Seminars Archive

Spectromicroscopy investigation of nitrogen-doped carbon nanomaterials

Abstract
In order to exploit and tailor the extraordinary properties of sp2 carbon nanostructures, the grafting of functional groups in a controllable way has been proposed as a feasible reproducible solution for band gap engineering and controllable doping. In this framework nitrogen doped graphene and carbon nanotubes gained a lot of interest from both technological and fundamental point of view. Nevertheless, a strategy to control precisely over the different nitrogen configurations in the hexagonal carbon lattice is still lacking, leading to difficulties in understanding how the C-N bonds impact in the electronic properties of the carbon nanostructures. Among the methods used to incorporate nitrogen atoms in the hexagonal carbon lattice, post-synthesis plasma-based functionalization and ion implantation methods have the advantage to be solvent-free, time efficient and flexible. Within this context, we will discuss the nitrogen incorporation in different carbon nanostructures: vertical aligned carbon nanotubes [1,2], suspended graphene [3] and graphene supported on copper foils [4]. Ultraviolet and x-ray photoemission spectroscopy and spectromicroscopy measurements were performed to characterize the impact of the nitrogen implantation in the hexagonal carbon nanostructure. The effect of thermal heating was evaluated: a surface rearrangement of the nitrogen components takes place, thus allowing the identification of the most thermal stable nitrogen species and the tuning of their presence in the carbon hexagonal lattice. This latter, in particular, allowed us to unravel the different contribution to charge carrier doping of nitrogen species in N-graphene on copper foil by studying the Dirac cone shift: we identify graphitic nitrogen as being responsible for n-doping when the counterbalancing action of pyridinic is reduced upon thermal heating. [1] M Scardamaglia et al. Carbon 77, 319-328 (2014). [2] M Scardamaglia et al. Carbon 83, 118-127 (2015). [3] M Scardamaglia et al. Carbon 73, 371-381 (2014). [4] M Scardamaglia et al., submitted (2015).