Pt/Sn Intermetallic, Core/Shell\nand Alloy Nanoparticles:\nColloidal Synthesis and Structural Control

Abstract

For the first time, shape-controlled Pt₃Sn,\nPtSn, and\nPtSn₂ intermetallic nanocrystals were synthesized in octadecene\n(ODE) by a versatile hot-injection method with 1,2-hexadecanediol\n(HDD) as the reducing agent. Transmission electron microscopy (TEM)\nmeasurements reveal that the metal composition has an influence on\nthe particle morphology: with the increase in the Sn content, the\nPt/Sn nanoparticles obtained by the hot-injection synthesis show flower-like,\nirregular faceted, cubic/tetrahedral, hexagonal, and spherical/nanowire\nstructures. A facile phase-transfer preparative procedure for the\nsynthesis of Pt/Sn core/shell nanoparticles was also developed, in\nwhich ligand-free Pt nanoparticles were used as precursors. X-ray\ndiffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements\nconfirm a Pt-core/Sn-shell structure. The surface characteristic of\nthe Pt/Sn core/shell nanoparticles was also investigated by IR spectroscopy\nof CO adsorption experiments (i.e., with a highly surface sensitive\ntechnique). These experiments reveal a few Pt atoms to be left on\nthe surface as adsorption sites for CO. However, the intensity of\nthe corresponding infrared (IR) bands is almost negligible. Furthermore,\nPt/Sn random-alloy nanoparticles with different metal compositions\nand particle sizes were synthesized in this work by heating-up methods.\nEnergy dispersive X-ray (EDX) and XRD analyses show different alloying\nextent of Sn with Pt.