Method to synthesize nanoparticle supercrystals
Highly ordered arrays of 3D faceted nanoparticle supercrystals are formed by self-assembly with controlled nanoparticle packing and unique facet dependent optical property by using a binary solvent diffusion method. The binary diffusion results in supercrystals whose size and quality are determined by initial nanoparticle concentration and diffusion speed. The supercrystal solids display unique facet-dependent surface plasmonic and surface-enhanced Raman characteristics. The supercrystals have potential applications in areas such as optics, electronics, and sensor platforms.
1. A method to synthesize nanoparticle supercrystals, comprising:
providing a colloidal suspension of ligand-capped nanoparticles in a non-polar solvent, and
counter-diffusing the non-polar solvent and a polar anti-solvent into each other to form a solvent/anti-solvent mixture, thereby slowly precipitating nanoparticle supercrystals from the colloidal suspension, wherein the concentration of nanoparticles in the solvent/anti-solvent mixture is greater than 2 mg/mL.
2. The method of claim 1 , wherein the nanoparticles comprise metal, semiconductor, or magnetic nanoparticles.
3. The method of claim 2 , wherein the nanoparticles comprise gold nanoparticles.
4. The method of claim 2 , wherein the nanoparticles comprise Ag, CdSe, PbS, PbSe, FePt, or Fe 3 O 4 nanoparticles.
5. The method of claim 1 , wherein the ligand comprises an alkyl thiol.
6. The method of claim 5 , wherein the alkyl thiol comprises dodecanethiol.
7. The method of claim 1 , wherein the ligand comprises an alkyl amine or an alkyl acid.
8. The method of claim 1 , wherein the non-polar solvent comprises toluene.
9. The method of claim 1 , wherein the non-polar solvent comprises hexane, benzene, or xylene.
10. The method of claim 1 , wherein the polar anti-solvent comprises isopropanol.
11. The method of claim 1 , wherein the polar anti-solvent comprises ethanol, methanol, or tetrahydrofuran.
12. The method of claim 1 , wherein the counter-diffusing comprises adding the polar anti-solvent on top of the colloidal suspension and allowing the non-polar solvent and the polar anti-solvent to counter-diffuse into each other.
13. The method of claim 1 , wherein the supercrystals are greater than one micrometer in size.
14. The method of claim 1 , wherein the supercrystals are greater than ten micrometers in size.
15. The method of claim 1 , wherein the supercrystals are greater than one hundred micrometers in size.
16. The method of claim 3 , wherein the gold nanoparticles of the supercrystals have a hexagonal close packed mesostructured.
17. The method of claim 3 , wherein the supercrystals have a faceted hexagonal disk shape.
18. The method of claim 1 , wherein the ligand-capped nanoparticles comprise dodecanethiol-capped gold nanoparticles, the non-polar solvent comprises toluene, and the polar anti-solvent comprises isopropanol, and the concentration in mg/mL of nanoparticles in the toluene/isopropanol mixture is greater than C NP =2.0e −3.9xIPA −0.040, where x IPA is the volume fraction of isopropanol in the mixture.