Direct Visualization of Surfactant Hemimicelles by Force Microscopy of the Electrical Double Layer

Manne, S.; Cleveland, J. P.; Gaub, Hermann E.; Stucky, Galen D.; Hansma, Paul K.

doi:10.1021/la00024a003

Cited by 611 publications

(695 citation statements)

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“…We believe that one structurally realistic possibility is the formation of hemimicelles along the chain, as has previously been observed with ionic surfactants adsorbed onto hydrophobic surfaces. 29 Significant differences were found between the specific conductivity of surfactant and surfactant-polymer solutions in DMSO-water mixtures (4% v/v) for small additions of surfactant in all of the systems studied, when the surfactant and polymer concentrations (in terms of repeat unit) are comparable (see Figure 9A). In the pure surfactant system, specific conductivity grows linearly over the whole concentration range up to the cmc with a constant slope of the plot of κ versus surfactant concentration.…”

Section: Resultsmentioning

confidence: 88%

Modulating the Emission Intensity of Poly-(9,9-bis(6‘-N,N,N-trimethylammonium)hexyl)-Fluorene Phenylene) Bromide Through Interaction with Sodium Alkylsulfonate Surfactants

et al. 2007

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The interaction between the cationic HTMA-PFP (Poly-(9,9-bis(6′-N,N,N-trimethylammonium)hexyl-fluorene phenylene) bromide) and oppositely charged sodium n-alkyl sulfonate surfactants of different chain lengths has been studied in DMSO-water solutions (4% v/v) by UV-visible absorption, fluorescence spectroscopy, fluorescence lifetimes, electrical conductivity, and 1 H NMR spectroscopy. Polymer-surfactant interactions lead to complex spectroscopic behaviors which depends on surfactant concentration. At low surfactant concentrations, the observed strong static fluorescence quenching of fluorescence seems to be associated with formation of aggregates between polymer chains neutralized through interaction with surfactants. This is supported by conductivity and by analysis of absorption spectra deconvoluted at each surfactant concentration using an adapted iterative method. In contrast, above the surfactant critical micelle concentration, there is a strong fluorescence enhancement, leading in some cases to higher intensities than in the absence of surfactants. This is attributed to the transformation of the initially formed aggregates into some new aggregate species involving surfactant and polymer. These changes in HTMA-PFP fluorescence as a function of n-alkyl sulfonate concentration are important for the general understanding of polymer-surfactant interactions, and the aggregates formed may be important as novel systems for applications of these conjugated polyelectrolytes.

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Section: Resultsmentioning

confidence: 88%

Modulating the Emission Intensity of Poly-(9,9-bis(6‘-N,N,N-trimethylammonium)hexyl)-Fluorene Phenylene) Bromide Through Interaction with Sodium Alkylsulfonate Surfactants

et al. 2007

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“…This is an important advance because there are relatively few techniques for probing and visualizing charge at interfaces. Although atomic force microscopy (AFM) can be used, [24][25][26][27] it employs a tip of (nominally) fixed charge that may change during a scan (e.g. by contamination or tip wear), and the force-distance characteristics are influenced by several forces as well as electrostatic forces.…”

Section: Introductionmentioning

confidence: 99%

Surface Charge Mapping with a Nanopipette

et al. 2014

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Nanopipettes are emerging as simple but powerful tools for probing chemistry at the nanoscale.In this contribution the use of nanopipettes for simultaneous surface charge mapping and topographical imaging is demonstrated, using a scanning ion conductance microscopy (SICM) format. When a nanopipette is positioned close to a surface in electrolyte solution the direct ion current (DC), driven by an applied bias between a quasi-reference counter electrode (QRCE) in the nanopipette and a second QRCE in the bulk solution is sensitive to surface charge. The charge sensitivity arises because the diffuse double layers at the nanopipette and the surface interact, creating a perm-selective region which becomes increasingly significant at low ionic strengths (10 mM 1:1 aqueous electrolyte herein). This leads to a polarity-dependent ion current and surface-induced rectification as the bias is varied. Using distance-modulated SICM, which induces an alternating ion current component (AC) by periodically modulating the distance between the nanopipette and the surface, the effect of surface charge on the DC and AC is explored and rationalized. The impact of surface charge on the AC phase (with respect to the driving sinusoidal signal) is highlighted in particular; this quantity shows a shift that is highly sensitive to interfacial charge and provides the basis for visualizing charge simultaneously with topography. The studies herein highlight the use of nanopipettes for functional imaging with applications from cell biology to materials characterization where understanding surface charge is of key importance.3

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“…35,36 Pioneered by Manne and co-workers, this technique revealed that surfactants form surface aggregates in the shape of full 36 or half [35][36][37][38] cylinders or full 36 or half 39 spheres, as well as flat layers, 36,40 depending on the system under investigation. These findings have been confirmed by computational investigations.…”

Section: Introductionmentioning

confidence: 99%

“…These findings have been confirmed by computational investigations. 41 AFM imaging of surfactant surface micelles, however, has been limited to extremely flat substrates such as atomically smooth graphite [35][36][37][42][43][44][45] and mica. 36,40,42 Amorphous silica that forms as a native oxide on highly smooth silicon has been the third most popular substrate.…”

Section: Introductionmentioning

confidence: 99%

Surfactant Aggregates at Rough Solid−Liquid Interfaces

et al. 2007

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We demonstrate improved atomic force microscopic imaging of surfactant surface aggregates, featuring an increase in the topography contrast by several hundred percent with respect to all previous studies. Surfactant aggregates on rough gold surfaces, which could not be imaged previously because of low resolution, display substantially different morphologies when compared with atomically smooth materials.

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Direct Visualization of Surfactant Hemimicelles by Force Microscopy of the Electrical Double Layer

Cited by 611 publications

References 0 publications

Modulating the Emission Intensity of Poly-(9,9-bis(6‘-N,N,N-trimethylammonium)hexyl)-Fluorene Phenylene) Bromide Through Interaction with Sodium Alkylsulfonate Surfactants

Modulating the Emission Intensity of Poly-(9,9-bis(6‘-N,N,N-trimethylammonium)hexyl)-Fluorene Phenylene) Bromide Through Interaction with Sodium Alkylsulfonate Surfactants

Surface Charge Mapping with a Nanopipette

Surfactant Aggregates at Rough Solid−Liquid Interfaces

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