Thursday, June 26, 2008 - 1:50 PM South American AB (Capital Hilton) 165
“Green” and Size-Controlled Synthesis and Seed-Mediated Growth of Pd Nanoparticles
Juncheng Liu and Christopher B. Roberts. Auburn University, Auburn, AL
Central to the concept of seed-mediated growth of nanoparticles is that small nanoparticle seeds serve as nucleation centers to precisely grow nanoparticles to a desired size. Herein we present an environmentally benign and size-controlled seed-mediated growth method coupled with an organic phase extraction to yield monodisperse dodecanethiol capped Pd nanoparticles. Monodisperse Pd nanoparticles (ca. 3.4 nm, standard deviation: 0.6 nm) were first synthesized and stabilized by a “green” and inexpensive polysugar, sodium carboxymethyl cellulose (CMC) in aqueous solution. The monodisperse Pd nanoparticles were subsequently employed as seeds on the surface of which fresh Pd2+ions were reduced by weak reducing agent ascorbic acid. We optimized the processing conditions that favor controlled growth on the nanoparticle seeds versus formation of new nucleation sites, thereby yielding improved control over particle size with narrow size distribution. Using different amount of salt in this seed-mediated growth process, different sized Pd nanoparticles were controllably synthesized. Finally, the nanoparticles were extracted from aqueous solution into an organic phase by using dodecanethiol as extractant with the assistance of HCl. The advantage of the seed-mediated growth method used in this study is that the Pd nanoparticle size could be precisely controlled (from 3.4 to 7.6 nm) by simply varying the ratio of the seed to Pd salt added in the growth stage. Furthermore, the use of environmentally friendly reagents, such as water (solvent), CMC (capping agent) and ascorbic acid (reducing agent) in the system provides both “green” and cost-effective merits for this precise size-controlled particle synthesis method.