Researchers from Brown University used pyramid-shaped nanoparticles to create complex macroscale superstructure
A research led by Ou Chen, an assistant professor of chemistry at Brown University developed the building blocks used in the current research in 2017. The building blocks are quantum dots particles of nanoscale semiconductors that can absorb and emit light. The tetrahedral shape of building blocks is beneficial while building larger structures as these packs require less void space than spheres and make structures potentially more robust. Moreover, the anisotropic nature of the particles offer different properties depending upon their orientation relative to each other.
Anisotropy in tetrahedral quantum dots was generated by treating one flat face of each pyramid with a different ligand than the other facets. The researchers dissolved the tetrahedral quantum dots in solution. The particles were later allowed to assemble into three different types of superstructures namely, one-dimensional strands, two-dimensional crystal lattices, and three-dimensional supercrystals. The 3D supercrystals possess extreme complexity. A ball-like clusters of 36 particles each were initially formed by the individual nanoparticles. The clusters later formed the larger superstructures. The detail characterization of the structure using x-ray scattering revealed that the atomic structure of the lattice was aligned. The researchers further aim to interrogate the properties of nanoparticle superstructures.
The quantum dot building blocks have interesting photon dynamics that can facilitate the blocks with optical properties in the superstructures. “We need to understand how to assemble these larger and more complex structures,” Ou Chen said. “I think these will be a bridge that will bring nanoscale dynamics into the macroscale and enable new types of metamaterials and devices.” The research was supported by Hua Zhu, Rui Tan, Ruipeng Li, Yuzi Liu, Dennis Eggert, Yimin Wu, and Zhongwu Wang. The Brown University Salomon Research Fund, Brown’s Institute for Molecular and Nanoscale Innovation (IMNI), and the National Science Foundation supported the research that was published in the journal Nature on September 19, 2018.