Nanoscience for Energy Technology and Sustainability, Department of Mechanical and Process Engineering, Eidgenössische Technische Hochschule (ETH) Zürich , Zürich CH-8092, Switzerland.
Engineering Directorate, Lawrence Livermore National Laboratory , Livermore CA 94650, United States.
Langmuir. 2017 Jul 18;33(28):6999-7006. doi: 10.1021/acs.langmuir.7b01186. Epub 2017 Jul 10.
Surface adsorption plays a critical role in a wide variety of fields from surface catalysis to molecular separation. Despite the importance, limited access to simultaneously sensitive and selective detection mechanisms has hampered the acquisition of comprehensive and versatile experimental data needed to understand the complex aspects of mixture adsorption, calling for a molecular detection method capable of obtaining the surface adsorption isotherms over a wide range of concentrations as well as distinguishing the competitive adsorption of different adsorbates. Here, we test surface-enhanced Raman spectroscopy (SERS) as an effective analysis tool of surface adsorption phenomena. Using a sensitive SERS substrate, we characterize the adsorption isotherms of chemical species of various binding energies. We obtained the isotherms for strongly binding species in a concentration range from subpicomolar to micromolar. A log-sigmoidal dependency of the SERS signals to the analyte concentration could be modeled by surface binding theories accurately using molecular dynamics simulations, thereby bringing out the potential capability of sensitive SERS for describing a single-compound adsorption process. SERS also enabled the determination of competitive adsorption isotherms from a multiple-compound solution for the first time. The successful demonstration of the sensitive and selective characterization of surface adsorption lends SERS adaptability to a cheap, facile, and effective solution for chemical analysis.
表面吸附在从表面催化到分子分离的各种领域中起着至关重要的作用。尽管其重要性不言而喻，但缺乏同时具有灵敏度和选择性的检测机制，这阻碍了获得全面和通用的实验数据，从而无法深入了解混合物吸附的复杂方面，因此需要一种能够在广泛浓度范围内获取表面吸附等温线并区分不同吸附物竞争吸附的分子检测方法。在这里，我们测试了表面增强拉曼光谱（SERS）作为表面吸附现象的有效分析工具。我们使用灵敏的 SERS 衬底来表征各种结合能化学物质的吸附等温线。我们在亚皮摩尔到微摩尔的浓度范围内获得了强结合物质的等温线。通过分子动力学模拟，SERS 信号与分析物浓度的对数-西格玛依赖性可以准确地用表面结合理论来建模，从而展现出灵敏 SERS 描述单一组分吸附过程的潜在能力。SERS 还首次能够从多组分溶液中确定竞争吸附等温线。表面吸附的灵敏和选择性特征的成功演示表明，SERS 具有适应廉价、简便和有效的化学分析的能力。
