Determination of Handedness in a Single Chiral Nanocrystal via Circularly Polarized Luminescence

The occurrence of biological homochirality is attributed to symmetry breaking mechanisms which are still debatable1. Studies of symmetry breaking require tools for monitoring the population ratios of individual chiral nano-objects, such as molecules, polymers or nanocrystals. Moreover, mapping their spatial distributions may elucidate on the symmetry breaking mechanism. Recently, researchers have utilized differential scattering or circular dichroism microscopy to identify chirality on individual plasmonic nanostructures and inorganic nanocrystals. However, these measurements are prone to optical system artifacts. While luminescence is preferred for detecting single particle chirality, the typical low optical activity of chromophores limits its applicability. Here, we report on handedness determination of single chiral lanthanide based nanocrystals, using circularly polarized luminescence, with total photon count of $2\times 10^4$. We also utilize a machine learning approach for correlative microscopy to determine and spatially map handedness of individual nanocrystals with high accuracy. This technique may become invaluable in studies of spontaneous symmetry breaking in chiral materials.