title: Ag-Ag2S Hybrid Nanoprisms: Structural versus Plasmonic Evolution.
abstract: Recently, Ag-Ag2S hybrid nanostructures have attracted a great deal of attention due to their enhanced chemical and thermal stability, in addition to their morphology- and composition-dependent tunable local surface plasmon resonances. Although Ag-Ag2S nanostructures can be synthesized via sulfidation of as-prepared anisotropic Ag nanoparticles, this process is poorly understood, often leading to materials with anomalous compositions, sizes, and shapes and, consequently, optical properties. In this work, we use theory and experiment to investigate the structural and plasmonic evolution of Ag-Ag2S nanoprisms during the sulfidation of Ag precursors. The previously observed red-shifted extinction of the Ag-Ag2S hybrid nanoprism as sulfidation occurs contradicts theoretical predictions, indicating that the reaction does not just occur at the prism tips as previously speculated. Our experiments show that sulfidation can induce either blue or red shifts in the extinction of the dipole plasmon mode, depending on reaction conditions. By elucidating the correlation with the final structure and morphology of the synthesized Ag-Ag2S nanoprisms, we find that, depending on the reaction conditions, sulfidation occurs on the prism tips and/or the (111) surfaces, leading to a core(Ag)-anisotropic shell(Ag2S) prism nanostructure. Additionally, we demonstrate that the direction of the shift in the dipole plasmon is a function of the relative amounts of Ag2S at the prism tips and Ag2S shell thickness around the prism.
authors.affiliation: Department of Chemistry and International Institute for Nanotechnology, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208, United States.|School of Materials Science and Engineering, Nanyang Technological University , 50 Nanyang Avenue, Singapore 639798.|Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University , 29 Oxford Street, Cambridge, Massachusetts 02138, United States.
authors.forename: Mohammad M
authors.initials: MM
authors.lastname: Shahjamali
authors.affiliation: Department of Chemistry and International Institute for Nanotechnology, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208, United States.|Department of Physics, Anhui Normal University , 1 Beijing East Road, Wuhu, Anhui 241000, China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Zhou
authors.affiliation: Department of Chemistry and International Institute for Nanotechnology, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208, United States.|Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University , 29 Oxford Street, Cambridge, Massachusetts 02138, United States.
authors.forename: Negin
authors.initials: N
authors.lastname: Zaraee
authors.affiliation: School of Materials Science and Engineering, Nanyang Technological University , 50 Nanyang Avenue, Singapore 639798.
authors.forename: Can
authors.initials: C
authors.lastname: Xue
authors.affiliation: Department of Materials Science and Engineering and NUANCE Center, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208, United States.
authors.forename: Jinsong
authors.initials: J
authors.lastname: Wu
authors.affiliation: Department of Chemistry and International Institute for Nanotechnology, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208, United States.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Large
authors.affiliation: Department of Chemistry and International Institute for Nanotechnology, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208, United States.
authors.forename: C Michael
authors.initials: CM
authors.lastname: McGuirk
authors.affiliation: School of Materials Science and Engineering, Nanyang Technological University , 50 Nanyang Avenue, Singapore 639798.
authors.forename: Freddy
authors.initials: F
authors.lastname: Boey
authors.affiliation: Department of Materials Science and Engineering and NUANCE Center, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208, United States.
authors.forename: Vinayak
authors.initials: V
authors.lastname: Dravid
authors.affiliation: Department of Physics, Anhui Normal University , 1 Beijing East Road, Wuhu, Anhui 241000, China.
authors.forename: Zhifeng
authors.initials: Z
authors.lastname: Cui
authors.affiliation: Department of Chemistry and International Institute for Nanotechnology, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208, United States.
authors.forename: George C
authors.initials: GC
authors.lastname: Schatz
authors.affiliation: Department of Chemistry and International Institute for Nanotechnology, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208, United States.|Department of Materials Science and Engineering and NUANCE Center, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208, United States.
authors.forename: Chad A
authors.initials: CA
authors.lastname: Mirkin
keywords: DDA; anisotropic core−shell nanoparticles; anisotropic reaction; discrete dipole approximation; hybrid nanoplate; metal−semiconductor; sulfidation