2.7. ζ-Potential Measurements

Zeta-potential (ζ) was determined using a Zetasizer Nano-S (Malvern Instrument, Worcestershire, UK) using capillary cells. Emulsions were diluted 500 times in distilled water. The analyses were performed by applying a voltage of 50 mV. Zeta-potential (ζ) was calculated from the electrophoretic mobility (μ) using Henry’s equation:

where η is viscosity of the buffer (1.033 × 10⁻³ Pa·s⁻¹), μ is electrophoretic mobility (V Pa⁻¹·s⁻¹), and ε is the medium dielectric constant (dimensionless). Debye length (k⁻¹) measured the thickness of the double electric layer around the molecule (nm). Rh (= ¼D_h/2) is particle hydrodynamic radius (nm), whereas f(kRh) is Henry’s function. A value of 1.5 was adopted for f(kRh), which is referred to as the Smoluchowski approximation.