Building quantum dots into solids with well-defined shapes

Quantum dots (QDs) chemically synthesized in solution at a higher temperature (85degreesC) were built in situ into a variety of three-dimensional (3D) close-packed QD ensembles (QD solids) with well-defined shapes: needles, disks, rods, spheres, bundles, stars, ribbons, and transition structures (TSs). Design strategies using a novel cold-treatment (-25 to 0degreesC) process immediately following the synthesis of the QDs provided control over these shapes, independently from the II-VI materials used. Transformation occurred between different shapes by the rearrangement of the QDs within the QD ensembles. The QD solids were characterized by advanced electron microscopy and photoluminescence spectroscopy. The cold treatment strategy is versatile and has been applied to several II-VI QDs (CdS, ZnS, and CdSe) and may be extended to other QD systems and other chemical approaches.