Synthesis of spherical copper-platinum nanoparticles by sonoelectrochemistry followed by conversion reaction Samuel Levi a , Valérie Mancier a , Céline Rousse a , Omar Lozano Garcia b , Jorge Mejia b , Maribel Guzman c , Stéphane Lucas b , Patrick Fricoteaux a, * a LISM, EA 4695, UFR Sciences Exactes et Naturelles, BP 1039, F-51687 Reims Cedex 2, France b Namur Nanosafety Center (NNC), NAmur Research Institute for LIfe Sciences (NARILIS), Research Centre for the Physics of Matter and Radiation (PMR), University of Namur (UNamur), rue de Bruxelles 61, B-5000 Namur, Belgium c PUCP, Engineering Department, Av. Universitaria 1801, Lima-32, Peru A R T I C L E I N F O Article history: Received 8 December 2014 Received in revised form 25 February 2015 Accepted 25 June 2015 Available online 17 July 2015 Keywords: nanoparticles copper platinum sonoelectrochemistry dissolved oxygen A B S T R A C T Cu-Pt nanopowders were prepared by sonoelectrochemistry followed by a displacement reaction. The first method provides pure copper particles. In the second method the surface copper atoms are replaced by platinum atoms. The influence of dissolved oxygen during the conversion reaction was also studied. Nanoparticles (NPs) were observed by transmission electron microscopy (TEM) and their size distribution was determined by centrifugal liquid sedimentation (CLS). The mean diameter of isolated particles was found to be around 8 nm. Their composition was studied by energy dispersive X-ray spectroscopy (EDXS) and X-Ray photoelectron spectrometry (XPS). These analyses and X-ray diffraction (XRD) patterns showed that the particle shell is a solid solution of Cu and Pt. The shell composition is heterogeneous with a richer Pt percentage on its surface. ã 2015 Elsevier Ltd. All rights reserved. 1. Introduction Over the last two decades the interest for nanotechnology has increased markedly. This interest for nanoparticles can be explained by their various fields of application. Among them, medicine (cancer therapy [1,2], IRM contrasting agent [3] or drug delivering [4]), sensors [5], energy storage [6] and catalysis [7,8] can be cited. Nanoparticles are characterized by a high surface- to-volume ratio. As the properties of a material mainly depend on its surface, nanoparticles synthesis is an interesting way to enhance the materials characteristics. Nowadays a large range of nanoparticles production methods are available: chemical or physical vapor deposition (CVD [9] and PVD [10]), laser ablation [11], sol-gel and solvothermal synthesis [12], reduction in emulsion [13,14] and thermal decomposition [15]. Other simple ways of producing nanoparticles are classical electrochemistry - under pulsed current [16] or not [17] - and sonoelectrochemistry. High intensity ultrasounds have been used in chemistry [18] since 1934 and are still used now to synthesize advanced materials such as nanomaterials and nanoalloys [19,20]. The combination of electrodeposition and ultrasound was first employed around 1950 [21] . The major effect of ultrasound propagation in an aqueous solution is acoustic cavitation i.e. formation, growth and collapse of microbubbles. During the negative pressure phase, bubbles are formed and grow to a size of 5 to 20 mm [22]. During the compression cycle, these bubbles rapidly collapse, local temperature rises to a thousand kelvin and pressure to hundreds of bars. Strong shock waves and very high cooling rate can also be observed around the bubbles. When they collapse a liquid jet forms. If the cavitation takes place nearby, the jet erodes the surface. Other physical and chemical effects have been observed such as: mass transport improvement, diffusion layer decrease, cleaning and degreasing of the electrode surface and formation of radicals like OH  [23–25]. Several sonoelectrochemical setups were elaborated. The first one used a classical electrochemical cell dipped into an ultrasound bath with the power transmitted to the electrochemical cell varying according to the spatial configuration of the setup [26]. Next, another configuration was developed in which the cathode (working electrode) is coupled to the transducers; this new electrode was named sonotrode [27]. With this specific device, Reisse et al. [28] studied copper electrodeposition and showed the interest of ultrasound to produce copper nanopowders. This setup was later used to produce various nanoparticles such as: pure metals (Zn [29] , Ni [29], Pt [30], Au [31], Ag [32] ), alloys * Corresponding author. Tel.: +33 326 91 85 82; fax: +33 326 91 89 15. E-mail address: patrick.fricoteaux@univ-reims.fr (P. Fricoteaux). http://dx.doi.org/10.1016/j.electacta.2015.06.155 0013-4686/ ã 2015 Elsevier Ltd. All rights reserved. Electrochimica Acta 176 (2015) 567–574 Contents lists available at ScienceDirect Electrochimica Acta journa l home page : www.e lsevier.com/loca te/ele cta cta