A Technique to Functionalize and Self-assemble Macroscopic Nanoparticle-ligand Monolayer Films onto Template-free Substrates

The overall goal of this procedure is to develop macroscopic, nanoparticle, ligand, monolayer films. This is accomplished by using a single one-pot self-assembly technique. First metallic nanoparticles, a rapidly functionalized with ligands in a water tetrahedran or THF solvent.

Next, the ligand kept nanoparticles phase separate to the air solvent interface. Finally, the nanoparticles are transported onto template free substrates using surface tension gradients, self assembling into macroscopic nanoparticle, ligand monolayer films. Ultimately, this procedure provides a simple, robust, and scalable technique to functionalize and self-assemble macroscopic nanoparticle, ligand monolayer films onto template free substrates.

The main advantage of this technique over other interfacial assembly methods is the rapid and efficient nanoparticle functionalization and self-assembly into macroscopic monolayer films. Though this method can provide insight into the organic inorganic interface at do nanoscale level, it can also be applied to a wide variety of application such as metamaterials, photovoltaic, and molecular sensors. To begin concentrate commercially available 15 nanometer gold nanospheres by placing 15 milliliters of the dilute nanosphere of water suspension into an ultra centrifugal filter.

Then centrifuge the unit at 4, 500 Gs for two minutes or until only a few microliters remain in the filter chamber. Re suspend the nanosphere in 1.5 milliliters of deionized or DI water or such that the nanoparticle concentration is approximately 10 to the 13th particles per milliliter. The suspension is stable for several hours.

Once resuspended in di water, to verify the number density and confirm the nanoparticles have not aggregated first pipette 150 microliters of the suspension into a vet. Also dilute the concentrated nanoparticle suspension with 1.35 milliliters of di water. Next, place the vet into an ultraviolet visible spectrometer and measure the absorbent spectrum of the prepared suspension as well as that of the original suspension.

Compare the peak position in full width at half maximum to ensure aggregation has not occurred. The magnitude of the absorbance peaks for both samples should be approximately the same. Thus ensuring the concentrated sample is denser by a factor of 10 in a separate clean 20 milliliter bur silicate glass file at one milliliter of tetra hydro furin.

Next, add thiol alkane ligands to the THF and shake. The solution to mix uniformly enough. Ligand should be added to cover at least the entire surface area of the suspended nanoparticles.

Excess ligand increases the speed and deficiency of the reaction in a fume hood. Place one milliliter from the vial containing the gold nanospheres into the vial of THF ligands. Quickly screw on the lid and shake the vial vigorously for 15 seconds.

Remove the lid and set the vial down. In the fume hood, Depending on the ligands, used domains of golden nanoparticles quickly form at the air liquid interface. The films then begin to translate up the side of the vial.

Nearly all the nanoparticles have been capped with thal ligands removed from suspension and transported to the side of the vials within an hour. To transfer the films onto removable glass substrates, cut the substrates into an area of 12.5 by 25.4 millimeters using a scribing pen or wheel for glass substrates clean, using an acetone rinse, followed by an isopropyl alcohol rinse. And finally, a di water rinse.

Before allowing the substrates to dry, see the text protocol for preparation of silicon wafers. Next, insert the substrate into the previously prepared vial of nanospheres and ligands. Screw on the lid and shake.

After shaking, remove the lid using tweezers. Position the substrate nearly vertical against the vial wall. Then use a pipette to coat the reaction mixture onto the substrate.

The reaction stops when all the organic solvent has evaporated or all the nanoparticles have been removed from the suspension. Estimate the packing efficiency of the nanospheres in the monolayer by observing the transmission and reflective properties of the film. Illuminate the monolayer on glass substrates from behind with a white light source.

A uniform colored film should be observed for high density nanoparticle, monolayer films in transmission and a gold like reflection observed in reflection. Next, use a spectrometer to quantify the macroscopic absorbent spectrum from the monolayers. As before, normalize the absorbent spectrum with a clean glass slide.

Then mount the monolayer film on a glass substrate in the beam path of the spectrometer and collect the absorbent spectrum. The absorbent peak should be significantly redshifted several hundred nanometers depending on the ligand used. If the absorbent peak is very broad or not well-defined, then the monolayer films are probably of poor quality.

To use the technique as an efficient means to functionalize the nanoparticles with thal ligands. Decant the remaining from the bottom of the vial. After the reaction is complete, then dry the material in the vial under nitrogen.

Add an organic solvent to resuspend the nanoparticles with nearly 100%particle phase transfer and recovery ensure the nanoparticles have not aggregated upon resuspension into the organic solvent as before, if the absorbence peak is broad relative to the original suspension, sonicate the sample for 15 minutes to help re disperse the nanoparticles. A thi alkane kept 15 nanometer gold nanosphere monolayer film on a glass substrate is observed partially reflecting light, signifying the high volume fraction of nanospheres and transmitting light, demonstrating the preservation of the plasma and resonances Uniformity and optical clarity shown here are false colored scanning electron microscopy images of athe acan capped 15 nanometer gold nanosphere monolayer film on a silicon wafer substrate. The edge of the film demonstrates that the films are monolayers and that the nanospheres pack into amorous domains at microscopic length scales.

At nanoscopic length scales. The films contain hexagon close, packed domains as demonstrated by the Fourier transform of the image.Shown. Here is the normalized experimental absorbance from a monolayer film consisting of thiol acan ca 15 nanometer gold nanospheres on a glass substrate.

A suspension of 15 nanometer gold nanospheres in water and phase transferred into chloroform Once mastered. This technique can be done in less than an hour if performed properly. After washing this video, you should have a good understanding of how to efficiently functionalize and self assemble metallic nanoparticles into microscopic monolith films.