Galvanic Replacement Reaction: A Route to Highly Ordered Bimetallic Nanotubes

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• 作者：Abdel-Aziz El Mel ; Meriem Chettab ; Eric Gautron ; Adrien Chauvin ; Bernard Humbert ; Jean-Yves Mevellec ; Cyril Delacote ; Damien Thiry ; Nicolas Stephant ; Junjun Ding ; Ke Du ; Chang-Hwan Choi ; Pierre-Yves Tessier
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：August 11, 2016
• 年：2016
• 卷：120
• 期：31
• 页码：17652-17659
• 全文大小：522K
• 年卷期：0
• ISSN：1932-7455

文摘

Hollow bimetallic nanostructures are of great importance for various applications. Understanding the fundamental mechanisms occurring during the synthesis of such nanomaterials by wet chemistry remains very challenging. This Article reports a mechanistic study on the galvanic replacement reaction between planar arrays of silver nanowires grown site-specifically on tall silicon nanogratings and HAuCl₄ in lack of any stabilizing or capping agent, which might complicate and alter the conversion process of silver nanowires into silver–gold nanotubes. The direct contact of the silver nanowires with the substrate is found to modify the reaction as compared to nanowires in suspension. We show that when using diluted HAuCl₄, AgCl nanoclusters precipitate on the surface during the process resulting in an increased surface roughness of the nanotubes. Overcoming this drawback requires saturating the HAuCl₄ solution with NaCl; this allows distributing the anodic and cathodic sites over the surface of the nano-objects in a homogeneous manner, allowing in turn obtaining nanotubes with a smooth surface. For both protocols (i.e., pure HAuCl₄ or HAuCl₄ saturated with NaCl), the conversion rate was found to increase with the concentration of HAuCl₄ in the solution. We further show that the kinetic of the reaction and the surface roughness of the nanotubes become more important when raising the temperature from 0 to 100 °C. Furthermore, we show that by using the proposed approach, one can synthesize double-walled bimetallic nanotubes.