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

Abstract

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).

Molecular Langmuir–Blodgett Film for Silicon Anode Interface Engineering

“…The evolution of SA monolayer during compressing underwent a typical process successively consisting of the gaseous state, liquid state, solid state, and collapsed state (as area per molecule decreasing). The transition point between the liquid condensed state and the solid state, namely, the curve slope changing point in the compressed state, was observed at a surface pressure of 25 mN/m, which is consistent with previous reports. − SA monolayers were transferred onto the Si wafer via vertical dipping method, and FTIR spectrum of the thin films on the Si wafer is shown in Figure b. The peak at 1705 cm –1 is ascribed to carbonyl stretching, and the peaks at 2917, 2849, and 1460 cm –1 are attributed to CH 2 groups. − The large background peaks at 1235 and 1105 cm –1 originated from the oxide species at the silicon wafer surface .…”

Physicochemical Properties of a Bi-aromatic Heterocyclic-Azo/BSA Hybrid System at the Air–Water Interface

“…The structural characterization is easier in the case of solid-supported LB films than that of Langmuir films . Thus, a good alternative to in situ characterization of Langmuir monolayer in a LB trough is to imitate the assembly on the substrate using LB deposition. , Monolayer (upstroke), bilayer (downstroke–upstroke), and trilayer (upstroke–downstroke–upstroke) depositions of floating molecules were chosen for the preparation of LB films on desired Si surfaces at surface pressure π = 30 mN/m. Nevertheless, for monolayer (1s) and trilayer (3s) depositions, hydrophilic native-oxide covered Si surfaces were used, whereas for bilayer (2s) deposition hydrophobic oxide-free H-passivated Si was used.…”

Improvement of Moist Heat Resistance of Ascorbic Acid through Encapsulation in Egg Yolk–Chitosan Composite: Application for Production of Highly Nutritious Shrimp Feed Pellets

“…The main characteristic peaks of AA were detected at 1751 cm −1 (C=O stretching) and 1653 cm −1 (C=C ring stretching) [ 46 , 47 ]. Different vibrational bands of AA observed in the region of 1500–1200 cm −1 were attributed to the CH 2 scissoring, twisting, and wagging as well as C-H deformation modes [ 48 ]. The band at 1150–1100 cm −1 was assigned to C-O-C stretching.…”