Solution-based synthesis of doped ZnO nanostructures
Methods of making electrically conductive, doped zinc oxide nanowires and nanowire films are provided. The methods comprises the steps of forming an aqueous solution comprising a dopant-containing precursor salt, a zinc-containing precursor salt and a pH buffering agent and heating the aqueous solution to a temperature below its boiling point in the presence of seed crystals, whereby doped zinc oxide nanowires are grown in situ from the seed crystals in the aqueous solution.
1. A method of making conductive, doped zinc oxide nanowires, the method comprising:
forming an aqueous solution comprising a chloride-containing or fluoride-containing precursor salt, a zinc-containing precursor salt and a pH buffeting agent; and
heating the aqueous solution to a reaction temperature below its boiling point in the presence of a substrate comprising seed crystals, wherein the aqueous solution has a pH in the range from about 5 to about 7 at the reaction temperature;
whereby chloride- or fluoride-doped zinc oxide nanowires are grown in situ from the seed crystals in the aqueous solution.
2. The method of claim 1 , wherein the aqueous solution has a pH in the range from about 5.3 to about 6 at the reaction temperature.
3. The method of claim 1 , wherein the substrate is a non-electrically conducting substrate.
4. The method of claim 1 , wherein the aqueous solution further comprises an acid that, together with the pH buffering agent, provides the pH in the range from about 5 to about 7 at the reaction temperature.
5. The method of claim 4 , wherein the acid comprises one or more of acetic acid, phosphoric acid, and citric acid.
6. The method of claim 1 , wherein the chloride dopant concentration or fluoride dopant concentration in the doped zinc oxide nanowires is at least 0.1 atomic %.
7. The method of claim 6 , wherein the chloride dopant concentration or fluoride dopant concentration in the doped zinc oxide nanowires is in the range from about 0.2 atomic % to about 2 atomic %.
8. The method of claim 1 , wherein the aqueous solution comprises the chloride-containing precursor salt.
9. The method of claim 8 , wherein the chloride-containing precursor salt is aluminum chloride.
10. The method of claim 9 , wherein the doped zinc oxide nanowires have a chloride dopant concentration of at least about 1 atomic %.
11. The method of claim 9 , wherein the zinc-containing precursor salt is zinc nitrate.
12. The method of claim 11 , wherein the substrate is a non-electrically conducting substrate and the reaction temperature is in the range from about 80 to about 98° C.
13. The method of claim 8 , wherein the aqueous solution further comprises an acid that, together with the pH buffering agent, provides the pH in the range from about 5 to about 7 at the reaction temperature and further wherein the aqueous solution comprises a chloride-containing precursor salt selected from ammonium chloride, zinc chloride or potassium chloride.
14. The method of claim 13 , wherein the chloride-containing precursor salt is zinc chloride or potassium chloride.
15. The method of claim 8 , wherein the doped nanowires have a chloride dopant concentration of at least about 0.1 atomic %.
16. The method of claim 8 , wherein the zinc-containing precursor salt is zinc nitrate.
17. The method of claim 8 , wherein the substrate is a non-electrically conducting substrate.
18. The method of claim 1 , wherein the aqueous solution comprises the fluoride-containing precursor salt.
19. The method of claim 18 , wherein the fluoride-containing precursor salt is sodium fluoride.
20. The method of claim 1 , wherein the aqueous solution has a pH in the range from about 5 to about 5.7 at the reaction temperature.