Catalyst particles on a tip

1. A method for forming nanostructures on a metal tip, comprising:

disposing the metal tip to be spaced apart from an electrolyte solution, the electrolyte solution containing metal catalyst ions;

applying a voltage to the electrolyte solution to emit the metal catalyst ions from the electrolyte solution, wherein the metal tip is spaced apart from the electrolyte solution while applying the voltage;

attaching the emitted metal catalyst ions to the metal tip to form metal catalyst particles on the metal tip; and

providing a reaction gas to the metal catalyst particles on the metal tip to form nanostructures on the metal tip.

2. The method of claim 1 , wherein the metal tip is formed by electrochemically etching a metal wire within a metal hydroxide solution.

3. The method of claim 2 , wherein the metal hydroxide solution comprises potassium hydroxide or sodium hydroxide.

4. The method of claim 1 , wherein the metal tip is formed of at least one material selected from the group consisting of tungsten, nickel, aluminum, molybdenum, tantalum and niobium.

5. The method of claim 1 , wherein the metal catalyst ions comprise at least one ion selected from the group consisting of nickel ions, cobalt ions, molybdenum ions and iron ions.

6. The method of claim 1 , wherein attaching the emitted metal catalyst ions to the metal tip comprises reducing or oxidizing the emitted metal catalyst ions into metal catalyst particles on the metal tip.

7. The method of claim 1 , wherein the voltage is applied to allow the electrolyte solution to have a positive potential and the metal tip to have a negative potential.

8. The method of claim 1 , wherein the voltage is applied to allow the electrolyte solution to have a negative potential and the metal tip to have a positive potential.

9. The method of claim 1 , wherein attaching the emitted metal catalyst ions to the metal tip comprises controlling a size of the metal catalyst particles by adjusting the voltage and/or time the voltage is applied.

10. The method of claim 1 , wherein the electrolyte solution is disposed within a container.

11. The method of claim 1 , wherein the nanostructures comprise carbon nanotubes.

12. The method of claim 11 , wherein the reaction gas comprises a hydrocarbon.

13. The method of claim 12 , wherein the hydrocarbon is selected from the group consisting of carbon monoxide, acetylene, ethane, methane, propane, and a combination thereof.

14. The method of claim 1 , wherein an electrode is disposed apart from the metal tip and a voltage is applied between the metal tip and the electrode while the nanostructures are being formed.

15. The method of claim 1 , wherein the reaction gas comprises SiO and/or C 6 H 18 Si 2 .

16. The method of claim 1 , wherein heat, plasma radiation and/or microwave radiation are applied while the nanostructures are being formed.