Catalytic Nanopatterning of Few-Layer Graphene

Georgian Melinte(1,2,3), Simona Moldovan(1,4), Charles Hirlimann(1), Walid Baaziz(1,2), Sylvie Begin-Colin(1), Cuong Pham-Huu(2), and Ovidiu Ersen(1,3,5), 2017

Image courtesy of ACS Catalysis

Abstract

The catalytic nanopatterning of few-layer graphene (FLG) sheets using metallic nanoparticles as catalytic “nanogouges” is a promising method for fabricating graphene nanoribbons. However, in the absence of in situ observations of the active nanoparticles during the catalytic process, a unified model of the channeling mechanism is unavailable. On the basis of a real-time TEM investigation of iron nanoparticle patterning of FLG, this study addresses key aspects of the channeling mechanism. As the catalytic reactions take place at temperatures at which the active nanoparticles present a melted superficial layer, the adhesion forces at the nanoparticle/FLG interface were found to have a crucial role in defining their faceting geometry. Mono- and multifaceted frontal geometries are induced by the interaction with the vertical FLG edges, and only such faceting arrangements can support a controlled anisotropic channeling. When the channeling direction is changed, nanoparticles go through a process of surface rearrangement that aims at rebuilding a faceting geometry in equilibrium with the FLG edge. The melted superficial layer appears as the main nanoparticle region that supports the dissolution of FLG edges, and a concentration gradient is moving the dissolved carbon atoms from the interface regions toward the rear side of the nanoparticles. Keywords: catalytic cutting; environmental TEM; graphene; nanoparticles; nanopatterning; operando TEM

Impact Statement

Here, the authors observed the “cutting” of few layer graphene sheets into “nanoribbon” by reducing iron oxide NPs to iron NPs and using them to preferentially etch the sheets into strips. They were able to do this at high temperatures and in environments that one would see the synthesis process control. Through Atmosphere, they were able to observe the orientation of the NPs throughout the etching process in order to control future edge states and properties of graphene nanoribbons.