Multifunctional Organically Modified Graphene with Super-Hydrophobicity
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Nano Research 1 DOINano 10.1007/s12274-014-0408-0Res Multifunctional organically modified graphene with super-hydrophobicity 1 1 1 1 1 1 Huawen Hu , Chan C. K. Allan , Jianhua Li , Yeeyee Kong , Xiaowen Wang , John H. Xin (), and Hong Hu1 () Nano Res., Just Accepted Manuscript • DOI: 10.1007/s12274-014-0408-0 http://www.thenanoresearch.com on January 4 2014 © Tsinghua University Press 2014 Just Accepted This is a “Just Accepted” manuscript, which has been examined by the peer-review process and has been accepted for publication. A “Just Accepted” manuscript is published online shortly after its acceptance, which is prior to technical editing and formatting and author proofing. Tsinghua University Press (TUP) provides “Just Accepted” as an optional and free service which allows authors to make their results available to the research community as soon as possible after acceptance. After a manuscript has been technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Please note that technical editing may introduce minor changes to the manuscript text and/or graphics which may affect the content, and all legal disclaimers that apply to the journal pertain. In no event shall TUP be held responsible for errors or consequences arising from the use of any information contained in these “Just Accepted” manuscripts. To cite this manuscript please use its Digital Object Identifier (DOI®), which is identical for all formats of publication. TABLE OF CONTENTS (TOC) Multifunctional organically modified graphene with super-hydrophobicity Huawen Hu, Chan C.K. Allan, Jianhua Li, Yeeyee Kong, Xiaowen Wang, John H. Xin,* Hong Hu* The Hong Kong Polytechnic University, Hong Kong, China Page Numbers. The font is ArialMT 16 (automatically A multifunctional organically modified graphene with super-hydrophobicity has been synthesized by a novel one-step organic modification of a inserted by the publisher) low-temperature thermally functionalized graphene. Unique structural topology is found to exist in the as-prepared low-temperature thermally functionalized graphene, along with a portion of reactive oxygen functionalities preserved (see Figure), which facilitates the subsequently highly effective fabrication of an organically modified graphene derivative with multifunctional applications in liquid marbles and polymer nanocomposites. 1 Nano Res DOI (automatically inserted by the publisher) Research Article Multifunctional organically modified graphene with super-hydrophobicity Huawen Hu1, Chan C.K. Allan1, Jianhua Li1, Yeeyee Kong1, Xiaowen Wang1, John H. Xin1 (), and Hong Hu1 () 1 Institute of Textiles and Clothing, The Hong Kong Polytechnic University, Hong Kong 999077, China Received: day month year / Revised: day month year / Accepted: day month year (automatically inserted by the publisher) © Tsinghua University Press and Springer-Verlag Berlin Heidelberg 2011 ABSTRACT In order to bring graphene materials much closer to real word applications, it is imperative to have simple, efficient and eco-friendly ways to produce processable graphene derivatives. In this study herein, a hydrophilic low-temperature thermally functionalized graphene and its super-hydrophobic organically modified graphene derivative were fabricated. A unique structural topology and a part of oxygen functionalities were found to exist on the thermally functionalized graphene surfaces, which facilitated the subsequently highly effective organic modification reaction and led to the super-hydrophobic organically modified graphene with multifunctional applications in liquid marbles and polymer nanocomposites. The organic modification reaction could also restore the graphenic conjugation structure of the thermally functionalized graphene, particularly for the organic modifier having longer alkyl chains, confirmed by various characterization techniques such as electrical conductivity measurement, ultraviolet/visible spectroscopy and selected area electron diffraction. The free-standing soft liquid marble was fabricated by wrapping a water droplet with the super-hydrophobic organically modified graphene, which showed a potential value in micro-reactors. As for the polymer nanocomposites, a strong interfacial adhesion was believed to exist between an organic polymer matrix and the modified graphene because of the organophilic coating formed on the graphene base, which resulted in large improvements in the thermal and mechanical properties of the polymer nanocomposites with the modified graphene even at a very low loading level. A new avenue was therefore opened up for large-scale production of processible graphene derivatives with various practicable applications. KEYWORDS low-temperature thermally functionalized graphene, organic modification, organically modified graphene, liquid marbles, polymer nanocomposites ———————————— Address correspondence to J. H. Xin, [email protected]; H. Hu, [email protected] 2 reduced graphene sheet onto another [9,17], but to a 1 Introduction portion of oxygen functionalities remained, which Graphene, a two-dimensional carbon honeycomb can impart hydrophilicity and reactivity to the nanostructure, has attracted substantial attention in resulting TrG. In addition, compared with the various areas owning to its extraordinary chemical reduction, the technique is more mechanical [1], thermal [2] and electrical [3] environmentally friendly because of the absence of properties. Unfortunately, the cost of graphene, its any harmful chemical reducer such as availability and the challenges that remain to commonly-used hydrazine and its derivatives. On achieve good dispersion pose significant obstacles another aspect, the present strategy of thermal to realization of these superior properties. Various reduction and functionalization of GO involves the methods have thus been explored to produce heating temperature of 400 oC which is much lower graphene effectively, among which a well-known as compared to the conventional thermal reduction and cost-effective graphite oxide (GO) exfoliation approach involving the temperature of more than has been considered the most promising approach 1000 oC [9,18-21]. This thereby indicates that the to mass-scale production of graphene materials. present technique is of much lower energy Starting from naturally abundant graphite, GO can consumption. be first prepared based on Staudenmaier [4], Brodie Furthermore, by considering the fact that the [5], or Hummers and Offeman [6] oxidation method. thermal exfoliation of GO is currently used for Reduced graphene derivative can be subsequently industrial production of functionalized graphene prepared via various reduction strategies [7-9]. [22], organic modification of thermally However, reduction of GO usually cannot result in functionalized graphene accordingly shows a single-layer graphene because of the irreversible significance for large-scale production of agglomeration and restacking of the reduced organophilic graphene derivatives. Although graphene which eventually lead to the graphene organically modified graphene can be prepared precipitate. This is caused by the strong interplanar starting from GO which has abundant reactive π-π stacking and van der Waals interactions oxygen functionalities on its surfaces [23-29], many between reduced graphene [10,11]. Many in-plane properties of GO is heavily impaired modification approaches have thus been developed during its harsh preparation process. These for fabrication of soluble graphene such as sacrificed properties of the prepared organically noncovalent modification through π-π interactions modified graphene oxide should thus be further [12], covalent sulfonation modification [13], and restored by reduction processing, e.g., using chemical reduction under controlled conditions [14, chemical reducer such as hydrazine, sodium 15]. borohydride and hydroquinone to chemically Alternatively, the disturbing problem of convert the organically modified graphene oxide to graphene agglomeration has been addressed first graphene, which thereby violates the environment through a low-temperature thermal reduction of safety due to the harmfulness of these chemicals. GO in the present study. This technique leads not Fortunately, this problem can be avoided using the only to a thermally reduced and functionalized present approach of organic modification of TrG. graphene (TrG) with a buckled, folded and On the other hand, a different and unique structure wrinkled surface topology, as reported similarly in is introduced to the organically modified graphene the Ref. [9,16], which can prevent re-graphitization by the initial low-temperature thermal of the graphene sheets by inhibiting layering of one functionalization of GO as compared to the main 3 chemical reduction way [7,30], which might system with OA-G, together with large facilitate the subsequent applications, e.g., the bent improvement in the mechanical properties structure formed can be favorable for wrapping including Young’s modulus and tensile strength. water droplet and yielding liquid marble. Moreover, In summary, the developed environmentally compared with some other reported approaches for friendly efficient strategies for preparation of preparation of organically modified graphene, such low-temperature thermally functionalized graphene as ball-milling intercalation and hydrothermal and its organically modified graphene derivatives reduction and modification [31,32] which involves has opened up new avenues to