Tran Lisa, Kim Hye-Na, Li Ningwei, Yang Shu, Stebe Kathleen J, Kamien Randall D, Haase Martin F
Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104, USA.
Department of Materials Science and Engineering, University of Pennsylvania, 3231 Walnut Street, Philadelphia, PA 19104, USA.
Sci Adv. 2018 Oct 12;4(10):eaat8597. doi: 10.1126/sciadv.aat8597. eCollection 2018 Oct.
The ordering of nanoparticles into predetermined configurations is of importance to the design of advanced technologies. Here, we balance the interfacial energy of nanoparticles against the elastic energy of cholesteric liquid crystals to dynamically shape nanoparticle assemblies at a fluid interface. By adjusting the concentration of surfactant that plays the dual role of tuning the degree of nanoparticle hydrophobicity and altering the molecular anchoring of liquid crystals, we pattern nanoparticles at the interface of cholesteric liquid crystal emulsions. In this system, interfacial assembly is tempered by elastic patterns that arise from the geometric frustration of confined cholesterics. Patterns are tunable by varying both surfactant and chiral dopant concentrations. Adjusting the particle hydrophobicity more finely by regulating the surfactant concentration and solution pH further modifies the rigidity of assemblies, giving rise to surprising assembly dynamics dictated by the underlying elasticity of the cholesteric. Because particle assembly occurs at the interface with the desired structures exposed to the surrounding water solution, we demonstrate that particles can be readily cross-linked and manipulated, forming structures that retain their shape under external perturbations. This study serves as a foundation for better understanding inter-nanoparticle interactions at interfaces by tempering their assembly with elasticity and for creating materials with chemical heterogeneity and linear, periodic structures, essential for optical and energy applications.
将纳米颗粒排列成预定构型对于先进技术的设计至关重要。在此，我们使纳米颗粒的界面能与胆甾相液晶的弹性能达到平衡，以在流体界面动态塑造纳米颗粒聚集体。通过调节起双重作用的表面活性剂的浓度，即调节纳米颗粒的疏水性程度并改变液晶的分子锚定，我们在胆甾相液晶乳液的界面上对纳米颗粒进行图案化。在这个系统中，界面组装受到由受限胆甾相的几何受挫产生的弹性图案的调节。通过改变表面活性剂和手性掺杂剂的浓度，图案是可调的。通过调节表面活性剂浓度和溶液pH值更精细地调节颗粒疏水性，进一步改变了聚集体的刚性，产生了由胆甾相的潜在弹性决定的惊人组装动力学。由于颗粒组装发生在所需结构暴露于周围水溶液的界面处，我们证明颗粒可以很容易地交联和操控，形成在外部扰动下保持其形状的结构。这项研究为通过用弹性调节纳米颗粒组装来更好地理解界面处纳米颗粒间相互作用，以及为制造具有化学异质性和线性、周期性结构的材料奠定了基础，这些结构对于光学和能源应用至关重要。
