Surface Chemistry of Thiomalic Acid Adsorption on Planar Gold and Gold Nanoparticles

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• 作者：Julio C. Azc谩rate ; Mar铆a Alejandra Floridia Addato ; Aldo Rubert ; Gast贸n Corthey ; Germ谩n S. K眉rten Moreno ; Guillermo Ben铆tez ; Eugenia Zelaya ; Roberto C. Salvarezza ; Mariano H. Fonticelli
• 刊名：Langmuir
• 出版年：2014
• 出版时间：February 25, 2014
• 年：2014
• 卷：30
• 期：7
• 页码：1820-1826
• 全文大小：389K
• 年卷期：v.30,no.7(February 25, 2014)
• ISSN：1520-5827

文摘

The self-assembly of thiomalic acid (TMA) on Au(111) and on preformed Au nanoparticles (AuNPs) protected by weak ligands has been studied by X-ray photoelectron spectroscopy (XPS) and electrochemical techniques. Results show that TMA is adsorbed on the Au(111) surface as thiolate species with a small amount of atomic sulfur (10%) and a surface coverage lower than that found for alkanethiols due to steric factors. The amount of atomic sulfur markedly increases when the TMA is adsorbed on AuNPs by the ligand exchange method. We propose that the atomic sulfur is produced as a consequence of C鈥揝 bond cleavage, a process that is more favorable at defective sites of the AuNPs surface. The bond scission is also assisted by the presence of the electron-withdrawing carboxy moiety in the 伪-position relative to the C鈥揝 bond. Moreover, the high local concentration of positively charged species increases the stability of the negatively charged leaving group, leading to a higher amount of coadsorbed atomic sulfur. Our results demonstrate that the terminal functionalities of thiols are conditioning factors in the final structure and composition of the adlayers.