Controlled Fabrication of Multitiered Three‐Dimensional Nanostructures in Porous Alumina

Ho, Audrey Yoke Yee; Gao, Han; Lam, Yee Cheong; Rodríguez, Isabel

doi:10.1002/adfm.200800061

Cited by 61 publications

(40 citation statements)

References 23 publications

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“…[17] The biofunctionalization of 3D ordered porous nanostructures with high surface areas, large pore volume, and narrow pore-size distribution provides one efficient avenue for meeting these requirements. [18] Herein, a novel biofunctionalized 3D ordered nanoporous SiO 2 film with streptavidin is developed on a glass slide for preparation of high efficient chemiluminescent (CL) immunosensor.…”

Section: Introductionmentioning

confidence: 99%

Streptavidin‐Functionalized Three‐Dimensional Ordered Nanoporous Silica Film for Highly Efficient Chemiluminescent Immunosensing

Yang

Xie

Liu

et al. 2008

Adv Funct Materials

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A novel biofunctionalized three‐dimensional ordered nanoporous SiO2 film is designed for construction of chemiluminescent analytical devices. The nanoporous SiO2 film is prepared with self‐assembly of polystyrene spheres as a template and 5‐nm SiO2 nanoparticles on a glass slide followed by a calcination process. Its functionalization with streptavidin is achieved by using 3‐glycidoxypropyltrimethoxysilane as a linker. Based on the high‐selectivity recognition of streptavidin to biotin‐labeled antibody a novel immunosensor is further constructed for highly efficient chemiluminescent immunoassay. The surface morphologies and fabrication processes of both the biofunctionalized film and the immunosensor are characterized using scanning electron microscopy, atomic‐force microscopy, X‐ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy. The three‐dimensional ordered nanopores have high capacity for loading of streptavidin and antibody and promote the mass transport of immunoreagents for immunoreaction, thus the resulting chemiluminescent immunosensor shows wide dynamic range for fast immunoassay, and good reproducibility and stability. Using carbohydrate antigen 125 (CA 125) as a model, the highly efficient chemiluminescent immunosensing shows a linear range of three orders of magnitude, from 0.5 to 400 U mL−1. This work provides a biofunctionalized porous nanostructure for promising biosensing applications.

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Section: Introductionmentioning

confidence: 99%

Streptavidin‐Functionalized Three‐Dimensional Ordered Nanoporous Silica Film for Highly Efficient Chemiluminescent Immunosensing

Yang

Xie

Liu

et al. 2008

Adv Funct Materials

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“…Non-steady-state formation of branched pores by potential reduction was systematically investigated by Ho and coworkers [159]. The authors fabricated three-dimensional (3D) two and three-tiered branched AAOs by stepping down anodizing potential for each anodizing step while thinning of the barrier layer is performed after each step; AAOs with the first tier having an average pore diameter of 285 nm branching into four 125 nm sub-pores in the second-tier and four 55 nm sub-pores in the third tier (Fig.…”

Section: Potential Reductionmentioning

confidence: 99%

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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confidence: 99%

“…20 Ho et al fabricated a multi-tiered branched PAA film consisting of an array of big pores branching into 2-4 smaller pores in succeeding tiers, by sequentially stepping down the anodization potential while etching the barrier layer after each step. 22 Meng et al 24,25 and Zaraska et al 26 attempted to produce hierarchical PAA films with root-like pore channels by reducing the anodizing potential by a factor of 1/ √ n(n = 2, 3) in an oxalic acid solution from 72 V to 50 V 24 or from 60 V to 30 V 26 to increase the pore cell numbers. However, most of the previous works could only fabricate PAA films with decreasing pore size.…”

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confidence: 99%

“…Alternatively, several studies reported another type of 3D porous alumina films that consisted of two to four segments with stepwise changes in pore diameters. [20][21][22][23] For instance, Krishnan et al reported a PAA film whose pore diameters changed in a stepwise manner from 55 to 85 nm or vice z E-mail: chusongz@iwate-u.ac.jp versa, via two-step anodization in oxalic and phosphoric acid solutions, assisted by an interface lithography process.20 Ho et al fabricated a multi-tiered branched PAA film consisting of an array of big pores branching into 2-4 smaller pores in succeeding tiers, by sequentially stepping down the anodization potential while etching the barrier layer after each step.22 Meng et al 24,25 and Zaraska et al 26 attempted to produce hierarchical PAA films with root-like pore channels by reducing the anodizing potential by a factor of 1/ √ n(n = 2, 3) in an oxalic acid solution from 72 V to 50 V 24 or from 60 V to 30 V 26 to increase the pore cell numbers. However, most of the previous works could only fabricate PAA films with decreasing pore size.…”

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confidence: 99%

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Facile Fabrication of Ordered Multi-Tiered Hierarchical Porous Alumina Nanostructures with Multiple and Fractional Ratios of Pore Interval toward Multifunctional Nanomaterials

Kure‐Chu

Osaka

Yashiro

et al. 2016

ECS J. Solid State Sci. Technol.

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Conventional nanoporous anodic alumina films are composed of one-tiered pore arrays that can only render to one-dimensional (1D) nano-structures if they are used as nano-templates. Hence, three-dimensional (3D) nanoporous alumina films are desirable to dramatically increase the variety of nanostructures by template-fabrication for various potentially enhanced performances. Herein we report a facile approach to fabricate a variety of ordered multi-tiered 3D porous alumina nanostructures with multiple integer (m = 2, 3, 4, 5, 7, 9, and 10) and fractional ratios (n = 1/2 and 1/3) of the pore interval and pore diameter among different tiers on ITO/glass and Al sheets. The multi-tiered nanostructures and the pore interval ratios of the neighboring tiers can be accurately and independently controlled by a tailored multiple stepwise anodization, successively in appropriate acidic electrolytes of sulfuric, oxalic, and/or phosphoric solutions at designed voltages of 15-180 V, corresponding to the multiple or fractional ratios of pore interspacing. Moreover, the multi-tiered hierarchical nanoporous alumina films on ITO/glass substrates exhibited a lower transmittance compared with that of the single-tiered films with ordered cylindrical pores, which can be attributed to the diffusive reflection from the tier interface with different pore intervals. In past decades, porous anodic alumina (PAA) films have attracted considerable attention in both scientific and technical applications owing to the unique geometric structure with ordered hexagonal arrays of cylindrical nano-pores, similar to a nano-scaled honeycomb.1-4 In recent years, PAA nanostructures have been extensively used as a core nanotemplate to fabricate various one-dimensional (1D) functional nanostructures, such as nanowires 5-9 and nanotubes, 10-14 which can be used in a wide variety of applications including DNA and gas sensors, electro-chromic devices, light-emitting diodes, field emitters, super-capacitors, nano-electronic devices, and nano-generators. In order to facilitate the functional integration of nanostructures, template synthesis is evolving towards the fabrication of nanomaterials with increasing geometric complexity, i.e., going from two-dimensional (2D) to three-dimensional (3D) nanostructures. However, a major challenge in obtaining 3D nanostructures is the prior fabrication of ordered 3D nanoporous template with independently controllable size, spacing, position, and shape of the pore arrays as required for various applications.Many studies so far have attempted to fabricate various porous alumina nanostructures with variable pore diameters using tailored anodization methods assisted by chemical dissolution at different operating temperatures. Lee at al. reported first on the fabrication of ordered PAA films with variable pore diameters from 40 to 59 nm by combining mild anodization (MA) with hard anodization (HA) in oxalic acidic electrolytes. 15 This approach was further developed to achieve 3D PAA films with shaped pore geometries in periodic...

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Controlled Fabrication of Multitiered Three‐Dimensional Nanostructures in Porous Alumina

Cited by 61 publications

References 23 publications

Streptavidin‐Functionalized Three‐Dimensional Ordered Nanoporous Silica Film for Highly Efficient Chemiluminescent Immunosensing

Streptavidin‐Functionalized Three‐Dimensional Ordered Nanoporous Silica Film for Highly Efficient Chemiluminescent Immunosensing

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

Facile Fabrication of Ordered Multi-Tiered Hierarchical Porous Alumina Nanostructures with Multiple and Fractional Ratios of Pore Interval toward Multifunctional Nanomaterials

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