Au / Ag nanowires atomic distribution revealed by XAFS

HERRERA, F. C.; GIOVANETTI L. J.; GUTIÉRREZ-WING, C.; REQUEJO F. G.

Campinas

Congreso; 25th RAU Annual Users Meeting LNLS/CNPEM.; 2015

LNLS/CNPEM

Nanowires which were defined as having at least two dimensions between 1 and 100 nm, have received a great interest due to their unique optical, electrical, magnetic, and thermal properties with dimensionality and size confinement [1-4]. The intrinsic properties of nanowires are mainly determined by its size and composition. To study the size dependent properties, it is the crucial task to synthesize size-controlled nanowires. In order to investigate the local and electronic structure of Ag-Au(1-D) nanowires we perform a comprehensive study by XAFS in the Au-L3, Ag-L23 and Ag-K edges of isolated Ag-Au(1-D) nanowires with different Au:Ag molar ratio. Ag-Au(1-D) nanowires were synthesized by a method of colloid chemistry in a first stage (Ag), followed by a galvanic reaction to incorporate the second metal in the structure (Au). Au L3 EXAFS data shows that every Au atom, independently of the Au:Ag molar ratio, are incorporated in the Ag lattice surrounded by 8 and 4 Au and Ag atoms respectively. Ag K EXAFS data analysis shows that depending on the Au:Ag molar ratio the Ag atoms change their environment. This result is also supported by Ag L23 XANES data that shows different hole density in the Ag 4d level depending on the Ag-Au(1-D) nanowires stoichiometry.1 - Y. Wu, J. Xiang, C. Yang, W. Lu, C. M. Lieber, Nature, 430 7000 704-704, 0028-0836, (2004).2 - A. P. Alivisatos, P. F. Barbara, A. W. Castleman, J. Chang, D. A. Dixon, M. L. Klein, G. L. Mc Lendon, J. S. Miller, M. A. Ratner, P. J. Rossky. Advanced Materials, 10 16 1297- 1336, 0935-9648, (1998).3 - Z. L. Wang. Advanced Materials, 12 17 1295-1298, 0935-9648, (2000)4 - Y. G. Sun, B. T. Mayers, Y. N. Xia. Nano Letters, 2 5 481-485, 0028-0836, (2002)