4(%3)3 - Ecole nationale supérieure de chimie de Montpellier

Figure – 3.10: Scanning Electron Microscopy images obtained for, a-b) Silica SP1 series with two populations of NPs,c-d) Silica SP2 series with two populations of NPsAgain as in case of Polystyrene NPs, an optimum concentration of silica particles was obtained inorder to avoid clogging as well as to be able to detect translocated particles in the permeates by PCCS.Hence concentration calibration curves (Figure – 3.11) were obtained for both the series. Based on thesecurves, 2.4 X 10 -4 g.ml -1 was taken to prepare the feed solution. As compared to Polystyrene NPs, SilicaNPs tend to aggregate due to strong interparticle attraction and settle down to the bottom in a solventlike water which has high dielectric constant. Hence, their feed solutions as well as retentates andpermeates were ultrasonicated prior to any analysis.83