Three-Dimensional Electron Microscopy of Chiral Nanoparticles: From Imaging to Measuring.

The increasing interest in plasmonic nanoparticles with intrinsic chirality, i.e., reduced symmetry and strong optical activity, calls for characterization beyond qualitative imaging. In this context, three-dimensional electron microscopy (3D EM), which provides images containing information on the particles' surface and may even retrieve the explicit 3D shapes, is seeing exciting developments and applications. In this Mini-Review, we focus on scanning electron microscopy (SEM), electron tomography, and secondary electron electron-beam-induced current (SEEBIC). We highlight the recent advances in these 3D EM techniques and the analysis of their data that relate to chiral metallic nanoparticles. The study of shape-property relationships, in particular by quantitatively analyzing geometric chirality and informing electromagnetic simulations, is covered. New ways in which 3D characterization is revealing the growth pathways of the nanoparticles are also presented. Finally, we provide an outlook on future opportunities for 3D EM to further guide the understanding and development of (chiral) nanoparticles.