PNNL

Abstract

Homogeneous Au-Ag alloy nanoparticles have been synthesized in the cavity of horse spleen apoferritin (HSAF) by a diffusion technique. Low concentration of NH4OH solution has been used stabilize Ag(I) ions at pH 8.3, where channels between the subunits of HASF are open for the diffusion of metal ions. The Au-Ag nanoparticle cores are 5.6-6.3 nm in diameter with narrow size distribution (= 1.0 nm), and their average diameter was gradually increased with an increase of Ag content. The core formation ratios of Au-Ag-HASF samples are higher than 80%. These series of nanoparticles were applied for the reduction of 4-nitrophenol in the presence of NaBH4. As the Au content was increased in the Au-Ag-HSAF nanoparticles, the rate constant of the reduction was exponentially increased from 1.3 x 10-3 s-1 (pure Ag-HSAF) to 7.58 x 10-2 s-1 (pure Au-HSAF). These synthesized Au-Ag nanoparticles with different compositions will be further applicable in catalysis, sensing, and biomedical areas.