Contribution to the Theory of Surface Conductivity at Solid-Liquid Interfaces

Urban, Frank J.; White, H. L.; Strassner, E. A.

doi:10.1021/j150363a001

Cited by 40 publications

(21 citation statements)

References 7 publications

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“…The EDL contains more ions than the bulk, which results in a surface conductance due to their motion in the electric field ͑Urban et al., 1934;Kittaka and Morimoto, 1976͒, and this conductance can be measured in an ac field at sufficiently high frequency. Such conductance measurements can also be performed in a dc field, but the electro-osmotic contributions ͑see Sec.…”

Section: Surface Conductancementioning

confidence: 99%

Transport phenomena in nanofluidics

2008

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The transport of fluid in and around nanometer-sized objects with at least one characteristic dimension below 100 nm enables the occurrence of phenomena that are impossible at bigger length scales. This research field was only recently termed nanofluidics, but it has deep roots in science and technology. Nanofluidics has experienced considerable growth in recent years, as is confirmed by significant scientific and practical achievements. This review focuses on the physical properties and operational mechanisms of the most common structures, such as nanometer-sized openings and nanowires in solution on a chip. Since the surface-to-volume ratio increases with miniaturization, this ratio is high in nanochannels, resulting in surface-charge-governed transport, which allows ion separation and is described by a comprehensive electrokinetic theory. The charge selectivity is most pronounced if the Debye screening length is comparable to the smallest dimension of the nanochannel cross section, leading to a predominantly counterion containing nanometer-sized aperture. These unique properties contribute to the charge-based partitioning of biomolecules at the microchannel-nanochannel interface. Additionally, at this free-energy barrier, size-based partitioning can be achieved when biomolecules and nanoconstrictions have similar dimensions. Furthermore, nanopores and nanowires are rooted in interesting physical concepts, and since these structures demonstrate sensitive, label-free, and real-time electrical detection of biomolecules, the technologies hold great promise for the life sciences. The purpose of this review is to describe physical mechanisms on the nanometer scale where new phenomena occur, in order to exploit these unique properties and realize integrated sample preparation and analysis systems.

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Section: Surface Conductancementioning

confidence: 99%

Transport phenomena in nanofluidics

2008

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“…Bikerman (1942) suggested that materials such as clays, which are capable of swelling in aqueous media, form a gel la3,er on the surface that is conductive but electrokinetically inactive. Other theories have suggested mobility of ions in the Stern layer (Urban et al, 1935) and conduction by ionizable surface hydroxyl groups (Holmes et al, 1965). These ideas are not mutually exclusive.…”

Section: Introductionmentioning

confidence: 99%

Surface Conductance and Electrokinetic Properties of Kaolinite Beds

Lorenz

1969

Clays and clay miner.

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Abstract-A technique was developed for forming clay beds of uniform porosity between 48 and 62 per cent. The surface conductance and streaming potential of sodium kaolinite were determined over a range of values. Zeta potential as calculated from the classical formula was about -30 mV at neutral pH and changed sign at pH 4. The surface conductivity of the sodium clay at various pH values was directly proportional to the zeta potential and from 12 to more than 30 times as large as the calculated electrokinetic surface conductivity. Similar measurements were made on kaolinite in the acid (hydrogen-aluminum) and calcium forms. The acid clay fitted the experimental correlation found for the sodium series, but the calcium clay, with less than one-tenth of the zeta potential of the sodium clay at neutral pH, had half its surface conductance. The results are interpreted as showing that exchangeable ions on kaolinite are mostly in a condensed layer on the surface where the mobility determines surface conductance. The surface mobilities for Na, Ca and H-A1 are 20, 8 and 0 per cent of normal, respectively. Apparently hydrogen ion from the solution is very effective in replacing sodium, which exhibits its electrokinetic and conductive properties in proportion to its concentration on the surface.

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“…Urban, White, and Strassner (1935) also state that the ,con Srnoluchowski conductance of pyrex glass is very slight at 1000 cycles. It is not possible, however, to choose between a normal and a tangential conductance explanation of the data on suspended cells.…”

Section: Discussionmentioning

confidence: 87%

Electric Impedance of Asterias Eggs

Cole

1936

Journal of General Physiology

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Several years ago the absolute value of the alternating current impedance of suspensions of Arbacia eggs was measured at frequencies from 1 to 15,000 kc. (Cole, 1928b). I t was concluded that the egg membrane capacity was not as nearly a static capacity as the capacity of the red blood cell membrane (Fricke, a, 1933, but was of the polarization impedance type, similar to that which could be attributed to the cell membranes of tissues (Cole, 1932(Cole, , 1933Bozler and Cole, 1935). Recent measurements (Cole, 1935) of both the resistance and reactance components of suspensions of Hipponog eggs at frequencies from 1.1 to 2,300 kc. showed the membranes to have static capacities and suggested complicating phenomena at the upper end of the frequency range. I t was then obvious that more complete measurements should be made not only on Arbacia eggs, but also on the eggs of other echinoderms. MaterialThe availability and the large size of the eggs of the common starfish, Asterias forbesi, made them good material for this work. As soon as the animals were collected, the ovaries were removed and placed in sea water until the eggs had been shed. The eggs were washed once or twice, centrifuged lightly, and drawn into the conductivity cell. The suspension of eggs separated by jelly reached a constant resistance in 15 or 20 minutes which was maintained for an hour or two. When the suspension was removed from the cell it was found that very little cytolysis had taken place A singular scarcity of ripe males prevented tests of viability and measurements of fertilized eggs. All measurements were made between 21 and 22°C.

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Contribution to the Theory of Surface Conductivity at Solid-Liquid Interfaces

Cited by 40 publications

References 7 publications

Transport phenomena in nanofluidics

Transport phenomena in nanofluidics

Surface Conductance and Electrokinetic Properties of Kaolinite Beds

Electric Impedance of Asterias Eggs

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