Electric field induced permeability modulation in pure and mixed Langmuir-Blodgett multilayers of hemicyanine dyes and octadecanoic acid on nanoporous solid supports

Steehler, Jack K.; Lu, Wu; Kemery, Paula J.; Bohn, Paul W.

doi:10.1016/s0376-7388(97)00261-5

Cited by 14 publications

(8 citation statements)

References 74 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In the absence of an electric field, probe transport is driven by the imposed concentration gradient. Previously published findings indicate this flux fits a planar solution to Fick's second law of diffusion for a random pore areal distribution . Ion concentration, and therefore double layer structure, within the pores is expected to play a dominant role in determining field-off permeability for charged probes, especially when the pore is essentially plugged with cations.…”

Section: Resultsmentioning

confidence: 63%

See 1 more Smart Citation

Electric Field Mediated Transport in Nanometer Diameter Channels

1998

View full text Add to dashboard Cite

Nanoporous polycarbonate (PCTE) nuclear-track-etched membranes were used to effect electric field modulation of the mass transport of cationic, anionic, and neutral species in aqueous buffer. The permeability response to electric fields depended on the molecular charge and electrolyte concentration. Solute and solvent fluxes through nanopores under an electrical potential result from a balance of diffusion, electroosmosis, and ion migration. The Debye length, κ -1 , associated with the electrical double layer within the pores relative to the pore diameter, 2a, plays a critical role in determining electrokinetic transport behavior. The channel walls adsorb anions preferentially to produce a largely immobile negative charge density, leaving a large and mobile cation population to mediate transport in the channel. By adjusting the supporting electrolyte concentration, κa can be tuned such that the electrical double layer is either small in relation to the pore (κa g 1) or more diffuse and spanning the pore (κa < 1). Electroosmotic transport, mediated primarily by buffer cations, dominates when κa < 1. In this case the pores are essentially permselective, and anion electromigration is virtually eliminated. When κa g 1, the sign of the applied potential can be used to select for anion vs cation/neutral molecule transport.

show abstract

Section: Resultsmentioning

confidence: 63%

“…Results are reported in terms of permeability trends in response to electric field application. Field-off flow rates represent normal Fickian diffusion of fluorescent molecules through membrane channels along the concentration gradient …”

Section: Resultsmentioning

confidence: 99%

Electric Field Mediated Transport in Nanometer Diameter Channels

1998

View full text Add to dashboard Cite

show abstract

“…A classic example is in the area of gas separations, where LB films have generally been found to exhibit permeation selectivities that follow Graham’s law. Such a finding, in and of itself, indicates that the primary pathway for transport of gases across the membrane is diffusion through defects. – …”

Section: Introductionmentioning

confidence: 95%

Probing the Gas Permeability of an Ionically Cross-Linked Langmuir–Blodgett Bilayer with a “Touch” of Salt

2008

View full text Add to dashboard Cite

The main barrier for gas permeation across ionically cross-linked Langmuir-Blodgett (LB) bilayers, made from a 5,11,17,23,29,35-hexakis[( N, N, N-trimethylamonium)-N-methyl-37,38,39,40,41,42-hexakis-n-hexamedecyloxy-calix[6]arene hexachloride (1) and poly(sodium 4-styrenesulfonate) (PSS), has been determined by measuring the effects of NaCl on the thickness of the PSS layer encased between the calixarene layers and the permeation characteristics of the resulting membrane. Specifically, the fact that NaCl increases the uptake of PSS by the LB film and increases the permeance of these membranes toward N2 and CO2 but not He provides compelling evidence that the main barrier for permeation is the calixarene layers and not the PSS layer that is encased between them. The effects of NaCl on ionic cross-linking, surface pressure, and surface viscosities are discussed.

show abstract

“…Unfortunately, in nearly all studies reported to date, LB films have been found to exhibit gas permeation selectivities that follow Graham's law. Such a finding, in and of itself, indicates that diffusion is occurring through defects in the membrane. − …”

Section: Introductionmentioning

confidence: 95%

“…Such a finding, in and of itself, indicates that diffusion is occurring through defects in the membrane. [7][8][9][10][11][12][13][14][15][16][17] In an effort to improve the cohesiveness of surfactant monolayers, and to eliminate defects in LB films, we have introduced the concept of "gluing". 18 In essence, a glued monolayer is one that is made from a multiply charged surfactant that has been ionically cross-linked using a water-soluble, polymeric counterion.…”

Section: Introductionmentioning

confidence: 99%

Insight into the Permeation Barrier of Glued Langmuir−Blodgett Bilayers

et al. 2007

View full text Add to dashboard Cite

Permeation measurements have been made for He, CO2, and N2 across single Langmuir-Blodgett (LB) bilayers derived from 1,2,4,5-tetrakis[(N-(undecanoamidoethyl)-N,N-dimethyl ammonium) methyl]benzene tetrabromide (2) and 1,2,4,5-tetrakis[(N-(perfluoroundecanoamidoethyl)-N,N-dimethyl ammonium)methyl]benzene tetrabromide (3) in the absence and in the presence of entrapped poly(acrylic acid) (PAA). In the absence of PAA, single LB bilayers of 3 show a higher permeance for He and N2 but a lower permeation rate of CO2, as compared with analogous LB bilayers made from 2. The relatively low permeation rate of CO2 for the former has been attributed to reduced associative interactions with the fluorocarbon-rich bilayer. The same behavior has also been observed for LB bilayers containing PAA, formed under conditions that yield glued bilayers of 2 and 3 having similar diffusional pathways, as judged by He/N2 selectivities. These results, together with the fact that glued bilayers of 2 (having a thinner PAA layer as compared with those made from 3) exhibit lower He and N2 permeances, provide compelling evidence that the main barrier for gas transport is the combination of surfactant plus PAA and not simply a thin PAA layer that is encased within the surfactant bilayer.

show abstract

Electric field induced permeability modulation in pure and mixed Langmuir-Blodgett multilayers of hemicyanine dyes and octadecanoic acid on nanoporous solid supports

Cited by 14 publications

References 74 publications

Electric Field Mediated Transport in Nanometer Diameter Channels

Electric Field Mediated Transport in Nanometer Diameter Channels

Probing the Gas Permeability of an Ionically Cross-Linked Langmuir–Blodgett Bilayer with a “Touch” of Salt

Insight into the Permeation Barrier of Glued Langmuir−Blodgett Bilayers

Contact Info

Product

Resources

About