3D reconstruction and correlative imaging of graphene nanocomposites: combining scanning electron and optical microscopies

Microscopy is routinely applied to characterize nanomaterials and nanocomposites. Optical microscopy (OM) and scanning electron microscopy (SEM) are frequently adopted for their simple sample preparation and efficient image acquisition. The majority of literature analyses rely on 2D surface imaging or cross-sectional imaging, often at a single magnification, although they may not be representative, due to the multiscale nature of the structures, as well as preparation and projection artifacts. This paper presents a comprehensive 3D imaging workflow combining serial sectioning OM and SEM to obtain realistic volumetric nanocomposite structures. The relationship between SEM acceleration voltage, electron penetration depth, and image contrast is investigated to enhance sub-surface imaging. Correlative OM and SEM characterization is achieved through multimodal imaging and landmark-based registration. Multiscale reconstruction is demonstrated on three representative ‘graphene’ nanocomposite systems, providing rich datasets on dispersion, distribution, orientation, and morphology. The methodology presented is broadly applicable to other nanocomposites and hierarchical systems.