Complex Intergrowth LnCuOSe Nanocrystals via Precursor-Directed Colloidal Synthesis

Colloidal synthesis of multielement nanocrystals demands precise control over precursor reactivity and compatibility. These challenges are amplified when combining elements that span the periodic table, which has limited the complexity of crystal structures and compositions that are readily accessible in solution. Intergrowth structures, which feature alternating layers with distinct compositions and crystallographic motifs, have proven particularly challenging to access in nanocrystalline forms. Here, we present a direct, solution-phase synthesis of LnCuOSe intergrowth nanocrystals incorporating six different lanthanide cations (Ln = La, Ce, Pr, Nd, Sm, and Eu). These nanocrystals exhibit a consistent anisotropic nanoflower morphology, reflecting the layered crystal structure of alternating Cu-Se and Ln-O planes. The synthesis leverages a preformed lanthanide-selenium interaction in a coordination complex precursor that thermally decomposes to yield the quaternary product. Formation proceeds via a crystalline Cu₂Se intermediate that templates the final structure. The resulting nanocrystalline samples are stable in solution up to 350 °C but are unstable at higher temperatures out of solution, showing evidence for anisotropic thermal expansion upon traditional annealing that is not observed in bulk samples of the same material. The nanoflowers are semiconductors with wide band gaps that show evidence of possible quantum confinement and structural defects.