Grzegorz Celichowski

Rather than quote zeta potential, which is ambiguous for high aspect ratio particles such as your nanowires, it is best to quote what is actually measured - mobility - rather try to deal with a conversion. Be aware that the surface of the Ag nanowires will actually be Ag2O - silver in the +1 oxidation state.

Please make a suspension in water then measure zeta potential (ZP) putting other necessary parameters!

Md. Aminul Islam

One does not measure zeta potential.....

It is inferred from mobility measurements in an electrical or acoustic field.

The conversion of mobility to zeta potential is this case illustrates a common misunderstanding. The calculations make very specific assumptions, including that the particles are hard spheres without surface conductivity. Definitely not the case for silver nanowires. Having the amines dangling off the wires further complicates things. Now you have something that resembles a porous object with charges at fixed locations.

People have spent decades developing theories to calculate zeta potential for such kinds of particles. Actually, they've spent the time developing models to calculate mobility from the zeta potential. The models usually require serious numerical processing way beyond the capabilities of the instruments.

I like to thanks for all answers an suggestions. Especially answer of John Francis Miller assured me that measuring of zeta potential of such object as silver nanowires are difficult and tricky.

The question is what kind of parameters are the most suitable and informative for AgNW?

Thank you, Alan F Rawle , for the suggestion about measuring the mobility of AgNW - is this parameter informative about stability (especially long term) of colloidal solution of AgNW?

I hope this discussion will be interesting for all who works with this kind of nanomaterials.

Grzegorz Celichowski Regarding stability prediction, I doubt just the mobility or zeta potential information would be enough by themselves to help. There are other factors such as the composition of the liquid and the inherent attraction between the particles.

The best approach is that used in the pharmaceutical industry. If you believe that mobility could predict stability, you need to demonstrate it and determine the range of mobilities that would indicate stability/instability. This is an example of a "potential critical quality attribute". Basically, measure variations of your product that are considered stable and some that are considered unstable and see if there is a relationship between observed stability and mobility.

Another option is to deliberately induce instability using a method that affects the electrostatic charge. This could be salt concentration or pH. If you can prepare variations of your dispersion at different pHs (e.g., just add dilute HCl or KOH), then measure the mobility and look at the stability. This can help identify if electrostatic repulsion is a key mechanism aiding stability or not, and if mobility can help predict it. A similar thing can be done by adding simple salts (e.g, KCl) at a range of concentrations (say 1mM up to 1M).

By way of contrast, most simple inorganic oxide dispersions (silica, titania) rely on electrostatic charge and are readily destabilized at salt concentrations above a few 10mM or at pHs near to the "isoelectric point". Proteins, on the other hand, can be stable even when the mobility/zeta is close to zero and the salt concentration very high (>1M). So, the simple "rules" (such as if the magnitude of zeta is

Grzegorz Celichowski

In terms of 'stability', what is going to be much more important here is the size and the density of the 'particles'. Ag is dense (10.5 g/cm3 in old money) Have you carried out a Stokes' Law calculation to see where sedimentation is likely to occur?

John Francis Miller comments above are also very useful.

John Francis Miller, very insightful comment, however, one correction. Silica dispersions usually have exceptional stability at their isoelectric point, though, do not tolerate high electrolyte content.