Electrokinetic phenomena, zetapotential, methods of measurement. The ratio between zeta potential and surface potential depends on double layer. This layer attracts counter ions from the medium which form a second layer of opposite charges. The counterions in the compact layer are immobile due to the strong electrostatic attraction. The double layer interaction energy is usually estimated using zeta potential data inferred from electrophoretic mobility measurements 10, 18. Simply explained, the double layer is a structure that forms on the surface of an object in a liquid. The distance, d, will be that to the center of the. A potential difference is set up between these two layers and is called electrokinetic potential or zeta potential. Electrical double layer the development of a net charge at the particle surface affects the distribution of ions in the surrounding interfacial region, resulting in an increased concentration of counter ions ions of opposite charge to that of the. Electrical double layer an overview sciencedirect topics. Unfortunately, the fundamental interfacial property. Zeta potential of artificial and natural calcite in. The zeta potential is the electrical potential located at the shear plane 18, 19.
Review 1 zeta potential of microfluidic substrates. What can be derived and measured is an electrokinetic potential termed the zeta potential. Zeta potential and the electrical double layer 161 2. Your browser does not currently recognize any of the video formats available. Eisenthal chemistry department, columbia university, new york, new york 10027. Zeta potential can be calculated with the following smoluchowskis formula.
Zeta potential is a function of the surface charge of a particle, any adsorbed layer at the interface and the nature and composition of the surrounding medium in which the particle is suspended. The magnitude of the zeta potential indicates the degree of electrostatic repulsion between adjacent, similarly charged particles in a dispersion. Feb 23, 2016 it is usually denoted using the greek letter zeta. The electrical double layer is divided in an inner stern layer, inside the surface of hydrodynamic shear of dna, and a gouy. Nevertheless, zeta potential is often the only available path for characterization of double layer properties. Information from its description page there is shown below. This process is experimental and the keywords may be updated as the learning algorithm improves. To show that the zeta potential depends not only on the ph of the solution, but also on the charge of 82 anielak a. The particle continues to attract more counterions but now these counterions are being repelled by other counterions in the vic. Application of the edl uses of zeta potential is to study colloidelectrolyte interactions. Electrical double layer theory linkedin slideshare. The second layer, known as the diffusive layer, is made of free ions attracted to the surface due to the influence of electric attraction and thermal motion.
A double layer dl, also called an electrical double layer, edl is a structure that appears on the surface of an object when it is exposed to a fluid. The electrical double layer edl is the result of the variation of electric potential near a surface, and has a significant influence on the behaviour of colloids and other surfaces in contact with solutions or solidstate fast ion conductors. In this section, a cursory introduction to electrical double layer theory is presented with specific attention to both the zeta potential and the resulting electroosmotic flow observed in an electric field. Zeta potential of artificial and natural calcite in aqueous. Water flow also drags the excess counterions in the diffuse layer along the pores surface and creates a macroscopic current density, the streaming current and a macroscopic electrical potential difference, the streaming potential 14, 17.
Where q is cell surface charge, a is the radius of cell. Modeling electroosmotic flow and the electrical double layer. Electroosmotic flow or electroosmotic flow, often abbreviated eof. The acidity of the solution was altered using various bases. Electrochimica acta 46 2001 30333040 thickness of electrical double layer. The double layer model is used to visualize the ionic environment in the vicinity of a charged surface. The zeta potential is an important parameter for a number of applications including characterization of biomedical polymers 1,2, electrokinetic transport of. Zeta potential measurement electrophoresis smoluchowski formula 1921 assumed. Ep11 electric double layer edl and dlvo forces nano 202 ucsd darren lipomi duration.
Since zeta potential is not equal to the electric surface potential in a double layer or to the stern potential, it is often the only value that can be used to describe doublelayer properties of. Oct 28, 20 the second layer, known as the diffusive layer, is made of free ions attracted to the surface due to the influence of electric attraction and thermal motion. The ratio between the np velocity and the external applied field, known as electrophoretic mobility, is then measured and converted to the zeta. Click here to visit our frequently asked questions about html5. Zeta potential is a property of an electric structure that is usually built up at interfaces, in a region referred to as the double layer dl.
Cbse sample papers for class 12 chemistry solved 2016 set 1. The zeta potential is the electrical potential at the slipping plane. Electrokinetic phenomena, zeta potential, methods of measurement. This force can be double layer calculated using urface potential. Electrical double layer, zeta potential, and electrophoretic charge of. Phenomena involving the electrical double layer are common in. Zeta potential, also known as electrokinetic potential, is measured in millivolts mv. For cell, the radius a is much larger than the double layer. Sep 05, 2017 electrical double layer theory under surface and colloidal chemistry slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. Electrical double layer article about electrical double. Chapman type diffuse ionic atmosphere with cylindrical symmetry outside the shear surface. Electrical double layer and electrokinetic effects.
Water flow also drags the excess counterions in the diffuse layer along the pores surface and creates a macroscopic current density, the streaming current and a macroscopic electrical potential difference, the. Positive counterions first attach to the negatively charged particle, forming a rigid layer called the stern layer. When an electric field is applied to the fluid usually via electrodes. This natural method of stacking the spheres creates one of two similar patterns called cubic close packing and hexagonal close packing.
The object might be a solid particle, a gas bubble, a liquid droplet, or a porous body. In aqueous media, the ph of the sample is one of the most important factors that affects its zeta potential. Double electric layer can be formed by directionally absorbing the polar group of a phase to another phase, which can be carried out by the electrons on the polymer functional groups going through the phase interface. Zeta potential is more important than nernst potential because the electrical double layer also moves, when the particle is under motion. Oct 16, 2014 electrical double layer and zeta potential the surface of colloidal particles acquires a positive or negative charge by selective adsorption of a layer of positive and negative ions around it. Since zeta potential is not equal to the electric surface potential in a double layer or to the stern potential, it is often the only value that can be used to describe double layer properties of a colloidal dispersion. These along with the ions in the stern layer form the electrical double layer at the. Thus, the double layer is formed in order to neutralize the charged surface and, in turn, causes an electrokinetic potential between the surface and any point in the mass of the suspending liquid.
However, because of their excess of electrical charges at the solidwater interface and very high surfaceto. New method for determination of surface potential of microscopic particles by second harmonic generation elsa c. There is a thin layer of counterions immediately next to the charged solid surface, called the compact layer. Original research significance of zeta potential in the. Debye parameter a particle radius electrical double layer thickness much smaller than particle v velocity. Zeta potential is an effective tool for coagulation control because changes in zeta potential indicate changes in the repulsive force between colloids. Method for determination of surface potential of charged particles by second harmonic.
Electrical double layer zeta potential dlvo theory disperse system electrical double layer. This plane is the interface which separates mobile fluid from fluid that remains attached to the surface. When clay particles are fully hydrated, the negative charge is balanced by the cations in the soil solution attracted by the coulomb forces. The surface charge potential is linearly dissipated from the surface to the contertions satisfying the charge. In the paper electrokinetic phenomena in this contact are described. This chapter describes a method for the measurement of the electrostatic potential at the electrical double layer surrounding a nanoparticle in solution.
During a zeta potential measurements, an electrical field is applied across the sample, inducing the movement of charged particles. Everything you want to know practical zeta potential. Importance of double layer force between a plat and a nano. Zetapotential measurement using the smoluchowski equation. This voltage difference is on the order of millivolts and is referred to as the surface potential. New method for determination of surface potential of. If you continue browsing the site, you agree to the use of cookies on this website. This negative charge on the clay surface and positive charge of the balancing cations create an electrical double layer around the clay particle. Hence, it can be seen that the electric potential depends through.
The difference in potential between the adsorbed and diffuse layer is called electrokinetic or zeta potential. Jan 26, 2018 ep11 electric double layer edl and dlvo forces nano 202 ucsd darren lipomi duration. This equation strictly only applies for isolated particles of zeta potential less than around 25 mv. The electrical double layer consists of 2 parts, the inner part described as the stern layer, which can be envisaged as 2 layers of water approximately 5. Pdf electrical double layer and zeta potential researchgate. Because electroosmotic velocities are independent of conduit size, as long as the electrical double layer is much smaller. Apr 16, 2020 hello students, in this video i explain electrical properties of colloidal solution,origin of charge on colloidal solution, helmholtz double layer, cottrell precipitator, zeta potential. Highconcentration zeta potential measurements using light. Within the diffuse layer there is a notional boundary. The combination of the two layers of opposite charges around colloidal particle, is called helmholtz electrical double layer. Because the chemical equilibrium between a solid surface and an electrolyte solution typically leads to the interface acquiring a net fixed electrical charge, a layer of mobile ions, known as an electrical double layer or debye layer, forms in the region near the interface.
For details of the theory of electrical doublelayer a. The electrical double layer 162 the immersion of a calcite mineral in aqueous solution leads to a separation of electrical 163 charge at the mineralsolution interface. Physical and analytical chemistry ii lecture 6 colloidal systems. Effect of ion size klemen bohinc a, veronika kraljiglic. May 24, 2018 positive counterions first attach to the negatively charged particle, forming a rigid layer called the stern layer. The first layer, the surface charge either positive or negative, consists of ions. An 107 zeta potential elecrophoresis, electroacoustics and streaming potential rev 1. The zeta potential is a key indicator of the stability of colloidal dispersions. Surface charge double layer zeta potential electrical double layer electrical characteristic these keywords were added by machine and not by the authors. Further improvement of these systems and their single components is needed to meet the future requirements in terms of higher energy and power densities. It can be either a metal under potential or due to ionic groups on the surface of a, an electrical double layer exists round each particle. Electric double layer an overview sciencedirect topics. Its a measure of the electrical charge of particles are that are suspended in liquid. The socalled zeta potential can be determined through electrokinetic measurements, and indicates the status regarding surface charges along the interface between solids and liquids.
Zeta potential is the electrical potential at the slipping plane. Zeta potential the liquid layer surrounding the particle exists as two parts. Pdf when clay particles are fully hydrated, the negative charge is balanced by the cations in the soil solution attracted by the coulomb forces. The dl refers to two parallel layers of charge surrounding the object. The following factors significantly affect the magnitude of electrokinetic potential. This second layer screens the surface charge and its net charge is equal to the surface charge, but has the opposite polarity.
In the colloidal chemistry literature, it is usually denoted using the greek letter zeta. Influence of surface conductivity on the apparent zeta. Electrical doublelayer capacitors, lithiumion batteries, and fuel cells are among the most important devices for storage and conversion of electrochemical energy. Zeta potential is the electric potential at the shear plane of a particle. Sep 28, 2010 schematic showing the electrical double layer that surrounds a particle in an aqueous medium and the position of the slipping plane. Formation of these two layers leads to definition of and double layer forces. The net charge density on a microfluidicsubstrate incontact with an aqueous solution gives rise to an electrical double layer and, in the pres.
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