A seed mediated procedure for the synthesis of hydrophobic AucoreAgshell nanoparticles in toluene is demonstrated. The reaction proceeds by way of the interfacial reduction of silver ions by 3-pentadecylphenol followed by their deposition on hydrophobized An nanoparticles. Such a hitherto unreported interfacial seeded growth reaction leads to the formation of phase pure AucoreAgshell nanoparticles that retain the hydrophobicity of the seed particles and remain stable in toluene. Such core-shell structures are however not formed in the aqueous phase. The core-shell architecture was verified using TEM analysis and the formation process was studied by recording the UV-vis spectra of the organic phase nanoparticles as a function of time. TEM kinetics also showed gradual increase in the silver layer thickness. Conclusive evidence was however obtained on examination of the HRTEM images of the products formed. Elemental analysis using X-ray photoelectron spectroscopy of the AucoreAgshell nanostructure revealed the presence of metallic silver. Moreover changing the surface capping of the Au seed does not affect the formation of the AucoreAgshell nanostructure. (c) 2007 Elsevier Inc. All rights reserved.