The role of dodecylamine (DDA) as surface ligand in the initial nucleation and growth processes of CdSe nanocrystals was studied by in-situ extended X-ray absorption fine structure and a microfluidic reactor. The results combined with ex-situ UV vis absorbance spectra provided the kinetic information of the nanocrystals grown in a noncoordinating solvent octadecene. We found that the initial nucleation stage is significantly accelerated by the presence of DDA: without addition of DDA the nucleation took about 5 s, while it was shortened to within I s with the presence of 5 and 10 wt % DDA. Increasing the DDA concentration from 5 to 10 wt % increased the starting particle size but reduced the growth rate of the nanocrystals. The results may indicate two competitive roles of DDA in the current system, namely, activating reagent of the precursors in the initial nucleation stage and passivating ligand of the nanocrystals surfaces during the subsequent growth process.
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