Optical response of Ag-Au bimetallic nanoparticles to electron storage in aqueous medium

Date
2008
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Source Title
Journal of Nanoscience and Nanotechnology
Print ISSN
1533-4880
Electronic ISSN
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Volume
8
Issue
6
Pages
3003 - 3007
Language
English
Type
Article
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Abstract

Composition and structure dependence of the shift in the position of the surface plasmon resonance band upon introduction of NaBH 4 to aqueous solutions of gold and silver nanoparticles are presented. Silver and gold nanoalloys in different compositions were prepared by co-reduction of the corresponding salt mixtures using sodium citrate as the reducing agent. After addition of NaBH 4 to the resultant nanoalloys, the maximum of their surface plasmon resonance band, ranging between that of pure silver (ca. 400 nm) and of pure gold (ca. 530 nm), is blue-shifted as a result of electron storage on the particles. The extent of this blue shift increases non-linearly with the mole fraction of silver in the nanoparticle, parallel to the trends reported previously for both the frequency and the extinction coefficient of the plasmon band shifts. Gold(core)@silver(shell) nanoparticles were prepared by sequential reduction of gold and silver, where addition of NaBH 4 results in relatively large spectral shift in the plasmon resonance band when compared with the nanoalloys having a similar overall composition. The origin of the large plasmon band shift in the core-shell is related with a higher silver surface concentration on these particles. Hence, the chemical nature of the nanoparticle emerges as the dominating factor contributing to the extent of the spectral shift as a result of electron storage in bimetallic systems. Copyright © 2008 American Scientific Publishers All rights reserved.

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Keywords
Core-shell structure, Gold and silver nanoparticles, Spectral shifts, Aqueous medium, Bi-metallic nanoparticles, Charge storage, Electron storage, Optical responses, Structure dependence, Gold, Surface plasmon resonance, Silver
Citation
Published Version (Please cite this version)