Rare earth nanorods
A process for the production of nanorods containing a rare earth metal is disclosed. The process comprises the steps of: (a) increasing the pH of an aqueous solution of the formula MX 3 , where M is a trivalent rare earth metal cation and X is a monovalent anion so as to produce a reaction product containing X anions in solution and a precipitate in the form of trivalent rare earth hydroxide nanoparticles of the formula M(OH) 3 , the nanoparticles having a hexagonal crystal structure; and, (b) ageing the nanoparticles of step (a) in the presence of the reaction product containing X anions in solution so as to cause rod-like anisotropic growth of the nanoparticles and form rare earth hydroxide nanorods.
1. A process for the production of nanorods containing a rare earth metal, the process comprising the steps of:
(a) increasing the pH of an aqueous solution of the formula MX 3 , wherein M is a trivalent rare earth metal cation and X is at least one halide anion, so as to produce a reaction product containing X anions in solution and a precipitate in the form of trivalent rare earth hydroxide nanoparticles of the formula M(OH) 3 , the nanoparticles having a hexagonal crystal structure; and
(b) ageing the nanoparticles of step (a) in the presence of the reaction product containing X anions in solution so as to facilitate rod-like anisotropic growth of the nanoparticles and form rare earth hydroxide nanorods, wherein the step of ageing is conducted at atmospheric pressure and at a temperature less than 80° C.
2. The process of claim 1 , wherein the step of increasing the pH comprises the step of introducing a base or basic solution to the aqueous solution of the formula MX 3 .
3. The process of claim 2 , wherein the basic solution comprises ammonia.
4. The process of claim 1 , further comprising the step of washing the nanorods after the step of ageing using one or more washing cycles.
5. The process of claim 4 , further comprising the step of drying the washed nanorods.
6. The process of claim 1 , further comprising the step of calcining the nanorods to produce nanorods of an equivalent rare earth oxide.
7. The process of claim 1 , further comprising the step of sulfurising the nanorods to produce nanorods of an equivalent rare earth sulfide or oxysulfide.
8. The process of claim 7 , wherein the monovalent anion X comprises chloride.
9. The process of claim 7 , wherein the step of ageing is conducted at ambient temperature.
10. The process of claim 1 , wherein the trivalent rare earth metal cation M is cerium and the step of ageing is conducted under reducing conditions so as to maintain the cerium ions in a trivalent oxidation state.
11. The process of claim 1 , wherein M is cerium and the process further comprises the step of oxidizing Ce(III) to Ce(IV) state after the step of aging to produce nanorods of Ce(IV) oxide.
12. The process of claim 1 , wherein the step of ageing is conducted at a temperature less than 60° C.
13. The process of claim 1 , wherein the step of ageing is conducted at a temperature less than 40° C.
14. The process of claim 1 , wherein the rare earth hydroxide nanorods are solid.
15. The process of claim 1 , wherein the step of ageing is conducted for up 2 hours.
16. The process of claim 1 , wherein the step of ageing is conducted for up to 8 hours.
17. The process of claim 1 , wherein the step of ageing is conducted for up to 15 hours.
18. The process of claim 1 , wherein the pH is increased above 8.
19. The process of claim 1 , wherein the pH is increased above 9.
20. The process of claim 1 , wherein the pH is increased above 9.5.
21. The process of claim 1 , wherein the pH is increased above 10.