Simple Method for the Covalent Immobilization of Graphene

Abstract

We present a simple and efficient method to covalently immobilize graphene on silicon wafers using perfluorophenylazide (PFPA) as the coupling agent. Graphene sheets were covalently attached to PFPA-functionalized wafer surface by a simple heat treatment under ambient conditions. The formation of single and multiple layers of graphene were confirmed by Raman spectroscopy, and optical and atomic force microscopy. Evidence of covalent bond formation between graphene and PFPA decorated silicon wafer was given by X-ray photoelectron spectroscopy and sonication treatment.Graphene, a two-dimensional atomic thin layer of carbon nanostructure, has emerged as a unique nanoscale material with promising applications in electronics due to its stable crystal structure, optical transparency, and its exceptional electronic properties of high electron mobility and high saturation velocity for both electrons and holes [1][2][3][4][5][6][7] . However, realization of these potentials has been severely hampered by the availability of large-scale and stable graphene structures that are needed for electronic device fabrication. Furthermore, graphene films with well-defined and controllable surface and interface properties are important for both fundamental studies and practical applications of the material. 8,9 Among various reported preparation methods, 10-17 mechanical cleavage of highly oriented pyrolytic graphite (HOPG) remains to be the most popular and successful in producing single or few layers of graphene sheets. 18 The earliest approach involves the use of a Scotch tape to peel multiple layers of graphene from HOPG, and transfer the sheets to a substrate by pressing followed by releasing. The films obtained in this manner contain different numbers of graphene layers, and the percentage of single graphene sheets varies from sample to sample. An improved version of the mechanical cleavage technique involves applying external pressure to press HOPG on the substrate and thus physically transferring the material from HOPG to the substrate. 19,20 Chou and coworkers used the pillars on a stamp fabricated by nanoimprinting to cut and exfoliate graphene islands from HOPG, and then transferred the films from the stamp to the device active areas on a substrate. 19 Padture et al. fabricated a graphite stamp by etching into HOPG using the technique of photolithography. The HOPG stamp was then pressed onto a silicon wafer creating arrays of multi-layered graphene sheets on the substrate surface. 20 The graphene sheets deposited by these transferring methods are physisorbed on the substrate and can be easily removed by solvent wash (with isopropanol or acetone) or sonication. 21 Here, we report a method to covalently attach graphene to silicon wafers using perfluorophenylazides (PFPA) as the coupling agent. Upon photochemical or thermal activation, the azido group gives the highly reactive singlet perfluorophenylnitrene that can subsequently undergo C-H insertion and/or C=C addition reactions with the neighboring molecules (Scheme...

Synthesis of graphene

“…This peeling/exfoliation can be done using a variety of agents like scotch tape [15], ultrasonication, [64] electric field [65] and even by transfer printing technique [66,67], etc. In certain studies the HOPG has also been bonded to the substrate either by regular adhesives like epoxy resin [64,68] or even by SAMs [69] to improve the yield of single and few layer graphene flakes. A recent study also demonstrates transfer printing of macroscopic graphene patterns from patterned HOPG using gold films [70].…”

Controlled Covalent Functionalization of Thermally Reduced Graphene Oxide To Generate Defined Bifunctional 2D Nanomaterials

“…The functionalization of graphene under ambient conditions by perfluoroazides as precursors of the highly reactive nitrenes has been explored to overcome this drawback 13. The mild reaction conditions and well‐defined functionality provide superior efficiency and simplicity compared to common methods for the functionalization of nitrenes 17, 18. In addition to efficiency and simplicity, a universal and affordable functionalization method should also involve readily available starting materials and provide reactive functional groups for flexible post‐modification.…”

Janus graphene from asymmetric two-dimensional chemistry

“…Physisorption of chemical species on graphene would provide a facile way to alter its electronic properties 12 , however, covalent chemical modification shows a great advantage in achieving permanent stabilisation for long-term usage 13 . Previous attempts towards fundamental research on covalent functionalisation of graphene mainly involved the development of new modification strategies (for example, hydrogenation [14][15][16][17] , fluorination [18][19][20] , chlorination 21,22 , diazotization [23][24][25][26][27] and other cycloaddition reactions [28][29][30][31] ), covalent addition of edge and defects 27,32 , fabrication of chemical superlattices 26,33 and quantum effects in graphene modification 17,34 . Of the various significant research activities on graphene chemistry that have been conducted, nearly no work to date has been focused on the asymmetric chemistry of this ideal 2D atomic crystal via covalently attaching different functional groups on its two faces simultaneously.…”