Stable Silver Colloids and Silica-Coated Silver Colloids, and Methods of Preparing Stable Silver Colloids and Silica-Coated Silver Colloids

• US 20100062033A1
• Filed: 09/09/2008
• Published: 03/11/2010
• Est. Priority Date: 09/09/2008
• Status: Active Grant

• Current Assignee: Guardian Glass LLC (KOCH Industries Incorporated)
• Original Assignee: Guardian Industries Corporation (KOCH Industries Incorporated)
• Inventors: SHARMA, PRAMOD K.
• Granted Patent: US 8,647,652 B2
• Time in Patent Office: Days
• US Class Current: 424/421
• CPC Class Codes: A01N 25/04 Dispersions, emulsions, suspoemulsions, suspension concentrates or gels foams A01N25/16
• CPC Class Codes: A01N 25/08 containing solids as carriers or diluents
• CPC Class Codes: A01N 25/26 in coated particulate form
• CPC Class Codes: A01N 59/16 Heavy metals; Compounds thereof

Abstract

Methods for preparing silver colloids and silica-coated silver colloids are disclosed. The silver colloids may be prepared by heating a silver-containing solution, combining the heated silver-containing solution with an acid solution, and cooling the combined solutions to form a silver colloid containing silver particles. The silver particles in the silver colloid can further be coated with silica. A method for preparing antimicrobial coatings is also disclosed.

Claims

1. A method of preparing a silver colloid, comprising:

heating a silver-containing solution;

combining the heated silver-containing solution with an acid solution; and

cooling the combined solutions to form a silver colloid comprising silver particles.

2. The method of claim 1, wherein said silver-containing solution comprises an aqueous solution of silver nitrate.

3. The method of claim 1, wherein said acid solution comprises at least one acid chosen from sodium citrate, citric acid, malic acid, and alkali-based acids.

4. The method of claim 3, wherein said at least one acid solution comprises sodium citrate.

5. The method of claim 1, wherein said silver particles have a particle size that ranges from about 10 nm to about 200 nm.

6. The method of claim 5, wherein said silver particles have a particle size that ranges from about 20 nm to about 150 nm.

7. The method of claim 1, wherein said silver colloid is stable for at least about 24 hours.

8. The method of claim 7, wherein said silver colloid is stable for at least about 10 days.

9. A method of preparing a silica-coated silver colloid, comprising:

heating a silver-containing solution;

combining the heated silver-containing solution with an acid solution;

cooling the combined solutions to form a silver colloid comprising silver particles;

adding aqueous ammonia and ethanol to the silver colloid; and

adding tetraethoxysilane to the silver colloid to form a silica-coated silver colloid comprising silica-coated silver particles.

10. The method of claim 9, wherein said silver-containing solution comprises an aqueous solution of silver nitrate.

11. The method of claim 9, wherein said acid solution comprises at least one acid chosen from sodium citrate, citric acid, malic acid, and alkali-based acids.

12. The method of claim 9, wherein said silica-coated silver particles have a particle size less than about 300 nm.

13. The method of claim 9, wherein said silica-coated silver colloid is stable for at least about 24 hours.

14. The method of claim 13, wherein said silica-coated silver colloid is stable for at least about 10 days.

15. A method of forming an antimicrobial coating, comprising:

providing a substrate;

preparing a silver colloid by heating a silver-containing solution, combining the heated silver-containing solution with an acid solution; and

cooling the combined solutions to form a silver colloid comprising silver particles,

coating the substrate with the silver colloid; and

drying the coated substrate.

16. The method of claim 15, wherein said silver particles have a particle size that ranges from about 10 nm to about 200 nm.

17. The method of claim 16, wherein said silver particles have a particle size that ranges from about 20 nm to about 150 nm.

18. The method of claim 15, wherein the silver particles are coated with silica prior to coating the substrate.

19. The method of claim 18, wherein the silica-coated silver particles have a particle size less than about 300 nm.

20. The method of claim 15, wherein said substrate comprises a glass substrate.