Observation of graphene grain boundaries through selective adsorption of rhodamine B using fluorescence microscopy

Abstract

The graphene grain boundary (GGB), line defect, has a marked influence on an electrical properties and mechanical strength of graphene. Observation of the grain size and defect distribution is important for tuning the properties of graphene. Here we show imaging GGBs with rhodamine B (RB) by fluorescence microscopy (FM), and demonstrate the selective adsorption of RB molecules on the GGBs after a pre-annealing process and RB treatment. The hill structure of oxidized Cu below GGB is formed by a pre-annealing process, and induces RB molecules to selectively physisorb on GGBs due to the interplay between graphene and oxidized Cu, which is directly confirmed by kelvin probe force microscopy (KPFM) and density function theory (DFT) calculation. The selectively adsorbed RB was completely removed by acetone rinsing without disrupting the graphene sheets. This simple observation method provides an efficient and convenient means of evaluating the quality and reliability of graphene as well as other two-dimensional materials, such as WS2, WSe2, MoS2, MoSe2 and BN.