Our fabrication protocol is based on the electrodeposition with a nano-porous aluminum oxide, which is the only method that can give the nanowires properties we need. The main advantage of this technique, is it facilitates a simple and fast fabrication of highly ordered nano-porous aluminum oxide templates with a wide range of pore sizes. Magnetic nano materials have attracted a lot of interest due to their It can be useful in or in vitro diagnosis, or even for the treatment of medical conditions.
These methods require considerable amount of effort and time to obtain reproducible results. Follow the protocol carefully and practice to achieve a good outcome. After washing the aluminum discs three times with deionized water, use tweezers to transfer the disc into an acetone wash, followed by an isopropyl alcohol wash, and four deionized water washes.
After the last water wash, sonicate the discs in acetone for 10 minutes. After three washes in deionized water, use dressing forceps to immerse the cleaned aluminum templates in a beaker containing four degrees Celsius electropolishing solution, and a platinum mesh electrode. Connect the aluminum disc to the positive terminal, and the platinum mesh electrode to the negative terminal of the power supply.
Then apply a voltage of 20 volts while the current is limited to two amps. Polish the discs for three minutes at 400 rotations per minute, before washing the discs with fresh deionized water. For hard anodization, place the discs into the cell assembly and fill the cell with 0.3-Molar Oxalic Acid.
Place the cell on a four degrees Celsius cold plate. When the oxalic acid temperature reaches two to five degrees Celsius, apply 40 volts for 20 minutes to mildly anodize the templates, before increasing the voltage in 0.1 volt per second step increases until the voltage reaches 140 volts. TheN hold the discs at this voltage for 45 minutes.
When the template is anodized, it will turn a bright golden color. To prepare the discs for deposition, after washing with deionized water and drying with nitrogen, place the discs back into the cell and add freshly prepared copper solution and a magnetic stir bar to the cell. Agitate the stir bar to 300 rotations per minute for 15 minutes.
When the solution becomes transparent, replace the solution with fresh copper solution for five more minutes of agitation. After washing and drying as demonstrated, place the sample's back side up in a petri dish on a pH strip, and completely cover the membrane with 10 weight phosphoric acid for a six and a half hour incubation at room temperature. At the end of the treatment, wash and dry the discs as demonstrated, and sputter deposit 200 nanometers of gold onto the discs.
For nanowire deposition, mount the aluminum membrane into the 15 millimeter diameter of the cell, and pour a freshly prepared iron sulfate boric acid L-ascorbic acid solution into the cell. Connect the source meter with the negative contact attached to the copper plate, and connect the positive contact to the platinum mesh. Then apply a constant current of 2.5 milliamps to start the electrodeposition.
To release the nanowires, fill a 1.5 millimeter micro tube with one milliliter of freshly prepared chrome solution and the small pieces of membrane containing the nanowires for a 24-hour incubation at 40 degrees Celsius. When the nanowires are completely released, no black particles should be observed with the naked eye. Then place the microtube on a magnetic rack, and replace the chrome solution with 1 milliliter of ethanol at least 10 times to wash the nanowires.
After electropolishing, the aluminum discs reflect light well. If any small scratches or dots are observed, discard the disc. The plot of the applied current during the anodizatiom process should be smooth and follow the three steps of anodization.
In the case of a contaminated solution, excessive defects on the disc's surface, incorrect preparation of the cell, or the solution being too warm, the applied current plot curves will show peaks and irregularities. Anodization takes place on one side of the aluminum disc. After removing the aluminum back, the membrane should be clearly visible from both sides.
And the pore opening can be checked using scanning electron microscopy on the bottom side. Here, an image of one micrometer iron nanowire was taken after breaking the membrane. The nanowire is clearly recognizable from the aluminum membrane due to its higher electron density.
It is important that the site temperature is between two to five degrees Centigrade when the anodization step begins, or the samples may burn. set each MSDS before using them. and use the pin proof as necessary.
