Controlling Growth of CdSe Nanowires through Ligand Optimization

We have successfully synthesized nearly monodisperse CdSe nanowires with a length of 220 nm and a diameter of 8 nm. We achieved this through a systematic investigation of the reaction parameters, including the type of ligand for both Cd complexes and Se complexes, the reaction temperature, the precursor concentration, and the precursor injection process. It is proposed that the formation of high aspect ratio nanocrystals is the result of achieving a good balance between nucleation and growth. The optimum conditions to achieve a high aspect ratio require the use of dodecylphosphonic acid (DDPA) and trioctylphosphine (TOP) as the complexing ligands for Cd and Se respectively and a high precursor concentration. Contrary to the previous findings, we found that a high reaction temperature (310 °C) favors a higher aspect ratio nanocrystal growth than a low reaction temperature (250 or 280 °C). The effective monomer model can still be used to explain the shape evolution of CdSe nanowires. Although the aspect ratio (28) of the CdSe nanowires produced using this method is smaller than that obtainable using the solution−liquid−solid method (>100), this study demonstrates a promising way of producing nanowires via a catalyst-free and solution-based method.