Possible socket-plug standard connection for functionalized graphene e Validation by DFT Valentina Cantatore * , Itai Panas Chalmers University of Technology, Department of Chemistry and Chemical Engineering, Energy & Materials, Gothenburg, Sweden article info Article history: Received 9 December 2015 Received in revised form 21 March 2016 Accepted 23 March 2016 Available online 25 March 2016 abstract A possible Socket-Plug standard coupling to connect molecular moieties to graphene is proposed whereby the electronic characteristics in the vicinity of the Fermi energy become virtually independent of choice of molecular “antenna”. Proof of concept is offered by means of DFT. A Lewis acid e base coupling is utilized. Thus, the socket property is obtained by boron atoms introduced in the graphene matrix, while the plug property is offered by a lone-pair of the molecular adsorbate. Standard electronic response of boron doped graphene to three different nucleophilic adsorbates is demonstrated. Moreover, conceptual connection is made to hydrogenated pristine graphene and the origins of the similarities in the electronic structures are analyzed. Boron doping introduces holes in the valence band while the dative bonding between electrophilic boron sites and nucleophilic lone-pairs effectively achieves elec- tronic undoping of the boron doped graphene. The Lewis acid e base connection is understood to render the socket-plug functionality robust to adsorptionedesorption of the “antenna” molecules. This socket- plug standard may well comprise a necessary prerequisite for making systematic progress in contem- porary graphene technology. © 2016 Elsevier Ltd. All rights reserved. 1. Introduction Realization of the full potential of graphene e a single layer of carbon atoms with lateral extension that is readily tailored e re- quires the merging of its essential physical and chemical properties. While this implies trading away some of the ideal band structure characteristics of graphene, such as the ideal Dirac cone [1] origi- nating in the fundamental symmetry of the underlying honeycomb structure, we expect complementary electronic properties e some hitherto unknown e to emerge. The electrical properties of gra- phene are indeed extremely sensitive to even traces of adsorbed molecules making this material eligible to use as platform for molecular sensor applications [2] [3] [4] [5]. A straight-forward way to achieve local modifications in the graphene electronic structure is by adsorption of atoms or molecules. However, binding in general tends to cause irreversible damage to the material, and often in an unpredictable manner. Interfacing the graphene platform with molecules possessing tailored properties in a robust and stan- dardized way requires utilizing generic electronic features in the former. Doping of graphene with foreign atoms (for example ni- trogen, boron, sulfur and phosphorous), thus a priori compromising the material, provides an effective approach to modify the elec- tronic properties e.g. as a way to improve sensors performances. So, it is common to find in the recent literature applications of doped graphene used as sensor for small gas molecules like ammonia [6] [7] or to detect biological compounds [8] [9] [10] [11]. The present computational approach is motivated by the search for a “socket-plug standard” with generic properties for interfacing e.g. a local photo-electrocatalytic site or molecular sensor with the support. Here we utilize universal qualitative properties of super- cell calculations employing periodic boundary conditions. Elec- tronic structure due to double absorption at different lattice sites is described and employed to identify a class of interfaces between adsorbate and platform. Pair wise, single atom sp 2 e sp 3 rehy- bridization and binding is reflected in the attenuations of p and p* bands in the vicinity of the Fermi Level (E F ). The well known pair wise same/different sub-lattice oscillatory binding [12] previously reported for hydrogenated graphene from periodic boundary con- ditions calculations is thus used here as a signature of a class of systems which possess analogous electronic properties. We demonstrate proof of concept by comparing electronic signatures of two apparently unrelated systems: the inter-site dependence of * Corresponding author. E-mail address: valcan@chalmers.se (V. Cantatore). Contents lists available at ScienceDirect Carbon journal homepage: www.elsevier.com/locate/carbon http://dx.doi.org/10.1016/j.carbon.2016.03.051 0008-6223/© 2016 Elsevier Ltd. All rights reserved. Carbon 104 (2016) 40e46