Hi everyone,
I synthesized the Bismuth Nanoparticles by Glucose and PVP. The biggest inquiry that the zeta potential is really low although I used PVP: -0.59mV (I repeated and discovered -1.02, -0.68, -2.13.....). According to TEM, they were monodisperse and non-aggreagted.
Could anyone explain to me why zeta is near zero ? Is my dispersion stable or not ?
J. C. Tarafdar Your answer simply isn't true. The fact that PVP was used suggests that it may be acting as a steric stabilizer. A large zeta potential is NOT an absolute requirement for colloidal stability. Other mechanisms exist that can promote stability. Indeed, charge-"stabilized" dispersions aren't strictly stable - it's only the rate of aggregation that is slowed. Sterically-stabilized dispersions, on the other hand, are thermodynamically stable.
The presence of polymer at the surface of the particle pushes the slipping plane further away and, for a given amount of particle charge, the zeta potential will be decreased. This decrease becomes greater with increasing molecular weight of the polymer, too.
@ Khoa, Zeta potential is the potential difference between the dispersion medium and the stationary layer of fluid attached to the dispersed particle. It is related to the stability of colloidal dispersion. So, colloids with high zeta potential (negative or positive) are electrically stabilized while colloid with low zeta potentials tend to coagulate or flocculate. As your value is -0.59 mV, your dispersion is not stable. In your case the electric charge density on the surface is near zero. So, your particles are remain stationary in an electric field causes minimum stability i.e. exhibits maximum coagulation/flocculation rate.
J. C. Tarafdar Your answer simply isn't true. The fact that PVP was used suggests that it may be acting as a steric stabilizer. A large zeta potential is NOT an absolute requirement for colloidal stability. Other mechanisms exist that can promote stability. Indeed, charge-"stabilized" dispersions aren't strictly stable - it's only the rate of aggregation that is slowed. Sterically-stabilized dispersions, on the other hand, are thermodynamically stable.
The presence of polymer at the surface of the particle pushes the slipping plane further away and, for a given amount of particle charge, the zeta potential will be decreased. This decrease becomes greater with increasing molecular weight of the polymer, too.
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