Name: simultaneous multi-surface anodizations and stair-like reverse biases detachment of anodic aluminum oxides in sulfuric and oxalic acid electrolyte
Uploaded: 2017-10-05T14:00:00
Description: Watch this Scientific Journal Video about Simultaneous Multi-surface Anodizations and Stair-like Reverse Biases Detachment of Anodic Aluminum Oxides in Sulfuric and Oxalic Acid Electrolyte at JoVE.com

The authors have nothing to disclose.

Please be aware of all the related materials safety data sheets (MSDS) before beginning. In spite of the eco-friendly nature of this protocol, a few acids and oxidizers are used in the corresponding procedures. Also, use all the proper personal protective equipment (lab coat, gloves, safety glasses, etc.).
1. Preparation of Solution
Note: After complete sealing of the solution-containing vessel, vigorous magnetic stirring was applied to all the solutions at r...

In this paper, we successfully demonstrated a facile, high yield, and environmentally clean method to fabricate nanoporous AAOs through SMSA and SRBs-detachment, which could be repeated to the same Al substrate for significantly enhancing mass-producibility as well as usability of limited natural resource. As shown in the flow chart of Figure 1a, our AAO fabricating strategy is based on the conventional two-step anodization, which was modified on multi-surfaces situation. Individual procedur...

AAOs which were formed by anodizing Al substrate in an acidic electrolyte, have attracted great interest in diverse fundamental science and industry, for example, hard templates for nanotubes/nanowires1,2,3,4,5, energy storage devices6,7,8,9, bio-sensing10,11, filtering applications12,13,14, masks for evaporating and/or etching15,16,17, and capacitive humidity sensors18,19,20,21,22, owing to their self-ordered honeycomb structure, high aspect ratio of nanopores, and superior mechanical properties23. For applying the nanoporous AAOs to these various applications, they should be freestanding forms with a highly and long-range ordered array of nanopores. In this regard, strategies for obtaining AAOs must consider both formation (anodizing) and separation (detaching) procedures.
In the viewpoint of the AAO formation, mild anodization (hereafter referred as MA) was well established under sulfuric, oxalic, and phosphoric acidic electrolytes23,24,25,26,27. However, MA processes exhibited low-yields of AAO fabrication due to their slow growth rate depending on relatively low intensities of anodic voltages, which would further deteriorate through a two-step MA process for improving nanopores&#39; periodicity28,29. Thus, hard anodization (HA) techniques were proposed as alternatives of MA by applying higher anodic voltages (oxalic/sulfuric acid electrolyte) or using more concentrated electrolyte (phosphoric acid)30,31,32,33,34,35,36,37,38,39,40. HA processes show distinct enhancements of growth rates as well as periodic arrangements, whereas resulting AAOs became more fragile, and the density of nanopores were reduced30. In addition, an expensive cooling system is required for dissipating Joule&#39;s heating caused by high current density31. These results restrict the potential applicability of the AAOs via HA processes.
For separating an AAO from the corresponding surface of Al plate, selective chemical etching of the remaining Al substrate was most widely utilized in both the MA and HA processes using toxic chemicals, such as copper chloride35,39,41,42 or mercury chloride16,17,43,44,45,46,47,48,49. However, this method induces disadvantageous side effects, e.g., a longer reaction time proportional to the remaining thickness of the Al, contamination of AAO by heavy metal ions, harmful residues to human body/natural environments, and inefficient usage of valuable resources. Therefore, many attempts have been made for realizing direct detachment of an AAO. Although both cathodic voltage delamination50,51 and anodic voltage pulse detachment7,41,42,52,53,54,55 present a merit that the remaining Al substrate can be reused, the former technique takes almost comparable time with those in chemical etching methods50. Notwithstanding clear reduction of the processing time, harmful and highly reactive chemicals, for examples butanedione and/or perchloric acid, were used as detaching electrolytes in the latter techniques55, where an additional cleaning procedure is needed because of the changing electrolyte between the anodizing and detaching procedure. Especially, the detaching behaviors and quality of the detached AAOs severely influence the thickness. In the case of the AAO with relatively thinner thickness, the detached one might contain cracks and/or apertures.
All the experimental approaches listed above have been applied to a &#34;single-surface&#34; of the Al specimen, excluding surface protecting/engineering purposes, and this feature of the conventional technologies exhibits critical limitations of the AAO fabrication in terms of yield as well as processibility, which also influences the potential applicability of the AAOs56,57.
To satisfy the increasing demands in the AAO-related fields in terms of facile, high yield, and green technological approaches, we previously reported on SMSA and direct detachment through SRBs under sulfuric56 and oxalic57 acid electrolyte, respectively. It is a well-known fact that plural AAOs can be formed on the multiple surfaces of the Al substrate immersed into acidic electrolytes. However, SRBs, a key distinction of our methods, enable the detachment of those AAOs from the corresponding multi-surfaces of the Al substrate in the same acidic electrolyte used for the SMSAs indicating mass-production, simplicity, and green technological characteristics. We would like to point out that SRBs-based detachment is an optimal strategy for plural AAOs fabricated by SMSAs56,57 and even valid for relatively thinner thicknesses of AAOs57 when compared with cathodic delamination (i.e., constant reverse bias) on single-surface51. Finally, a unit sequence consisting of the SMSAs sequentially combined with SRBs-based detachment can be applied repeatedly to the same Al substrate, avoiding complicated procedures and toxic/reactive chemicals, which reinforces the advantages of our strategies and also guarantees the efficient usage of natural resources.

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			<td height="21" style="height:21px;width:352px;">Sulfuric Acid &#62;98%</td>
			<td style="width:212px;">DUKSAN reagent</td>
			<td style="width:119px;">5950</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:352px;">Oxalic Acid Anhydrous, 99.5-100.2%</td>
			<td style="width:212px;">KANTO chemical</td>
			<td style="width:119px;">31045-73</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:352px;">Phosphoric Acid, 85%</td>
			<td style="width:212px;">SAMCHUN chemical</td>
			<td style="width:119px;">P0463</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:352px;">Perchloric Acid, 60%</td>
			<td style="width:212px;">SAMCHUN chemical</td>
			<td style="width:119px;">P0181</td>
			<td>Highly Reactive</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:352px;">Chromium(VI) Oxide</td>
			<td style="width:212px;">Sigma Aldrich</td>
			<td style="width:119px;">232653</td>
			<td>Strong Oxidizer</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:352px;">Ethanol, 95%</td>
			<td style="width:212px;">SAMCHUN chemical</td>
			<td style="width:119px;">E0219</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:352px;">Absolute Ethanol, 99.9%</td>
			<td style="width:212px;">SAMCHUN chemical</td>
			<td style="width:119px;">E1320</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:352px;">Double Jacket Beaker</td>
			<td style="width:212px;">iNexus</td>
			<td style="width:119px;">27-00292-05</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:352px;">Low Temperature Bath Circulator</td>
			<td style="width:212px;">JEIO TECH</td>
			<td style="width:119px;">AAH57052K</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:352px;">Programmable DC Power Supply</td>
			<td style="width:212px;">PNCYS</td>
			<td style="width:119px;">EDP-3001&#160;</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:352px;">Aluminum Plate, &#62;99.99%</td>
			<td style="width:212px;">Goodfellow</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:352px;">Platinum Cylinder</td>
			<td style="width:212px;">Whatman</td>
			<td style="width:119px;">444685</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:352px;">Pure &#38; Ultra Pure Water System (Deionized Water)</td>
			<td style="width:212px;">Human Science</td>
			<td style="width:119px;">Pwer II &#38; HIQ II</td>
			<td></td>
		</tr>
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simultaneous multi-surface anodizations and stair-like reverse biases detachment of anodic aluminum oxides in sulfuric and oxalic acid electrolyte

After reporting on the two-step anodization, nanoporous anodic aluminum oxides (AAOs) have been widely utilized in the versatile fields of fundamental sciences and industrial applications owing to their periodic arrangement of nanopores with relatively high aspect ratio. However, the techniques reported so far, which could be only valid for mono-surface anodization, show critical disadvantages, i.e., time-consuming as well as complicated procedures, requiring toxic chemicals, and wasting valuable natural resources. In this paper, we demonstrate a facile, efficient, and environmentally clean method to fabricate nanoporous AAOs in sulfuric and oxalic acid electrolytes, which can overcome the limitations that result from conventional AAO fabricating methods. First, plural AAOs are produced at one time through simultaneous multi-surfaces anodization (SMSA), indicating mass-producibility of the AAOs with comparable qualities. Second, those AAOs can be separated from the aluminum (Al) substrate by applying stair-like reverse biases (SRBs) in the same electrolyte used for the SMSAs, implying simplicity and green technological characteristics. Finally, a unit sequence consisting of the SMSAs sequentially combined with SRBs-based detachment can be applied repeatedly to the same Al substrate, which reinforces the advantages of this strategy and also guarantees the efficient usage of natural resources.

Flow chart of nth AAO fabricating sequence mainly consisting of two-step SMSAs, SRBs-detachment, and related chemical etching was presented schematically in Figure 1a. Each inset show a scanning electron microscope (SEM) image of the corresponding surface morphology at each individual procedure and a photograph taken immediately after SRBs-detachment. A schematic illustration after the total 5th repetition of the unit sequence e...

Watch this Scientific Journal Video about Simultaneous Multi-surface Anodizations and Stair-like Reverse Biases Detachment of Anodic Aluminum Oxides in Sulfuric and Oxalic Acid Electrolyte at JoVE.com

Simultaneous Multi-surface Anodizations and Stair-like Reverse Biases Detachment of Anodic Aluminum Oxides in Sulfuric and Oxalic Acid Electrolyte

A protocol for fabricating nanoporous anodic aluminum oxides via simultaneous multi-surfaces anodization followed by stair-like reverse biases detachments is presented. It can be applied repeatedly to the same aluminum substrate, exhibiting a facile, high-yield, and environmentally clean strategy.

After reporting on the two-step anodization, nanoporous anodic aluminum oxides (AAOs) have been widely utilized in the versatile fields of fundamental ...

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