Triphenylphosphine-Stabilized Gold Nanoparticles

Submitted by JAMES E. HUTCHISON, EVAN W. FOSTER, MARVIN G. WARNER, SCOTT M. REED, and WALTER W. WEARE Checked by WILLIAM BUHRO and HENG YU  

Auioi(PPh3)2iCl5 + PPh3 + NaCl + 3HC1 

Department of Chemistry and Materials Science Institute, University of Oregon, Eugene, OR 97403. Department of Chemistry, Washington University, One Brookings Drive, St. Louis, MO 63130. Average composition for 1.5 0.4 nm particles prepared using this procedure. 

An improved synthesis of this type of phosphine-stabilized gold nanoparticle was necessary to make them convenient for use as synthetic intermediates in materials applications. We developed a safer, more convenient, and more versatile synthesis of phosphine-stabilized nanoparticles analogous to those originally reported by Schmid. The synthesis described here eliminates the use of diborane and can be carried out quickly with minimal concern for inert conditions. The nanoparticle product is comparable to that prepared by the Schmid procedure, possessing a core diameter of 1.5 0.4 nm and the same reactivity. In addition, the new synthesis can be adapted to permit the use of a variety of phosphines as passivating ligands and provide control over particle core size.  

The aqueous and organic layers are separated using a 500-mL separatory funnel. The organic layer is washed 3 times with 100 mL of deionized water. An emulsion commonly forms during this step, so saturated sodium chloride may be added to the mixture or used instead of water to aid in the separation of the layers. The organic layer is separated, filtered to remove precipitates, and evaporated to dryness under flowing nitrogen. The crude product is transferred to a 500-mL Erlenmeyer flask with 35 mL of chloroform. To this solution, 300 mL of pentane is added to precipitate the product. 

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Ligand-stabilized metal nanoparticles such as triphenylphosphine-stabilized gold nanoparticles were usually synthesized by reduction of the corresponding metal ions or complexes with excess diborane. Tetraalkylammonium salts of hydro-... 

Purification yields 200-300 mg of triphenylphosphine-stabilized gold nanoparticles, which should be stored cold (—20°C) in the sofid state, or immediately converted to thiol- or amine-stabilized nanoparticles through subsequent reaction with the appropriate ligand. The particles decompose in solution thus manipulation of the product in solution should be minimized. 

The 1.5-nm nanoparticles readily react with thiol or amine-terminated ligands under mild conditions to yield thiol- or amine-stabilized nanoparticles. Triphenylphosphine-stabilized particles thermally decompose with the production of (PPh3)AuCl and metallic gold. 

P21AU101CI5C378H315, Gold, triphenylphosphine-stabilized nanoparticles, 34 228 P3oH372h Ioi32N4205Q4-—3OOH2O, Molybdate, polyoxo-, spherical cluster with hypopho-sphite ion, hydrate, 34 196... 

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