AVS 59th Annual International Symposium and Exhibition
    Graphene and Related Materials Focus Topic Wednesday Sessions
       Session GR+AS+BI+PS+SS-WeM

Paper GR+AS+BI+PS+SS-WeM2
In Situ FT-IR Study of Graphene Fluorination using XeF2

Wednesday, October 31, 2012, 8:20 am, Room 13

Session: Graphene Surface Chemistry, Functionalization, Biological and Sensor Applications
Presenter: J.-F. Veyan, University of Texas at Dallas
Authors: J.-F. Veyan, University of Texas at Dallas
N. Shafiq, University of Texas at Dallas
K. Novoselov, University of Manchester, UK
Y.J. Chabal, University of Texas at Dallas
Correspondent: Click to Email
Graphene fluorination to obtain fluorographene has been successfully realized by exposing graphene flakes to molecular Xenon-Difluroride 1-3. To gain a mechanistic understanding of XeF2 reaction with the graphene flakes, an all-aluminum custom-made two-stage reaction cell has been designed to fit into the main sample compartment of an FTIR Nicolet 6700 interferometer, for in situ infrared absorption spectroscopy. The first stage is a clean expansion chamber to isolate the pure XeF2 in its gas phase, from solid XeF2 (powder) stored in a storage vessel. The XeF2 vapor is extracted by opening the valve V1 to the storage chamber and its pressure (up to ~4 Torr) is controlled by the valve V2. The second stage is a reactor equipped with two KBr windows, allowing the IR beam to penetrate and exit the enclosure. A pneumatic valve allows the transfer of gaseous XeF2 from stage 1 into stage 2. Pressures in both storage and reactor chambers are measured with Baratron gauges (Ga1, Ga2). To avoid any contamination of the reactor and sample holders during sample preparation and loading, a N2-purged glove bag is placed over the reactor to maintain a controlled environment. The graphene flakes in suspension in a NMP (N-Methylpyrrolidon) solution, are transferred onto three mechanically polished Aluminum plates at a temperature of 70oC. The plates are then mounted on the specially designed 3-reflection sample holder flange designed to fit stage 2.

By varying the sample temperature from 20 to 200oC as well as the XeF2 pressure in the reactor stage from 0.1 to 4 Torr, the chemical attachment of fluorine on graphene is identified from a comprehensive FT-IR study performed under under industrial conditions. Fluorine attached out of plane can be easily differentiated from fluorine attached at edges (i.e. remaining within the basal plane) and terminating the edge atoms.

1 R. R. Nair, et al., Small 6, 2877 (2010).

2 J. T. Robinson, et al., Nano Letters 10, 3001 (2010).

3 K.-J. Jeon, et al., Acs Nano 5, 1042 (2011).