Dilip Kumar

The 'normal' diluent in nano work is the 'mother liquor' - the same ionic and surfactant mix as in your continuous phase. This mother liquor could be recovered by centrifuge or by knowledge of the make up/constitution.

Your question 2. indicates that you need not proceed with question 1. What do you mean by 'stable'? See: https://www.materials-talks.com/characterization-is-a-number-42-not-a-goal/

The size and density of the material may be the more or most important factors in settling/sedimentation.

Dear Prof. Alan F Rawle Sir,

Thank you Sir for your response, we have prepared a graphite colloidal solution with the assistant of US. The problem that I am facing in doing zeta potential is due to the presence of dark liquid of graphite. If I diluted how to prepare the solution to find zeta for different concentrations of surfactant.

Can you provide me with any article related to the information you have provided sir,

Size of particles-300-350nm

Density-2.37 g/mL.

Thank you, sir,

Dilip Kumar In answer to your questions:

1. The same vehicle the particles are dispersed in. Hence, either filter your dispersion through an appropriately sized filter or centrifuge the dispersion

2. "Zeta potential" assumes the presence of electrolyte in solution and the existing mathematical models are unlikely to apply in your case. You should concern yourself with electrophoretic mobility (or whatever the fundamental property your chosen technique measures).

Please see my PhD thesis in my profile. I developed the technique of Phase Analysis Light Scattering specifically to aid the measurement of electrophoretic mobility in non-polar liquids. There is a discussion of the role of electrostatic charge in the stabilization of particles in non-polar liquids.

Although it isn't discussed in my thesis, I did a lot of work looking at carbon black in kerosene. I also looked at calcium carbonate nanoparticles dispersed in engine oils. This work was published.

Measurement of electrophoretic mobility of such samples is challenging, in large part because of the sensitivity to trace amounts of water as well as any leachable materials from the cuvette, electrode assembly etc.

I also note your high particle concentration (10%wt) and large size will either require you dilute the sample for traditional electrophoretic light scattering or use another technique (e.g., electroacoustic).

I'm happy to provide more guidance about these challenging measurements. It's easy to make the measurement - but it isn't easy to do it properly.

are you sure you need the zeta potential, which is ill defined in nonpolar solvents. You will need rather steric stabilization and you will not obtain a graphite solution.

https://www.researchgate.net/project/nanoparticle-solutions-search-for-a-perpetuum-mobile-there-are-no-particle-solutions-only-particle-dispersions

Just from an experimental standpoint: for absorbing materials, you may have to dilute your sample. This may seem counter intuitive, typically higher concentration gives more signal. But for absorbing situations, lower sample concentration gives you relatively more signal.

Also consider that your sample should not be too opaque for sufficient scattering signal to reach the detector.