▎ 摘　　要

Efficient large-scale nondestructive quality assessment of graphene on Pt is essential to the in-depth growth research and practical applications of graphene. Here, we present a very simple method for directly observing the domains and defects in graphene on Pt using an ordinary optical microscope. This was achieved by modifying graphene on Pt using methylene blue (MB). Because the chemical activities of graphene and Pt surface differ significantly, the adsorption and reaction of MB on graphene and platinum surface differ. We can determine the distribution of graphene crystal domains and defects by comparing the colors in the optical images. In addition, this characterization method causes no obvious damage to the Pt substrate and graphene. Moreover, it does not affect the recycling of the substrate or the subsequent characterization or application of graphene. Our study provides a nondestructive method for measuring the quality of graphene on Pt on a large scale, as well as a reference for the characterization and doping of other two-dimensional materials.