<> "The repository administrator has not yet configured an RDF license."^^ . <> . . "Liquid phase exfoliation and size dependent properties of van der Waals crystals"^^ . "Van der Waals crystals exhibit comparatively strong, typically covalent bonds in two dimensions and comparatively weak, typically non-covalent bonds between the two-dimensional lattice. This enables to separate individual two-dimensional layers of a van der Waals crystal which can be thinned down to atomic thickness in a process called exfoliation. The resulting nanosheets typically exhibit completely different properties compared to their corresponding bulk counterparts which can be exploited for various applications in advanced devices. Different methods have been presented for preparation of two-dimensional nanomaterials each with their respective up- and downsides. While some techniques can provide materials of highest quality, suitable for fundamental studies of inherent material properties, they typically lack scalability. Other methods focus on a high production rate of the nanomaterial, but introduce imperfections to the material due to the harsh conditions required. In recent years, exfoliation in the liquid phase has emerged to a widely used production technique due to the scalability and its wide applicability.\r\nWhile the industrial relevance of two-dimensional nanomaterials is somewhat linked to the quality of the material that can be prepared by high throughput methods, a deeper understanding of underlying fundamentals for the nanosheet preparation is required to improve state-of-the-art techniques. In the case of liquid-exfoliated nanosheets, this can be achieved by statistical studies of the nanomaterial dimensions that can be prepared and isolated by size selection techniques. In this work, sonication-assisted liquid phase exfoliation using different conditions and solvents and subsequent size selection was applied to a total of 17 different van der Waals crystals. The material dimensions of all fractions were quantified through statistical atomic force microscopy. The findings presented in this work demonstrate a fundamental correlation between the nanomaterial lateral size and thickness which is ascribed to equipartition of energy between processes of nanosheet delamination and tearing. This provides an experimental proxy to determine the ratio between the in-plane binding strength and the out-of-plane interlayer attraction. \r\nIsolation of different size-fractions of the same material and the knowledge over the nanomaterial dimensions in these fractions enables to study size-dependent changes of material properties in a quantitative manner. Measurements of optical properties on different sizes of dispersed nanosheets reveal systematic changes of the spectra with nanosheet size and enable to de-rive spectroscopic metrics for the size, thickness and concentration for different van der Waals nanomaterials, typically using extinction and absorbance spectroscopy. Structurally and compositionally different materials show similar changes in their optical response with changing material size which can be ascribed to a combination of confinement and dielectric screening effects, as well as changing contributions form scattering and electronically different material edges. Unifying principles across various materials were identified for the changes of the optical spectra with material dimensions. \r\nThe knowledge of material dimensions and the understanding of the optical spectra enables to study the stability of different nanomaterial systems as function of time using optical spectroscopy such as extinction, absorbance or photoluminescence. A dependence of the speed and degree of the material decomposition on the storage temperature and the water content of the solvent is conveniently accessible for different material dimensions. \r\nThe results presented within this work provide an advanced understanding of the exfoliation of layered crystals, unifying principles of optical properties as function of nanomaterial dimensions and proof-of-concept experiments for quantification of the material decomposition."^^ . "2021" . . . . . . . "Kevin"^^ . "Synnatschke"^^ . "Kevin Synnatschke"^^ . . . . . . "Liquid phase exfoliation and size dependent properties of van der Waals crystals (PDF)"^^ . . . "Dissertation_-_Kevin_Synnatschke.pdf"^^ . . . "Liquid phase exfoliation and size dependent properties of van der Waals crystals (Other)"^^ . . . . . . "lightbox.jpg"^^ . . . "Liquid phase exfoliation and size dependent properties of van der Waals crystals (Other)"^^ . . . . . . "preview.jpg"^^ . . . "Liquid phase exfoliation and size dependent properties of van der Waals crystals (Other)"^^ . . . . . . "medium.jpg"^^ . . . "Liquid phase exfoliation and size dependent properties of van der Waals crystals (Other)"^^ . . . . . . "small.jpg"^^ . . . "Liquid phase exfoliation and size dependent properties of van der Waals crystals (Other)"^^ . . . . . . "indexcodes.txt"^^ . . "HTML Summary of #29493 \n\nLiquid phase exfoliation and size dependent properties of van der Waals crystals\n\n" . "text/html" . . . "000 Allgemeines, Wissenschaft, Informatik"@de . "000 Generalities, Science"@en . .