Silver nanoplate compositions and methods
Embodiments of the present invention relate to methods for preparing high optical density solutions of nanoparticle, such as nanoplates, silver nanoplates or silver platelet nanoparticles, and to the solutions and substrates prepared by the methods. The process can include the addition of stabilizing agents (e.g., chemical or biological agents bound or otherwise linked to the nanoparticle surface) that stabilize the nanoparticle before, during, and/or after concentration, thereby allowing for the production of a stable, high optical density solution of silver nanoplates. The process can also include increasing the concentration of silver nanoplates within the solution, and thus increasing the solution optical density.
1. A process for making concentrated silver nanoplates that preserve shape post-concentration while increasing optical density, the process comprising:
adding a stabilizing agent to a pre-concentrated solution, wherein the stabilizing agent comprises at least one of the group consisting of: an aminopropyltriethoxysilane (APTES), an amine moiety, a lipoic acid, a mercaptohexadecanoic acid, a mercaptoundecanoic acid, and a dihydrolipoic acid;
wherein the pre-concentrated solution comprises silver nanoplates,
wherein each of the silver nanoplates has a plate shape,
wherein the pre-concentrated solution has a peak optical density at a first wavelength; and
increasing a concentration of the silver nanoplates in the pre-concentrated solution to generate a concentrated solution,
wherein the concentrated solution has a peak optical density at a second wavelength,
wherein the first wavelength is substantially the same as the second wavelength, wherein the peak optical density of the concentrated solution is greater than the peak optical density of the pre-concentrated solution, and
wherein at least a portion of the silver nanoplates in the pre-concentrated solution retain the plate shape in the concentrated solution, wherein the peak optical density of the concentrated solution is at least ten times higher than the peak optical density of the pre-concentrated solution and wherein the peak optical density of the concentrated solution is at least 100 cm −1 .
2. The process of claim 1 ,
wherein the second wavelength of the concentrated solution is in a range between 300 nm and 1500 nm, and
wherein at least one optical property of the concentrated solution is substantially the same as the pre-concentrated solution in that the peak optical density of the pre-concentrated solution and the peak optical density of the concentrated solution occurs at substantially the same wavelength, and
wherein the portion of the silver nanoplates that retain the plate shape is greater than 90% in the concentrated solution.
3. The process of claim 1 ,
wherein the silver nanoplates are prepared via a seed mediated growth mechanism,
wherein the seed mediated growth mechanism comprises:
combining citrate, polystyrene sodium sulfonate (PSSS), and sodium borohydride in a first solution,
adding silver nitrate to the first solution to form a seed solution,
adding a portion of the seed solution to a second solution, wherein the second solution comprises ascorbic acid, and
adding silver nitrate to the second solution to form the pre-concentrated solution.
4. The process of claim 1 ,
wherein increasing the concentration is performed using a filter membrane with pores with a molecular weight cutoff in a range between 10 kDa and 0.05 micron.
5. The process of claim 1 , further comprising coating the silver nanoplates with silica, wherein coating the silver nanoplates with silica comprises:
adding ethanol to the pre-concentrated solution,
adding a base to the pre-concentrated solution, and
adding a silane to the pre-concentrated solution.
6. The process of claim 1 , wherein the stabilizing agent comprises at least one of the group consisting of: an aminopropyltriethoxysilane (APTES) and an amine moiety.
7. The process of claim 1 , wherein the stabilizing agent comprises at least one of the group consisting of: a lipoic acid, a mercaptohexadecanoic acid, a mercaptoundecanoic acid, and a dihydrolipoic acid.
8. The process of claim 1 , further comprises adding a stabilizing agent containing a polymer, wherein the polymer is a polystyrene sodium sulfonate.
9. The process of claim 1 , further comprising forming a metal oxide shell on the surface of the silver nanoplate.
10. The process of claim 9 , wherein the metal oxide shell is any of the group consisting of: a silica shell and a titanium dioxide shell, wherein the metal oxide shell has a thickness in a range between 1 nm to 100 nm.
11. The process of claim 1 , wherein the portion of the concentrated silver nanoplates that retain the plate shape after increasing the concentration is greater than 80%.
12. The process of claim 1 , wherein the pre-concentrated solution is centrifuged.
13. The process of claim 1 , where the pre-concentrated solution is incubated with a substrate, wherein the substrate comprises a fiber.