TEM images and the corresponding size distribution histograms of representative Ag nano-particles fabricated in the aqueous solutions of polysorbate 80 with different concentrations: (a) and (b) 20% v/v, and (c) and (d) 25% v/v, respectively. (e) The curve of the mean diameter of Ag nano-particles versus the polysorbate 80 concentration (V_polysorbate: V_water= 5% v/v–25% v/v). The inset shows the detailed functional form and the fit parameters.