2.5.1. Nanoparticle Size and Polydispersity Index (PDI) by Dynamic Light Scattering (DLS)

The analysis of the average hydrodynamic diameter and PDI of nanoparticles was performed through the DLS technique. The samples were diluted (200×) in the aqueous phase of each formulation to obtain a suitable scattering intensity. Precise measurements were conducted at room temperature employing a VascoKin particle analyzer (Cordouan Technologies, Pessac, France) featuring a 638-nanometer laser. Additionally, particle behaviour was investigated utilizing an in situ probe operating in back-scattering mode with a scattering angle of 170°. Calibration was executed by using a standardized colloidal dispersion of 1% latex containing 100 nm sized particles. The size distribution (nm) based on intensity (a.u.) was assessed for each NLC sample using the Cumulant algorithm, which is correlated with the autocorrelation function expressed in time (µs) relative to intensity (a.u.). The resulting data were fitted using the Rayleigh model [57,58,59,60]. The samples were analyzed immediately after preparation and after 30 days (for stability evaluation).