Chemical Functionalization of graphene edges are an interesting research field due to its importance for fundamental understanding and applications. Platelet graphene nanofibers (PGNFs) which have a perpendicular orientation of the graphene sheets to the long axis of the fiber exhibit a large number of edge-plane sites and provide a unique structure for experimental observation of edge functionalization. Here we demonstrate functionalization of PGNFs using plasma treatment with SF6, CF4, and O2 gases. The influence of plasma treatment was analyzed by Raman spectroscopy and x-ray photoelectron spectroscopy (XPS). XPS demonstrates that functionalization using fluorine is more effective than oxygen. For fluorination, with the increasing power and exposure time increase the fluorine over carbon ratio (F/C). Raman Spectroscopy also shows an increasing ID/IG ratio of functionalized PGNFs due to high number of edges of the graphene sheets exposed. By using liquid exfoliation method with NMP solvent, PGNFs can be exfoliated with the sortest length ~8-10 nm which confirmed by AFM and TEM.

[1] Geim AK, Novoselov KS. The rise of graphene. Nat Mater. 2007;6(3):183-91.
[2] Jia X, Campos-Delgado J, Terrones M, Meunier V, Dresselhaus MS. Graphene edges: a review of their fabrication and characterization. Nanoscale. 2011;3(1):86-95.
[3] Zhang X, Xin J, Ding F. The edges of graphene. Nanoscale. 2013;5(7):2556-69.
[4] Ambrosi A, Bonanni A, Pumera M. Electrochemistry of folded graphene edges. Nanoscale. 2011;3(5):2256-60.
[5] Brownson DAC, Munro LJ, Kampouris DK, Banks CE. Electrochemistry of graphene: not such a beneficial electrode material? Rsc Advances. 2011;1(6):978-88.
[6] Ambrosi A, Sasaki T, Pumera M. Platelet Graphite Nanofibers for Electrochemical Sensing and Biosensing: The Influence of Graphene Sheet Orientation. Chemistry-an Asian Journal. 2010;5(2):266-71.
[7] Yuan W, Zhou Y, Li Y, Li C, Peng H, Zhang J, et al. The edge- and basal-plane-specific electrochemistry of a single-layer graphene sheet. Scientific Reports. 2013;3.
[8] Keeley GP, McEvoy N, Nolan H, Holzinger M, Cosnier S, Duesberg GS. Electroanalytical Sensing Properties of Pristine and Functionalized Multilayer Graphene. Chemistry of Materials. 2014;26(5):1807-12.
[9] Li D, Muller MB, Gilje S, Kaner RB, Wallace GG. Processable aqueous dispersions of graphene nanosheets. Nature Nanotech. 2008;3:101-5.
[10] Gooding JJ, Wibowo R, Liu JQ, Yang WR, Losic D, Orbons S, et al. Protein electrochemistry using aligned carbon nanotube arrays. Journal of the American Chemical Society. 2003;125(30):9006-7.
[11] Patolsky F, Weizmann Y, Willner I. Long-range electrical contacting of redox enzymes by SWCNT connectors. Angewandte Chemie-International Edition. 2004;43(16):2113-7.
[12] Chou A, Bocking T, Singh NK, Gooding JJ. Demonstration of the importance of oxygenated species at the ends of carbon nanotubes for their favourable electrochemical properties. Chemical communications. 2005(7):842-4.
[13] Nair RR, Blake P, Grigorenko AN, Novoselov KS, Booth TJ, Stauber T, et al. Fine structure constant defines visual transparency of graphene. Science. 2008;320(5881):1308-.
[14] Tressaud A, Durand E, Labrugère C. Surface modification of several carbon-based materials: comparison between CF4 rf plasma and direct F2-gas fluorination routes. Journal of Fluorine Chemistry. 2004;125(11):1639-48.
[15] Ko S, Tatsuma T, Sakoda A, Sakai Y, Komori K. Electrochemical properties of oxygenated cup-stacked carbon nanofiber-modified electrodes. Physical chemistry chemical physics : PCCP. 2014;16(24):12209-13.
[16] Chamssedine F, Dubois M, Guérin K, Giraudet J, Masin F, Ivanov DA, et al. Reactivity of Carbon Nanofibers with Fluorine Gas. Chemistry of Materials. 2006;19(2):161-72.
[17] Ahmad Y, Guérin K, Dubois M, Zhang W, Hamwi A. Enhanced performances in primary lithium batteries of fluorinated carbon nanofibers through static fluorination. Electrochimica Acta. 2013;114:142-51.
[18] Yazami R, Hamwi A, Guérin K, Ozawa Y, Dubois M, Giraudet J, et al. Fluorinated carbon nanofibres for high energy and high power densities primary lithium batteries. Electrochemistry Communications. 2007;9(7):1850-5.
[19] Zhu S, Zhang J, Qiao C, Tang S, Li Y, Yuan W, et al. Strongly green-photoluminescent graphene quantum dots for bioimaging applications. Chemical communications. 2011;47(24):6858-60.
[20] Jing Y, Zhu Y, Yang X, Shen J, Li C. Ultrasound-Triggered Smart Drug Release from Multifunctional Core−Shell Capsules One-Step Fabricated by Coaxial Electrospray Method. Langmuir : the ACS journal of surfaces and colloids. 2010;27(3):1175-80.
[21] Sun X, Liu Z, Welsher K, Robinson JT, Goodwin A, Zaric S, et al. Nano-Graphene Oxide for Cellular Imaging and Drug Delivery. Nano Res. 2008;1(3):203-12.
[22] Robinson JT, Tabakman SM, Liang Y, Wang H, Sanchez Casalongue H, Vinh D, et al. Ultrasmall Reduced Graphene Oxide with High Near-Infrared Absorbance for Photothermal Therapy. Journal of the American Chemical Society. 2011;133(17):6825-31.
[23] Zhao J, Chen G, Zhu L, Li G. Graphene quantum dots-based platform for the fabrication of electrochemical biosensors. Electrochemistry Communications. 2011;13(1):31-3.
[24] Yan X, Cui X, Li B, Li L-s. Large, Solution-Processable Graphene Quantum Dots as Light Absorbers for Photovoltaics. Nano letters. 2010;10(5):1869-73.
[25] Peng J, Gao W, Gupta BK, Liu Z, Romero-Aburto R, Ge L, et al. Graphene Quantum Dots Derived from Carbon Fibers. Nano letters. 2012;12(2):844-9.
[26] Hamilton IP, Li B, Yan X, Li L-s. Alignment of Colloidal Graphene Quantum Dots on Polar Surfaces. Nano letters. 2011;11(4):1524-9.
[27] Mueller ML, Yan X, Dragnea B, Li L-s. Slow Hot-Carrier Relaxation in Colloidal Graphene Quantum Dots. Nano letters. 2010;11(1):56-60.
[28] Ponomarenko LA, Schedin F, Katsnelson MI, Yang R, Hill EW, Novoselov KS, et al. Chaotic dirac billiard in graphene quantum dots. Science. 2008;320(5874):356-8.
[29] Hernandez Y, Nicolosi V, Lotya M, Blighe FM, Sun Z, De S, et al. High-yield production of graphene by liquid-phase exfoliation of graphite. Nature nanotechnology. 2008;3(9):563-8.
[30] Li Z, Cui X, Zheng J, Wang Q, Lin Y. Effects of microstructure of carbon nanofibers for amperometric detection of hydrogen peroxide. Analytica Chimica Acta. 2007;597(2):238-44.
[31] Niyogi S. Solution properties of graphite and graphene. J Am Chem Soc. 2006;128:7720-1.
[32] O'Connell MJ, Boul P, Ericson LM, Huffman C, Wang Y, Haroz E, et al. Reversible water-solubilization of single-walled carbon nanotubes by polymer wrapping. Chemical Physics Letters. 2001;342(3-4):265-71.
[33] Ros TG, van Dillen AJ, Geus JW, Koningsberger DC. Surface Oxidation of Carbon Nanofibres. Chemistry – A European Journal. 2002;8(5):1151-62.
[34] Boehm HP. Surface oxides on carbon and their analysis: A critical assessment. Carbon. 2002;40(2):145-9.
[35] Haydar S, Moreno-Castilla C, Ferro-García MA, Carrasco-Marín F, Rivera-Utrilla J, Perrard A, et al. Regularities in the temperature-programmed desorption spectra of CO2 and CO from activated carbons. Carbon. 2000;38(9):1297-308.
[36] Zhou JH, Sui ZJ, Li P, Chen D, Dai YC, Yuan WK. Structural characterization of carbon nanofibers formed from different carbon-containing gases. Carbon. 2006;44(15):3255-62.
[37] Singh B, Murad L, Laffir F, Dickinson C, Dempsey E. Pt based nanocomposites (mono/bi/tri-metallic) decorated using different carbon supports for methanol electro-oxidation in acidic and basic media. Nanoscale. 2011;3(8):3334-49.
[38] Beuvelot J, Bergeret C, Mallet R, Fernandez V, Cousseau J, Baslé MF, et al. In vitro calcification of chemically functionalized carbon nanotubes. Acta Biomater. 2010;6(10):4110-7.
[39] Hiura H, Ebbesen TW, Tanigaki K. Opening and purification of carbon nanotubes in high yields. Advanced Materials. 1995;7(3):275-6.
[40] Wang W, Kunwar S, Huang JY, Wang DZ, Ren ZF. Low temperature solvothermal synthesis of multiwall carbon nanotubes. Nanotechnology. 2005;16(1):21-3.
[41] Felten A, Bittencourt C, Pireaux JJ, Van Lier G, Charlier JC. Radio-frequency plasma functionalization of carbon nanotubes surface O-2, NH3, and CF4 treatments. Journal of Applied Physics. 2005;98(7).
[42] Eckmann A, Felten A, Verzhbitskiy I, Davey R, Casiraghi C. Raman study on defective graphene: Effect of the excitation energy, type, and amount of defects. Physical Review B. 2013;88(3):035426.