www.afm-journal.de © 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 1910186 (1 of 11) 2D monoelemental group 14 materials beyond graphene, such as silicene and germanene, have recently gained a lot of attention. Covalent functionalization of group 14 layered materials can lead to signifcant tuning of their proper- ties. While optical and electronic properties of germanene, silicene, and their derivatives have been studied in detail previously, there is no information on their electrochemistry and toxicity. Herein, electrochemical applications of 2D siloxene, germanane, and methylgermanane, specifcally for detection of an important biomarker, dopamine, as well as catalyzation of oxygen reduction and hydrogen evolution reactions, which are important in energy applica- tions, are explored. Among the three materials, germanane portrays most superior properties for the electrochemical applications mentioned. All three materials possess fast heterogeneous electron transfer rates, relative to bare glassy carbon electrodes. In addition, toxicity studies of these materials are conducted to gain insights on their possible harmful efects toward human health. The results of this study show siloxene nontoxic while germanane and methylgermanane impose dose-dependent toxicity. Interestingly, methylation successfully reduce the toxicity of methylgermanane at lower concentrations. These studies provide fundamental insights into electrochemical and toxic properties of functionalized group 14 layered materials for future electrochem- ical applications. 1. Introduction The groundbreaking research on gra- phene [1] has ignited intense interest in various 2D elemental nanomaterials. [2-9] These materials include group 14 mono- elemental graphene analogs known as silicene and germanene. Similar to gra- phene, they are 2D materials arranged in a honeycomb structure. [10] However, they have buckled sheets unlike graphene which is planar. [11,12] They exhibit similar promising electronic properties to gra- phene including low efective masses and high carrier mobilities but have a simi- larly negligible bandgap, which restricts their applications in electronics. [13] In addition, silicene and germanene are mainly synthesized on substrates due to lack of thermodynamic stability. [2,14] Hence, various modifcations of silicene and germanene have been carried out to improve their stability and increase their bandgaps. Several modifed silicene and germanene analogs were reported, e.g., N. F. Rosli, N. Rohaizad, Prof. R. D. Webster Division of Chemistry and Biological Chemistry School of Physical and Mathematical Sciences Nanyang Technological University 21 Nanyang Link, Singapore 637371, Singapore N. Rohaizad NTU Institute for Health Technologies Interdisciplinary Graduate School Nanyang Technological University 61 Nanyang Drive, Singapore 637335, Singapore Dr. J. Sturala Department of Inorganic Chemistry University of Chemistry and Technology Prague Technická 5, 166 28 Prague 6, Czech Republic Prof. A. C. Fisher Department of Chemical Engineering and Biotechnology University of Cambridge New Museums Site Pembroke Street, Cambridge CB2 3RA, UK FULL PAPER Siloxene, Germanane, and Methylgermanane: Functionalized 2D Materials of Group 14 for Electrochemical Applications Nur Farhanah Rosli, Nasuha Rohaizad, Jiri Sturala, Adrian C. Fisher, Richard D. Webster, and Martin Pumera* DOI: 10.1002/adfm.201910186 The ORCID identifcation number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adfm.201910186. Prof. M. Pumera Center for Advanced Functional Nanorobots Department of Inorganic Chemistry University of Chemistry and Technology Prague Technická 5, 166 28 Prague 6, Czech Republic E-mail: martin.pumera@ceitec.vutbr.cz, pumera.research@gmail.com Prof. M. Pumera Department of Chemical and Biomolecular Engineering Yonsei University 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, South Korea Prof. M. Pumera Department of Medical Research China Medical University Hospital China Medical University No. 91 Hsueh-Shih Road, Taichung 40402, Taiwan Prof. M. Pumera Future Energy and Innovation Laboratory Central European Institute of Technology Brno University of Technology Purkyňova 656/123, Brno CZ-616 00, Czech Republic Adv. Funct. Mater. 2020, 1910186