Theoretical curve showing the dependence of the true zeta potential (ζ) on the apparent zeta potential ζapp in PEG coated silicon nanomembranes with slit-shaped pores of 10 nm width (Table 1), calculated using Equations (1), (2), (3), and (4). The ordinates of the filled/hollow circles are the two ζ values on the curve that correspond to the given observed experimental ζapp =-4.42 mV inputted as the abscissa. The lower ζ value (ζ1=-12.19 mV) corresponding to the filled circle is taken as the true zeta potential, as discussed in the text. The larger zeta value, ζ2=-155.50 mV.