Chitosan-fatty acid interaction mediated growth of Langmuir monolayer and Langmuir-Blodgett films

Because of the antioxidant activity of vitamin C (Vit C) polar heads, they can be used as a protective agent for fatty acids. Hence, the study on the growth of Vit C/stearic acid (SA) mixed binary films at air–water interface (known as Langmuir monolayer) and air–solid interface (known as Langmuir–Blodgett films) is of paramount interest. Although Vit C is situated at subsurface beneath SA molecules and interacts via hydrogen bonding between the hydroxyl groups of Vit C and SA, several Vit C molecules may infiltrate within SA two-dimensional matrix at the air–water interface. The increased mole fraction of Vit C (0.125–0.5) and the reduction of temperature (from 22 to 10 °C) of the subphase water result in an increase in the amount of adsorbed Vit C at the air–water interface. The surface pressure (π)–area ( A ) isotherms illustrate that such inclusion of Vit C provokes a spreading out of Vit C/SA binary monolayers, which leads to an alteration of different physicochemical parameters such as elasticity, Gibbs free energy of mixing, enthalpy, entropy, interaction energy parameter, and activity coefficient. However, being polar in nature, the transfer of pure Vit C on substrates gets affected. It can be transferred onto substrate by mixing suitably with SA as confirmed by infrared spectra. Their structures, extracted X-ray reflectivity, and atomic force microscopy (topography and phase imaging) are found to be strongly dependent on the nature of the substrate (hydrophilic and hydrophobic).

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“…A similar phenomenon was encountered in our previous study on chitosan–fatty acid mixed monolayer. 6…”

Section: Results and Discussionmentioning

confidence: 99%

Vitamin C/Stearic Acid Hybrid Monolayer Adsorption at Air–Water and Air–Solid Interfaces

et al. 2018

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“…After 3 h (to guarantee toluene evaporation), the Ru film was immersed in the solution in the trough such that the sample plane was orthogonal to the trough plane. The setup barriers were adjusted to reach a surface tension of 20 mN m −1 , which is the first derivative turning point of surface tension isotherm expected to correspond to one monolayer [ 33 ] (see Figure S2, Supporting Information). The substrate was pulled out at a rate of 0.5 mm/min while the surface tension was kept constant at 20 mN m −1 .…”

Section: Methodsmentioning

confidence: 99%

Xenon Trapping in Metal‐Supported Silica Nanocages

Mello

Zhou

et al. 2021

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Xenon (Xe) is a valuable and scarce noble gas used in various applications, including lighting, electronics, and anesthetics, among many others. It is also a volatile byproduct of the nuclear fission of uranium. A novel material architecture consisting of silicate nanocages in contact with a metal surface and an approach for trapping single Xe atoms in these cages is presented. The trapping is done at low Xe pressures and temperatures between 400 and 600 K, and the process is monitored in situ using synchrotron‐based ambient pressure X‐ray photoelectron spectroscopy. Release of the Xe from the cages occurs only when heating to temperatures above 750 K. A model that explains the experimental trapping kinetics is proposed and tested using Monte Carlo methods. Density functional theory calculations show activation energies for Xe exiting the cages consistent with experiments. This work can have significant implications in various fields, including Xe production, nuclear power, nuclear waste remediation, and nonproliferation of nuclear weapons. The results are also expected to apply to argon, krypton, and radon, opening an even more comprehensive range of applications.

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“…A further analysis of isotherms provides compressional modulus ( C s –1 ) and plotted it as a function of area/molecule (shown in Figure 1 b). To extract the information of elastic properties of the monolayers, the reciprocal of monolayer compressibility ( C s ), that is, the compressional modulus ( C s –1 , also known as in-plane elasticity) was calculated from the isotherms of the azo-containing monolayer at the air–water interface using the following expression 33 , 34 where A is the area per molecule. Numerical value of C s –1 , tabulated in Table 1 , increases when the monolayer attains its condensed state.…”

Section: Results and Discussionmentioning

confidence: 99%

Structure and Elastic Properties of an Unsymmetrical Bi-Heterocyclic Azo Compound in the Langmuir Monolayer and Langmuir–Blodgett Film

et al. 2020

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We study the structure and elastic properties of the bi-heterocyclic azo compound at the air–water interface through surface pressure (π)–area ( A ) isotherm recording followed by transferring them on hydrophilic and hydrophobic Si surfaces by the Langmuir–Blodgett (LB) deposition method. A substantial change in the area/molecule is observed as a function of subphase pH and temperature. Such parameters strongly influence intramolecular interactions within azo molecules and the interactions between azo molecules and water that manifested in higher surface activity at low temperature and high pH, which in turn modifies the elasticity of azo assembly at the air–water interface. A large pH-dependent hysteresis with negative change in entropy, indicating molecular rearrangements, is observed. Molecular assembly formed at the air–water interface is then transferred onto hydrophilic and hydrophobic Si surfaces at two different surface pressures (5 and 30 mN/m) by the LB technique. The structural analysis performed by X-ray reflectivity and atomic force microscopy techniques suggests that the LB films exhibit an abrupt layered structure on hydrophilic Si, whereas an overall rough film is formed on hydrophobic Si. The coverage and compactness of individual layers are found to increase with the deposition pressure (5 to 30 mN/m).

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Chitosan-fatty acid interaction mediated growth of Langmuir monolayer and Langmuir-Blodgett films

Cited by 29 publications

References 41 publications

Vitamin C/Stearic Acid Hybrid Monolayer Adsorption at Air–Water and Air–Solid Interfaces

Vitamin C/Stearic Acid Hybrid Monolayer Adsorption at Air–Water and Air–Solid Interfaces

Xenon Trapping in Metal‐Supported Silica Nanocages

Structure and Elastic Properties of an Unsymmetrical Bi-Heterocyclic Azo Compound in the Langmuir Monolayer and Langmuir–Blodgett Film

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