Surface conductivity

A layer of counter ions of the opposite polarity to the surface charge exists close to the interface.

[2] There is a detailed description of surface conductivity by Lyklema in "Fundamentals of Interface and Colloid Science"[3] The Double Layer (DL) has two regions, according to the well established Gouy-Chapman-Stern model.

[5] He derived a simple equation that links surface conductivity κσ with the behaviour of ions at the interface.

For symmetrical electrolyte and assuming identical ions diffusion coefficients D+=D−=D it is given in the reference:[1] where The parameter m characterizes the contribution of electro-osmosis to the motion of ions within the DL: The Dukhin number is a dimensionless parameter that characterizes the contribution of the surface conductivity to a variety of electrokinetic phenomena, such as, electrophoresis and electroacoustic phenomena.

[7] Additionally, surface conductivity is measured in coupled phenomena such as photoconductivity, for example, for the metal oxide semiconductor ZnO.