Simultaneous Dynamic Light Scattering, Absorbance and Photoluminescence Measurements of Colloidal Nanoparticles. Application to Colloidal Stability and Aggregation Kinetics of CsPbBr ₃ Nanocrystals

Abstract An original but simple instrument is developed, capable of performing simultaneous Dynamic Light Scattering (DLS), Absorbance (ABS), and Photoluminescence (PL) measurements on suspensions of colloidal nanoparticles. The instrument is designed as a standard laboratory tool that, by using only commercial components, enables rapid analysis of the sample under investigation. The setup offers two significant benefits: first, it allows for the simultaneous analysis of the very same sample, overcoming limitations arising from the measurements being performed on distinct specimens, under diverse experimental settings, at different times; second, it enables to monitor the kinetic evolution of nanocrystals (Ncs) colloidal stability in time, with a time resolution of ≈ 100 s, which is considerably shorter than typical timescales related to aggregation kinetics or other colloidal instability‐related phenomena. The suitability of the instrument for characterizing time‐resolved processes is assessed through the case study of the long‐term instability of oleic acid/oleylamine‐capped colloidal CsPbBr ₃ NCs suspensions driven by dilution. It is found that, as ligands gradually desorb from the surface, the suspension becomes unstable, displaying two rather unexpected processes: the formation of transient randomly arranged NCs aggregates that reach micron‐sized dimensions, followed by the coalescence of the original NCs into larger crystalline domains.