- I am conducting a zeta-potential experiment but it shows I have a poor quality result and my sample conductivity is low. My sample is copper nanoparticles dispersed in propylene glycol.
Henry Nwachukwu
Now tell me why you would think 'zeta potential' analysis is useful in your application... If you post your .zet file then we can be more specific in our comments.
It would be great if you could post the ".dts" file of your sample here. In general, for non-aqueous dispersants, it might be better to use a dip cell with closer spacing between the electrodes. That configuration allows for creation of a higher field strength, which may be needed in the case of lower dielectric constant media. [~6cm in the cell you used, about 2mm in the dip cell]
https://www.materials-talks.com/blog/2018/09/05/find-the-field-strength-in-your-zetasizer/
Thanks for your responses, I'm conducting my analysis in order to study my nanoparticles and possible charge they carry. The .dts file is attached.
Henry Nwachukwu
Your size results look pretty good to me. There are plenty of counts (attenuator on the sweet spot of 7). The size quality reports are good. And there's little or no evidence of large particles in the far-field part of the correlogram. Because of the density of Cu (the chemical symbol for copper in Scotland) then size and the density difference with the medium are important.
As you say, the zeta measurements are another can of sild. See
https://www.john-west.co.uk/products/sild-in-tomato-sauce/
As well as the dip cell you could try increasing the conductivity of the propylene glycol, as this is probably the problem, as you correctly state. In the old Coulter counter days we'd dissolve ammonium thiocyanate into the system. I feel that wouldn't be good for copper or the cell electrodes but may be worth a try if you're quick. I've absorbed HCl gas into EtOH in the past - not sure what the solubility is in your glycol. The barrier method may help here.
Thanks, Alan F Rawle for your responses. I will make more research on how I can increase the conductivity of my sample. I'm also considering increasing the voltage of my analysis to about 150V during my zeta-potential analysis. Do you think this might be of help or will have an adverse effect on the results from my sample.
Henry Nwachukwu
Increasing the voltage may lead to problems e.g. bubble formation at electrodes in organic solvents. I would look for routes to increase the conductivity of the continuous phase. Your size results were fine as I said earlier, so your concentration is good.
However, anything that works is good! And I learn more when I'm wrong...
Thanks, Alan F Rawle for your suggestions, they are really quite helpful for me. I will consider the options available to increase conductivity.
You don’t need to increase the conductivity by much. We can take good measurements directly in EtOH or IPA in the disposable cell. Also look at temperature equlibration.
Thanks for sharing the data file. The DLS results look very good, quite monodisperse with low PDI. For your ELS data, I think you could also just try using just monomodal analysis, and put a wait in between repeated runs. The voltage in your automatic runs was already at the maximum 150V, so you would have to go to the dip cell to increase the field strength further.
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