Effect of Ionic Surfactants for Tetrapod‐Shaped CdSe Quantum Dots

We explore the effect of ionic surfactants on the photoluminescence (PL) of single emissive CdSe nano‐tetrapods. In the presence of the cationic surfactant cetyltrimethylammonium bromide (CTAB), effective quenching of PL is observed for tetrapods. X‐ray photoelectron spectroscopy (XPS) reveals the adsorption of negatively charged Br − ions onto the nanocrystal surface, which leads to efficient PL quenching. In particular, the longer‐lived trap‐state emission is suppressed due to the accumulation of surfactant counterions at the tetrapod surface. In contrast, sodium dodecyl sulfate (SDS), an anionic surfactant, shows negligible interaction with the negatively charged Se 2− ‐terminated surface, resulting in sustained PL intensity. These results demonstrate that the immediate surface environment and counterion adsorption play a critical role in modulating the photoluminescence properties of CdSe nano‐tetrapods.