Subashini Asokan, Department of Chemistry, Rice University, Houston, TX 77005, Karl M. Krueger, Chemistry, Rice University, Houston, TX 77005, Vicki Colvin, Rice University, 6100 Main Street, Houston, TX 77005, and Michael S. Wong, Chemical and biomolecular engineering, Rice University, Houston, TX 77005.
CdSe quantum dots are colloidal semiconductor nanoparticles that are nanometer sized fragments of the corresponding bulk crystals. They are being probed as a very interesting system for their applications in LEDs, solar cells and biomedical labeling because of their rich photophysics arising from their size dependent properties and flexible processing chemistry. The ability to synthesize CdSe quantum dots with shapes besides spheres, e.g., rods, rice-shaped, teardrop-shaped, arrows, and tetrapods, widens the applicability of quantum dots. There are general strategies for particle shape control, e.g., monomer concentration, injection volume, reaction temperature, reaction time and alkylphosphonic acid ligand ratio. The largest influence on shape control is the presence of the alkylphosphonic acid ligands. However, these compounds are expensive and large amounts are required to induce anisotropic CdSe nanoparticle growth. In this talk, we will discuss the use of a new class of ligands as an alternative to the currently used phosphonic ligands. These ligands are more environmentally friendly and cost effective, and they lead to the formation of CdSe quantum dots of uniformly-sized tetrapod shapes with minimal formation of other shapes.