Title

Thermal Stability And Segregation Processes In Self-Assembled Size-Selected Au XFe 1-X Nanoparticles Deposited On Tio 2(110): Composition Effects

Abstract

In-situ scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS) measurements have been performed to investigate the formation and thermal stability of mono- and bimetallic Au xFe 1-x (x 1, 0.8, 0.5, 0.2, 0) nanoparticles (NPs) supported on TiO 2(110). Nearly hexagonal arrangements of sizeselected Au, Fe, and Au-Fe NPs with well-defined interparticle distances have been achieved by diblockcopolymer encapsulation. Upon stepwise annealing from 300 to 1060 °C, a remarkable thermal stability of the Au-Fe NPs was observed, maintaining their original spatial arrangement on the TiO 2 surface up to 900 °C. A majority phase of a gold-iron alloy (solid solution) was achieved for our Au 0.5Fe 0.5 NPs in the temperature range of 700 °C - 800 °C, and for Au 0.2Fe 0.8 NPs at 800 °C, while a phase mixture of bcc Fe and Au-Fe alloy was observed for the Au 0.8Fe 0.2 system at 800 °C-900 °C. For all samples the segregation of Au atoms toward the NP surface was detected upon high temperature annealing (800 °C) in vacuum. Nearly complete Au desorption was observed by XPS at 900 °C for Au 0.2Fe 0.8 NPs, at 1000 °C for Au 0.5Fe 0.5 NPs, and at 1060 °C for Au 0.8Fe 0.2 NPs. The enhanced thermal stability of Au in the Au 0.8Fe 0.2 NPs is believed to be related to the formation of core(Fe)/shell(Au) structures. Furthermore, contrary to the case of pure Fe or Fe-rich NPs where nearly complete Fe desorption or Fe diffusion into TiO 2 was observed at 1000 °C, an Fe signal was detected at this temperature for the Au-rich samples (Au 0.8Fe 0.2 and Au 0.5Fe 0.5). © 2009 American Chemical Society.

Publication Date

1-29-2009

Publication Title

Journal of Physical Chemistry C

Volume

113

Issue

4

Number of Pages

1433-1446

Document Type

Article

Personal Identifier

scopus

DOI Link

https://doi.org/10.1021/jp806570a

Socpus ID

65249086849 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/65249086849

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