In Situ Non-DLVO Stabilization of Surfactant-Free, Plasmonic Gold Nanoparticles: Effect of Hofmeister's Anions
In Situ Non-DLVO Stabilization of Surfactant-Free, Plasmonic Gold Nanoparticles: Effect of Hofmeister's Anions
复制标题
DOI：
10.1021/la404556a
复制
发表时间：
2014-04-22
期刊：
影响因子：
3.9
通讯作者：
Barcikowski, Stephan
中科院分区：
文献类型：
--
作者：
Merk, Vivian;Rehbock, Christoph;Barcikowski, Stephan
霍夫迈斯特序列中的特定离子效应排序在生化、工业和大气过程中普遍存在。在这项实验研究中，在没有任何有机稳定剂的情况下，在液体中通过激光烧蚀过程合成的金纳米粒子的弯曲水金属界面上研究了经典 DLVO 理论无法解释的特定离子效应。值得注意的是，在低于 50 μM 的极低盐度的 Huckel 体系中，胶体稳定性中的离子特异性差异发生，并且发现了离子特异性效应对纳米颗粒形成过程的直接影响的迹象。 UV-vis、zeta 电位和 XPS 测量有助于阐明原始金纳米颗粒的凝固特性、动电势和氧化态。结果清楚地表明，无配体金纳米颗粒的稳定性与极化率成正比，与位于阴离子直接霍夫迈斯特序列中指定位置的阴离子的水合成反比。这些特定的离子效应可能是由于金/水界面上离液阴离子（Br-、SCN-或I-）的吸附导致纳米颗粒形成过程中部分氧化的金颗粒之间产生排斥相互作用。另一方面，亲液阴离子（F- 或 SO42-）似乎会使金胶体不稳定，而 Cl- 和 NO3- 则产生中等稳定性。表面电荷密度的量化表明颗粒稳定主要由离子吸附而非表面氧化决定。除了纯粹的静电相互作用之外，对无配体水性金纳米粒子的特定离子效应的基本了解在生物医学或催化应用中至关重要，因为胶体稳定性似乎很大程度上取决于盐的类型而不是数量。
Specific ion effects ranking in the Hofmeister sequence are ubiquitous in biochemical, industrial, and atmospheric processes. In this experimental study specific ion effects inexplicable by the classical DLVO theory have been investigated at curved water metal interfaces of gold nanoparticles synthesized by a laser ablation process in liquid in the absence of any organic stabilizers. Notably, ion-specific differences in colloidal stability occurred in the Huckel regime at extraordinarily low salinities below 50 mu M, and indications of a direct influence of ion-specific effects on the nanoparticle formation process are found. UV-vis, zeta potential, and XPS measurements help to elucidate coagulation properties, electrokinetic potential, and the oxidation state of pristine gold nanoparticles. The results clearly demonstrate that stabilization of ligand-free gold nanoparticles scales proportionally with polarizability and antiproportionally with hydration of anions located at defined positions in a direct Hofmeister sequence of anions. These specific ion effects might be due to the adsorption of chaotropic anions (Br-, SCN-, or I-) at the gold/water interface, leading to repulsive interactions between the partially oxidized gold particles during the nanoparticle formation process. On the other hand, kosmotropic anions (F- or SO42-) seem to destabilize the gold colloid, whereas Cl- and NO3- give rise to an intermediate stability. Quantification of surface charge density indicated that particle stabilization is dominated by ion adsorption and not by surface oxidation. Fundamental insights into specific ion effects on ligand-free aqueous gold nanoparticles beyond purely electrostatic interactions are of paramount importance in biomedical or catalytic applications, since colloidal stability appears to depend greatly on the type of salt rather than on the amount.