Synthesis of highly ordered nanoparticle arrays in anisotropic nanoreactors
Disclosed herein are methods for forming one or more nanoparticles. The methods include depositing a solution comprising a block copolymer and a metal salt into one or more square pyramidal nanoholes formed in a substrate, and annealing the substrate to provide a single nanoparticle in each of the one or more square pyramidal nanoholes.
1. A method of forming one or more nanoparticles, the method comprising:
depositing a solution comprising a block copolymer and a metal salt into one or more square pyramidal nanoholes formed in a substrate; and,
annealing the solution containing substrate under conditions to reduce the metal salt in the solution to a metal and form a single nanoparticle in of the one or more square pyramidal nanoholes,
wherein the substrate has a solvent contact angle of about 20° to about 40°.
2. The method of claim 1 , wherein the block copolymer is selected from the group consisting of poly(ethylene oxide)-block-poly(2-vinyl pyridine) (PEO-b-P2VP), poly(ethylene oxide)-block-poly(4-vinyl pyridine) (PEO-b-P4VP), poly(ethylene oxide)-block-poly(acrylic acid) (PEO-b-PAA).
3. The method of claim 1 , wherein the block copolymer is present in the solution in an amount of about 2 mg/mL to about 20 mg/mL.
4. The method of claim 1 , wherein the metal of the metal salt is selected from the group consisting of gold, silver, copper, nickel, cobalt, germanium, selenium, tantalum, and any combination thereof.
5. The method of claim 1 , wherein the metal salt is selected from the group consisting of gold (III) chloride trihydrate (HAuCl 4 .3H 2 O), silver nitrate (AgNO 3 ), copper (II) nitrate hemi(pentahydrate) (Cu(NO 3 ) 2 2.5H 2 O), nickel (II) nitrate hexahydrate (Ni(NO 3 ) 2 .6H 2 O), cobalt (II) nitrate hexahydrate (Co(NO 3 ) 2 .6H 2 O), germanium tetrachloride (GeCl 4 ), selenium tetrachloride (SeCl 4 ), tantalum (V) ethanolate (CH 3 CH 2 O) 5 Ta), and any combination thereof.
6. The method of claim 1 , wherein the metal salt is present in the solution in an amount of about 1.5 mg/mL to about 15 mg/mL.
7. The method of claim 1 , wherein the solution comprises a solvent selected from the group consisting of ethanol, toluene, methanol, isopropanol, and any combination thereof.
8. The method of claim 1 , wherein the solution has a pH of about 1 to about 3.
9. The method of claim 1 , wherein annealing comprises a first annealing step and a second annealing step, and
wherein the first annealing step comprises annealing at a temperature of about 100° C. to about 200° C. and the second annealing step comprises annealing at a temperature of about 400° C. to about 600° C.
10. The method of claim 9 , wherein the first annealing step is performed for 10 hours to about 20 hours.
11. The method of claim 9 , wherein the second annealing step is performed for about 4 hours to about 8 hours.
12. The method of claim 1 , further comprising preparing the substrate, wherein preparing the substrate comprises:
patterning a substrate with a photoresist material arranged in an array of squares, thereby providing a patterned substrate;
depositing a mask over the patterned substrate;
performing a lift-off process to remove the photoresist material and corresponding mask disposed on the photoresist material, thereby exposing an array of squares of uncovered substrate with a remaining portion of the substrate being masked;
etching the exposed array of squares of uncovered substrate to form an array of square pyramidal nanoholes in the substrate; and,
removing the mask.
13. The method of claim 12 , wherein the exposed array of squares is etched with a basic solution.
14. The method of claim 13 , wherein the basic solution comprises potassium hydroxide (KOH), tetramethylammonium hydroxide, ethylenediamine pyrocatechol (EDP), or a mixture thereof.
15. The method of claim 12 , wherein the array of square pyramidal nanoholes has an average spacing between adjacent ones of nanoholes of about 300 nm to about 500 nm.
16. The method of claim 12 , wherein the one or more square pyramidal nanoholes has an edge length of about 150 nm to about 300 nm.
17. The method of claim 12 , further comprising surface treating the substrate comprising the array of square pyramidal nanoholes with 02 plasma and a surface treatment solution, thereby adjusting the solvent contact angle of the substrate.
18. The method of claim 17 , wherein the surface treatment solution comprises octadecyltrichlorosilane (OTS) in an amount of about 40 vol % to about 60 vol %, based on the total weight of the solution.
19. The method of claim 1 , wherein the solution is deposited in the one or more square pyramidal nanoholes by coating the substrate with the solution, wherein the substrate has a top surface that is dewetted such that the solution preferentially deposits into the nanoholes.
20. The method of claim 1 , wherein the solution is deposited into the one or more square pyramidal nanoholes by selectively depositing the solution directly into each of the one or more nanoholes.