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Iowa State University

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Chemistry Publications

Nanoscience and Nanotechnology

Articles 1 - 3 of 3

Full-Text Articles in Physics

Kinetics, Energetics, And Size Dependence Of The Transformation From Pt To Ordered Ptsn Intermetallic Nanoparticles, Minda Chen, Yong Han, Tian Wei Goh, Rong Sun, Raghu V. Maligal‐Ganesh, Yuchen Pei, Chia‐ Kuang Tsung, James W. Evans, Wenyu Huang Jan 2019

Kinetics, Energetics, And Size Dependence Of The Transformation From Pt To Ordered Ptsn Intermetallic Nanoparticles, Minda Chen, Yong Han, Tian Wei Goh, Rong Sun, Raghu V. Maligal‐Ganesh, Yuchen Pei, Chia‐ Kuang Tsung, James W. Evans, Wenyu Huang

Chemistry Publications

The outstanding catalytic activity and chemical selectivity of intermetallic compounds make them excellent candidates for heterogeneous catalysis. However, the kinetics of their formation at the nanoscale is poorly understood or characterized, and precise control of their size, shape as well as composition during synthesis remains challenging. Here, using well-defined Pt nanoparticles (5 nm and 14 nm) encapsulated in mesoporous silica, we study the transformation kinetics from monometallic Pt to intermetallic PtSn at different temperatures by a series of time-evolution X-ray diffraction studies. Observations indicate an initial transformation stage mediated by Pt surface-controlled intermixing kinetics, followed by a second stage with ...


Squeezed Nanocrystals: Equilibrium Configuration Of Metal Clusters Embedded Beneath The Surface Of A Layered Material, Scott E. Julien, Ann Lii-Rosales, Kai-Tak Wan, Yong Han, Michael C. Tringides, James W. Evans, Patricia A. Thiel Jan 2019

Squeezed Nanocrystals: Equilibrium Configuration Of Metal Clusters Embedded Beneath The Surface Of A Layered Material, Scott E. Julien, Ann Lii-Rosales, Kai-Tak Wan, Yong Han, Michael C. Tringides, James W. Evans, Patricia A. Thiel

Chemistry Publications

Shapes of functional metallic nanocrystals, typically synthesized either free in solution or supported on surfaces, are key for controlling properties. Here, we consider a novel new class of metallic nanocrystals, copper islands embedded near the surface of graphite, which can be considered a model system for metals embedded beneath surfaces of layered materials, or beneath supported membranes. We develop a continuum elasticity (CE) model for the equilibrium shape of these islands, and compare its predictions with experimental data. The CE model incorporates appropriate surface energy, adhesion energies, and strain energy. The agreement between the CE model and the data is ...


Reverse-Engineering Of Graphene On Metal Surfaces: A Case Study Of Embedded Ruthenium, Ann Lii-Rosales, Yong Han, Ka Man Yu, Dapeng Jing, Nathaniel Anderson, David Vaknin, Michael C. Tringides, James W. Evans, Michael S. Altman, Patricia A. Thiel Oct 2018

Reverse-Engineering Of Graphene On Metal Surfaces: A Case Study Of Embedded Ruthenium, Ann Lii-Rosales, Yong Han, Ka Man Yu, Dapeng Jing, Nathaniel Anderson, David Vaknin, Michael C. Tringides, James W. Evans, Michael S. Altman, Patricia A. Thiel

Chemistry Publications

Using scanning tunneling microscopy, x-ray photoelectron spectroscopy, and x-ray absorption spectroscopy, we show that Ru forms metallic nanoislands on graphite, covered by a graphene monolayer. These islands are air-stable, contain 2–4 layers of Ru, and have diameters on the order of 10 nm. To produce these nanoislands two conditions must be met during synthesis. The graphite surface must be ion-bombarded, and subsequently held at an elevated temperature (1000–1180 K) during Ru deposition. A coincidence lattice forms between the graphene overlayer and the Ru island top. Its characteristics—coincidence lattice constant, corrugation amplitude, and variation of carbon lattice appearance ...