Hi. I have some query on this matter. Is zeta potential and surface charge differ? I know it is not the same but many researcher refer both topics as equal. Because i want to justify to my panel that doing surface charge is enough instead of doing zeta potential. In addition do you have any core paper that can help me to justify this matter? Thank you in advance
They are not the same though they may often be correlated. It is possible to have positive surface charge but negative zeta potential (not common but it does exist).
Whether surface charge measurements are appropriate instead of zeta potential depends on what exactly you are trying to do. If, for example, you need to control the surface chemistry for ion exchange or surface modification, knowing the charge may be important (determined by titration, for example). If you need to control the colloidal stability of a system then measuring and interpreting zeta potential is much more relevant.
If you can describe what your research is then I (and others) will be better able to address the question to suit your need.
Of course, you could measure zeta potential as well (if you have the capability) and show if (or not) it is a better indicator than surface charge for your need.
Read my answer to the same question.
https://www.researchgate.net/post/What_is_the_difference_between_surface_charge_and_zeta_potential
Please check my recent paper where I have used a (widely-accepted) correlation between surface charge and zeta potential (known as Grahame equation) for a validation. Let me know if you have more questions.
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The Grahame equation assumes that there is a non-interacting 1:1 electrolyte and a mono-functional acidic surface. It can't account for heterogeneous surfaces, asymmetric electrolytes, adsorbing ions etc.
There are plenty of real-world examples that demonstrate that iso-electric points (iep) determined by electrokinetics do not agree with points of zero charge (pzc).
Many people confuse surface charge with zeta potential. The latter is more accessible in industry and a valuable tool for indicating the electrokinetic properties of the system. But, unless you have an almost ideal system, you cannot assume that the zeta potential is related to the surface charge.
Models such as Gouy-Chapman-Stern-Grahame are important for understanding the general nature of the interface between a charged particle and an ionic solution. Real-world systems are not that simple and too much faith is placed in the theories for such systems. Too many assumptions are made by the theories and too little information is known about the system.
And there's another important - and usually ignored - factor. Measurement of zeta potential via electrophoresis (the most common) makes many assumptions. Fulfilling the requirements of the models to convert electrophoretic mobility to zeta potential is unrealistic. However, it is usual to blindly use the Huckel, Henry or Smoluchowski equations with no regard to the assumptions made.
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