Two simple ways of making clean nitrogen-doped graphene for TEM studies

Abstract Graphene is the ideal transmission electron microscopy (TEM) support when it comes to imaging, but often offers poor interaction with samples due to its inert nature, making preparation of the TEM samples difficult. Graphitic nitrogen substitutions in graphene could boost its reactivity while simultaneously bringing minimal disturbance to its periodic structure. Here, two straightforward and easy to implement methods are shown for nitrogen doping of graphene that is already freely suspended on a TEM grid. One procedure utilizes a standard plasma cleaner capable of generating radio frequency plasma, for the other a simple direct current glow discharge plasma chamber was built. Successful implantation of graphitic nitrogen was achieved via both methods and verified by high resolution TEM. A series of experiments allowed to find satisfactory conditions for doping, yielding samples where nitrogen substitutions can be found and imaged within otherwise clean areas of graphene. Interaction of an adsorbate with graphitic nitrogen was observed on an atomic level, demonstrating its capability to bind other materials.