Changes on the Stokes Shift in Large CdSe Colloidal Quantum Dots by a Ligand Exchange

In this work, we have studied the optical properties of CdSe colloidal quantum dots (CQDs) that undergo a ligand exchange. The QDs were synthesized by the thermal decomposition method and characterized by using optical spectroscopy techniques and Density Functional Theory (DFT) calculations. Trioctylphosphine (TOP) and Oleic acid (OA) ligands were replaced by Formic acid. This ligand exchange seems to cause an increment of the Stokes shift on the nanostructures. As a result a surface underpassivation of the nanostructures appears. This could be related to the generation of non-radiative states that decreases the quantum yield in our samples and a redistribution of the band edge electronic states that explain to some extent our observed results.