The overall goal of this protocol is to produce water-soluble metal core nanoparticles. This general method uses a silicon-based surfactant as both a reducing and a stabilizing agent. This method helps answer key questions about control of self-assembly functionality, passivity, and the stability of nanostructured materials.
The main advantage of this technique is that a water-soluble silicon compound can reduce metal precursors to metal nanoparticles and efficiently stabilize them. It uses green conditions to create silox and metal nanocomposites which have applications in therapeutics drug delivery and heterogeneous catalyses. The implications of this technique are far-reaching because the surfactant can cross-link to form organo-silene gels impregnated with metallic nanoparticles.
This method can be applied to create hybrids of most noble metals and can provide mechanistic insights into the formation of nanoparticles. By controlling the concentrations of salt and silene it is possible to control the reaction rates, particle size, and nanoparticle coating. To start the procedure first weigh out 16.9 milligrams of silver nitrate into a 50 milliliter erlenmyer flask equipped with a magnetic stir bar.
Add 20 milliliters of 18.2 megaohm ultra-pure water to the flask and stopper it. Place the flask in an oil bath on a hot plate at 60 degrees Celsius and stir the solution. Next slowly add 144 microliters of 2-AST to the flask, using a precision micropipette.
Flush the pipette several times with the mixture to ensure that all of the 2-AST is transferred. Every half-hour remove 100 microliters of the mixture using a precision micropipette and place it into a plastic cuvette for UV-Vis spectroscopy analysis. To the plastic cuvettes containing the sample add one milliliter of ultra-pure water and mix the sample in each of the cuvettes thoroughly by repeat pipetting.
Transfer the cuvette to a UV-Vis spectrophotometer and record the absorbance spectrum. Discard the sample in an appropriate container when finished. After six hours, remove the flask from the oil bath and transfer the nanoparticle mixture to a 20 milliliter scintillation vial for storage.
To begin the sample preparation for electron microscopy place a 200 carbon mesh Formvar coated copper grid onto a clean piece of filter paper. Once the sample has cooled to room temperature cast drop approximately 60 microliters of the nanoparticle mixture directly onto the grid using a one milliliter plastic Pasteur pipette. Allow the grid to dry for 24 hours.
Load the grid into a transmission electron microscope and record images using 10 microampere current and 100 kilovolt accelerating voltage. To prepare the NMR sample, first use a precision pipette to transfer 50 microliters of deuterium oxide into a clean NMR tube. Next, slowly pipette 400 microliters of the nanoparticle mixture into the same NMR tube.
Cap the tube and shake the top of the tube to force the mixture to the bottom. Mix the sample by shaking and repeatedly inverting the NMR tube. Insert the sample tube into the NMR magnet and record the NMR spectrum.
To prepare the FTIR sample first place two milliliters of the nanoparticle mixture into a one dram glass vial. Continue by placing the vial into a vacuum dessicator. Connect the dessicator stopcock to a vacuum pump.
Open it and then evacuate the dessicator. Use caution when drying the sample in a vacuum dessicator as rapid reduction of pressure may cause samples to flash boil, expelling some of the material out of the container. Once the vial no longer contains visible liquid, remove it from the dessicator, and scrape out the remaining solid sample using a clean spatula.
Finally, place the sample onto an FTIR spectrometer fitted with zinc selenide crystal diode laser and record the FTIR spectrum. The formation of silver nanoparticles was monitored by UV-Vis Spectrometry analysis. The silver nanoparticles have a characteristic peak at 414 nanometers that increases with reaction time.
Transmission electron microscopy was used to confirm the presence of silver nanoparticles. Analysis of the images shows that the majority of the nanoparticles were in the 10 nanometer size range. Fourier transform infrared spectroscopy was used to verify the complexation of the nanoparticles with 2-AST.
Absorption at around 1000 reciprocal centimeters shows the presence of silicon-oxygen-silicon linkages and peaks at 3000 to 2750 reciprocal centimeters and 1550 to 1650 reciprocal centimeters are attributed to the amino group. Analysis of the NMR spectrum of the nanoparticles shows the coordination to the 2-AST by the shift in and appearance of new peaks between 2.72 to 3.40 parts per million. Once mastered, the reaction process can be set up within an hour.
While performing this procedure, it's important to ensure the purity of the water. All experiments were carried out in ultra-pure, 18.2 megaohm water. Following this procedure, scanning electron microscopy or x-ray powder diffraction can be used to further elucidate structural features, such as morphology, size and particle roughness of the hybrid nanocomposites.
After watching this video, you should have a good understanding of how to generate and analyze the stabilized metal-core nanoparticles. This method produces large quantities of water-soluble metal nanohybrids which can be capped with ligands for drug delivery applications. Don't forget that working with silver nitrate and other reagents can be hazardous.
The use of protective equipment such as gloves, goggles and lab coats is strongly advised while performing this procedure. Thanks for watching, good luck with your experiments.
