Doped nanoparticles and methods of making and using same
Doped nanoparticles, methods of making such nanoparticles, and uses of such nanoparticles. The nanoparticles exhibit a metal-insulator phase transition at a temperature of −200° C. to 350° C. The nanoparticles have a broad range of sizes and various morphologies. The nanoparticles can be used in coatings and in device structures.
1. A VO 2 nanoparticle doped with a plurality of metal cations selected from the group consisting of K cations, Na cations, Cs cations, Sr cations, Ba cations, Ca cations, W cations, Mo cations, Ag cations, Pb cations Nb cations, Cr cations, Al cations, Fe cations, Ti cations, Zr cations, Ta cations, Sc cations, Ga cations, Cu cations, Co cations, Ni cations, rare-earth element cations, and combinations thereof,
wherein the dopant is present in the nanoparticle at 0.1 to 10% by weight,
wherein the dopants do not segregate into distinct phases and the dopants are substitutionally incorporated within a VO 2 structure such that they replace vanadium atoms in the VO 2 structure; and
wherein the nanoparticle exhibits a metal-insulator transition at a temperature of from −200° C. to 350° C.
2. The nanoparticle of claim 1 , wherein the nanoparticle has a morphology selected from the group consisting of nanowires, nanostars, nanosheets, nanobelts, nanotetrapods, nanorods, nanospheres, nanoobelisks, nanodendrites, aligned nanowire arrays, and combinations thereof.
3. The nanoparticle of claim 1 , wherein the nanoparticle has monoclinic, triclinic, or rutile crystal symmetry.
4. The nanoparticle of claim 1 , wherein the nanoparticle has a size of 1 nm to 1 micron.
5. The nanoparticle of claim 1 , wherein the nanoparticle is doped with a plurality of anion dopants, the dopants do not segregate into distinct phases and the anion dopants are substitutionally incorporated within a VO 2 structure such that they replace oxygen atoms in the VO 2 structure.
6. The nanoparticle of claim 1 , wherein the nanoparticle is at least partially covered by a layer of metal oxide selected from the group consisting of TiO 2 , ZnO, CeO 2 , HfO 2 , ZrO 2 , and combinations thereof.
7. A coating comprising a plurality of VO 2 nanoparticles of claim 1 .
8. The coating of claim 7 , wherein the VO 2 nanoparticles are disposed in a polymer.
9. The coating of claim 8 , wherein the polymer is selected from the group consisting of polymethylmethacrylate, polyethylenimine, polyetherimide, polycarbonate, polyethylene oxide, polypyrrole, polystyrene, and combinations thereof.
10. The coating of claim 7 , wherein the coating exhibits thermochromic behavior, electrochromic behavior, or mechanochromic behavior based on a metal-insulator transition.
11. The coating of claim 10 , wherein the metal-insulator transition is induced by heating the coating, application of voltage to the coating, flowing a current through the film, or by imposition of strain on the coating.
12. The coating of claim 7 , wherein the coating is disposed on the inner surface of the outer pane of a dual pane window.
13. A method for making the doped VO 2 nanoparticles of claim 1 comprising the steps of:
a) contacting
a vanadium oxide source,
a dopant source,
a reducing agent selected from the group consisting of oxalic acid, citric acid, ascorbic acid, methanol, ethanol, butanediol, acetone, 2-propanol, n-propanol, butanol, pentanol, glycerol, ethylene glycol, polyvinyl alcohol and combinations thereof,
optionally, a structure-directing agent selected from the group consisting of sodium dodecyl sulfate, cetyltrimethylammonium bromide, ethylene oxide and propylene oxide block copolymer surfactants, polyethyleneoxide surfactants, and combinations thereof, in a solvent to form a reaction mixture;
b) heating the reaction mixture to a temperature of from 25° C. to 300° C. under autogeneous pressure for 0.5 hours to 336 hours;
c) allowing the reaction mixture to cool to ambient temperature; and
d) isolating the doped VO 2 nanoparticles.
14. The method of claim 13 , wherein the vanadium oxide source is V 2 O 5 , V 2 O 4 , CuV 2 O 6 , NaVO 3 , vanadium foil, VO, or V 2 O 3 .
15. The method of claim 13 , wherein the dopant source comprises a metal and the dopant source is a nitrate salt of the metal, acetate salt of the metal, oxalate salt of the metal, oxide of metals, or a combination thereof.
16. The method of claim 13 , wherein the dopant source is tungstic acid, chromic acid, molybdic acid, lead acetate, tungsten oxide, molybdenum oxide, niobium oxide, chromium oxide, aluminum oxide, iron oxide, titanium oxide, zirconium oxide, tantalum oxide, scandium oxide, or gallium oxide.
17. The method of claim 13 , wherein the solvent is an organic solvent or an aqueous medium.
18. The method of claim 17 , wherein the organic solvent is toluene, anisole, ethylene glycol, or a combination thereof and the aqueous medium is water or a solution comprising an alcohol and water.
19. The method of claim 13 , wherein V 6 O 13 or other substoichiometric oxides are not detectible in the isolated product.