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Title: Direct Observation of the Growth of Au-Pd Core-Shell Nanoparticles Using in situ Low-Dose Liquid Cell STEM imaging

Abstract

Bimetallic core-shell nanoparticles are widely used as catalysts in several industrial reactions, with core-shell structures permitting facile surface modification and allowing increased stability and durability, and cost-effectiveness of the catalysts. We report, for the first time, on observing the early stages of the formation of Au-Pd core-shell bimetallic nanoparticles via the seed-mediated growth in the presence of reducing agent, while employing the low-dose scanning transmission electron microscopy imaging with the fluid cell in situ. Use of the continuous flow in situ fluid cell platform allows for delivery of reagent solutions and generation of near-native reaction environment in the reaction chamber, and permits direct visualization of the early stages of formation of Au-Pd core-shell structures at low dose rate (0.1 e -/(Å 2s)) in the presence of ascorbic acid. No core-shell structures were detected in the absence of reducing agent at the electron dose of 32.6 e -2. While the core-shell structures formed in situ under the low-dose imaging closely resemble those obtained in solution synthesis, the reaction kinetics in the fluid cell is affected by the radiolysis of liquid reagents induced by electron beam, altering the rate-determining reaction steps. The enhanced reduction of Pd ions leads to initial rapidmore » growth of the nascent Pd shell along the <111> direction at the Au interface, followed by a slower rearrangement of the outer Pd layer. The latter becomes the rate-determining step in the in situ reaction and appears to follow the oriented attachment-like movement to yield a remodeled, compact and stable Au-Pd core-shell nanostructure. Our findings highlight the differences between the two reaction pathways and aid in understanding the mechanism of formation of the core-shell nanostructure in situ.« less

Authors:
 [1];  [1]
  1. Ames Lab., Ames, IA (United States). Division of Materials Sciences and Engineering
Publication Date:
Research Org.:
Ames Laboratory (AMES), Ames, IA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1350059
Report Number(s):
IS-J-8931
Journal ID: ISSN 0897-4756; PII: S1431927616004578
Grant/Contract Number:  
AC02-07CH11358
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Chemistry of Materials
Additional Journal Information:
Journal Volume: 22; Journal Issue: S3; Journal ID: ISSN 0897-4756
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Low-dose HAADF-STEM; in situ; continuous flow; core-shell; electron dose; bimetallic; AuPd; liquid cell

Citation Formats

Bhattarai, Nabraj, and Prozorov, Tanya. Direct Observation of the Growth of Au-Pd Core-Shell Nanoparticles Using in situ Low-Dose Liquid Cell STEM imaging. United States: N. p., 2016. Web. doi:10.1017/S1431927616004578.
Bhattarai, Nabraj, & Prozorov, Tanya. Direct Observation of the Growth of Au-Pd Core-Shell Nanoparticles Using in situ Low-Dose Liquid Cell STEM imaging. United States. doi:10.1017/S1431927616004578.
Bhattarai, Nabraj, and Prozorov, Tanya. Mon . "Direct Observation of the Growth of Au-Pd Core-Shell Nanoparticles Using in situ Low-Dose Liquid Cell STEM imaging". United States. doi:10.1017/S1431927616004578. https://www.osti.gov/servlets/purl/1350059.
@article{osti_1350059,
title = {Direct Observation of the Growth of Au-Pd Core-Shell Nanoparticles Using in situ Low-Dose Liquid Cell STEM imaging},
author = {Bhattarai, Nabraj and Prozorov, Tanya},
abstractNote = {Bimetallic core-shell nanoparticles are widely used as catalysts in several industrial reactions, with core-shell structures permitting facile surface modification and allowing increased stability and durability, and cost-effectiveness of the catalysts. We report, for the first time, on observing the early stages of the formation of Au-Pd core-shell bimetallic nanoparticles via the seed-mediated growth in the presence of reducing agent, while employing the low-dose scanning transmission electron microscopy imaging with the fluid cell in situ. Use of the continuous flow in situ fluid cell platform allows for delivery of reagent solutions and generation of near-native reaction environment in the reaction chamber, and permits direct visualization of the early stages of formation of Au-Pd core-shell structures at low dose rate (0.1 e-/(Å2s)) in the presence of ascorbic acid. No core-shell structures were detected in the absence of reducing agent at the electron dose of 32.6 e-/Å2. While the core-shell structures formed in situ under the low-dose imaging closely resemble those obtained in solution synthesis, the reaction kinetics in the fluid cell is affected by the radiolysis of liquid reagents induced by electron beam, altering the rate-determining reaction steps. The enhanced reduction of Pd ions leads to initial rapid growth of the nascent Pd shell along the <111> direction at the Au interface, followed by a slower rearrangement of the outer Pd layer. The latter becomes the rate-determining step in the in situ reaction and appears to follow the oriented attachment-like movement to yield a remodeled, compact and stable Au-Pd core-shell nanostructure. Our findings highlight the differences between the two reaction pathways and aid in understanding the mechanism of formation of the core-shell nanostructure in situ.},
doi = {10.1017/S1431927616004578},
journal = {Chemistry of Materials},
number = S3,
volume = 22,
place = {United States},
year = {Mon Jul 25 00:00:00 EDT 2016},
month = {Mon Jul 25 00:00:00 EDT 2016}
}

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Works referenced in this record:

Shape-Controlled Synthesis of Metal Nanocrystals: Simple Chemistry Meets Complex Physics?
journal, December 2008

  • Xia, Younan; Xiong, Yujie; Lim, Byungkwon
  • Angewandte Chemie International Edition, Vol. 48, Issue 1, p. 60-103
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