Electronic Structure of Fluorinated Carbon Nanotubes

Abstract

Chemical functionalization of carbon nanotubes (CNTs), i.e., attachment of individual atoms/molecules or their aggregates to CNTs, can extend the field of application of these nanosystems in nanoelectronics, sensorics, hydrogen power engineering, bioengineering, medicine, etc. (Dresselhaus & Dresselhaus, 2001; Burghard, 2005). In this respect, the fluorination of CNTs is of special interest because the fluorination results in a considerable decrease in the chemical inertness of the initial systems. Therefore, the fluorination is considered as a promising technological process for the first stage of the CNT chemical functionalization (Mickelson et al., 1998; Mickelson et al., 1999; Khabashesku et al., 2002; Lee, 2007). However, carbon materials react with fluorine over a wide range of external conditions. Consequently, the chemical composition, as well as the atomic and electronic structures of fluorinated carbon nanotubes (F-CNTs), depends substantially on the structure and properties of the initial materials and fluorination conditions, such as the reaction temperature and duration, the presence of catalysts, pressure, and concentration of fluorinating reactants (Touhara & Okino, 2000). All these factors need comprehensive investigations of fluorination products by different experimental methods. Fitting of fluorination conditions that are necessary to perform the preset controllable restructuring of the CNT electronic structure remains at present the most topical problem of the carbon nanomaterial chemistry. Therefore, their atomic and electronic structures have been studied by using a limited number of experimental techniques. First and foremost, these are different microscopic techniques ensuring their visualization (Mickelson et al., 1998; Mickelson et al., 1999; Khabashesku et al., 2002; Lee, 2007; Touhara & Okino, 2000), Hamwi et al., 1997; Yudanov et. al., 2002; Hayashi et al., 2002; Lee et al., 2003), x-ray diffraction methods characterizing the degree of F-CNT crystallinity (Hamwi et al., 1997; Yudanov et. al., 2002) UV spectroscopy (Mickelson et al., 1999), Raman spectroscopy (Mickelson et al., 1998; Mickelson et al., 1999; Khabashesku et al., 2002; Lee, 2007; Touhara & Okino, 2000; Hamwi et al., 1997; Lee et al., 2003) and C 1s and F 1s core-level x-ray photoelectron spectroscopy (XPS) (Touhara & Okino, 2000; Hamwi et al., 1997; Lee et al., 2003; An et al, 2002) which provide information on the nature of chemical bonding between 4