I have capped ironoxide nano particles with hydrophillic amino acids which show good stabilisation ( no sedimentation ) in neutra pH. How ever when the Zeta potential was measured, the value is ~ -8mV. As per my understanding the stable supensions have zeta potential value of |30| mV or higher. would anyone please help on this regard. Thank you in advance.
Amal T Babu Yes. Research steric stabilization through many questions and answers on RG…
Amal T Babu BTW, this 'rule' of 30 mV is nonsense as a little research on RG will show you.
According to my experimental analysis, when I synthesize a colloidal nanoparticle solution at a zeta potential smaller than 20 mV (+/-), sedimentation occurs in less than 24 hours. I can recommend checking one of my studies about short-term stability. Please click the link here Article Green synthesis of iron oxide nanoparticles using Ceratonia ...
The theories used to calculate zeta potential from the experimentally measured electrophoretic mobility assume various things all of which your particles certainly will not meet.
1. Spherical, impermeable particles.
2. Uniformly distributed electrical charge. This cannot be the case for your system because you have discrete, localized charges arising from the amino acids..
Because of #2, your particles are likely zwitterionic and so, even though the net charge is low, there will be highly +ve and highly -ve localized regions. Models for calculating zeta potential from electrophoretic mobility for such particles are highly complex and not offered by instrument vendors.
John Francis Miller thank you sir. Would you please suggest me a few references where I can read more on it.
Alan F Rawle Derya Aksu Demirezen thank you
Thank you John Francis Miller would you please suggest me few references where I can read further on this.
Amal T Babu Anything by Robert J Hunter regarding zeta potential… For example: Zeta Potential in Colloid Science: Principles and Applications (Colloid Sciences Series) R J Hunter Academic Press (1989)
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