Method for forming thermally stable nanoparticles on supports
An inverse micelle-based method for forming nanoparticles on supports includes dissolving a polymeric material in a solvent to provide a micelle solution. A nanoparticle source is dissolved in the micelle solution. A plurality of micelles having a nanoparticle in their core and an outer polymeric coating layer are formed in the micelle solution. The micelles are applied to a support. The polymeric coating layer is then removed from the micelles to expose the nanoparticles. A supported catalyst includes a nanocrystalline powder, thin film, or single crystal support. Metal nanoparticles having a median size from 0.5 nm to 25 nm, a size distribution having a standard deviation ≦0.1 of their median size are on or embedded in the support. The plurality of metal nanoparticles are dispersed and in a periodic arrangement. The metal nanoparticles maintain their periodic arrangement and size distribution following heat treatments of at least 1,000° C.
1. An inverse micelle-based method for forming nanoparticles on supports, comprising:
dissolving a polymeric material in a solvent, wherein polymeric micelles are formed to provide a micelle solution;
dissolving a nanoparticle source in said micelle solution, wherein a plurality of loaded micelles having a nanoparticle ion core and an outer polymeric coating layer that includes a plurality polymeric ligands are formed in said micelle solution;
applying said plurality of loaded micelles to a surface of a support, and
removing said polymeric coating layer from said loaded micelles while forming nanoparticles from said nanoparticle ion cores to expose at least a portion of said nanoparticles.
2. The method of claim 1 , wherein said support comprises a nanocrystalline powder, and wherein said applying comprises impregnation.
3. The method of claim 1 , wherein said support comprises a thin film or a single crystal surface, and wherein said applying comprises dip coating.
4. The method of claim 3 , wherein said thin film or said single crystal surface comprises a titania surface.
5. The method of claim 4 , wherein said nanoparticles comprise a metal or metal alloy, further comprising heating to a temperature between 900 and 1,200° C., wherein raised titania stripes are formed on said titania surface, and wherein said raised titania stripes are raised 0.3 to 0.6 nm above surrounding portions of said titania surface.
6. The method of claim 1 , wherein said nanoparticle source comprises a first metal salt and a second metal salt different from said first metal salt, and wherein said nanoparticles comprise bimetallic nanoparticles.
7. The method of claim 1 , wherein said polymeric material comprises a block copolymer.
8. The method of claim 7 , wherein said block copolymer comprises a polystyrene block copolymer.
9. The method of claim 7 , wherein said polystyrene block copolymer comprises polystyrene-block-poly-2-vinylpyridine (PS-P2VP).
10. The method of claim 1 , wherein said polymeric coating layer is a continuous layer that encapsulates said nanoparticles and is 2 to 75 nm thick.
11. The method of claim 1 , wherein said removing comprises heating to 400 to 600° C. in an oxygen comprising ambient.
12. The method of claim 1 ,
wherein said nanoparticles comprise a plurality of metal nanoparticles;
wherein said support comprises a nanocrystalline powder, a thin film, or a single crystal,
and wherein method produces a supported catalyst, said supported catalyst comprising:
said plurality of metal nanoparticles having a median size from 0.5 nm to 25 nm, and a size distribution having a standard deviation ≦0.1 of said median size on or embedded in said support,
wherein said plurality of metal nanoparticles are dispersed from one another and positioned in a periodic arrangement.