Synthesis of substantially monodispersed colloids

Abstract

A method of forming ligated nanoparticles of the formula Y(Z) x where Y is a nanoparticle selected from the group consisting of elemental metals having atomic numbers ranging from 21-34, 39-52, 57-83 and 89-102, all inclusive, the halides, oxides and sulfides of such metals, and the alkali metal and alkaline earth metal halides, and Z represents ligand moieties such as the alkyl thiols. In the method, a first colloidal dispersion is formed made up of nanoparticles solvated in a molar excess of a first solvent (preferably a ketone such as acetone), a second solvent different than the first solvent (preferably an organic aryl solvent such as toluene) and a quantity of ligand moieties; the first solvent is then removed under vacuum and the ligand moieties ligate to the nanoparticles to give a second colloidal dispersion of the ligated nanoparticles solvated in the second solvent. If substantially monodispersed nanoparticles are desired, the second dispersion is subjected to a digestive ripening process. Upon drying, the ligated nanoparticles may form a three-dimensional superlattice structure.

We claim:  
     
         1 . A colloidal nanoparticle dispersion comprising nanoparticles saturated in a molar excess of a first solvent, a second solvent different than the first solvent, and a quantity of ligand moieties.  
     
     
         2 . The dispersion of  claim 1 , said first solvent having a boiling point at least about 25° C. below the boiling point of the second solvent.  
     
     
         3 . The dispersion of  claim 2 , the first solvent having a boiling point at least about 40° C. below the boiling point of the second solvent.  
     
     
         4 . The dispersion of  claim 1 , wherein said first solvent is selected from the group consisting of ketones of the formula  
       
         
           
           
               
               
           
         
       
       where R 1  and R 2  are independently and respectively selected from the group consisting of straight and branched chain C1-C5 alkyl and alkenyl groups, and the C1-C5 straight and branched chain alcohols.  
     
     
         5 . The dispersion of  claim 3 , said first solvent being acetone.  
     
     
         6 . The dispersion of  claim 1 , said second solvent being an aryl organic solvent.  
     
     
         7 . The dispersion of  claim 6 , said second solvent selected from the group consisting of solvents of the formula  
       
         
           
           
               
               
           
         
       
       where X 1  and each X 2  are each independently and respectively selected from the group consisting of H and C1-C5 straight and branched chain alkyl and alkenyl groups, n is from 0 to 3, and each X 2  may be independently located at any unoccupied ortho, meta or para position relative to X 1 .  
     
     
         8 . The dispersion of  claim 7 , said second solvent being toluene.  
     
     
         9 . The dispersion of  claim 1 , said colloidal nanoparticles selected from the group consisting of the elemental metals having atomic numbers ranging from 21-34, 39-52, 57-83 and 89-102, all inclusive, the halides, oxides and sulfides of such metals, and the alkali metal and alkaline earth metal halides.  
     
     
         10 . The dispersion of  claim 1 , said colloidal nanoparticle selected from the group consisting of elemental gold and silver.  
     
     
         11 . The dispersion of  claim 1 , said dispersion formed by vaporizing a solid substance and said first solvent, depositing the vaporized atoms or molecules and first solvent onto a cold surface, to give a mixture, warming the mixture and forming nanoparticles by aggregation of the atoms or molecules, allowing the nanoparticles and first solvent mixture to mix with said second solvent and ligand moieties.