Pt/Sn Intermetallic, Core/Shell and Alloy Nanoparticles: Colloidal Synthesis and Structural Control

For the first time, shape-controlled Pt3Sn, PtSn, and PtSn2 intermetallic nanocrystals were synthesized in octadecene (ODE) by a versatile hot-injection method with 1,2-hexadecanediol (HDD) as the reducing agent. Transmission electron microscopy (TEM) measurements reveal that the metal composition has an influence on the particle morphology: with the increase in the Sn content, the Pt/Sn nanoparticles obtained by the hot-injection synthesis show flower-like, irregular faceted, cubic/tetrahedral, hexagonal, and spherical/nanowire structures. A facile phase-transfer preparative procedure for the synthesis of Pt/Sn core/shell nanoparticles was also developed, in which ligand-free Pt nanoparticles were used as precursors. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements confirm a Pt-core/Sn-shell structure. The surface characteristic of the Pt/Sn core/shell nanoparticles was also investigated by IR spectroscopy of CO adsorption experiments (i.e., with a highly surface sensitive technique). These experiments reveal a few Pt atoms to be left on the surface as adsorption sites for CO. However, the intensity of the corresponding infrared (IR) bands is almost negligible. Furthermore, Pt/Sn random-alloy nanoparticles with different metal compositions and particle sizes were synthesized in this work by heating-up methods. Energy dispersive X-ray (EDX) and XRD analyses show different alloying extent of Sn with Pt.