Stable silver colloids and silica-coated silver colloids, and methods of preparing stable silver colloids and silica-coated silver colloids

• US 8,647,652 B2
• Filed: 09/09/2008
• Issued: 02/11/2014
• 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
• Primary Examiner(s): Wax, Robert A
• Assistant Examiner(s): AL-AWADI, DANAH J
• Application Number:
  US12/207,076
• Publication Number:
  US 20100062033A1
• Time in Patent Office: 1,981 Days
• Field of Search: None
• US Class Current: 424/411
• 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 silica-coated silver colloid, the method consisting essentially of:

(a) heating a silver-containing solution;

(b) combining the heated silver-containing solution with an acid solution;

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

(d) adding aqueous ammonia and ethanol to the silver colloid; and

(e) adding tetraethoxysilane to the silver colloid to form a silica-coated silver colloid comprising silica-coated silver particles,

wherein said silica-coated silver colloid is stable for at least about 24 hours.

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 1, wherein said silica-coated silver particles have a particle size less than about 300 nm.

5. The method of claim 1, wherein said silica-coated silver colloid is stable for at least about 10 days.

6. A method of forming an antimicrobial coating, the method consisting essentially of:

(a) providing a substrate;

(b) 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;

(c) adding aqueous ammonia and ethanol to the silver colloid; and

(d) adding tetraethoxysilane to the silver colloid to form a silica-coated silver colloid comprising silica-coated silver particles;

(e) coating the substrate with the silica coated silver particles; and

(f) drying the coated substrate,

wherein said silica-coated silver colloid is stable for at least about 24 hours.

7. The method of claim 6, wherein said silver particles have a particle size that ranges from about 10 nm to about 200 nm.

8. The method of claim 7, wherein said silver particles have a particle size that ranges from about 20 nm to about 150 nm.

9. The method of claim 6, wherein the silica-coated silver particles have a particle size less than about 300 nm.

10. The method of claim 6, wherein said substrate comprises a glass substrate.