Cyclic Voltammetry as a powerful tool for the study of the evolution in time of bimetallic Au/Pt nanoparticles

Bimetallic systems have attracted more and more interest in recent years due to their novel optical, catalytic, magnetic, and sensing properties, often different from the corresponding monometallic counterparts. Novel ways to fabricate, characterize and explore these fascinating systems represent an important research topic in this field. In fact, studies directed towards the size, shape, composition, and functionalization of the particles allow leading to sophisticated nanomaterials specifically designed for their intended applications. For these reasons, not only the type and the quantity of the two metals are to be evaluated, but also the distribution of the two components, when passing from an alloy to a core-shell system or vice versa. In this context, techniques such as transmission electron microscopy (TEM), dynamic light scattering (DLS), and optical spectroscopy are generally used for this routine characterization. Recently, electrochemistry has been employed as an alternative and complementary technique with very promising results [1-3], allowing the discrimination of an alloy from a broken or perfect core-shell system after synthesis. However, a remaining challenge in this area lies in the difficulty of following the formation of these nanomaterials during the synthetic procedure. The formation of these bimetallic systems is dependent on the rate of production of each component and can show different intermediate structures. Cyclic voltammetry (CV) can be used to cover also the gap in this field. In the present work, bimetallic systems based on Au and Pt nanoparticles, in the form of alloy (Au+P) or core-shell (Au@Pt and Pt@Au) structures, are deeply investigated. HR-TEM images confirm the expected alloyed structure for Au+Pt; Au@Pt particles tend be alloyed, while Pt@Au systems present an alloyed core with an external shell Pt enrichment. These considerations are confirmed by CV experiments, which can also permit to follow the synthetic evolution of these systems in time. References [1] L. R. Holt, B.J. Plowman, N.P. Young, K. Tschulik, R.G. Compton, Angew. Chem. Int. Ed. 55 (2016) 397–400. [2] K. Tschulik, K. Ngamchuea, C. Ziegler, M.G. Beier, C. Damm, A. Eychmueller, R.G. Compton, Adv. Funct. Mater. 25 (2015) 5149–5158. [3] V. Pifferi, C. Chan-Thaw, S. Campisi, A. Testolin, A. Villa, L. Falciola, L. Prati, Molecules 21 (2016) 261.