Synthesis and Functionalization of Nitrogen-doped Carbon Nanotube Cups with Gold Nanoparticles as Cork Stoppers

The overall goal of the following experiment is to synthesize individual hydrophilic graphitic nano cups isolated from nitrogen, dumped carbon nano tubes, and functionalize them with gold nanoparticles as cork stoppers. This is achieved first by chemical vapor deposition to synthesize nitrogen doped carbon nanotubes consisting of stacked nano cups. As a second step, the stacked nano cups are treated with strong acid oxidation and probe tips on occasion, which effectively isolates the individual nano cups out of their stacks.

Next gold nanoparticles are synthesized by sodium citrate reduction of chloro oric acid in the presence of isolated nano cups in order to cork the nano cups at their opening results are obtained that show gold nanoparticles effectively corking the opening of the nano cups based on transmission electron microscopy and UV vis spectroscopy characterization. We first had the idea of separating and corking the carbon tube cups when we analyzed the transmission electron microscope images of nitrogen dope carbon tubes, and noticed that they're comprised of individual cup shaped segments. This method can help answer key questions in the nanoscience and nanotechnology field such as and properties of nanostructures with control, shape, and functionalities.

The implication of this technique extend towards the fabrication of nanoscale containers and drug delivery carriers because the nano cups have a unique shape and more versatile functionalities compared to other nanomaterials. To begin synthesis place a one inch by 12 inch quartz plate inside a three foot long, one inch inner diameter quartz tube. Then seal the quartz tube using steel caps with built-in gas and liquid injection connections.

Place the quartz tube in a Lindberg blue tube. Next, make a solution of liquid precursor containing ferne, acetyl nitrile, and xylenes. Draw about five milliliters of liquid precursor into a gas tight syringe.

Place the syringe on a syringe pump and connect it to the inlet of the quartz tube. At this point, assemble the CVD system by connecting all gas inlets and outlets. Flow 845 standard cubic centimeters per minute of Argonne through the system for 20 minutes to purge the system and check for leaks after purging is complete.

Start a flow of molecular hydrogen at 37.5 standard cubic centimeters per minute and adjust the argonne to flow at 127 standard cubic centimeters per minute. Turn on the furnace and set its temperature to 800 degrees Celsius once it is stable at that temperature. Set the injection rate of the syringe pump to nine milliliters per hour for six minutes.

After six minutes, set the injection rate to one milliliter per hour for the growth of nitrogen doped carbon nano tube cups. After 90 minutes of growth, turn off the syringe pump and hydrogen gas flow and shut down the furnace. Keep argonne flowing to maintain an inner atmosphere until the furnace cools to room temperature.

When the system is at room temperature, disconnect all gas inlets and outlets and the injection system under a fume hood or with respiratory protection. Disassemble the CVD system and take the quartz plate out. Use a one-sided razor blade to carefully peel the nitrogen doped carbon nano tube cups Film from the plate.

Transfer the film using tweezers and an antistatic gun for dispersal in ethanol for the oxidation process. First, take precautions to safely handle highly corrosive fluids. Transfer about 10 milligrams of as synthesized NC NCS to a 200 milliliter round bottom flask.

Add 7.5 milliliters of concentrated nitric acid to the flask. Briefly sonicate the mixture in a water bath for better dispersion. Next, slowly add 22.5 milliliters of concentrated sulfuric acid with the reaction mixture in a water bath at room temperature sonicate for four hours.

Then dilute the reaction mixture with 100 milliliters of water and place the mixture in an ice bath. After the mixture is cooled down to room temperature, use a water aspirator to filter the mixture through a POLYTETRAFLUOROETHYLENE or PTFE membrane with a pore size of 220 nanometers. Wash the material on the filter membrane with 200 milliliters of 0.01 molar sodium hydroxide to remove any acidic residual byproducts.

Then wash the material with 200 milliliters of 0.01 molar hydrogen chloride solution. Next, wash the material with water until the filtrate has a neutral pH. Finally, put the oxidized NC NCS in 50 milliliters of water.

Sonicate the mixture to disperse the material. Typically about five minutes, the resulting suspension can be stored at room temperature for experiments. To separate the NC ncs, transfer the suspension of oxidized material in water to a 100 milliliter plastic cup placed in an ice bath.

Fill the plastic cup with water to the 50 milliliter mark. Equip a probe tip ator with a quarter inch diameter titanium micro tip and set it at 60%maximum magnitude. Submerge the micro tip to the center of the solution process for 12 hours with a 32nd on off interval.

Change the ice every 30 minutes to prevent overheating. After 12 hours, stop the sonication Filter the NC NC suspension through a 220 nanometer pore size PTFE filter membrane to remove any large particles. Again, the resultant NC NC samples can be stored at room temperature for further applications.

Analysis begins with the preparation of two reagents A and B reagent. A contains phenol, ethanol purine, and hydrant danin in water. Reagent B is hyran dissolved in ethanol.

Fill small test tubes with 600 microliters of ethanol. Add 400 microliters of NC NNC solution, or 400 microliters water as controls to each of the tubes. Add 100 microliters of reagent A and 25 microliters of reagent B to the tubes.

Seal the test tubes with params and heat them in a 100 degree Celsius oil bath for 10 minutes. Filter the sample through a syringe filter to remove solid particles and collect the filtrate solution for the analysis. Take visible spectra of the filtrates with and without NC NCS and employ colorimetry.

Record the absorbance of the peak centered at 570 nanometers for use with the Beer Lambert Law to calculate the amine loadings to introduce gold particles into the NC ncs. Begin with four milliliters of aqueous suspension containing separated NC NCS with concentration. 0.01 milligrams per milliliter.

Sonicate the suspension in a water bath sonicate for five minutes. During the last minute of sonication, add one milliliter of one milligram per milliliter. Aqueous solution chloro ORIC acid.

Once done, place the solution on a stirring hot plate at 70 degrees Celsius. Add 250 of 1%by weight. Try sodium citrate aqueous solution dropwise vigorously Stir the reaction mixture on the hot plate for two hours.

Next, centrifuge the reaction mixture at 3, 400 RPM for 15 minutes. Then remove the supernatant to leave the precipitate containing the NC NCS functionalized with gold nanoparticles disperse the precipitate in four milliliters of water and centrifuge. Again, transmission electron microscopy shows the fibrile structure of the nitrogen dope nanotubes their typical length of several microns and their diameters of 20 to 30 nanometers.

Higher resolution images show the nano tube cups that stack on top of each other. Here, the transmission electron microscopy images show NC NCS after acid oxidation. The oxidation process has cut the fibers into sections of one micron in length, but with the IC cups still stacked after probe tips, sonication and filtration, the NC NCS appear as individual cups less than 200 nanometers in length.

The oxidation process results in a change of the zeta potential of the NC NCS from positive to negative. As shown on the left, the plot on the right shows according to the Kaiser test, the inherent amine groups of NC NCS were not affected as seen on the left. When the NC NCS were functionalized with gold nanoparticles, almost all of the NC NCS acquired one.

Many of the gold nanoparticles formed corks to the cups as shown at the right here. The inset photograph shows the color difference after centrifugation between the free gold nanoparticles from the supernatant on the left and the gold nanoparticles on the NNC NCS on the right. The more purple color corresponds to a red shift of the gold surface plasmin resonance band in the visible spectrum seen in the data.

Once master, this technique can be done in one day if it's performed properly. Don't forget that working with carbon nanomaterials can be hazardous and precautions such as respirators should be taken while performing this procedure After its development. This technique paved the way for researchers in the field of nanoscience and specifically nanomedicine to explore applications of these functional nano carriers for targeted therapeutics and controlled drug release.