Hi everyone,
I read this article "Preparation and morphology of SiO2/PMMA
nanohybrids by microemulsion polymerization" and observed that the zeta potential become more negative as pH increases. I know that the negative charge is from the deprotonated silanol groups (SiO-), but in the pH range from 4 to 8, why does the zeta potential keep decreasing while the the deprotonation process should not occur in this wide pH range (4 pH unit instead of 2 pH unit as in Henderson-Hasselbalch equation)? Is there any other factors that can influence the zeta potential of silica nanoparticles?
Thank you.