Microparticles and methods for their production

• US 20050106098A1
• Filed: 01/07/2003
• Published: 05/19/2005
• Est. Priority Date: 01/07/2002
• Status: Abandoned Application

• Current Assignee: University of Reading
• Original Assignee: University of Reading
• Inventors: Tsang, Shik Chi, Chan, Henry Bo So
• Application Number:
  US10/500,842
• Publication Number:
  US 20050106098A1
• Time in Patent Office: Days
• US Class Current: 424/1.110
• CPC Class Codes: A61K 51/1244 microparticles or nanoparticles, e.g. polymeric nanoparticles
• CPC Class Codes: B01J 13/025 Applications of microcapsules not provided for in other subclasses
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: C01G 49/00 Compounds of iron
• CPC Class Codes: C01G 49/0018 Mixed oxides or hydroxides, C01G49/0009 takes precedence
• CPC Class Codes: C01G 49/02 Oxides; Hydroxides C01G49/0018 takes precedence
• CPC Class Codes: C01G 49/08 Ferroso-ferric oxide [Fe3O4]
• CPC Class Codes: C01G 51/00 Compounds of cobalt
• CPC Class Codes: C01G 51/04 Oxides; Hydroxides
• CPC Class Codes: C01P 2002/72 by d-values or two theta-values, e.g. as X-ray diagram
• CPC Class Codes: C01P 2002/85 by XPS, EDX or EDAX data
• CPC Class Codes: C01P 2004/04 obtained by TEM, STEM, STM or AFM
• CPC Class Codes: C01P 2004/64 Nanometer sized, i.e. from 1-100 nanometer
• CPC Class Codes: C01P 2004/84 one phase coated with the other
• CPC Class Codes: C01P 2006/42 Magnetic properties
• CPC Class Codes: C09C 1/24 Oxides of iron
• CPC Class Codes: C09C 3/12 Treatment with organosilicon compounds C09C3/006 takes precedence

Abstract

Microparticles having a metal-containing core encapsulated in a graphitic shell containing hetero atoms are made by forming, in a liquid medium, colloidal particles containing a metal-oxo species of Fe, Co, Ni and Pd, colloidally stabilized by a surfactant and containing source material of carbon and the hetero atoms. These particles are pyrolyzed in inert gas to yield the microparticles. In an alternative method, silica gel coated particles are formed by colloidally stabilizing particles containing metal species and forming silica at the boundary of the stabilized particle.

Claims

1. Method of making microparticles having a metal-containing core encapsulated in a graphitic shell containing hetero atoms, including the steps of

(i) forming, in a liquid medium, colloidal particles containing a first metal in the form of a metal-oxo species, the first metal being selected from Fe, Co, Ni and Pd, the particles being colloidally stabilized by a surfactant and containing in addition to the first metal source material of carbon and the hetero atoms, and

(ii) separating said particles from the liquid medium and pyrolyzing them in inert gas to yield the microparticles having said core and said graphitic shell containing said hetero atoms encapsulating the core.

2. Method according to claim 1 wherein said metal containing core contains at least one phase selected from metal, alloy, metal carbide and metal oxide and, optionally, is ferromagnetic.

3. Method according to claim 1 or 2 wherein in step (i) at least one second metal is incorporated in said colloidal particles and is present in the core of the microparticles obtained.

4. Method according to claim 3 wherein said second metal is a radionuclide.

5. Method according to claim 1 wherein step (i) is performed by forming a solution of a compound of said first metal in said liquid medium which is a polar solvent and heating said solution in the presence of said surfactant and an oxidizing agent to convert said compound to said metal-oxo species and form said colloidal particles.

6. Method according to claim 5 wherein said oxidizing agent is selected from oxygen and a compound of a second metal which becomes incorporated in the colloidal particles.

7. Method according to claim 1 wherein step (i) is performed by forming an emulsion having dispersed phase droplets stabilized by said surfactant and containing a dissolved compound of said first metal and oxidizing said compound of said first metal to produce said metal-oxo species and form said colloidal particles.

8. Method according to claim 7 wherein said dispersed phase droplets include a dissolved oxidizing agent which is a compound of a second metal which becomes incorporated in said colloidal particles.

9. Method according to claim 1 wherein said hetero atoms are selected from N, B, P, S and O.

10. Method according to claim 9 wherein said hetero atoms are N.

11. Method according to claim 1 wherein said metal-oxo species is a metal complex including ligands selected from cyanide, isocyanide, cyanate and isocyanate, thereby acting as a source of carbon and nitrogen as said hetero atom.

12. Microparticles having a core containing a radionuclide encapsulated by a graphitic shell.

13. Microparticles according to claim 12 wherein said core contains, in addition to said radionuclide, at least one of Fe, Co, Ni and Pd.

14. Microparticles according to claim 12 or 13 wherein said graphitic shell contains chemically bound hetero atoms such that graphitic layers of the shell are curved.

15. Microparticles according to claim 14 wherein the hetero atoms are N.

16. Method of making solid microparticles having a metal-containing core surrounded by a silica coating, including the steps of

(i) forming, in a liquid medium, colloidal particles containing a metal-containing species and colloidally stabilized by a surfactant, and

(ii) forming a silica coating around said colloidal particles by hydrolyzing a silicon compound in the region of the interface between the colloidal particle and the liquid medium.

17. Method according to claim 16 wherein the colloidal particles contain a plurality of said metal-containing species of different metals.

18. Method according to claim 16 or 17 wherein the or each said metal-containing species is selected from metal, alloy, metal oxide, metal hydroxide and metal carbide.

19. Method according to claim 16 wherein said metal-containing species is ferromagnetic and/or contains a radionuclide.

20. Method according to claim 16 wherein in step (i) said colloidal particles are made by forming an emulsion having dispersed phase droplets stabilized by said surfactant containing a dissolved compound of the metal and causing said metal-containing species to precipitate thereby forming said colloidal particles.

21. Method according to claim 20 wherein the precipitation of the metal-containing species is caused by addition of alkali.

22. Method according to claim 16 wherein the silicon compound which is hydrolyzed is an alkoxy silane compound.

23. Microparticles each having a core comprising at least one metal-containing species which is ferromagnetic and/or contains a radionuclide and a coating of silica gel encapsulating the core.

24. Microparticles according to claim 23 wherein said metal-containing species is selected from metal, alloy, metal oxide, metal hydroxide and metal carbide.

25. Microparticles according to claim 23 or 24 wherein said silica gel has at its surface functional groups for the attachment of other species.

26. Microparticles according to claim 23 wherein said silica gel is porous.

27. Microparticles according to claim 26 wherein said cores have an average diameter in the range 1 to 100 nm, preferably 1 to 50 nm.

28. Microparticles according to claim 27 wherein said coatings have an average thickness in the range 1 to 50 nm, preferably 2 to 10 nm.