Controlled Solvothermal Routes to Hierarchical 3D Superparticles of Nanoscopic CdS

Micrometer-sized superparticles, self-assembled from metallic or semiconducting nanoclusters, can be used as convenient building blocks for preparing functional materials, utilizing the electronic and optical properties resulting from the quantum confinement as well as from the coupling between nanoscopic constituents. Herein, we describe a facile route to prepare crystalline, cubic superparticles of monodisperse nanoclusters of CdS 1.9 nm in size by means of the thermally induced conversion of the readily prepared cadmium thiophenolate complex (Me4N)2[Cd­(SPh)4]. Furthermore, we illustrate the effects that additional quaternary ammonium salts can have on the size and dispersity of the nanoclusters formed and on the nature of their self-assembly into secondary structures, with the preparation and characterization of spherical superparticles of CdS, composed of individual nanoclusters 2.3 nm in size. Details on the formation, structural characterization (via powder and single crystal X-ray diffraction, HRTEM, STEM, and SEM), and optical properties of these hierarchical assemblies and their constituents are described.