Representative Chemical Formulas of Cadmium Selenide Quantum Dots Determined with a Combination of Mass Spectrometry and Nuclear Magnetic Resonance

Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) has the potential to characterize the size and composition of quantum dots (QDs). However, examples of its usage in the literature are limited. In this study, we perform an in-depth characterization of the size and composition of the CdSe QD system using a combination of MALDI MS and nuclear magnetic resonance (NMR). Using these techniques, we determine the size and composition of a series of wurtzite and zincblende CdSe QDs. The composition ranges from 176 to 1202 CdSe units per QD. With this information, we construct a sizing curve for the QDs and compare it with sizing curves from the literature obtained using other techniques such as transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS). These results will be insightful for the community developing complex multilayer QD compositions for photonic applications.