Research reported in this publication was supported by the King Abdullah University of Science and Technology (KAUST).

CAUTION: Please consult all relevant material safety data sheets (MSDS) before use. Several of the chemicals used in these fabrications are acutely toxic and carcinogenic. Nanomaterials may pose additional hazards compared to their bulk counterparts. Please use all appropriate safety practices when performing a nanocrystal reaction, including the use of engineering controls (fume hood) and personal protective equipment (safety glasses, gloves, lab coat, full length pants, closed-toe shoes).
1. Preparations of aluminum templates
<ol>
	<li>Cleaning the aluminum discs
	<ol>
		<li>Wash the Al discs in a beaker with deionized (DI) water. Repeat 3 times.</li>
		<li>Hold the Al disc with tweezers and wash with acetone followed by isopropyl alcohol (IPA) and DI water.</li>
		<li>Place the Al discs in a beaker with acetone and sonicate for 10 min.</li>
	</ol>
	</li>
	<li>Electropolishing of aluminum discs
	<ol>
		<li>Prepare the electropolishing solution, 3 M perchloric acid in ethanol. Cool the electropolishing solution in a fridge at 4 &#176;C before use.</li>
		<li>Wash the Al discs in a beaker with DI water. Repeat 3 times.</li>
		<li>Grip the cleaned Al template with the dressing forceps and immerse it inside the beaker filled with electropolishing solution along with the platinum (Pt) mesh electrode. Keep the forceps out of the solution as much as possible.</li>
		<li>Stir the solution at 400 rpm.</li>
		<li>Connect the Al disc to the positive terminal and Pt to the negative terminal of the power supply. Apply a voltage of 20 V while the current is limited to 2 A.</li>
		<li>Polish the discs for 3 min and wash the discs with DI water.</li>
	</ol>
	</li>
</ol>
2. Hard anodization
<ol>
	<li>Preparing the cells
	<ol>
		<li>Wash the cell parts (copper plate, PDMS/rubber O rings, cell, Pt mesh cap) with DI water.</li>
		<li>Take the electropolished Al discs out of the DI water and place it on the cell holes with O-rings. Check carefully that there are no leaks.</li>
	</ol>
	</li>
	<li>Anodization
	<ol>
		<li>Fill the assembled cell with 0.3 M oxalic acid and place it on the cold plate at 4 &#176;C.</li>
		<li>Once the oxalic acid is between 2-5 &#176;C, apply 40 V for 20 min (mild anodization). Then, increase the voltage in steps of 0.1 V/s up to 140 V.</li>
		<li>Keep this voltage constant for 45 min. The anodized template will be a bright golden color.</li>
		<li>Open the cell and wash the Al disc with DI water and dry with nitrogen (N2).</li>
	</ol>
	</li>
</ol>
3. Preparation for deposition
<ol>
	<li>Removal of Al back
	<ol>
		<li>Prepare a copper solution with 0.1 M of CuCl2&#183;2H2O and 6 M of HCl.</li>
		<li>Place the anodized template in a cell (with a 10 mm hole diameter) with the back side facing upwards.</li>
		<li>Pour the copper solution and a magnetic stirrer into the cell and agitate at 300 rpm.</li>
		<li>After around 15 min, the solution becomes transparent. Replace it with fresh solution and agitate for 5 min more.</li>
		<li>Wash the discs with DI water and dry with N2.</li>
	</ol>
	</li>
	<li>Opening the pores
	<ol>
		<li>Place the sample (back side facing upwards) in a Petri dish on a pH strip.</li>
		<li>Deposit 10 wt% phosphoric acid to completely cover the membrane. Add more phosphoric acid every hour to avoid dryness.</li>
		<li>After 6.5 h, wash with DI water, and dry with N2.</li>
	</ol>
	</li>
	<li>Gold sputtering
	<ol>
		<li>Prepare the sputtering machine. Open the inert gas valve and vent the chamber.</li>
		<li>Tape the Al disc onto the sputter stage with the back side facing up.</li>
		<li>Adjust parameters to deposit 200 nm and run the profile.</li>
	</ol>
	</li>
</ol>
4. Deposition of nanowires
<ol>
	<li>Prepare a solution of 0.2 M of iron (II) sulfate, 0.16 M of boric acid and 0.05 M of L-ascorbic acid.</li>
	<li>Mount the Al membrane into the cell (15 mm diameter hole)</li>
	<li>Pour the solution into the cell and connect the source meter with the negative contact attached to the copper plate and the positive contact to the platinum mesh.</li>
	<li>Apply a constant current of 2.5 mA to start electrodeposition. The length of the nanowire is directly proportional to the electrodeposition time.</li>
</ol>
5. Membrane removal and washing of nanowires
<ol>
	<li>Gold etching
	<ol>
		<li>Break the membrane using a tweezer. Select small pieces (around 1 or 2 mm2).</li>
		<li>Prepare one or more small pieces for dry etching using reactive ion etching (RIE) equipment. Glue the pieces to a dummy wafer using lubricant, keeping the gold face up.</li>
		<li>Etch the gold in the RIE equipment for 2 min using the following parameters: T = 25 &#176;C, P = 150 W and argon flow rate = 25 cm3/min. Repeat in shorter cycles if some gold is still present.</li>
	</ol>
	</li>
	<li>Nanowire release
	<ol>
		<li>Prepare the chrome solution using 0.2 M of CrO3 and 0.5 M of H3PO4.</li>
		<li>Fill a 1.5 mL microtube tube with 1 mL of the chrome solution and the small pieces of membrane containing nanowires.</li>
		<li>Leave the solution working for 24 h at 40 &#176;C.</li>
		<li>When the nanowires are completely released, no black particles should be observed with the naked eye.</li>
		<li>Wash the nanowires by placing the microtube in a magnetic rack and replacing the chrome solution with 1 mL of ethanol.</li>
		<li>Repeat the washing process at least 10 times.</li>
	</ol>
	</li>
</ol>

<ol>
	<li>Mohammed, H., Moreno, J., Kosel, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Advanced+Fabrication+and+Characterization+of+Magnetic+Nanowires.">Advanced Fabrication and Characterization of Magnetic Nanowires.</a> Magnetism and Magnetic Materials. , (2018).</li><li>Alfadhel, A., Li, B., Zaher, A., Yassine, O., Kosel, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+magnetic+nanocomposite+for+biomimetic+flow+sensing.">A magnetic nanocomposite for biomimetic flow sensing.</a> Lab on Chip. 14, 4362-4369 (2014).</li><li>Fratila, R. M., Rivera-Fernandez, S., Jesus, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Shape+matters:+Synthesis+and+biomedical+applications+of+high+aspect+ratio+magnetic+nanomaterials.">Shape matters: Synthesis and biomedical applications of high aspect ratio magnetic nanomaterials.</a> Nanoscale. 7, 8233-8260 (2015).</li><li>Alnassar, M., Alfadhel, A., Ivanov, Y. P., Kosel, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Magnetoelectric+polymer+nanocomposite+for+flexible+electronics.">Magnetoelectric polymer nanocomposite for flexible electronics.</a> Journal of Applied Physics. 117, 17D711 (2015).</li><li>Contreras, M. F., Sougrat, R., Zaher, A., Ravasi, T., Kosel, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Non-chemotoxic+induction+of+cancer+cell+death+using+magnetic+nanowires.">Non-chemotoxic induction of cancer cell death using magnetic nanowires.</a> International Journal of Nanomedicine. 10, 2141-2153 (2015).</li><li>Yassine, O., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Highly+efficient+thermoresponsive+nanocomposite+for+controlled+release+applications.">Highly efficient thermoresponsive nanocomposite for controlled release applications.</a> Scientific Reports. 6, 28539 (2016).</li><li>Mart&#237;nez-Banderas, A. I., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Functionalized+magnetic+nanowires+for+chemical+and+magneto-mechanical+induction+of+cancer+cell+death.">Functionalized magnetic nanowires for chemical and magneto-mechanical induction of cancer cell death.</a> Scientific Reports. 6, 35786 (2016).</li><li>Shore, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrodeposited+Fe+and+Fe-Au+nanowires+as+MRI+contrast+agents.">Electrodeposited Fe and Fe-Au nanowires as MRI contrast agents.</a> Chemical Communications. 52, 12634-12637 (2016).</li><li>Garc&#237;a-Mart&#237;n, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Imaging+magnetic+vortices+by+magnetic+force+microscopy:+Experiments+and+modelling.">Imaging magnetic vortices by magnetic force microscopy: Experiments and modelling.</a> Journal of Physics D: Applied Physics. 37, 965 (2004).</li><li>Piraux, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Giant+magnetoresistance+in+magnetic+multilayered+nanowires.">Giant magnetoresistance in magnetic multilayered nanowires.</a> Applied Physics Letters. 65, 2484-2486 (1994).</li><li>Piraux, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Template-grown+NiFe/Cu/NiFe+nanowires+for+spin+transfer+devices.">Template-grown NiFe/Cu/NiFe nanowires for spin transfer devices.</a> Nano Letters. 7, 2563-2567 (2007).</li><li>Wang, Z., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spin-wave+quantization+in+ferromagnetic+nickel+nanowires.">Spin-wave quantization in ferromagnetic nickel nanowires.</a> Physical Review Letters. 89, 027201 (2002).</li><li>Wernsdorfer, W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measurements+of+magnetization+switching+in+individual+nickel+nanowires.">Measurements of magnetization switching in individual nickel nanowires.</a> Physical Review B. 55, 11552 (1997).</li><li>Kou, X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Memory+effect+in+magnetic+nanowire+arrays.">Memory effect in magnetic nanowire arrays.</a> Advanced Materials. 23, 1393-1397 (2011).</li><li>Mohammed, H., Vidal, E. V., Ivanov, Y. P., Kosel, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Magnetotransport+measurements+of+domain+wall+propagation+in+individual+multisegmented+cylindrical+nanowires.">Magnetotransport measurements of domain wall propagation in individual multisegmented cylindrical nanowires.</a> IEEE Transactions on Magnetics. 52, 1-5 (2016).</li><li>Goktas, N. I., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanowire+for+energy:+A+review.">Nanowire for energy: A review.</a> Applied Physics Reviews. 5, 041305 (2018).</li><li>Zongjie, W., Suwon, L., Kyo-in, K., Keekyoung, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanowire-Based+Sensors+for+Biological+and+Medical+Applications.">Nanowire-Based Sensors for Biological and Medical Applications.</a> IEEE Transactions on Nanobioscience. 15 (3), 186 (2016).</li></ol>

The authors have nothing to disclose.

As in any other nanomaterial production, high-quality solutions and materials are required in this protocol. Electropolishing and electrodepositing solutions can be reused several times. However, the anodization solution should only be used once and be freshly made. After removing the Al back, the membranes are extremely weak and can be broken if not handled carefully. The N2 should not be directly applied when drying the membranes. All processes prior to anodization are equally important for the self-ordering of pore structures. Surface impurities, pits, and scratches may lead to poorly ordered nanopores.
The thickness of the alumina membrane generated in step 2 is usually around 60&#160;&#181;m, much longer than the nanowire we require. If longer nanowires are needed, this protocol can be adapted to make thicker membranes by increasing the time of anodization. These nanopores can be used as templates for forming arrays of standing nanowires or released by a subsequent chemical removal of alumina structure. Furthermore, different metals can be electrodeposited using the same setup, including multisegmented nanowires15, by changing the solution and the applied current. Rate deposition would be different for each metal.
The main advantage of the anodization method presented is the high quality of the pores: constant diameter along tenths of micrometers, small diameter distribution, and high pore density. Further, this technique is efficient, economical, and highly reproducible. It can be done safely at ambient conditions in the general laboratory. Nanowires promise a lot in future energy conversion devices (including photovoltaics, thermoelectrics, and betavoltaics16) and as biological and medical sensors17. All of these applications will require extensive material and device development.

Cylindrical magnetic nanowires have attracted an enormous amount of interest in the last decade for a variety of promising applications. Nanowires are novel materials that possess unique properties, mainly due to a high aspect ratio and shape anisotropy1. Because of these properties, nanowires are considered unique systems and excellent model objects for a number of practical applications: flow sensors2, magnetic separation3, bio-inspired tactile sensors4, energy harvesting5, cancer treatments2,6, drug delivery7,8, and MRI contrast agents3,9. Nanowires are also considered ideal for other applications: magnetic force microscopy10, giant magnetoresistance11, spin transfer torque12,13, and data storage devices14,15.
In order to exploit these nanowires to their full advantage, a reproducible fabrication method that yields nanowires of high quality and specific properties is required. The anodization of aluminum produces self-organized, highly ordered cylindrical pores with controllable pore diameters. Because of this, AAO templates are preferred in nanotechnology applications over expensive lithographic techniques. Using these membranes as scaffolds, nanowires can be created by direct current (DC), alternating current (AC), or pulsed DC electrodeposition. Controlling the fabrication process of the membrane and the deposition of the nanowires, a wide range of magnetic nanowires can be created for particular applications1. Here, we report the fabrication of Fe nanowires, including the formation of the porous alumina membrane that is used as the template, electrodeposition into templates using electrolyte solution, and the release of the nanowires into the solution.

<table>
	<tbody>
		<tr>
			<td>Acetone</td>
			<td>Sigma Aldrich</td>
			<td>CAS 67-64-1</td>
			<td></td>
		</tr>
		<tr>
			<td>Aluminium Discs 99.999%</td>
			<td>GoodFellow</td>
			<td>AL000957</td>
			<td>Thickness: 0.50mm +/- 10%, Diameter 25.0mm +/- 0.5mm</td>
		</tr>
		<tr>
			<td>Big Beaker</td>
			<td></td>
			<td></td>
			<td>1000 mL</td>
		</tr>
		<tr>
			<td>Boric acid</td>
			<td>Sigma Aldrich</td>
			<td>101942058</td>
			<td>99%</td>
		</tr>
		<tr>
			<td>Cables</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Chromium (VI) oxide</td>
			<td>fisher chemical</td>
			<td>A98-212</td>
			<td></td>
		</tr>
		<tr>
			<td>Cold plate</td>
			<td>Thermo Scientific</td>
			<td>Accel 500 LC</td>
			<td></td>
		</tr>
		<tr>
			<td>Computer</td>
			<td></td>
			<td></td>
			<td>Used with LabView to control the Sourcemeter</td>
		</tr>
		<tr>
			<td>Copper (II) chloride</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Copper plate</td>
			<td></td>
			<td></td>
			<td>Custom made</td>
		</tr>
		<tr>
			<td>DC Power Source</td>
			<td>Agilent</td>
			<td>E3646A</td>
			<td></td>
		</tr>
		<tr>
			<td>DI Water</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Dressing Forceps</td>
			<td>fisher scientific</td>
			<td>12-460-164</td>
			<td>30.5 cm length, serrated tips</td>
		</tr>
		<tr>
			<td>Ethanol</td>
			<td>VWR International Ltd. (US)</td>
			<td>20823.327</td>
			<td></td>
		</tr>
		<tr>
			<td>Fume hood</td>
			<td>Flores valles</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Hydrochloric acid</td>
			<td>VWR International Ltd. (US)</td>
			<td>20255.290</td>
			<td></td>
		</tr>
		<tr>
			<td>Iron (II) sulfate</td>
			<td>Merck</td>
			<td>1.03965.1000</td>
			<td></td>
		</tr>
		<tr>
			<td>L-Ascorbic acid</td>
			<td>MP biomedicals</td>
			<td>100769</td>
			<td></td>
		</tr>
		<tr>
			<td>Magnetic rack</td>
			<td>life technologies</td>
			<td>DynaMag 2</td>
			<td></td>
		</tr>
		<tr>
			<td>Magnetic stirrer and hot plate</td>
			<td>IKA</td>
			<td>RCT basic</td>
			<td></td>
		</tr>
		<tr>
			<td>Mechanical stirrer</td>
			<td>Aslong</td>
			<td>JGB37-520</td>
			<td></td>
		</tr>
		<tr>
			<td>Mixer and heater</td>
			<td>Eppendorf</td>
			<td>ThermoMixer F1.5</td>
			<td></td>
		</tr>
		<tr>
			<td>Nylon cell</td>
			<td></td>
			<td></td>
			<td>Custum made</td>
		</tr>
		<tr>
			<td>Oxalic Acid</td>
			<td>VWR International Ltd. (US)</td>
			<td>20063.365-5L</td>
			<td></td>
		</tr>
		<tr>
			<td>PDMS O-ring</td>
			<td></td>
			<td></td>
			<td>Custom made</td>
		</tr>
		<tr>
			<td>Perchloric acid</td>
			<td>VWR International Ltd. (US)</td>
			<td>20583.327</td>
			<td>70-72 %</td>
		</tr>
		<tr>
			<td>Petri dish</td>
			<td></td>
			<td></td>
			<td>Or any other container</td>
		</tr>
		<tr>
			<td>pH strip</td>
			<td></td>
			<td></td>
			<td>Any pH strip</td>
		</tr>
		<tr>
			<td>Phosphoric acid</td>
			<td>acros organics</td>
			<td>201140010</td>
			<td>85%wt</td>
		</tr>
		<tr>
			<td>Platinum</td>
			<td>Goodfellow</td>
			<td>PT005115</td>
			<td>Diameter 0.05mm, 99.9% purity</td>
		</tr>
		<tr>
			<td>Platinum wire</td>
			<td>Goodfellow</td>
			<td>PT05120</td>
			<td>Diameter: 0.2 mm, Purity: 99.95%</td>
		</tr>
		<tr>
			<td>Power Supply</td>
			<td>Rhode &#38; Scharz</td>
			<td>NGPX 35/10</td>
			<td></td>
		</tr>
		<tr>
			<td>Retort stand (x2)</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Screws</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Small beaker</td>
			<td></td>
			<td></td>
			<td>50 mL</td>
		</tr>
		<tr>
			<td>Source meter</td>
			<td>Keithley</td>
			<td>2400-C</td>
			<td></td>
		</tr>
		<tr>
			<td>Sputter</td>
			<td>Quorum</td>
			<td>Q300T D</td>
			<td></td>
		</tr>
		<tr>
			<td>Tape</td>
			<td></td>
			<td></td>
			<td>Any temperature resistant tape</td>
		</tr>
		<tr>
			<td>Teflon propeller</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Ultrasonic cleaner</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

iron nanowire fabrication by nano-porous anodized aluminum and its characterization

Magnetic nanowires possess unique properties that have attracted the interest of different fields of research, including basic physics, biomedicine, and data storage. We demonstrate a fabrication method for iron (Fe) nanowires&#160;via electrochemical deposition into anodic&#160;alumina oxide (AAO) templates. The templates are fabricated by anodization of aluminum (Al) discs, and the pore length and diameter are controlled by changing the anodizing conditions. Pores with an average diameter of around 120 nm are created using oxalic acid as the electrolyte. Using this method, cylindrical nanowires are synthesized, which are released by dissolving the alumina using a selective chemical etchant.

After electropolishing, the Al disks reflect light well, as seen in Figure 1. If any small scratches or dots are observed, discard the disk. The plot of the applied current during the anodization process should be smooth and follow the three steps of anodization. In case of contaminated solution, excessive defects on the disk surface, incorrect preparation of the cell (see Figure 2), or the solution being too warm, the applied current plot curves will show peaks and irregularities. Two actual anodization curves are shown in Figure 3, including pictures of the samples. Anodization takes place on one side of the Al disk (top side). After removing the Al back, the membrane should be clearly visible from both sides. The pore opening can be checked using scanning electron microscopy (SEM) on the bottom side. Figure 4 shows a sample in which the pores were not completely opened. The deposition rate of Fe nanowires for membranes of this size is around 300 nm/min. As an example, Fe nanowire of around 1 &#181;m is shown in Figure 5. Note that this image was taken after breaking the membrane.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/60111/60111fig1.jpg" /> 
Figure 1: Aluminum disks. Before polishing (left) and after polishing (right). Marks on top of the polished disk are caused by the forceps. <a href="https://www.jove.com/files/ftp_upload/60111/60111fig01largev2.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/60111/60111fig2.jpg" /> 
Figure 2: Anodization cell. (A) Components of the cell. (B) Detail of the Al disk positioned over the PDMS O-ring. (C) Cell assembled. (D) Cell located over the cold plate and with the mechanical stirrer. <a href="https://www.jove.com/files/ftp_upload/60111/60111fig02largev2.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/60111/60111fig3.jpg" /> 
Figure 3: Applied current versus time during anodization for a successful (left) and unsuccessful (right) anodization. The three steps of anodization can be easily recognized. The stable 40 V (0&#8211;20 min); the constant increase up to 140 V (20&#8211;36:40 min), shown first as an increase of applied current and later as a constant current; and third, the stable 145 V until the end of the process. When anodization occurs properly, curves are smooth like the one on the left. When the curves show peaks or chaotic behavior (right) the sample would be burnt. In this case, the Al disk diameter was 25 mm. <a href="https://www.jove.com/files/ftp_upload/60111/60111fig03largev2.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/60111/60111fig4.jpg" /> 
Figure 4: SEM image of a membrane from the bottom side. This image shows the morphology of a membrane next to its edge. At any other point of the membrane, the membrane shows open pores like the ones in the picture. If the pores are not open properly, the hexagonal structure that is shown at the edge of the picture would be visible anywhere in the membrane. <a href="https://www.jove.com/files/ftp_upload/60111/60111fig04largev2.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/60111/60111fig5.jpg" /> 
Figure 5: Cross section SEM image of iron nanowires inside the membrane. The Fe nanowire is clearly recognizable from the alumina membrane due to its higher electron density. <a href="https://www.jove.com/files/ftp_upload/60111/60111fig05largev2.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Iron Nanowire Fabrication by Nano-Porous Anodized Aluminum and its Characterization at JoVE.com

Iron Nanowire Fabrication by Nano-Porous Anodized Aluminum and its Characterization

In this work, we describe a&#160;protocol to fabricate iron nanowires, including the formation of the porous alumina membrane that is used as the template, electrodeposition into templates using electrolyte solution, and the release of the nanowires into the solution.

Magnetic nanowires possess unique properties that have attracted the interest of different fields of research, including basic physics, biomedicine, and ...

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8.2K Views.  King Abdullah University of Science and Technology. In this work, we describe a protocol to fabricate iron nanowires, including the formation of the porous alumina membrane that is used as the template, electrodeposition into templates using electrolyte solution, and the release of the nanowires into the solution.

Video: Iron Nanowire Fabrication by Nano-Porous Anodized Aluminum and its Characterization

Synthesis and Characterization of Functionalized Metal-organic Frameworks

Metal-organic frameworks have attracted extraordinary amounts of research attention, as they are attractive candidates for numerous industrial and technological applications. Their signature property is their ultrahigh porosity, which however imparts a series of challenges when it comes to both constructing them and working with them. Securing desired MOF chemical and physical functionality by linker/node assembly into a highly porous framework of choice can pose difficulties, as less porous and more thermodynamically stable congeners (e.g., other crystalline polymorphs, catenated analogues) are often preferentially obtained by conventional synthesis methods. Once the desired product is obtained, its characterization often requires specialized techniques that address complications potentially arising from, for example, guest-molecule loss or preferential orientation of microcrystallites. Finally, accessing the large voids inside the MOFs for use in applications that involve gases can be problematic, as frameworks may be subject to collapse during removal of solvent molecules (remnants of solvothermal synthesis). In this paper, we describe synthesis and characterization methods routinely utilized in our lab either to solve or circumvent these issues. The methods include solvent-assisted linker exchange, powder X-ray diffraction in capillaries, and materials activation (cavity evacuation) by supercritical CO2 drying. Finally, we provide a protocol for determining a suitable pressure region for applying the Brunauer-Emmett-Teller analysis to nitrogen isotherms, so as to estimate surface area of MOFs with good accuracy.

Synthesis, activation, and characterization of intentionally designed metal-organic framework materials is challenging, especially when building blocks are incompatible or unwanted polymorphs are thermodynamically favored over desired forms. We describe how applications of solvent-assisted linker exchange, powder X-ray diffraction in capillaries and activation via supercritical CO2 drying, can address some of these challenges.

Metal-organic frameworks have attracted extraordinary amounts of research attention, as they are attractive candidates for numerous industrial and ...

In Situ Characterization of Hydrated Proteins in Water by SALVI and ToF-SIMS

This work demonstrates in situ characterization of protein biomolecules in the aqueous solution using the System for Analysis at the Liquid Vacuum Interface (SALVI) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The fibronectin protein film was immobilized on the silicon nitride (SiN) membrane that forms the SALVI detection area. During ToF-SIMS analysis, three modes of analysis were conducted including high spatial resolution mass spectrometry, two-dimensional (2D) imaging, and depth profiling. Mass spectra were acquired in both positive and negative modes. Deionized water was also analyzed as a reference sample. Our results show that the fibronectin film in water has more distinct and stronger water cluster peaks compared to water alone. Characteristic peaks of amino acid fragments are also observable in the hydrated protein ToF-SIMS spectra. These results illustrate that protein molecule adsorption on a surface can be studied dynamically using SALVI and ToF-SIMS in the liquid environment for the first time.

In Situ Characterization of Hydrated Proteins in Water by SALVI and ToF-SIMS

This work presents a protocol for liquid handling and sample introduction to a microchannel for in situ time-of-flight secondary ion mass spectrometry analysis of protein biomolecules in an aqueous solution.

This work demonstrates in situ characterization of protein biomolecules in the aqueous solution using the System for Analysis at the Liquid Vacuum ...

Synthesis and Characterization of Supramolecular Colloids

Control over colloidal assembly is of utmost importance for the development of functional colloidal materials with tailored structural and mechanical properties for applications in photonics, drug delivery and coating technology. Here we present a new family of colloidal building blocks, coined supramolecular colloids, whose self-assembly is controlled through surface-functionalization with a benzene-1,3,5-tricarboxamide (BTA) derived supramolecular moiety. Such BTAs interact via directional, strong, yet reversible hydrogen-bonds with other identical BTAs. Herein, a protocol is presented that describes how to couple these BTAs to colloids and how to quantify the number of coupling sites, which determines the multivalency of the supramolecular colloids. Light scattering measurements show that the refractive index of the colloids is almost matched with that of the solvent, which strongly reduces the van der Waals forces between the colloids. Before photo-activation, the colloids remain well dispersed, as the BTAs are equipped with a photo-labile group that blocks the formation of hydrogen-bonds. Controlled deprotection with UV-light activates the short-range hydrogen-bonds between the BTAs, which triggers the colloidal self-assembly. The evolution from the dispersed state to the clustered state is monitored by confocal microscopy. These results are further quantified by image analysis with simple routines using ImageJ and Matlab. This merger of supramolecular chemistry and colloidal science offers a direct route towards light- and thermo-responsive colloidal assembly encoded in the surface-grafted monolayer.

A protocol for the synthesis and characterization of colloids coated with supramolecular moieties is described. These supramolecular colloids undergo self-assembly upon the activation of the hydrogen-bonds between the surface-anchored molecules by UV-light.

Control over colloidal assembly is of utmost importance for the development of functional colloidal materials with tailored structural and mechanical ...

Functionalization of Single-walled Carbon Nanotubes with Thermo-reversible Block Copolymers and Characterization by Small-angle Neutron Scattering

We demonstrate a protocol for single-walled carbon nanotube functionalization using thermo-sensitive PEO-PPO-PEO triblock copolymers in an aqueous solution. In a carbon nanotube/PEO105-PPO70-PEO105 (poloxamer 407) aqueous solution, the amphiphilic poloxamer 407 adsorbs onto the carbon nanotube surfaces and self-assembles into continuous layers, driven by intermolecular interactions between constituent molecules. The addition of 5-methylsalicylic acid changes the self-assembled structure from spherical-micellar to a cylindrical morphology. The fabricated poloxamer 407/carbon nanotube hybrid particles exhibit thermo-responsive structural features so that the density and thickness of poloxamer 407 layers are also reversibly controllable by varying temperature. The detailed structural properties of the poloxamer 407/carbon nanotube particles in suspension can be characterized by small-angle neutron scattering experiments and model fit analyses. The distinct curve shapes of the scattering intensities depending on temperature control or addition of aromatic additives are well described by a modified core-shell cylinder model consisting of a carbon nanotube core cylinder, a hydrophobic shell, and a hydrated polymer layer. This method can provide a simple but efficient way for the fabrication and in-situ characterization of carbon nanotube-based nano particles with a structure-tunable encapsulation.

A method for the functionalization of carbon nanotubes with structure-tunable polymeric encapsulation layers and structural characterization using small-angle neutron scattering is presented.

We demonstrate a protocol for single-walled carbon nanotube functionalization using thermo-sensitive PEO-PPO-PEO triblock copolymers in an aqueous ...

Low-energy Cathodoluminescence for (Oxy)Nitride Phosphors

Nitride and oxynitride (Sialon) phosphors are good candidates for the ultraviolet and visible emission applications. High performance, good stability and flexibility of their emission properties can be achieved by controlling their composition and dopants. However, a lot of work is still required to improve their properties and to reduce the production cost. A possible approach is to correlate the luminescence properties of the Sialon particles with their local structural and chemical environment in order to optimize their growth parameters and find novel phosphors. For such a purpose, the low-voltage cathodoluminescence (CL) microscopy is a powerful technique. The use of electron as an excitation source allows detecting most of the luminescence centers, revealing their luminescence distribution spatially and in depth, directly comparing CL results with the other electron-based techniques, and investigating the stability of their luminescence properties under stress. Such advantages for phosphors characterization will be highlighted through examples of investigation on several Sialon phosphors by low-energy CL.

Low-energy Cathodoluminescence for OxyNitride Phosphors

An excellent chemical and luminescence stabilities of (oxy)nitride phosphors present it as an promising alternative to currently used sulfide and oxide phosphors. In this paper, we present the way to investigate its local luminescence properties using low-energy cathodoluminescence (CL).

Nitride and oxynitride (Sialon) phosphors are good candidates for the ultraviolet and visible emission applications. High performance, good stability and ...

Fabrication and Testing of Photonic Thermometers

In recent years, a push for developing novel silicon photonic devices for telecommunications has generated a vast knowledge base that is now being leveraged for developing sophisticated photonic sensors. Silicon photonic sensors seek to exploit the strong confinement of light in nano-waveguides to transduce changes in physical state to changes in resonance frequency. In the case of thermometry, the thermo-optic coefficient, i.e., changes in refractive index due to temperature, causes the resonant frequency of the photonic device such as a Bragg grating to drift with temperature. We are developing a suite of photonic devices that leverage recent advances in telecom compatible light sources to fabricate cost-effective photonic temperature sensors, which can be deployed in a wide variety of settings ranging from controlled laboratory conditions, to the noisy environment of a factory floor or a residence. In this manuscript, we detail our protocol for the fabrication and testing of photonic thermometers.

We describe the process of fabrication and testing of photonic thermometers.

In recent years, a push for developing novel silicon photonic devices for telecommunications has generated a vast knowledge base that is now being ...

In Situ Characterization of Shewanella oneidensis MR1 Biofilms by SALVI and ToF-SIMS

Bacterial biofilms are surface-associated communities that are vastly studied to understand their self-produced extracellular polymeric substances (EPS) and their roles in environmental microbiology. This study outlines a method to cultivate biofilm attachment to the System for Analysis at the Liquid Vacuum Interface (SALVI) and achieve in situ chemical mapping of a living biofilm by time-of-flight secondary ion mass spectrometry (ToF-SIMS). This is done through the culturing of bacteria both outside and within the SALVI channel with our specialized setup, as well as through optical imaging techniques to detect the biofilm presence and thickness before ToF-SIMS analysis. Our results show the characteristic peaks of the Shewanella biofilm in its natural hydrated state, highlighting upon its localized water cluster environment, as well as EPS fragments, which are drastically different from the same biofilm's dehydrated state. These results demonstrate the breakthrough capability of SALVI that allows for in situ biofilm imaging with a vacuum-based chemical imaging instrument.

In Situ Characterization of Shewanella oneidensis MR1 Biofilms by SALVI and ToF-SIMS

This article presents a method for growing a biofilm for in situ time-of-flight secondary ion mass spectrometry for chemical mapping in its hydrated state, enabled by a microfluidic reactor, System for Analysis at the liquid Vacuum Interface. The Shewanella oneidensis MR-1 with green fluorescence protein was used as a model.

Bacterial biofilms are surface-associated communities that are vastly studied to understand their self-produced extracellular polymeric substances (EPS) ...

Fabrication of Spherical and Worm-shaped Micellar Nanocrystals by Combining Electrospray, Self-assembly, and Solvent-based Structure Control

Micellar nanocrystals (micelles with encapsulated nanocrystals) have become an emerging major class of nanobiomaterials. We describe a method of fabricating micellar nanocrystals based on combining top-down electrospray, bottom-up self-assembly, and solvent-based structure control. This method involves first using electrospray to generate uniform ultrafine liquid droplets, each of which functions as a micro-reactor in which self-assembly reaction occurs forming micellar nanocrystals, with the structures (micelle shape and nanocrystal encapsulation) controlled by the organic solvent used. This method is largely continuous and produces high quality micellar nanocrystal products with an inexpensive structure control approach. By using a water-miscible organic solvent tetrahydrofuran (THF), worm-shaped micellar nanocrystals can be produced due to solvent-induced/facilitated micelle fusion. Compared with the common spherical micellar nanocrystals, worm-shaped micellar nanocrystals can offer minimized non-specific cellular uptake, thus enhancing biological targeting. By co-encapsulating multiple nanocrystals into each micelle, multifunctional or synergistic effects can be achieved. Current limitations of this fabrication method, which will be part of the future work, primarily include imperfect encapsulation in the micellar nanocrystal product and the incompletely continuous nature of the process.

The present work describes a method to fabricate micellar nanocrystals, an emerging major class of nanobiomaterials. This method combines top-down electrospray, bottom-up self-assembly, and solvent-based structure control. The fabrication method is largely continuous, can produce high quality products, and possesses an inexpensive means of structure control.

Micellar nanocrystals (micelles with encapsulated nanocrystals) have become an emerging major class of nanobiomaterials. We describe a method of ...

Preparation and Characterization of C60/Graphene Hybrid Nanostructures

Physical thermal deposition in a high vacuum environment is a clean and controllable method for fabricating novel molecular nanostructures on graphene. We present methods for depositing and passively manipulating C60 molecules on rippled graphene that advance the pursuit of realizing applications involving 1D C60/graphene hybrid structures. The techniques applied in this exposition are geared towards high vacuum systems with preparation areas capable of supporting molecular deposition as well as thermal annealing of the samples. We focus on C60 deposition at low pressure using a homemade Knudsen cell connected to a scanning tunneling microscopy (STM) system. The number of molecules deposited is regulated by controlling the temperature of the Knudsen cell and the deposition time. One-dimensional (1D) C60 chain structures with widths of two to three molecules can be prepared via tuning of the experimental conditions. The surface mobility of the C60 molecules increases with annealing temperature allowing them to move within the periodic potential of the rippled graphene. Using this mechanism, it is possible to control the transition of 1D C60 chain structures to a hexagonal close packed quasi-1D stripe structure.

Preparation and Characterization of C60/Graphene Hybrid Nanostructures

Here we present a protocol for the fabrication of C60/graphene hybrid nanostructures by physical thermal evaporation. Particularly, the proper manipulation of deposition and annealing conditions allow the control over the creation of 1D and quasi 1D C60 structures on rippled graphene.

Physical thermal deposition in a high vacuum environment is a clean and controllable method for fabricating novel molecular nanostructures on graphene. We ...

Extraction of Lignin with High &#946;-O-4 Content by Mild Ethanol Extraction and Its Effect on the Depolymerization Yield

Lignin valorization strategies are a key factor for achieving more economically competitive biorefineries based on lignocellulosic biomass. Most of the emerging elegant procedures to obtain specific aromatic products rely on the lignin substrate having a high content of the readily cleavable &#946;-O-4 linkage as present in the native lignin structure. This provides a miss-match with typical technical lignins that are highly degraded and therefore are low in &#946;-O-4 linkages. Therefore, the extraction yields, and the quality of the obtained lignin are of utmost importance to access new lignin valorization pathways. In this manuscript, a simple protocol is presented to obtain lignins with high &#946;-O-4 content by relatively mild ethanol extraction that can be applied to different lignocellulose sources. Furthermore, analysis procedures to determine the quality of the lignins are presented together with a depolymerization protocol that yields specific phenolic 2-arylmethyl-1,3-dioxolanes, which can be used to evaluate the obtained lignins. The presented results demonstrate the link between lignin quality and potential for the lignins to be depolymerized into specific monomeric aromatic chemicals. Overall, the extraction and depolymerization demonstrates a trade-off between the lignin extraction yield and the retention of the native aryl-ether structure and thus the potential of the lignin to be used as the substrate for the production of chemicals for higher-value applications.

Here, we present a protocol to perform ethanol extraction of lignin from several biomass sources. The effect of the extraction conditions on the lignin yield and &#946;-O-4 content are presented. Selective depolymerization is performed on the obtained lignins to obtain high aromatic monomer products.

Lignin valorization strategies are a key factor for achieving more economically competitive biorefineries based on lignocellulosic biomass. Most of the ...

Iron Nanowire Fabrication by Nano-Porous Anodized Aluminum and its Characterization

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Synthesis and Characterization of Functionalized Metal-organic Frameworks

In Situ Characterization of Hydrated Proteins in Water by SALVI and ToF-SIMS

Synthesis and Characterization of Supramolecular Colloids

Functionalization of Single-walled Carbon Nanotubes with Thermo-reversible Block Copolymers and Characterization by Small-angle Neutron Scattering

Low-energy Cathodoluminescence for (Oxy)Nitride Phosphors

Fabrication and Testing of Photonic Thermometers

In Situ Characterization of Shewanella oneidensis MR1 Biofilms by SALVI and ToF-SIMS

Fabrication of Spherical and Worm-shaped Micellar Nanocrystals by Combining Electrospray, Self-assembly, and Solvent-based Structure Control

Preparation and Characterization of C₆₀/Graphene Hybrid Nanostructures

Extraction of Lignin with High β-O-4 Content by Mild Ethanol Extraction and Its Effect on the Depolymerization Yield