Method for silica encapsulation of magnetic particles
View Patent ↗Provided is a method of inhibiting magnetically induced aggregation of ferrimagnetic and/or ferromagnetic nanoparticles by encapsulating the nanoparticles in a silica shell. The method entails coating magnetic nanoparticle surfaces with a polyacid polymer to form polymer-coated magnetic nanoparticles and treating the polymer-coated magnetic nanoparticles with a silica precursor to form uniform silica-coated magnetic nanoparticles. By controlling the thickness of the silica encapsulating the nanoparticles, the inherent magnetically induced aggregation of the nanoparticles can be completely inhibited.
1. A method comprising:
(a) treating magnetic nanoparticles with a polyacid polymer to form polymer-coated magnetic nanoparticles and ionizing the polymer-coated magnetic nanoparticles with a base, and
(b) reacting the polymer-coated magnetic nanoparticles with a silica precursor to form silica-coated magnetic nanoparticles,
wherein magnetically induced aggregation of the magnetic nanoparticles of step (a) is completely inhibited by the silica-coating of step (b),
wherein the magnetic nanoparticles are selected from the group consisting of ferrimagnetic nanoparticles and ferromagnetic nanoparticles.
2. The method of claim 1 , wherein the magnetic nanoparticles are selected from the group consisting of ferrimagnetic nanoparticles and ferromagnetic nanoparticles.
3. The method of claim 2 , wherein the nanoparticles comprise cobalt ferrite (CoFe 2 O 4 ).
4. The method of claim 1 , wherein the polyacid polymer is selected from the group consisting of poly(acrylic acid) (PAA), poly(methacrylic acid), poly(vinylsulfonic acid), poly(vinylphosphonic acid), and copolymers thereof.
5. The method of claim 4 , wherein the polyacid polymer is PAA.
6. The method of claim 1 , wherein the silica precursor is selected from the group consisting of tetraalkylorthosilicates (Si(OR 1 ) 4 ) and trialkoxyalkylsilanes (R 2 Si(OR 3 ) 3 ), wherein each of R1, R2, and R3 is hydrogen, a monovalent hydrocarbon radical comprising 1 to 30 carbons, or an aminoalkyl group comprising 1 to 5 carbons.
7. The method of claim 6 , wherein the silica precursor is selected from the group consisting of tetraethylorthosilicate (TEOS), tetramethylorthosilicate (TMOS), tetrapropylorthosilicate, methyltrimethoxysilane, and methyltriethoxysilane.
8. The method of claim 7 , wherein the silica precursor is TEOS.
9. The method of claim 1 , further comprising:
(c) reacting the silica-coated magnetic nanoparticles with a reactive silane to enable surface modification of the silica-coated magnetic nanoparticles with other organic functional groups.
10. The method of claim 9 , wherein the silica-coated magnetic nanoparticles are amine functionalized with reactive silane aminopropyltrimethoxysilane (APTMS).
11. The method of claim 10 , wherein the amine-functionalized silica-coated magnetic nanoparticles are further reacted with activated carboxylic acids to form amide bonds.
12. The method of claim 10 , wherein the amine-functionalized silica-coated magnetic nanoparticles are further reacted with acrylates to form secondary and tertiary amines.
13. The method of claim 10 , wherein the amine-functionalized silica-coated magnetic nanoparticles are further reacted with poly(ethylene glycol) acrylate to form poly(ethylene glycol) functionalized silica-coated magnetic nanoparticles.
14. The method of claim 1 , wherein the magnetic nanoparticles of step (a) have a diameter of 1 to 100 nm.
15. The method of claim 1 , wherein the magnetic nanoparticles of step (a) and the silica-coated magnetic particles of step (b) have the same core diameter.
16. The method of claim 1 , wherein the silica-coated magnetic nanoparticles of step (b) have a silica shell thickness of 1 to 100 nm.
17. A method comprising:
(a) treating ferrimagnetic and/or ferromagnetic nanoparticles with poly(acrylic acid) (PAA) to form PAA-modified magnetic nanoparticles and ionizing the PAA-modified magnetic nanoparticles with a base; and
(b) reacting the PAA-modified nanoparticles with tetramethylorthosilicate (TEOS) to form silica-coated magnetic nanoparticles,
wherein magnetically induced aggregation of the magnetic nanoparticles of step (a) is completely inhibited by the silica-coating of step (b).
18. The method of claim 17 , further comprising: (c) reacting the silica-coated magnetic nanoparticles with a reactive silane to enable surface modification of the silica-coated magnetic nanoparticles with other organic functional groups.
19. The method of claim 18 , wherein silica-coated magnetic nanoparticles are amine functionalized with the reactive silane aminopropyltrimethoxysilane (APTMS).
20. The method of claim 19 , wherein the amine-functionalized silica-coated magnetic nanoparticles are further reacted with activated carboxylic acids to form amide bonds.
21. The method of claim 19 , wherein the amine-functionalized silica-coated magnetic nanoparticles are further reacted with acrylates to form secondary and tertiary amines.
22. The method of claim 19 , wherein the amine functionalized silica-coated magnetic nanoparticles are further reacted with poly(ethylene glycol) acrylate to form poly(ethylene glycol) functionalized silica-coated magnetic nanoparticles.
23. The method of claim 17 , wherein the magnetic nanoparticles of step (a) have a diameter of 1 to 100 nm.
24. The method of claim 17 , wherein the magnetic nanoparticles of step (a) and the silica-coated magnetic particles of step (b) have the same core diameter.
25. The method of claim 17 , wherein the silica-coated magnetic nanoparticles of step (b) have a silica shell thickness of 1 to 100 nm.