Condensed Matter National Laboratory

Re-evaluating the surface energy of layered materials


(Internal): Seyed Mohammad Reza Taheri
(External): Ali Sanjari (Jetco Co.), Babak Zare (IUST), Hesam Nikfazan (Graphenex)
Mohsen Moazzami Gudarzi (University of Manchester), Alexandara Satalov (Leibniz University)

Funded by

Swiss National Science Foundation (P400P2_186747 & 174952), Iran Science Elites Federation (11/66332) and international affairs and technological exchange centre of vice presidency for science and technology (99/200/4419)

Published Papers

1- High-Performance Multifunctional Graphene-PLGA Fibers: Toward Biomimetic and Conducting 3D Scaffolds, Advanced Functional Materials, 2016, DOI: 10.1002/adfm.201505304.

2- Organic Solvent-Based Graphene Oxide Liquid Crystals: A Facile Route toward the Next Generation of Self-Assembled Layer-by-Layer Multifunctional 3D Architectures. ACS nano, 2013. 7(5): p. 3981-3990.

Summary in English and Photo

The surface energy of graphite and other layered materials supposedly plays a crucial role in their liquid phase exfoliation (LPE) into two-dimensional sheets. As such, surface energy matching of layered materials to liquid media is used unequivocally as a common practice to liquid exfoliate layered materials of choice. Though, surface energy is presumed to be a salient measure determining the quality and yield of the whole process, surprisingly a reliable value for this important physical quantity, in most cases, is missing and a large discrepancy in the reported surface energy of graphite and other layered materials is observed. As an example, in the case of graphite, the surface energy spans a broad range from 30 mJ∙m-2, which is substantially lower than many common polymers, up to 185 mJ∙m-2. Although of interest from both fundamental and practical perspectives, no explanation is provided to elucidate why such diverse and contested results are reported. Given the expanding landscape of two-dimensional materials, addressing this issue, therefore, can serve as a much-needed toolbox to offer particular design rules to facilitate the overall solvent selection process and enhance both quality and the yield. Having this in mind, we try to re-interpret the contact angle measurement results of high energy liquids on graphite samples, demonstrating that the contact angle results can, indeed, be translated into higher surface energies than the ones reported in the literature.



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