Perera Ganganath S, Nettles Charles B, Zhou Yadong, Zou Shengli, Hollis T Keith, Zhang Dongmao
Department of Chemistry, Mississippi State University , Mississippi State, Mississippi 39762, United States.
Department of Chemistry, University of Central Florida , Orlando, Florida 32816, United States.
Langmuir. 2015 Aug 25;31(33):8998-9005. doi: 10.1021/acs.langmuir.5b01903. Epub 2015 Aug 14.
Ion-pairing, the association of oppositely charged ionic species in solution and at liquid/solid interfaces has been proposed as a key factor for a wide range of physicochemical phenomena. However, experimental observations of ion pairing at the ligand/solid interfaces are challenging due to difficulties in differentiating ion species in the electrical double layer from that adsorbed on the solid surfaces. Using surface enhanced Raman spectroscopy in combination with electrolyte washing, we presented herein the first direct experimental evidence of ion pairing, the coadsorption of oppositely charged ionic species onto gold nanoparticles (AuNPs). Ion pairing reduces the electrolyte concentration threshold in inducing AuNP aggregation and enhances the competitiveness of electrolyte over neutral molecules for binding to AuNP surfaces. The methodology and insights provided in this work should be important for understanding electrolyte interfacial interactions with nanoparticles.
离子配对，即溶液中以及液/固界面处带相反电荷的离子物种之间的缔合，已被认为是众多物理化学现象的关键因素。然而，由于难以区分双电层中的离子物种与吸附在固体表面的离子物种，在配体/固体界面进行离子配对的实验观察颇具挑战性。我们结合表面增强拉曼光谱和电解质洗涤，首次在此展示了离子配对的直接实验证据，即带相反电荷的离子物种在金纳米颗粒（AuNPs）上的共吸附。离子配对降低了诱导AuNP聚集所需的电解质浓度阈值，并增强了电解质相对于中性分子与AuNP表面结合的竞争力。这项工作提供的方法和见解对于理解电解质与纳米颗粒的界面相互作用应具有重要意义。
