Stable silver colloids and silica-coated silver colloids, and methods of preparing stable silver colloids and silica-coated silver colloids
View Patent ↗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.
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.