored engineering of inverted nanoporous anodic alumina funnels: on the precise generation of 3D optical nanostructures

et al. 2014

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“…Similar structures have been reported recently by Shuoshuo and coworkers. 4 The Mi-Ha AAO can be employed as a membrane for the fabrication of magnetic nanowire arrays. Wires were grown either in the hard or mild side of these membranes.…”

Section: Resultsmentioning

confidence: 99%

“…2 Mild anodization methods have several limitations such as long processing times, limited domain sizes, and fixed interpore distances. In recent years, researchers have expanded on these techniques so as to prepare a variety of structures including AAO membranes with Y-branching, 3,4 six-membered rings, 5 and triangular and rectangular shapes, 6 by altering the anodization conditions or by a preprocessing of the anode via lithography or an imprinting method (a summary of these results is presented in ESI †, Table S1). Additionally, a 'hard' anodization process, which has a fast film growth rate (50-100 mm h À1 ) and a range of interpore distances, has been reported by several research teams to minimize the limitations in processing seen in the production of conventional AAO templates.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of mild–hard AAO templates for studying magnetic interactions between metal nanowires

et al. 2010

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A combination of mild and hard anodization processes have produced mild-hard AAO templates with selectively opened pores. Functional interpore distances were increased by as much as 3 times compared to conventional AAO templates. Magnetic nanowires with larger interpore distances show reduced wire-wire interactions in nanowire arrays.The sequential application of mild and hard anodization techniques in the fabrication of porous alumina membranes allows one to decrease the number of continuous pores in anodized aluminium oxide (AAO) templates. Initially, standard mild anodization techniques were used to create porous templates with 100 nm interpore distances and 70 nm pore diameters. Hard anodization treatment on the same membrane then produced interpore distances of about 265 nm with diameters of 110 nm. At the interface between the two anodization steps, many of the mild-side pores were terminated to create a mild-hard membrane (Mi-Ha AAO) where the functional interpore distances were 200-300 nm. Growth (electrodeposition) of nickel and cobalt nanowires in the various pore structures of the mild and hard sides of the Mi-Ha AAO templates allows one to probe magnetic interactions between nanowires and compares them to wires grown in standard mild templates (Mi-AAO). The magnetic properties of nanowires in Mi-Ha AAO and Mi-AAO showed distinct differences in the squareness of hysteresis loops and coercivity both as a function of pore structure and magnetic component. In general, the squareness of the hysteresis loops increased with aspect ratio and greater interpore distance. Coercivity also showed an increase with aspect ratio, but varied differently with interpore distance for Ni and Co. These various magnetic behaviors are discussed with respect to crystalline structure, morphology, and interactions of adjacent sets of nanowires.

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“…However, this equal-area model for the growth of Y-or n-branched pore channels was argued by Shuoshuo et al [158]. The authors claimed that it is impossible to control arbitrarily the growth of branched pore channels as a 1 0 n structure, because the growth of some n-branched pores (e.g., n = 2; Y-branched pores) could not be a steady process and thus such branched pores could not be obtained uniform in a large scale.…”

Section: Potential Reductionmentioning

confidence: 96%

“…Based on theoretical consideration on the geometric arrangement of the branched pores, Shuoshuo et al proposed that close-packed hexagonal arrangement of oxide cells can be achieved only for the potential reduction by the factors of 1= ffiffi ffi 3 p , 1= ffiffi ffi 4 p and their common multiples and powers (i.e., n = 3, 4, 9, 12, …) (see Fig. 4.14); otherwise, the number of branched pores cannot be grown proportionally from each of the stem pores [158].…”

Section: Potential Reductionmentioning

confidence: 98%

Structural Engineering of Porous Anodic Aluminum Oxide (AAO) and Applications

Lee

2015

Nanoporous Alumina

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Porous anodic aluminum oxide (AAO) films can be conveniently produced by anodization of aluminum. Porous oxide layer formed on aluminum contains a large number of mutually parallel pores. Each cylindrical nanopore and its surrounding oxide constitute a hexagonal cell aligned normal to the metal surface. Under proper conditions, the oxide cells are self-organized to form a hexagonally close-packed structure. The novel and tunable structural features of porous AAOs have been intensively exploited for templated synthesis of a variety of functional nanostructures and also for fabrication of nanodevices. On the other hand, porous AAOs with modulated pores may provide an additional degree of freedom in templated synthesis. In addition, they can be used as model systems for systematically investigating structure-property relations of nanostructured materials. Based on the anodization techniques developed recently, one can fabricate porous AAOs with tailor-made internal pore structures. This chapter is devoted to conveying the most recent advances in structural engineering of porous AAOs and nanotechnology applications. In order to provide context, a brief description is given of the general structure and fundamental electrochemical processes associated with pore formation. Subsequently, two common anodizing techniques (i.e., mild and hard anodizations) that have been explored for nanotechnology applications are discussed. Next, various nanostructuring approaches for custom-designed porous AAOs are reviewed. The chapter covers the properties of porous AAOs derived from structural engineering and their applications to various nanotechnology researches and finally presents the challenges and future prospects.

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Controlled growth of branched channels by a factor of 1/√n anodizing voltage?

Cited by 32 publications

References 25 publications

In situ monitored engineering of inverted nanoporous anodic alumina funnels: on the precise generation of 3D optical nanostructures

In situ monitored engineering of inverted nanoporous anodic alumina funnels: on the precise generation of 3D optical nanostructures

Synthesis of mild–hard AAO templates for studying magnetic interactions between metal nanowires

Structural Engineering of Porous Anodic Aluminum Oxide (AAO) and Applications

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