Abstract
Quantum dots (QDs) are versatile materials in part due to their size-dependent optical properties, which allow for precise tuning of absorbance and emission wavelengths. Surface ligands are essential to these properties, as they allow for colloidal stability and passivation of uncoordinated surface metals. Without surface passivation, these dangling metal bonds can lead to undesired trap emission and nonradiative recombination, and therefore, studying surface ligand coordination is essential for understanding QD function. In this work, we develop and test methodology for taking correlated measurements to track surface ligand coordination (quantitative 1H-NMR) and resulting optical properties (photoluminescence spectroscopy) using the exchange of surface ligands of varying length and head-group. These measurements both dramatically increase the accuracy of ligand quantification as compared to past measurements and expand the scope to which QD surfaces are studied, revealing novel results about ligand coverage and QD surface passivation. This includes potential turnover points for the addition of phosphonic acid ligands for the purpose of increased surface passivation. The methodology developed in this work will be essential to future study of QD surfaces.