The overall goal of this procedure is to fabricate an array of vertically aligned organic nanowires inside a porous template. This is accomplished by first preparing a substrate to anodize by either polishing the surface of an aluminum foil or depositing a thin film of aluminum on an arbitrary substrate. The second step is to anodize the polished aluminum foil or thin film of aluminum deposited on an arbitrary substrate.
The final step is to deposit organic material into the pores of the template using a novel centrifuge assisted template wedding. Ultimately, scanning electron microscopy is used to show the existence of organic nano wires within the pores of the nautic aluminum oxide template. The idea for this method first arose when I had trouble filling the pores of anodic aluminum templates using traditional template wetting methods.
I decided to use the centrifugal force of a centrifuge to push or assist the penetration of solution into the pores. First cut out approximately two centimeter by two centimeter sheets of high purity unpolished aluminum with a thickness of 250 micrometers, submerge a small number of the sheets and a beaker of nitric phosphoric acid etching at 80 degrees Celsius for five minutes after etching neutralize the foils by dipping them in water and placing in one molar sodium hydroxide for 20 minutes. Following this, rinse the foils with the ionized water.
Next, load the polished aluminum sheets into flat cells and fill them with 3%oxalic acid. Then anodize the sheets for 15 minutes at 40 volts DC bias after anodization, immerse the sample in a beaker of chromic phosphoric acid etching at 60 degrees Celsius for approximately 30 minutes. To remove the initial oxide layer, realign the foil in the flat cell, such that the same area anodized previously will again be exposed to the electrolyte.
Repeat the anodization process with 3%oxalic acid for 2.5 minutes at 40 volts dc. Bias submerge the A a O template in 5%phosphoric acid at room temperature to thin the barrier layer at the bottom of the nanopores and widen the nanopore diameter to approximately 60 to 70 nanometers after 40 minutes, remove the template from the beaker and rinse it with the ionized water. Deposit the following multi-layer system sequentially on clean glass.
Slides 20 nanometers of titanium dioxide via atomic layer deposition, seven nanometers of gold via sputtering and one micrometer of aluminum via sputtering. After removing the samples from the vacuum chamber, attach a foil electrode to the surface of the thin film of aluminum to be anodized. Using a conductive silver epoxy, load the sample into the flat cell and fill it with 3%oxalic acid.
Then anodize the aluminum thin film for four minutes at 30 volts DC bias without removing the sample from the flat cell. Rinse the cell out with deionized water. Pour 60 degrees Celsius ch chromic phosphoric acid etching into the flat cell, and set aside for one hour.
Following this, repeat the anodization and etching steps using the conditions described previously. After rinsing with de ionized water, fill the cell with 3%oxalic acid and anodize a final time using the same conditions as before. Monitor the current of the system and stop the anodization when a sharp increase in current is observed.
Next, perform a poor widening step by submerging the template in 5%phosphoric acid at room temperature. After 40 minutes, remove the template from the beaker and rinse it with deionized water. Load the templates into the bottom of a centrifuge test tube such that the anodized area is facing the top of the test tube.
Using a pipette fill the test tubes with enough PCBM solutions such that each template is completely submerged. Then load the test tubes in the centrifuge and run for five minutes at 6, 000 RPM. Once the centrifuge has stopped, unload the test tubes and pour out the PCBM solution.
Remove the templates from the test tubes and set them aside to dry. Repeat the previous steps so that a total of five to 10 centrifuge runs have been performed. Finally, remove each sample from the bottom of the test tubes and use a cotton swab soaked toluene to gently clean the surface of the, as evidenced by the images shown here.
This centrifuge assisted drop casting method produces continuous nano wires. The nano wires fabricated inside the pores of the a a O template are vertically aligned, uniform, and electrically isolated from one another with capped bottoms. This can be successfully fabricated on several different substrates, which lead to the potential application of these structures in many different devices.
To further verify that the material inside the pores is PCBM, nanowires Ramen spectroscopy of the field templates was performed. The ramen data was compared to the spectra of PCBM Thin films and fuller rings found in the literature. Peaks were observed at 14 30, 14 63, and 1577 inverse centimeters, which correspond to the T one, U four a G two, and HG eight modes respectively.
These numbers match well with the literature values of 14 29, 14 70, and 1575 inverse centimeters for pristine PCBM for the same respective modes. In addition, this shows that there is no significant shift in the ramen peaks due to nano wire geometry, and confirms the presence of PCBM nanowires within the pores Prior to we're following this procedure. Other methods like electro deposition of metallic nanowires or sputtering of thin film metals can be used to fabricate devices for applications like spintronics, Optive, electronics, photovoltaics, chemical sensing, and metamaterials.
