Methods for preparing single-walled carbon nanotubes
The present invention relates to cobalt and molybdenum doped mesoporous silica catalysts and methods for using the catalysts to making Single-Walled Carbon Nanotubes. The methods offer increased control over the orientation, length and diameter of the nanotubes produced.
1. A method for making a single-walled carbon nanotube, the method comprising:
affixing a catalyst precursor solution to a surface of a substrate, wherein the catalyst precursor solution comprises mesoporous silica, cobalt, and molybdenum, wherein the affixing the catalyst precursor solution comprises at least one of spin-coating, dip-coating, drop-coating, contact printing, or micro-patterning the catalyst precursor solution onto the surface of the substrate;
heating the substrate, for a time and temperature sufficient to calcine the catalyst precursor solution to form a calcined catalyst; and
contacting the calcined catalyst with a flow of carbon feedstock gas for a time and at a temperature sufficient to make a single-walled carbon nanotube.
2. The method of claim 1 , wherein the substrate comprises one of a silica wafer, a silicate, a flake, a silicon wafer, or a silicon wafer having an oxide layer.
3. The method of claim 1 , wherein the mesoporous silica comprises at least one of SBA16, SBA15, SBA11, MCM41, or MCM48.
4. The method of claim 1 , wherein the catalyst precursor solution is affixed to the substrate surface using at least one of spin-coating, dip-coating, or drop-coating.
5. The method of claim 1 , wherein the catalyst precursor solution is affixed to the substrate surface using contact printing.
6. The method of claim 5 , wherein the catalyst precursor solution is affixed to the substrate surface as a micro-pattern.
7. The method of claim 1 , comprising growing the nanotube in a direction parallel to the flow of carbon feedstock gas.
8. The method of claim 1 , wherein the nanotube has a diameter of from about 0.3 nm to about 4 nm.
9. The method of claim 8 , wherein the nanotube has a diameter of from about 0.5 nm to about 3 nm.
10. The method of claim 9 , wherein the nanotube has a diameter of from about 0.8 nm to about 1.8 nm.
11. The method of claim 1 , wherein the nanotube has a length of from about 1 nm to about 100 cm.
12. The method of claim 11 , wherein the nanotube has a length of from about 1 mm to about 10 cm.
13. The method of claim 11 , wherein the nanotube has a length of from about 100 mm to about 1 cm.
14. The method of claim 1 , wherein the nanotube is an individual nanotube.
15. The method of claim 1 , wherein the substrate is heated for about 2 hours at a temperature of about 550° C.
16. The method of claim 1 , wherein heating the substrate is carried out at a temperature of from about 350° C. to about 1000° C.
17. The method of claim 16 , wherein the temperature is from about 700° C. to about 850° C.
18. The method of claim 17 , wherein the temperature is about 850° C.
19. The method of claim 1 , wherein the carbon feedstock comprises ethanol.
20. The method of claim 1 , wherein the carbon feedstock is mixed with argon gas.
21. The method of claim 1 , wherein the flow rate of the carbon feedstock gas is between about 20 sccm to about 1000 sccm.
22. The method of claim 21 , wherein the flow rate of the carbon feedstock gas is between about 20 sccm to about 100 sccm.
23. The method of claim 21 , wherein the flow rate of the carbon feedstock gas is between about 500 sccm to about 800 sccm.
24. The method of claim 1 , wherein the surface of the substrate has one or more slits.
25. The method of claim 1 , wherein the surface of the substrate has one or more trenches.
26. The method of claim 15 , wherein the heating is performed in air.
27. The method of claim 1 , comprising preparing the catalyst precursor solution by preparing a mesoporous silica solution and incorporating cobalt and molybdenum into the mesoporous silica solution.