Thermal Stability of Core鈥揝hell Nanoparticles: A Combined in Situ Study by XPS and TEM

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• 作者：Cecile S. Bonifacio ; Sophie Carenco ; Cheng Hao Wu ; Stephen D. House ; Hendrik Bluhm ; Judith C. Yang
• 刊名：Chemistry of Materials
• 出版年：2015
• 出版时间：October 27, 2015
• 年：2015
• 卷：27
• 期：20
• 页码：6960-6968
• 全文大小：601K
• ISSN：1520-5002

文摘

In situ techniques of transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) were used to investigate the thermal stability of Ni鈥揅o core鈥搒hell nanoparticles (NPs). The morphological, structural, and chemical changes involved in the core鈥搒hell reconfiguration were studied during in situ annealing through simultaneous imaging and acquisition of elemental maps in the TEM, and acquisition of O 1s, Ni 3p, and Co 3p XP spectra. The core鈥搒hell reconfiguration occurred in a stepwise process of surface oxide removal and metal segregation. Reduction of the stabilizing surface oxide occurred from 320 to 440 掳C, initiating the core鈥搒hell reconfiguration. Above 440 掳C, the core鈥搒hell structure was disrupted through Ni migration from the core to the shell. This resulted in the formation of a homogeneous Ni鈥揅o mixed alloy at 600 掳C. This study provides a mechanistic description of the alteration in the core鈥搒hell structures of NPs under vacuum conditions and increasing annealing temperature, which is crucial for understanding these technologically important materials.