Ranendu Kumar Nath

Interaction of bacterial acidic polysaccharide with cationic dyes

The interaction of acidic capsular polysaccharide isolated fromKlebsiella K26 with cationic dyes pinacyanol chloride, acridine orange and phenosafranin has been studied by spectral measurements. The polymer induces metachromasy in pinacyanol chloride dye, indicating a blue shift in the visibly absorption spectrum of the dye from 600 to 500 nm. The stoichiometry of polymer/dye in the metachromatic compound, thermodynamic parameters of interaction, and effects of different cosolvents on the stability of the complex have been studied. Spectrophotometric and spectrofluorometric properties of the interaction between the polymer and all three dyes are presented. The chromotropic property of the polymer has been established.

General solvent-free ionic liquid catalyzed C-N/ C-C coupled cyclization to diverse dihydropyrimidinones and new organic materials: Langmuir-Blodgett film study†

An ionic liquid catalyzed dual C–N/C–C coupled cyclization of a three component assembly is demonstrated to access 3,4-dihydropyrimidin-2(1H)-one (DHPM) analogues under solvent-free green conditions. Innovative new organic materials are introduced with pure and mixed DHPM using LB high surface pressure, AFM and photophysical studies.

Induction of metachromasy in cationic dye by bacterial cell surface polysaccharide from Klebsiella K10

Abstract Interaction of acidic capsular polysaccharide isolated from Klebsiella serotype K10 with cationic dye pinacyanol chloride has been investigated by spectral measurements, and thermodynamic parameters of the interaction evaluated. The polysaccharide induces metachromasy in the dye, causing a blue-shift from 600 to 490 nm. The spectral properties exhibit chromotropic character of the polymer, and the metachromatic compound is formed with the polyanion/dye-cation stoichiometry of 1:1.

Formation of Complex Langmuir and Langmuir-Blodgett Films of DNA with a Dichain Cationic Surfactant

Formation of complex monolayers between a dichain cationic surfactant, namely, dihexadecyldimethylammonium bromide (DHDAB) and deoxyribonucleic acid (DNA) at the air-water interface was first time systematically investigated here. The adsorption of DNA onto DHDAB monolayer was monitored by observing the surface pressure vs. time graph. The polyion-complex monolayers formed in situ through the electrostatic attraction between cationic DHDAB and the phosphate groups of anionic DNA. The organization of the DNA-DHDAB complex at the air-water interface deduced from surface pressure-area (π-A) isotherms was compared with the spectroscopic data in Langmuir-Blodgett films. Study of UV-Vis absorption spectra of pure DNA solution and DNA adsorbed DHDAB complex Langmuir-Blodgett films confirms the successful transfer of the films onto quartz substrates.

Adsorption of Chicago Sky Blue on the Langmuir Monolayer and Langmuir-Blodgett Films of Octadecylamine

This paper reports the incorporation of an inhibitor of Human Immunodeficiency Virus (HIV), viz. Chicago Sky Blue (CSB) dye within an insoluble cationic octadecylamine (ODA) Langmuir monolayer. A surface pressure-area isotherm study confirmed the strong interaction between long chain amine and CSB dye. At higher surface pressure, CSB molecules tend to squeeze out from the octadecylamine monolayer. SEM study confirms this observation. Adsorption kinetics shows that the amount of dye adsorbed depends on the concentration of the dye present in the subphase. It was observed that the absorption process mainly occurred due to the electrostatic interaction between the cationic amino group of long chain amine and the sulphonate group of CSB dye. UV-Vis absorption spectroscopic study indicates the formation of aggregates of CSB dye in the mixed (ODA-CSB) LB films.

Investigation of Miscibility and Aggregate Formation in the Mixed Langmuir–Blodgett Films of 2-aminoanthracene by Surface Pressure and Spectroscopic Methods

Nonamphiphilic 2-aminoanthracene has been incorporated within the Langmuir monolayer and Langmuir–Blodgett (LB) films when mixed with behenic acid (BA). Miscibility of 2-aminoanthracene and BA at the air—water (A–W) interface has been studied by using surface phase rule and excess area criterion. Our studies reveal that repulsive type interactions exist between the component molecules in mixed monolayer and this may facilitate the formation of aggregates. Spectroscopic as well as morphological studies of mixed LB films of 2-aminoanthracene and BA undoubtedly confirms the formation of aggregates.

An Investigation of the Behavior of Binary Mixed Langmuir Monolayer of 2,2′-p-Phenylenebis (5-phenyloxazol) and Arachidic Acid

A systematic study is reported on the monolayer characteristics of 2,2′-p-phenylenebis (5-phenyloxazol) (POPOP) mixed with arachidic acid (AA) at the air-water interface, using surface pressure versus area per molecule (π-A) isotherms complemented with absorption spectroscopy as well as scanning electron microscopy. The (π-A) isotherms of POPOP mixed with AA at different mole fractions show a plateau like region at very low surface pressure, which suggests a phase transition corresponding to a reorientation of the POPOP molecules at the air-water interface. The mixing behavior was obtained from surface pressure-area isotherms by using the surface phase rule and excess area criterion. Results show that POPOP is immiscible in AA, leading to the formation of aggregates. These observations are confirmed by ultraviolet-visible absorption spectroscopy and scanning electron microscopy. Absorption spectra of the mixed LB films reveal that I-type of aggregates play their prominent role in the mixed LB films.

MONOLAYER CHARACTERISTICS OF CHITOSAN ASSEMBLED IN LANGMUIR FILMS MIXED WITH ARACHIDIC ACID

In this paper, we report our investigation on the monolayer characteristics of a nontoxic, biocompatible, and biodegradable polymer chitosan (CHS) using Langmuir–Blodgett technique. It has been observed that pure CHS do not form stable monolayer. However, when CHS is mixed with arachidic acid (AA), stable self supporting monolayer is formed at air–water interface. This also can be transferred onto solid substrate. CHS–AA mixed monolayer is extremely stable with variation of pH. Atomic force microscopy study confirms the formation of stable uniform CHS–AA films onto solid support.

Behavior of Coronene in the Mixed Langmuir-Blodgett (LB) Films of Two Different Matrixes on Water and Solid Surfaces

Excellent Langmuir-Blodgett films (LB) of non-amphiphilic coronene (COR) have been prepared by mixing with a long chain fatty acid, viz., arachidic acid (AA) and an inert polymer such as poly methyl methacrylate (PMMA) separately. Miscibility of the guest and host molecules in the mixed monolayer of COR and AA/PMMA have been studied with excess area criterion. Both the attractive and repulsive interactions are present in the COR/AA mixed monolayer, whereas only repulsive interaction is active between the component molecules of COR/PMMA mixed monolayer. Spectroscopic properties of COR in solution and mixed LB films have been compared by UV-Vis absorption spectroscopy. Surface morphology of mixed LB films has been examined by atomic force microscopy (AFM). Absorption spectroscopic study complemented with AFM image suggests the formation of some kind of aggregates in the mixed LB films.

Incorporation of Erythrosin B Within the Restricted Geometry of Langmuir Monolayer and Langmuir-Blodgett Films of Octadecylamine

This paper reports the monolayer characteristics of cationic octadecylamine (ODA) on both distilled water and aqueous Erythrosine B (EB) dye solution at the air-water interface. From the pressure-area isotherms at various pHs, EB anions in the subphase were found to interact with the insoluble monolayer of cationic octadecylamine (ODA). Adsorption kinetics shows that the amount of dye adsorbed depends on the concentration of the dye present in the subphase. It was observed that the adsorption process mainly occurred due to the electrostatic interaction between the cationic amino group of long chain amine and the anionic part of EB. The spectroscopic characteristics of the mixed LB films, solution, have been compared using UV-vis absorption and fluorescence spectroscopic data. These studies indicate the formation of aggregates in the thin films. Scanning electron microscopic study certainly confirms the presence of aggregates of EB dye in the (ODA-EB) mixed LB films.