title: Size-dependent adhesion energy of shape-selected Pd and Pt nanoparticles.
abstract: Thermodynamically stable shape-selected Pt and Pd nanoparticles (NPs) were synthesized via inverse micelle encapsulation and a subsequent thermal treatment in vacuum above 1000 °C. The majority of the Pd NPs imaged via scanning tunneling microscopy (STM) had a truncated octahedron shape with (111) top and interfacial facets, while the Pt NPs were found to adopt a variety of shapes. For NPs of identical shape for both material systems, the NP-support adhesion energy calculated based on STM data was found to be size-dependent, with large NPs (e.g. ∼6 nm) having lower adhesion energies than smaller NPs (e.g. ∼1 nm). This phenomenon was rationalized based on support-induced strain that for larger NPs favors the formation of lattice dislocations at the interface rather than a lattice distortion that may propagate through the smaller NPs. In addition, identically prepared Pt NPs of the same shape were found to display a lower adhesion energy compared to Pd NPs. While in both cases, a transition from a lattice distortion to interface dislocations is expected to occur with increasing NP size, the higher elastic energy in Pt leads to a lower transition size, which in turn lowers the adhesion energy of Pt NPs compared to Pd.
authors.affiliation: Department of Physics, University of Central Florida, Orlando, FL 32816, USA.
authors.forename: M
authors.initials: M
authors.lastname: Ahmadi
authors.affiliation: Department of Physics, University of Central Florida, Orlando, FL 32816, USA.
authors.forename: F
authors.initials: F
authors.lastname: Behafarid
authors.affiliation: Department of Physics, Ruhr-University Bochum, 44780 Bochum, Germany. Beatriz.Roldan@rub.de.
authors.forename: B Roldan
authors.initials: BR
authors.lastname: Cuenya