Dear all,
I prepared an AlN-C/EG nanofluid which has a good stability (more than two months), but, after measuring the zeta potential value, I found that this value is near zero. How can I justify this inconsistency?
If the particles are sterically stabilized (e.g. with a PEG coating) then the slipping plane lies inside the polymeric coating and a system can be perfectly stable with 0 mV zeta potential. With charge stabilized (sometimes called electrostatic stabilization) it's a different matter. The magnitude of the zeta potential is only a guide to the potential stability or instability of a system - it does not mean that it can unambiguously predict that a material will cluster or clump or precipitate: it's just most likely statistically at around 0 +/- 3 mV (for a charge stabilized system).
Many thanks for your reply. I appreciate your consideration. Regarding to polymeric coatings, could we expect the same role for EG? Could you give me some references for more investigation?
What is EG?
For papers, Google is your friend. Search on steric and electrostatic (I prefer 'charge') stabilization
I think this is related with electrostatic interactions and interaction with gravity.i mean there is no significant effect for buoyancy force. also, one more thing is important the concentration of particles in such case may be you used dilute concentration.
Thank you for your kindly responses. EG is ethylene glycol. I want to know whether this material can act as PEG.
I didn't understand what "interaction with gravity" means? Could you explain more for this case?
EG is a small molecule. PEG is a larger molecule. Depends on the relation of the size of the absorbed molecule to the size of the particle. On the latter we have absolutely no information.
I think interaction with gravity means that there are other factors that need to be taken into account when one considers 'stability'. Size and density of particles has an obvious role in whether settling will occur or not. Stokes' Law is an important rule of thumb here.
Hi,
I measured Zeta potential of one pesticide and it is showing zero.Can anyone suggest what is the reason.
Bhavya M B Please provide more information about your formulation.
Sir I measured Zeta for Malathion pesticide in ethanol ,but it showed zero value in Zeta. My question is if Malathion dissolve is ethanol it is suppose to show some value(negative or positive) in Zeta potential measurement.But I got zero value,can you please explain what may be the reason.
Naser Ali "Zeta potential < ±30 mV is highly agglomerative."
That simply is not true. It is dependent on the formulation. Many colloids can be stable in the absence of any charge. There are two major classes of colloids - lyophobic and lyophilic. The general rules about stability and electrolytes derive from observations and theories developed during and before the 1940s. They apply to simple lyophobic particles in a dilute electrolyte. No surfactants, polymers etc.
Bhavya M B If you have a true solution of Malathion in ethanol then the concept of zeta potential does not apply. Zeta potential relates to an electrical voltage that develops near a charged solid *surface* and a liquid. A true solution won't have a solid-liquid interface. Your instrument is probably just measuring nothing but still giving you a number,
Is there anything else in your formulation that could be considered as colloidal (e.g., nanoparticles, dissolved polymer)?
Thank you Sir for your kind response. Sir I am checking pure pesticide zeta,so pesticides I dissolved in ethanol. Pesticide chlorpyrifos in ethanol, Zeta showed -0.3 mV (negative) value. But the same is not in case of malathion, and malathion zeta value is zero. My confusion is any solid when dissolved in solvent it dissociates and that ions are they responsible for Zeta potential value?
If chlorpyrifos is giving some value why not malathion.
-0.3mV is zero.
What instrument are you using? Can you post example results from the instrument. I'm confident it is just because the instrument will give a number even if there aren't any particles to measure.
John Francis Miller : my niosome formulation zeta potential is -0.279. Is this less stable or how i justify this is stable product?
Arul Packiadhas The first thing is to define what you mean by stability. What does your product have to demonstrate to be considered "stable"? Typically, this will be related to aggregation. You need to determine if the mean particle size changes with time (e.g., use a Zetasizer for sizing). If the size remains within acceptable limits for the required amount of time (this could be days, months, years depending on your specific product's requirements and application), then it doesn't matter if the zeta potential is small.
However, if the stability (according to size) is unacceptable, then you can try to change things like the pH of the formulation or add ionic surfactants to see if you can increase the zeta potential.
In summary, you need to demonstrate that zeta potential is a critical quality attribute (CQA) for the intended use of your formulation.
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