Dependence of Langmuir-Blodgett film quality on fatty acid monolayer integrity. 1. Nucleation crystal growth avoidance in the monolayer through the optimized compression procedure

Morelis, Renée; Girard-Egrot, Agnès; Coulet, Pierre R.

doi:10.1021/la00035a058

Cited by 36 publications

(35 citation statements)

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“…Generally, at relatively low pressures, surface defects such as micro-collapses and pinholes are common. [48,49] The morphology of mixed LB films, namely, 3 : 1 PA-[C n -mim] Cl; n = 4; 8, were featureless with the absence of voids, which signify the formation of a close-packed monolayer due to the proposed interaction between the PA and the IL component. However, the film morphology of the 1 : 3 PA-[C 4 -mim]Cl showed irregular features similar to those observed in the case of pure PA, which could be explained by the water solubility of the butyl-IL as supported by the relaxation measurements (vide supra), particularly at high content of the C 4 -mim-IL.…”

Section: Resultsmentioning

confidence: 99%

Morphological and Interaction Characteristics of Surface‐Active Ionic Liquids and Palmitic Acid in Mixed Monolayers

et al. 2020

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A series of water soluble, surface‐active ionic liquids (SAILs), namely, 1‐alkyl‐3‐methyl imidazolium chlorides ([Cn‐mim]Cl) and their mixtures with palmitic acid (PA) are investigated in Langmuir monolayers and Langmuir–Blodgett films. It is inferred from the surface pressure‐area isotherms that C16‐mim‐IL mixes non‐ideally with PA and stabilizes the binary mixed films. In addition, the residence of mim‐IL at the water surface is enhanced as a function of the increasing alkyl side chain length. Generally, the compressional moduli values decrease upon increasing the content of the mim‐ILs over a wide range of compositions. Furthermore, film relaxation measurements indicate that the IL component is selectively excluded from the mixed films upon achieving a certain target pressure. Brewster angle microscope images demonstrate minimal changes on the PA domains in the presence of either C4‐ and C8‐mim‐ILs, whereas presence of the hexadecyl counterpart results in the formation of condensed sheets. Atomic force microscopy imaging of deposited films show the formation of propeller‐like aggregates when C8‐ or C16‐mim‐IL is present in the mixed films.

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Section: Resultsmentioning

confidence: 99%

Morphological and Interaction Characteristics of Surface‐Active Ionic Liquids and Palmitic Acid in Mixed Monolayers

et al. 2020

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“…Conversely, in LS conversion of standing phases to form lying-down phases, each molecule must not only desorb from the aqueous subphase but also reorient substantially to lie horizontal on the substrate (Figure ). Thus, experimental parameters (e.g., temperature, mean molecular area, pH or ionic strength of subphase) − that produce high transfer ratios , for LS transfer of standing phases are not necessarily optimal for LS conversion to form lying-down phases.…”

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confidence: 99%

Hierarchically Patterned Noncovalent Functionalization of 2D Materials by Controlled Langmuir–Schaefer Conversion

et al. 2018

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Noncovalent monolayer chemistries are often used to functionalize 2D materials. Nanoscopic ligand ordering has been widely demonstrated (e.g., lying-down lamellar phases of functional alkanes); however, combining this control with micro- and macroscopic patterning for practical applications remains a significant challenge. A few reports have demonstrated that standing phase Langmuir films on water can be converted into nanoscopic lying-down molecular domains on 2D substrates (e.g., graphite), using horizontal dipping (Langmuir-Schaefer, LS, transfer). Molecular patterns are known to form at scales up to millimeters in Langmuir films, suggesting the possibility of transforming such structures into functional patterns on 2D materials. However, to our knowledge, this approach has not been investigated, and the rules governing LS conversion are not well understood. In part, this is because the conversion process is mechanistically very different from classic LS transfer of standing phases; challenges also arise due to the need to characterize structure in noncovalently adsorbed ligand layers <0.5 nm thick, at scales ranging from millimeters to nanometers. Here, we show that scanning electron microscopy enables diynoic acid lying-down phases to be imaged across this range of scales; using this structural information, we establish conditions for LS conversion to create hierarchical microscopic and nanoscopic functional patterns. Such control opens the door to tailoring noncovalent surface chemistry of 2D materials to pattern local interactions with the environment.

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“…The platinum electrode (model XM 260, Soléa-Tacussel, France) was in the form of a plate (20 mm × 10 mm × 0.2 mm) specially designed for the LB deposition. These two types of substrates were thoroughly cleaned with TFD 4 detergent (Franklab, France) in a heating ultrasonic bath, as described elsewhere …”

Section: Methodsmentioning

confidence: 99%

“…Behenic acid solution (10 -3 M in CHCl 3 ) and 1.5 × 10 -3 M DPPC−DPPA (DPPC−DPPA molar ratio, 1:2) solution in CHCl 3 −CH 3 OH (CHCl 3 −CH 3 OH, 2:1, by volume) were used to prepare the monolayers as previously described. − Briefly, the water surface was cleaned by suction, and a known volume of the lipidic solution was spread. The monolayer was discontinuously compressed with steps of 2 mN·m -1 and transferred with the vertical dipping technique.…”

Section: Methodsmentioning

confidence: 99%

Influence of Lipidic Matrix and Structural Lipidic Reorganization on Choline Oxidase Activity Retained in LB Films

1998

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This work focuses on the influence of the nature of the lipidic matrix and of the hydrophobic or hydrophilic lipidic environment on choline oxidase activity retained in Langmuir−Blodgett (LB) films prepared with behenic acid or with mixed dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidic acid (DPPA). The enzyme activity was detected through an electrochemical sensor whose platinum electrode was coated with the protein−lipid LB films. It was shown that the hydrophilic environment provided by the phospholipidic LB films was directly responsible for an inactivation of choline oxidase likely due to a competition with the choline moiety of DPPC. The environment provided by the carboxylic groups of the fatty acid multilayers allowed retention of the higest activity. The absence of stability of choline oxidase activity in behenic acid LB films was explained by repulsive electrostatic interactions between the protein and the lipidic molecules, which appeared during the immersion of the LB films in the alkaline buffer required to detect the enzyme activity in optimal conditions. These unfavorable interactions, previously shown to be responsible for a lipidic structural reorganization of choline oxidase−behenic acid LB films, seem to be here responsible for a likely unfolding, yielding protein denaturation. Because it controls the electrostatic interactions between the protein and the lipidic molecules, which may be very unfavorable even in the optimal conditions of the enzyme activity, pH acts as a key parameter of the expression of the enzyme activity in the LB films.

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Dependence of Langmuir-Blodgett film quality on fatty acid monolayer integrity. 1. Nucleation crystal growth avoidance in the monolayer through the optimized compression procedure

Cited by 36 publications

References 1 publication

Morphological and Interaction Characteristics of Surface‐Active Ionic Liquids and Palmitic Acid in Mixed Monolayers

Morphological and Interaction Characteristics of Surface‐Active Ionic Liquids and Palmitic Acid in Mixed Monolayers

Hierarchically Patterned Noncovalent Functionalization of 2D Materials by Controlled Langmuir–Schaefer Conversion

Influence of Lipidic Matrix and Structural Lipidic Reorganization on Choline Oxidase Activity Retained in LB Films

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