The study conducted by Maenosono research group at the School of Materials Science has been published in Appl. Phys. Lett.
The synthesis of double shell (Au@Ag)@Au nanoparticles is accomplished through suppression of the galvanic replacement reaction caused by an electron transfer phenomenon. The resulting nanoparticles are monodisperse with a thin and uniform second Au shell. These particles are ultimately expected to lead to sensitive probes for biomolecular sensing and diagnostics.
We have found that an electron transfer from the Au core to the Ag shell takes place in Au@Ag core@shell NPs resulting in an enhancement of the oxidation resistivity of the Ag shell. The enhanced oxidation resistivity of the Ag shell effectively suppresses the galvanic replacement reaction during the Au second shell deposition process, and thus, the resultant (Au@Ag)@Au double shell NPs have a uniform size, shape, and structure without defects which cannot be avoided in the case of Ag@Au NP syntheses.
Dao T. N. Anh, P. Singh, C. Shankar, D. Mott, and S. Maenosono, Appl. Phys.Lett. 99, 073107 (2011)