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Salt-Induced Aggregation of Negatively Charged Gold Nanoparticles Confined in a Polymer Brush Matrix
Macromolecules ( IF 5.1 ) Pub Date : 2017-09-14 00:00:00 , DOI: 10.1021/acs.macromol.7b00866 Stephanie Christau 1, 2 , Tim Moeller 1 , Jan Genzer 2 , Ralf Koehler 3, 4 , Regine von Klitzing 5, 6
Macromolecules ( IF 5.1 ) Pub Date : 2017-09-14 00:00:00 , DOI: 10.1021/acs.macromol.7b00866 Stephanie Christau 1, 2 , Tim Moeller 1 , Jan Genzer 2 , Ralf Koehler 3, 4 , Regine von Klitzing 5, 6
Affiliation
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We report on the salt-induced aggregation of citrate-coated gold nanoparticles (AuNPs) confined within poly(N-isopropylacrylamide) (PNIPAM) brushes grafted from flat substrates. Compared to highly dispersed AuNPs, a red-shift and broadening of the surface plasmon (SP) band is observed when the AuNPs are confined by the PNIPAM brush matrix due to their close vicinity. Additional red-shifting and broadening occur upon immersion in aqueous salt solutions (1 M NaF, NaCl, NaBr, and KCl). Nanoparticle assemblies are established due to salt-induced aggregation of AuNPs and are dependent on the type of salt. In the presence of KCl, nanoparticle assemblies are built up that result in the formation a second plasmon peak at ∼700 nm. The color change of PNIPAM/AuNP is associated with (1) the collapse of the PNIPAM brushes in the presence of salt and (2) nanoparticle aggregation due to electrostatic screening of the negative charges around the AuNPs by the salt ions. Ion specificity is related to ion-pair association energies and adsorption behavior of ions at the AuNP surface. In addition, we perform a neutron reflectivity experiment to resolve the internal structure of swollen PNIPAM/AuNP hybrids and find that penetrated AuNPs cause PNIPAM chain stretching due to electrostatic repulsion between charged particles in the brush.
中文翻译：
盐诱导的聚合物刷基体中带负电的金纳米粒子的聚集。
我们报道了盐诱导的局限在聚N中的柠檬酸盐包覆的金纳米颗粒（AuNPs）的聚集-异丙基丙烯酰胺（PNIPAM）刷子是从平坦基材上接枝的。与高度分散的AuNPs相比，当AuNPs由于其附近而被PNIPAM刷基体限制时，观察到了表面等离子体激元（SP）带的红移和变宽。浸入盐水溶液（1 M NaF，NaCl，NaBr和KCl）后，会发生其他红移和增宽。由于盐诱导的AuNP聚集而建立了纳米粒子组件，并且取决于盐的类型。在存在氯化钾的情况下，会形成纳米粒子组件，从而导致在〜700 nm处形成第二个等离激元峰。PNIPAM / AuNP的颜色变化与（1）在存在盐的情况下PNIPAM刷的塌陷和（2）由于通过盐离子对AuNPs周围的负电荷进行静电筛选而导致的纳米粒子聚集有关。离子特异性与离子对缔合能和离子在AuNP表面的吸附行为有关。此外，我们进行了中子反射率实验，以解决膨胀的PNIPAM / AuNP杂化物的内部结构，发现渗透的AuNPs由于刷子中带电粒子之间的静电排斥而导致PNIPAM链拉伸。
更新日期：2017-09-14
中文翻译：
盐诱导的聚合物刷基体中带负电的金纳米粒子的聚集。
我们报道了盐诱导的局限在聚N中的柠檬酸盐包覆的金纳米颗粒（AuNPs）的聚集-异丙基丙烯酰胺（PNIPAM）刷子是从平坦基材上接枝的。与高度分散的AuNPs相比，当AuNPs由于其附近而被PNIPAM刷基体限制时，观察到了表面等离子体激元（SP）带的红移和变宽。浸入盐水溶液（1 M NaF，NaCl，NaBr和KCl）后，会发生其他红移和增宽。由于盐诱导的AuNP聚集而建立了纳米粒子组件，并且取决于盐的类型。在存在氯化钾的情况下，会形成纳米粒子组件，从而导致在〜700 nm处形成第二个等离激元峰。PNIPAM / AuNP的颜色变化与（1）在存在盐的情况下PNIPAM刷的塌陷和（2）由于通过盐离子对AuNPs周围的负电荷进行静电筛选而导致的纳米粒子聚集有关。离子特异性与离子对缔合能和离子在AuNP表面的吸附行为有关。此外，我们进行了中子反射率实验，以解决膨胀的PNIPAM / AuNP杂化物的内部结构，发现渗透的AuNPs由于刷子中带电粒子之间的静电排斥而导致PNIPAM链拉伸。
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