I am using the same sea water as autoclaved as well as non-autoclaved after adding the nanoparticle. I am getting different Hydrodynamic size for the same nanoparticle.
Anurag Nath Have you tested the ionic concentration, conductivity and pH of the seawater before and after autoclaving? All these factors might influence the hydrodynamic diameter of the nanoparticles. Also, test the non-autoclaved seawater for presence of microbial and endotoxins. These might give you some clue as per the diameter change.