Polymer nanoimprinting using an anodized aluminum mold for structural coloration

ECS Solid State Letters

2015

Ordered anodic porous alumina with large-scale periodicity was fabricated via phosphonoacetic acid anodizing. Aluminum specimens were anodized in a 0.1-0.9 M phosphonoacetic acid solution under various electrochemical operating conditions, and optimum anodizing at 205-225 V exhibited self-ordering growth of the porous alumina. These self-ordering voltages during phosphonoacetic acid anodizing filled an undiscovered vacant region in the linear relationship between the self-ordering voltage and the cell diameter. The nanostructured aluminum surface formed via self-ordering phosphonoacetic acid anodizing produced a bright structural coloration with a visible light wavelength of 500-700 nm, which is useful for optical nanoapplications. © The Author(s) 2015. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives 4.0 License (CC BY-NC-ND, http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial reuse, distribution, and reproduction in any medium, provided the original work is not changed in any way and is properly cited. For permission for commercial reuse, please email: oa@electrochem.org. [DOI: 10.1149/2.0021508ssl] All rights reserved. Self-ordered anodic porous alumina possesses a well-defined periodic porous structure with numerous nanopores that have high aspect ratios. [1][2][3] This characteristic nanoporous material is widely used for various novel nanoapplications, including electronic, optical, and sensing devices. [4][5][6][7][8][9][10][11][12] Ordered porous alumina can be fabricated by electrochemical anodizing in several acidic electrolyte solutions under appropriate experimental conditions such as concentration and applied voltage. The periodical size of the obtained ordered porous alumina, defined as the "cell size" or "interpore distance", is typically determined by the electrolyte species used.2,3,13 In self-ordered anodizing, the regularity of the pore arrangement in the porous structure can be accurately determined by a quantitative analysis based on Fourier transformation.14-19 Sulfuric, oxalic, and phosphoric acids were found early and have been commonly used as the standard self-ordering electrolytes to date. 13,20,21 However, the cell size of these ordered porous alumina is limited to the following narrow nanometer-scale regions: 50-60 nm in sulfuric acid, 100 nm in oxalic acid, and 405-500 nm in phosphoric acid.13 Therefore, the identification of novel electrolytes for self-ordered porous alumina with different cell sizes has been a recent challenge to extensively expand the nano-periodicity. Additional dicarboxylic acids with a large molecular structure, malonic and tartaric acids, for the fabrication of anodic porous alumina were reported by Ono et al., and self-ordering was achieved by anodizing with these acids for 300 and 500 nm intervals, respectively. Particularly, etidronic acid anodizing exhibited large-scale self-ordering behavior measuring 530-670 nm in cell diameter. Eti...

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

Self-Ordered Aluminum Anodizing in Phosphonoacetic Acid and Its Structural Coloration

Takenaga

ECS Solid State Letters

2015

“…The self-ordering voltage is determined and limited by the electrolyte species used, and the use of several electrolytes such as sulfuric (U s = 19-25 V) [6,7], oxalic (40 V) [7,29,30], selenic (42-48 V) [31][32][33], malonic (120 V) [34], phosphoric (160-195 V) [35,36], tartaric (195 V) [34], phosphonoacetic (205-225 V) [36], and etidronic acids (210-270 V) [38,39] have been reported to date through the optimum exploration for the self-ordering of porous alumina. Therefore, highly ordered porous alumina possessing a required cell diameter can be obtained by the choice of an optimal electrolyte solution and anodizing conditions.…”

Section: Introductionmentioning

confidence: 99%

Self-ordered Porous Alumina Fabricated via Phosphonic Acid Anodizing

Akiya

et al. 2016

Electrochimica Acta

Self Cite

Self-ordered periodic porous alumina with an undiscovered cell diameter was fabricated via electrochemical anodizing in a new electrolyte, phosphonic acid (H 3 PO 3 ). High-purity aluminum plates were anodized in phosphonic acid solution under various operating conditions of voltage, temperature, concentration, and anodizing time. Phosphonic acid anodizing at 150-180 V caused the self-ordering behavior of porous alumina, and an ideal honeycomb nanostructure measuring 370-440 nm in cell diameter was successfully fabricated on the aluminum substrate. Conversely, disordered porous alumina grew at below 140 V, and anodizing at above 190 V caused local thickening due to oxide burning. Two-step phosphonic acid anodizing allows the fabrication of high aspect ratio ordered porous alumina. HPO 3 2-anions originated from the electrolyte were incorporated into the porous oxide during anodizing. Consequently, a double-layered porous alumina consisting of a thick outer layer containing incorporated HPO 3 2-anions, and a thin inner layer without anions was constructed via phosphonic acid anodizing.

“…Notably, the hexagonal cells of the porous oxide are self-ordered during anodizing when aluminum is anodized in the appropriate acidic electrolyte solutions under the appropriate electrochemical conditions, and highly ordered porous oxides with an ideal cell arrangement can be easily fabricated [17,18]. For self-ordering of the porous alumina, several appropriate acidic electrolytes (i.e., sulfuric (H 2 SO 4 ) [19,20], selenic (H 2 SeO 4 ) [21,22], oxalic (HOOC-COOH) [23][24][25], malonic (HOOC-CH 2 -COOH) [26][27][28], phosphoric (H 3 PO 4 ) [18,29,30], tartaric (HOOC-(CHOH) 2 -COOH) [27], phosphonoacetic ((HO) 2 P(O)CH 2 COOH)) [31], and etidronic (CH 3 C(OH)[PO(OH) 2 ] 2 ) acid [32,33]) have been previously reported. In addition, additional acidic electrolytes and the use of organic solvents have also been reported by several research groups for novel porous alumina with different nanomorphologies [34][35][36][37][38][39].…”

Section: Introductionmentioning

confidence: 99%

Fabrication of a novel aluminum surface covered by numerous high-aspect-ratio anodic alumina nanofibers

Nakajima

Applied Surface Science

et al. 2015

Self Cite

The formation behavior of anodic alumina nanofibers via anodizing in a concentrated pyrophosphoric acid under various conditions was investigated using electrochemical measurements and SEM/TEM observations. Pyrophosphoric acid anodizing at 293 K resulted in the formation of numerous anodic alumina nanofibers on an aluminum substrate through a thin barrier oxide and honeycomb oxide with narrow walls. However, long-term anodizing led to the chemical dissolution of the alumina nanofibers. The density of the anodic alumina nanofibers decreased as the applied voltage increased in the 10 to 75 V range. However, active electrochemical dissolution of the aluminum substrate occurred at a higher voltage of 90 V.Low temperature anodizing at 273 K resulted in the formation of long alumina nanofibers measuring several micrometers in length, even though a long processing time was required due to the low current density during the low temperature anodizing. In contrast, high temperature anodizing easily resulted in the formation and chemical dissolution of alumina nanofibers. The structural nanofeatures of the anodic alumina nanofibers were controlled by choosing of the appropriate electrochemical conditions, and numerous high-aspect-ratio alumina nanofibers (>100) can be successfully fabricated. The anodic alumina nanofibers consisted of a pure amorphous aluminum oxide without anions from the employed electrolyte.