Dispersion and Sorting of Nanomaterials

在过去的二十年里，当今纳米科学和纳米技术的很大一部分活动致力于合成碳同素异形体(0维富勒烯、一维碳纳米管和二维石墨烯)，因为它们显示出优异的和独特的机械和电子性能。然而，尽管这一系列材料在分散、功能化、分类、表征和加工方面取得了压倒性的进展，但仍然缺乏大规模的工业应用，这突显了不断确定新的、高度有效的材料类别的必要性。目前，层状无机材料(如BN、过渡金属硫化物或氧化物)呈现出复兴的趋势，因为这些材料涵盖了金属、半导体和绝缘性能的全部光谱。如部分文献所述，它们在电子应用(作为透明电极的金属材料、作为晶体管的半导体材料或作为电容器中的介质的绝缘材料)和能量收集和存储方面都具有巨大的潜力--特别是作为以碳纳米管为热电器件的混合材料中的组件、锂离子电池中的超级电容器或阴极。到目前为止，层状无机材料的不溶性和多分散性使得溶液相处理--这是方便的薄膜应用的先决条件--几乎是不可能的。因此，在迈向高性能器件的过程链中，第一步一直是这些层状纳米材料的瓶颈，从物理学家的角度来看，这些纳米材料表现出非凡的性能。2011年，科尔曼和他的同事已经证明，与碳同素异形体类似，湿化学剥离是批量生产单层膜从而实现溶液相处理的一条可行途径。这当然需要化学家们现在来进一步研究和改进湿化学剥离，因为分散和分选技术的全部潜力还有待探索。这项建议是这项工作的一部分，旨在通过选择巧妙的稳定剂和制备条件来统一纳米材料分散和剥离的概念，特别是在水溶液中。此外，将首次开发有效的分选方案，将单个薄片从双层和多层薄片中分离出来，并通过基于离心机的技术分离不同大小的薄片。

In the past two decades, a significant share of the activities in today’s nanoscience and nanotechnology has been devoted to synthetic carbon allotropes (0-dimensional fullerenes, 1D carbon nanotubes and 2D graphene), as they exhibit outstanding and unique mechanical and electronic properties. However, despite overwhelming progress in the dispersion, functionalization, sorting, characterization and processing of this family of materials, large scale industrial applications are still lacking, underlining the need of constantly identifying new, highly potent classes of materials. Currently, layered inorganic materials (e.g. BN, transition metal chalcogenides or oxides) exhibit a renaissance, as these materials cover the whole spectrum of metallic, semiconducting and insulating properties. As already partly documented in literature, they bear great potential for both electronic applications (metallic materials as transparent electrodes, semiconducting materials as transistors or insulating materials as dielectrics in capacitors) and energy harvesting and storage - especially as components in hybrid materials with carbon nanotubes as thermoelectric devices, supercapacitors or cathodes in Li ion batteries. Up to now, the insolubility and polydispersity of the layered inorganic materials rendered solution phase processing - a prerequisite for convenient thin film applications - virtually impossible. Thus, the first step in the process chain towards high performance devices has been the bottleneck for these layered nanomaterials that exhibit extraordinary properties from a physicist’s point of view. In 2011, Coleman and co-workers have shown that, in analogy to carbon allotropes, wet chemical exfoliation is an accessible route towards bulk production of monolayers and thus solution-phase processing. This certainly calls for chemists now, in order to further elaborate and improve wet chemical exfoliation, as the full potential of dispersion and sorting techniques is yet to be explored. This proposal is part of this work and targets unifying concepts in dispersion and exfoliation of nanomaterials, especially in aqueous solution by the choice of clever stabilizers and preparation conditions. Furthermore, efficient sorting scenarios to separate individual flakes from bi- and multilayers, as well as flakes of different sizes by centrifugation-based techniques are to be developed for the first time.