Adsorption and Chemical Modification of Phenols on a Silver Surface.
Adsorption and Chemical Modification of Phenols on a Silver Surface.
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DOI：
10.1006/jcis.2000.7101
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发表时间：
2000-11
影响因子：
9.9
通讯作者：
S. Sánchez‐Cortés;J. García-Ramos
中科院分区：
文献类型：
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作者：
S. Sánchez‐Cortés;J. García-Ramos
利用表面增强拉曼光谱（Sers）研究了不同性质的酚类化合物在银胶体颗粒上的吸附。所研究的化合物可分为三类：（a）肉桂酸衍生物：咖啡酸和异阿魏酸;（B）儿茶酚;和（c）苯甲酸衍生的酚类：间-和对-羟基苯甲酸和水杨酸、香草酸和没食子酸。这些化合物的兴趣在于它们是天然存在的分子，对于植物代谢、土壤化学和植物食品稳定性具有重要意义。此外，这些化合物中的许多具有源自其对大气氧的高亲和力的抗氧化性质。它们表现出高反应性，在金属表面（例如用于Sers光谱的表面）的存在下可以增强。从Sers结果可以推断，咖啡酸和没食子酸和邻苯二酚发生了明显的化学变化。化学改性主要包括与分子中存在的邻二酚部分相关的聚合。在间羟基苯甲酸的情况下，化学变化可能发生在低pH值下，在该pH值下，分子在表面上发生重新取向，而在邻羟基苯甲酸中，唯一的化学变化似乎是由与金属络合引起的内部H键断裂。最后，异阿魏酸和对羟基苯甲酸在吸附在金属上时不显示任何化学改性，这通过羧酸酯基团采用分子直立取向而发生。香草酸的情况不是很清楚，尽管这种吸附物也可能发生化学修饰。从这项工作中发现的结果可以推断，影响可能的化学改性的因素是吸附物的化学结构及其取向和与表面的相互作用。版权所有2000学术出版社。
The adsorption of phenols of different natures on silver colloidal particles is studied here by surface-enhanced Raman spectroscopy (SERS). The studied compounds can be classified in three groups: (a) cinnamic acic derivatives: caffeic and isoferulic acids; (b) catechol; and (c) the phenols derived from benzoic acid: m- and p-hydroxybenzoic acids and salicylic, vanillic, and gallic acids. The interest of these compounds lies in the fact that they are naturally occurring molecules with significant importance in relation to plant metabolism, soil chemistry, and vegetal food stability. In addition, many of these compounds have antioxidant properties derived from their high affinity toward atmospheric oxygen. They exhibit high reactivity that may be enhanced in the presence of a metal surface such as those employed for SERS spectroscopy. From the SERS results it can be deduced that a clear chemical change of caffeic and gallic acid and catechol occurred. The chemical modification consists mainly of polymerization connected to existence in the molecule of o-diphenol moieties. In the case of m-hydroxybenzoic acid the chemical change may occur at low pH at which a reorientation of the molecule on the surface takes place, while in the o-hydroxybenzoic acid the only chemical change seems to be the internal H bond breakdown induced by the complexation with the metal. Finally, isoferulic and p-hydroxybenzoic acids do not show any chemical modification upon adsorption on the metal, which takes place through the carboxylate group adopting the molecule a standing up orientation. The case of vanillic acid is not so clear, although possible chemical modification is also possible for this adsorbate. From the results found in this work it can be inferred that the factors influencing possible chemical modification are the chemical structure of the adsorbate and its orientation and interaction with the surface. Copyright 2000 Academic Press.