Porous metal oxide particles and their methods of synthesis
Methods are generally disclosed for synthesis of porous particles from a solution formed from a leaving agent, a surfactant, and a soluble metal salt in a solvent. The surfactant congregates to form a nanoparticle core such that the metal salt forms about the nanoparticle core to form a plurality of nanoparticles. The solution is heated such that the leaving agent forms gas bubbles in the solution, and the plurality of nanoparticles congregate about the gas bubbles to form a porous particle. The porous particles are also generally disclosed and can include a particle shell formed about a core to define an average diameter from about 0.5 μm to about 50 μm. The particle shell can be formed from a plurality of nanoparticles having an average diameter of from about 1 nm to about 50 nm and defined by a metal salt formed about a surfactant core.
1. A method for synthesis of a porous particle, the method comprising
forming a solution from a leaving agent, a surfactant, a soluble metal salt, and a solvent, wherein the surfactant defines a surfactant molecule having a hydrophobic tail and a hydrophilic head;
evaporating the solvent from the solution to cause a plurality of the surfactant molecules to congregate to form a nanoparticle core as the solvent evaporates from the solution, wherein the metal salt forms about the nanoparticle core to form a plurality of nanoparticles having an average diameter of from about 1 nm to about 50 nm; and
heating the solution to cause the leaving agent to form gas bubbles in the solution, wherein the plurality of nanoparticles congregate about the gas bubbles to form a porous particle having an average diameter from about 0.5 μm to about 50 μm.
2. The method of claim 1 , wherein the leaving agent comprises urea.
3. The method of claim 1 , wherein the surfactant comprises a block copolymer.
4. The method of claim 3 , wherein the block copolymer comprises poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol).
5. The method of claim 1 , wherein the metal salt comprises a metal oxide.
6. The method of claim 1 , wherein the metal salt comprises a metal nitrate.
7. The method of claim 1 , wherein the metal salt comprises a metal acetate.
8. The method of claim 1 , wherein the metal salt comprises a metal ion formed from cobalt, cerium, strontium, iron, samaria, lanthanum, or combinations thereof.
9. The method of claim 1 , wherein the solvent is evaporated from the solution at a room temperature from about 20° C. to about 25° C.
10. The method of claim 1 , wherein heating the solution to cause the leaving agent to form gas bubbles in the solution comprises:
increasing the temperature of the solution at a rate slower than about 10° C. per minute.
11. The method of claim 10 , wherein the temperature of the solution is increased at a rate from about 0.5° C. per minute to about 5° C. per minute.
12. The method of claim 10 , wherein the temperature of the solution is increased at a rate from about 0.75° C. per minute to about 2° C. per minute.
13. The method of claim 10 , wherein the heating temperature is from about 350° C. to about 550° C.
14. The method of claim 10 , wherein the heating temperature is about 500° C.
15. The method of claim 1 , wherein heating the solution to cause the leaving agent to form gas bubbles in the solution comprises:
heating the solution at a heating temperature for a time sufficient to allow the gas bubbles to form in the solution, wherein the heating temperature is about 350° C. to about 550° C.
16. The method as in claim 15 , wherein the solution is heated at the heating temperature for about 1 hour to about 10 hours.