Novel synthesis of Au/Pd nanoalloys

SPITALE, A., MOIRAGHI, R., BAHENA, D., YACAMÁN, M.J., PERÉZ M. A. Y MARISCAL, M. M.

Cancún

Congreso; International Materials Research Congress, Cancún, Mexico; 2013

Metallic nanoparticles are perhaps one of the most interesting objects of study in nanoscience due to the potential use of these nanostructures on diverse fields, i.e. biosensors, catalysis, drug ?delivery? and construction of nano-circuits1,2,3. It is well known that physical properties of materials, in the form of nanostructures, can be drastically different than those of the bulk material4,5. One of the reasons of this phenomenon is the high surface ? volume ratio of nanoparticles, this is why controlling nanostructures morphology through synthesis and its dynamic behavior is relevant for the understanding of catalytic properties. There are a number of reports6 describing conditions to form and grow AuNPs. However, the dynamics of these processes is still not sufficiently understood and the stability and uniformity of the particles formed is too variable. We believe that the knowledge of kinetics as well as of the mechanism of AuNPs formation can give a chance to controllable synthesis of particles with well-defined shapes and sizes. In this study, we develop a novel method to prepare stable small AuNPs, controlling pH and reducing agent concentration, without any surfactant agents. Our goal was to reduce NPs size, in order to use them as seeds to grow palladium shells. Pd deposition onto our Au seeds was performed by using metastable Pd(II) solutions (baths). These baths contain both the palladium precursor (PdCl42-) and the reducing agent (1,4-parahydroquinone), but there are some extra species (i.e., halides ions and buffer) that prevent the homogenous nucleation of Pd NPs. When the gold seeds are added into these solutions, Pd(II) reduction is catalysed and leads to palladium deposition at the surface of gold NPs, yielding Au@Pd NPs. The NPs were characterized through UV-visible spectroscopy and transmission electron microscopy (TEM). Keywords: Au- Pd bimetallic nanoparticles; clean synthesis References: 1) A. Manna, T. Imae, K. Aoi, M. Okazaki, Mol. Simul. 29 (2003) 661 2) R. Hong, G. Han, J. M. Fernández, B. J. Kim, N. S. Forbes, V. M. Rotello, J. Am. Chem. Soc. 128 (2006) 1078 3) M. M. Mariscal and S. A. Dassie, Recent Advances in Nanoscience, Research Signpost Pub. - Trivandrum, India (2007) 4) R. L. Johnston , Atomic and Molecular Clusters, CRC Press, London, United Kingdom (2002) 5) R. Ferrando, J. Jellinek, R. L. Johnston, Chem. Rev. 3 (2008) 108 6) F. Dumur, A. Guerlin, E. Dumas, D. Bertin, D. Gigmes, C.R. Mayer Gold Bull. 44 (2011) 119