Magnetic nanoparticles
Methods for preparing magnetic nanoparticles comprising metal, metal carbide, metal nitride, metal sulfide, metal phosphide, metal oxide or a mixture thereof are disclosed. Methods for preparing magnetic nanoparticles having a core comprising metal, metal carbide, metal nitride, metal sulfide, metal phosphide, or a mixture thereof and a metal oxide shell are also disclosed. The methods comprise the solution-phase decomposition of a precursor at elevated temperature then exposure of the reaction mixture to an oxidizing medium, such as air.
1. A method for preparing magnetic nanoparticles, the method comprising:
(a) preparing a solution of a precursor comprising at least one metal compound in a liquid reaction medium, wherein the metal compound is an organoiron compound comprising at least one ligand that is not carbon monoxide;
(b) heating the solution in a reaction vessel under a reactive gas atmosphere to a first temperature and maintaining the first temperature for a first period of time to at least partially decompose the precursor;
(c) optionally, heating or cooling the reaction mixture from step (b) to a second temperature and maintaining the second temperature for a second period of time to further decompose the precursor;
(d) exposing the reaction mixture to an oxidising medium; and
(e) recovering the resulting nanoparticles.
2. A method as claimed in claim 1 , wherein the reactive gas atmosphere comprises a reducing agent.
3. A method as claimed in claim 2 , wherein the reactive gas atmosphere is a hydrogen atmosphere.
4. A method as claimed in claim 3 , wherein the organoiron compound is a sandwich or half sandwich compound.
5. A method as claimed in claim 4 , wherein the organoiron compound is Fe(C 5 H 5 )(C 6 H 7 ), Fe(C 5 H 5 ) 2 , or a salt of [Fe(C 5 H 5 )(C 6 H 6 )] + .
6. A method as claimed in claim 5 , wherein the organoiron compound is Fe(C 5 H 5 )(C 6 H 7 ).
7. A method, as claimed in claim 3 , the method comprising:
(a) preparing a solution of a precursor comprising at least one organoiron compound, which comprises at least one ligand that is not carbon monoxide, in a liquid reaction medium;
(b) heating the solution in a reaction vessel under a hydrogen atmosphere to a first temperature and maintaining the first temperature for a first period of time to at least partially decompose the precursor;
(c) exposing the reaction mixture to an oxidising medium; and
(d) recovering the resulting nanoparticles.
8. A method, as claimed in claim 3 , the method comprising:
(a) preparing a solution of a precursor comprising at least one organoiron compound, which comprises at least one ligand that is not carbon monoxide, in a liquid reaction medium;
(b) heating the solution in a reaction vessel under a hydrogen atmosphere to a first temperature and maintaining the first temperature for a first period of time to at least partially decompose the precursor;
(c) heating the reaction mixture from step (b) to a second temperature and maintaining the second temperature for a second period of time to further decompose the precursor;
(d) exposing the reaction mixture to an oxidising medium; and
(e) recovering the resulting nanoparticles.
9. A method as claimed in claim 3 , wherein the nanoparticles have a core comprising iron, iron carbide, or a mixture of iron and iron carbide and a shell comprising iron oxide.
10. A method as claimed in claim 3 , wherein the liquid reaction medium comprises a surfactant.
11. A method as claimed in claim 3 further comprising mixing the product nanoparticles with a ligand.
12. A method as claimed in claim 1 , wherein the reactive gas atmosphere is an ammonia gas atmosphere.
13. A method as claimed in claim 12 , wherein the iron compound comprises at least one polydentate ligand.
14. A method as claimed in claim 13 , wherein the iron compound comprises at least one bidentate ligand.
15. A method as claimed in claim 14 , wherein the iron compound is iron (II) acetylacetonate.
16. A method, as claimed in claim 12 , the method comprising:
(a) preparing a solution of a precursor comprising at least one iron compound, this comprises at least one ligand that is not carbon monoxide or bis(trimethylsilylamide), in a liquid reaction medium;
(b) heating the solution in a reaction vessel under an ammonia atmosphere to a first temperature and maintaining the first temperature for a first period of time to at least partially decompose the precursor;
(c) cooling the reaction mixture from step (b) to a second temperature and maintaining the second temperature for a second period of time to further decompose the precursor;
(d) exposing the reaction mixture to an oxidising medium; and
(e) recovering the resulting nanoparticles.
17. A method as claimed in claim 16 , wherein the nanoparticles comprise iron nitride or iron oxide.
18. A method as claimed in claim 12 , wherein the liquid reaction medium comprises a surfactant.
19. A method as claimed in claim 12 comprising mixing the product nanoparticles with a ligand.