Zeta Potential for measurement of stability of nanoparticles

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Zeta Potential for measurement of stability of nanoparticles:

Zeta potential is one of the important Physical properties that are exhibited by the nanoparticles present in suspension. It is explained as the difference in potential between the bulk solution (dispersing medium) and the stationary layer of fluid attached to the dispersed particle. It can be utilized to optimize the NP formulations and to predict long-term stability of the colloid suspension. All Colloidal particles dispersed either in suspension or solution is charged due their intrinsic ionic properties and other dipolar characteristics. Each nanoparticle that is dispersed in a suspension or solution is surrounded in a circumference by oppositely electrically charged ions designated as the fixed layer. Outside those fixed layer, a varying compositions of electrically oppositions of form a cloud-like area. This area is defined as the diffuse double layer, and the entire area is electrically neutral. When a particular voltage is introduced into the solution dispersed particles, then all the particles attracted to the opposite polarity electrode accompanied by the well-defined fixed layer and some part of the particular diffuse double layer. Zeta potential is defined electric potential of the specific inner area including theoretically defined as conceptual "sliding surface". As this electric potential closes to zero, particles have tendency to aggregate enormously. So Zeta potential is an indicator of the electrostatic or charge repulsion/attraction between the nanoparticles. For this reason zeta potential can be described as one of the important fundamental parameters to affect stability of the nanoparticles in a great extent. Its measurement brings detailed investigation into the main causes of dispersion, aggregation or flocculation, and can be applied to improve the formulation of dispersions, emulsions and suspensions. Measurement of the zeta potential helps the nano formulation scientist in various ways. First it will guide the formulation chemist to formulate more stable nanoparticles. As the nanoparticles have natural tendency to agglomerate in storage, so stability of the nanoparticles play an important role to function in long term basis.

Fig 1: Schematic diagram of zetapotential for nanoparticles

Zeta potential and nanoparticles stability:

The zeta potential is an important marker of the stability of various colloidal dispersions. The values of the zeta potential significantly show the extent of electrostatic repulsion between all the adjacent, like charged particles in a solution or dispersion. For molecules and particles in nano-scale a high zeta potential will improve the stability problems. When the potential is less this repulsion and the dispersion may break and flocculate the suspension.

As a result, suspension with high zeta potential are electrically more stabilized as compare to low zeta potentials nanoparticles. Stability of the suspension with various range of zeta potential (mV) is shown in Table 1

Table1: Stability behavior of the colloids at various zeta-potential

Range of Zeta potential [mV]

Stability behavior of the nanoparticles in colloid or suspension

0 to +-5,

Instant coagulation and flocculation

+-10 to +-30

Instable

+-30 to +-40

Moderately stable

+-40 to +-60

Good stable

> +-61

Highly stable

About the Author

Anirbandeep Bose's picture

I am Dr. Anirbandeep Bose working as an Asst. Prof in Acharya and Bm Reddy college of Pharmacy ,Bangalore.Before that I worked as postdoctoral fellow in Pharmacy department of University Technology Mara(UiTM),Malaysia.I was awarded the post doctoral fellowship by the Malaysian higher education Ministry. Before that I got awarded PhD in Pharmaceutics from Jadavpur University,Kolkata,India. I worked as production chemist(Tablets and Capsule manufacturing) in BHP(1981)PVT. LTD for more than 2 years. I have more than 30 international publications related this field and attended many international conference.

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