Twin Proliferation and Prolongation under Kinetic Control: Pd-Au Janus Icosahedra versus Pd@Au Core-Shell Starfishes

• Type of Material: Article
• Authors: Xiaoyu Qiu, Georgia Institute of Technology; Veronica Pawlik, Georgia Institute of Technology; Shan Zhou, Georgia Institute of Technology; Jing Tao, Brookhaven Natl Lab; Younan Xia, Emory University
• Language: English
• Date: 2023-06-09
• Publisher: AMER CHEMICAL SOC
• Publication Version: Final Published Version
• Copyright Statement: © 2023 The Authors. Published by American Chemical Society
• License: Creative Commons Attribution 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.1021/jacs.3c03682
• Title of Journal or Parent Work: JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
• Volume: 145
• Issue: 24
• Start Page: 13400
• End Page: 13410
• Keywords: Chemistry; Physical Sciences; CATALYSTS; DECAHEDRAL NANOCRYSTALS; Chemistry, Multidisciplinary; GROWTH; Science & Technology
• Research Categories: Engineering, Biomedical; Chemistry, Biochemistry

Abstract

Heterogeneous bimetallic nanocrystals featuring explicit spatial configurations and abundant twin defects can simultaneously enable geometric and ligand effects to enhance catalytic and photonic applications. Herein, we report two growth patterns of Au atoms on penta-twinned Pd decahedra, involving twin proliferation to generate asymmetric Pd-Au Janus icosahedra and twin elongation to produce anisotropic Pd@Au core-shell starfishes, respectively. Mechanistic analysis indicates that the injection rate determines the lower-limit number (nlow) of Au(III) ions in the steady state and thus controls the growth pattern. When nlow ≤ 5.5, the kinetic rate is slow enough to initiate asymmetrical one-side growth but fast enough to outpace surface diffusion; Au tetrahedral subunits are successively proliferated along the axial ⟨110⟩ direction of Pd decahedra to form Pd-Au Janus icosahedra. Composed of five Pd and 15 Au tetrahedral subunits, such a heterogeneous icosahedron supports high (2.2 GPa) tensile strain and high strain difference up to +21.9%. In contrast, when nlow > 5.5, the fast reduction kinetics promotes symmetric growth with inadequate surface diffusion. As such, Au atoms are laterally deposited along five high-indexed ⟨211⟩ ridges of Pd decahedra to generate concave Pd@Au core-shell starfishes with tunable sizes (28-40 nm), twin elongation ratios (33.82-162.08%), and lattice expansion ratios (8.82-20.10%).