Reaction chemistry/nanocrystal property relations in the hot injection synthesis of quantum dots

Quantum dots (QDs) or colloidal semiconductor nanocrystals attract extensive interest in both industry and science nowadays due to their opto-electronic properties that strongly depend on their size, structure, shape and composition. To further develop applications, providing a rational basis to explore and understand how hot injection synthesis parameters affect these properties is key. Various literature studies indicate that the composition of the reaction mixture in which nanocrystals are formed is related to the size the nanocrystals attain at the end of the reaction. We analyze several of these ‘reaction chemistry/nanocrystal property relations’ by combining reaction simulations with an experimental investigation on CdSe quantum dot syntheses. We find that increasing the free acid concentration in the reaction mixture has the same effect on a real synthesis as raising the solute solubility in the simulations and explain the increase of the QD size as result ing from an enhanced consumption of the solute by nanocrystal growth. Similarly, we address the effect of increasing precursor concentrations to an increasing monomer formation rate, which results in a higher nanocrystal concentration and therefore a smaller nanocrystal size. Finally, we relate size tuning by the ligand chain length to the coordination of the solute by these ligands