Department of Physical Chemistry, University of Geneva, 30 Quai Ernest-Ansermet, Geneva 4CH-1211, Switzerland.
Langmuir. 2023 Feb 14;39(6):2135-2151. doi: 10.1021/acs.langmuir.2c02715. Epub 2023 Feb 5.
Recently the focus of the Langmuir-Blodgett technique as a method of choice to transfer monolayers from the air/water interface onto solid substrates in a controllable fashion has been shifting toward purely hydrophobic gold and silver nanoparticles. The fundamental interactions between particles that become relevant in the absence of polar groups range from dispersive attractions from the metal cores and repulsions between ligand shells to weaker entropic factors. The layer evolution is explored, starting with interfacial self-assembly upon solution spreading and domain and circular island formation, which subsequently merge into a complete monolayer and finally form multilayers or macroscopic wrinkles. Moreover, structural properties such as the core:ligand size ratio are investigated in the context of dispersive forces, whereby the nanoparticles with small cores and long ligands tend not to aggregate sufficiently to produce continuous films, those with large cores and short ligands were found to aggregate irreversibly, and those in between the two extremes were concluded to be able to form highly organized crystalline films. Similarly, the characteristics of the spreading solution such as the concentration and the solvent type crucially influence the film crystallinity, with the deciding factor being the degree of affinity between the capping ligand and the solvent used for spreading. Finally, the most common strategies employed to enhance the mechanical stability of the metal nanoparticle films along with the recent attempts to functionalize the particles in attempts to improve their applicability in the industry are summarized and evaluated in relation to their future prospects. One of the objectives of this feature article is to elucidate the differences between hydrophobic metal nanoparticles and typical amphiphilic molecules that the majority of the literature in the field describes and to familiarize the reader with the knowledge required to design Langmuir-Blodgett nanoparticle systems as well as the strategies to improve existing ones.
最近，Langmuir-Blodgett 技术作为一种将单层从空气/水界面可控地转移到固体基底上的方法，其焦点已经从具有极性基团的单层转移到纯粹的疏水性金和银纳米粒子上。在没有极性基团的情况下，粒子之间的基本相互作用范围从金属核的分散吸引力和配体壳之间的排斥力到较弱的熵因素。我们探索了层的演化，从溶液扩散时的界面自组装以及畴和圆形岛的形成开始，随后这些岛合并成一个完整的单层，最后形成多层或宏观皱纹。此外，在分散力的背景下研究了结构特性，如核：配体大小比，其中具有小核和长配体的纳米粒子不太容易聚集形成连续的薄膜，具有大核和短配体的纳米粒子被发现不可逆地聚集，而处于两者之间的纳米粒子被认为能够形成高度有序的结晶薄膜。同样，铺展溶液的特性，如浓度和溶剂类型，对薄膜结晶度有至关重要的影响，决定因素是封端配体与用于铺展的溶剂之间的亲和力程度。最后，总结并评估了提高金属纳米粒子薄膜机械稳定性的最常见策略以及最近尝试对粒子进行功能化以提高其在工业中的适用性的尝试，以及它们的未来前景。本文的目的之一是阐明疏水性金属纳米粒子与该领域大多数文献所描述的典型两亲分子之间的区别，并使读者熟悉设计 Langmuir-Blodgett 纳米粒子系统所需的知识以及改进现有系统的策略。
