Size measurement of droplet emulsions
Oil droplet sizes were analyzed by dynamic light scatter- ing using a Malvern Zetasizer Nano ZS (Malvern Instru- ments Ltd, UK). The apparatus is equipped with a 4 mW He/Ne laser, emitting 633 nm, measurement cell,photomultiplier and correlator. Prior to measuring size, the samples were diluted (1:400) into a distilled water ultra-filtrate and placed in vertical cylindrical cuvettes (10 mm-diameter). Using an avalanche of photodiode detector set at 25°C, we measured the scattering intensity at a 173° angle relative to the source. Intensity autocorre- lation functions were analyzed by a General Purpose Algorithm (integrated into the Malvern Zetasizer soft- ware) in order to determine the distribution of the trans- lational z-averaged diffusion coefficient of the particles, DT (m2 s-1). The DT parameter and the hydrodynamic radius (Rh) of particles are related through the Stokes- Einstein equation: DT =k BT/6πhRh. In dispersion, parti- cles move in a constant random Brownian motion such as it causes the intensity of scattered light to fluctuate as a function of time. Therefore droplets’ sizes were mea- sured based on the correlation function as established by the dispersion technology software (DTS), using various algorithms. The refractive index (RI) and absorbance were set respectively at 1.471 and 0.01 at 25°C. Measure- ments were repeated five times.