Effect of Chloride Ligands on CdSe Nanocrystals by Cyclic Voltammetry and X‑ray Photoelectron Spectroscopy

Rod-like octadecylphosphonic acid (ODPA) capped CdSe nanocrystals (NCs) produced by hot injection in the presence of chlorinated cosolvents modify their shape and surface properties by incorporation of chloride in the capping ligand shell. Correlated cyclic voltammetry (CV) and X-ray photoelectron spectroscopy (XPS) studies have been performed to address the effect of this incorporation on the NCs surface. In contrast to ODPA capped rod-like NCs, the XPS studies confirm that, during the oxidation of NCs containing chloride, not only the oxidation of Se surface atoms but also of Cd atoms takes place. Furthermore, XPS studies also confirm the partial reversibility of the Se oxidation in the presence of chloride. Both CV and subsequent XPS measurements allows identifying chemical environments and surface site modifications, essential to understand the stability and performance of NCs acting as active layers in optoelectronic devices.