Combined Confocal Dynamic Light Scattering and Fluorescence Correlation Spectroscopy as an Advanced Technique to Characterize Colloidal Quantum Dot-Gold Nanoparticle Hybrid Systems

Combined confocal dynamic light scattering (DLS) and fluorescence correlation spectroscopy (FCS) experiments were developed to study covalently bound CdSe/ZnS core-shell quantum dot (QD)-Au nanoparticle (AuNP) hybrid systems formed via click chemistry. This experimental approach has the advantage of probing sequentially both AuNPs and QDs, despite their very different optical properties, and in the same experimental conditions. The dynamic properties of the AuNPs are probed through DLS measurement, whereas those of the QDs are obtained through FCS. As a result, the <i>in situ</i> formation of hybrid systems and their characterization can be accessed. Here, we also show that such experiments enabled us to distinguish the solutions of bound QD-AuNP systems from unbound ones (QDs and AuNPs mixture) and permitted us to monitor the kinetics of the click reaction. Finally, using hydrodynamic bead models, the nature of the formed hybrid systems was identified, even in complex cases where various types of particle assemblies were present.