I studied the dispersion of nanoparticles in surfactant. Nanoparticles that I studied are Multi-Walled Carbon Nanotubes (MWCNTs), Graphene Oxide (GO), Iron Oxide (Fe3O4) and Silica Dioxide (SiO2) and the surfactant used in this study is 2% Sodium Dodecyl Sulfate.
I initially sonicate the solution in Ultrasonic bath for 2 hrs and proceed with zeta potential measurement afterwards. I used ZetaSizer (Malvern) in this study.
However, zeta potential for all nanoparticles are around -3000mV, which is too small. The particles size obtained are around 100 nm.
It's kinda frustrating because I've done the experiment a couple of times but still obtained the same value. I really need help.
Please post your dts file for the measurement. I will take a look at the experimental settings. In my experience, such high values are due to mistakes with the values entered for viscosity or dielectric constant.
Look at the electrophoretic mobility values - if they are of the order of 1e-8, that's good.
Dear Shah,
I am very agree with Dr. John F. Miller. He raised great points.
If the values for electrophoretic mobility is in the order suggested by Dr. Miller then errors might be for the values used for viscosity during the measurements.
Cheers
Here is one of the experimental settings file for graphene oxide (GO). Thank you so much Sir. John Francis Miller
Nur BATRISYIA Razman Shah You have a dielectric constant of 3.60. You say your samples are in 2% SDS, so I assume the liquid is water. The dielectric constant at 25C is approx. 78. That means your zeta potential should be about -2280 x 3.6 / 78 = -105mV. This is possible given that you are using SDS. Your viscosity is 1.32. Water is approx. 0.89 but 2% SDS will increase the viscosity. Where did you get the value? Providing too large a viscosity will increase the calculated zeta potential. If the true viscosity is 0.89, then the zeta potential would be -2280 x 3.6 / 78 * 0.89 / 1.32 = -71mV, which is certainly realistic.
As I mentioned before, look at the electrophoretic mobility data. See attached screenshot. Choose Zeta in the Workspace drop-down list, then the Electrophoretic Mobility tab. Malvern uses non-SI units for mobility (um cm/Vs). You should have values somewhere between -1 and -10.
For the zeta potential graph, you will need to change the horizontal scale.
I see. Now I understand that. I measured the viscosity of SDS myself by using Vibro Viscometer which is 1.32. But since my surfactant is only 2% of SDS, should I neglect the viscosity of 2% SDS and I just assume it as water with 0.89 viscosity?
And should I assume the same too for dielectric constant? Using 78 instead of 3.6?
Again, I highly appreciate your explanation as it helps me a lot. Thank you very much, Dr John Francis Miller
Nur BATRISYIA Razman Shah SDS is a solid, so what did you measure the viscosity of?
2% SDS is high especially for nanoparticles at the concentration you most likely have for light scattering measurements. This means that the signal that the instrument detects could be dominated by SDS micelles and not your particles. To check this, measure just your 2% SDS solution without any particles and compare the results.
You should only need 1 to 5% SDS by weight of the nanoparticles, not the total mass.
EDIT: Also, by using SDS to help disperse the particles, you will likely observe the zeta potential for particles with SDS adsorbed. If you are interested in the zeta potential of the bare particles, you will need to find a different way to disperse them.
Hi Nur BATRISYIA Razman Shah
you can edit the existing record and change the viscosity and dielectric constant. Both are likely going to be close to that of water. You could measure the viscosity of your 2% SDS solution and use that viscosity for the calculation. You might find the Zetasizer Nano Self Install instructions useful at https://www.malvernpanalytical.com/en/campaigns/zetasizer-self-install
and there is a also a selection of youtube videos to get started at https://www.youtube.com/playlist?list=PL2wIBTZfZRjf_eFKDb2pGEqGvP1yVS9u9
And finally, you can post the dts file if you don't manage to edit the record, you can find the file as described here https://www.materials-talks.com/2014/08/19/faq-how-can-i-submit-a-data-file-to-the-help-desk/
John Francis Miller I measured the viscosity of the dissolved 2% SDS in distilled water. The amount of nanoparticles that are to be tested in this study are 0.05g, 0.1g, 0.5g and 1.0g.
I will look into all your suggestions. Thank you very much for your clear and unambiguous explanations on this topic. They have helped me tremendously. Since you're an expert of zeta potential, is it possible if I can get your email so I can contact you in the future?
Hi Sir Santosh K. Tiwari ,
I understand that now. Thank you so much for sharing your thoughts as well! Means a lot to me.
Hi, There are two main aspects to be considered in answering your query:
1. The exact theory behind the concept of Zeta Potential (ZP);
and
2. Functionality and setting parameters of the analytical instrument used to evaluate ZP.
For the former, I refer you to a recent publication:
Probing nanoliposomes using single particle analytical techniques: effect of excipients, solvents, phase transition and zeta potential.
M Danaei, M Kalantari, M Raji, HS Fekri, R Saber, GP Asnani, ... (2018)
Heliyon 4 (12), e01088
More explanations will follow.
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