The surface potential and charged density of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine liposomes with cholesterol is study by using the second harmonic generation. The Gouy-Chapman model is applied to data’s to find surface potential of samples. The result shows, the surface potential aren’t depends to the type of salts but change with the concentration and valence of the electrolyte in solution. The surface potential is changing from 40 to 15 mV with increase of salt concentration from 0 to 5 mM. The charge density was found to be 0.0136 Charge/Å2, which is consistent with the area of a lipid headgroup. Moreover, the surface potential of POPC/cholesterol is increasing with increase of cholesterol.

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