Ajitesh Pal

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.

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.

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.

COMPARATIVE STUDY OF THE BEHAVIOR OF BATHOPHENANTHROLINE IN THE RESTRICTED GEOMETRY OF LANGMUIR–BLODGETT FILM WITH TWO DIFFERENT FATTY ACIDS

This communication reports the successful fabrication and the comparative study of Langmuir and Langmuir–Blodgett (LB) films of nonamphiphilic phenanthrene derivative, 1, 10 phenanthroline (bathophenanthroline) (BATH), when incorporated to a long chain fatty acid viz. heptadecanoic acid and stearic acid. Measurements of compressibility modulus from the surface pressure versus area per molecule isotherm indicate that the mixed film of BATH and SA is harder than that with HA. The plot of area per molecule versus mole fraction is the indication of some repulsive interactions between binary components of the mixed monolayer which facilitates the formation of aggregates. UV–Vis absorption spectroscopy and steady-state fluorescence spectroscopy confirms the formation of microcrystalline aggregates in the mixed LB films. Scanning electron microscopic study supports this observation. The dependence of various LB parameters in the mixed films such as mole fraction, number of layers and surface pressure of lifting have also been investigated in the light of electronic absorption spectroscopy.

Behavior of 1-Pyrene-Carboxaldehyde Mixed with a Polymer Matrix within the Nano-Dimensional Langmuir-Blodgett Films

ABSTRACT Mixed films of a polycylic aromatic hydrocarbon 1-pyrene-carboxaldehyde (PyCHO) and a polymer matrix, viz. isotactic poly(methyl methacrylate) (PMMA) were studied at the air–water interface by surface pressure versus area per molecule (π-A) isotherms. The diagrams obtained by plotting the mean area per molecule as a function of the molar fraction of PyCHO showed positive deviations from ideal conditions with a small exception indicating a repulsive type of interaction between PyCHO and PMMA molecules, resulting in the formation of aggregates. Spectroscopic as well as scanning electron microscopy (SEM) studies revealed that aggregates were present when the mixed film was transferred onto quartz substrates at different mole ratios of PyCHO.

Spectroscopic Characterization Of Niagara Blue Dye In The Restricted Geometry Of Layer-By-Layer Self-Assembled Films

Multilayer films can be precisely engineered on solid substrate via layer-by-layer (LbL) self-assemble technique using negatively charged organic dye and positively charged polyelectrolytes or surfactants. This communication first time reports the successful incorporation of an anionic dye Niagara blue (NB) in Polyallylamine hydrochloride (PAH) by electrostatic sequential alternative LbL adsorption. The photo-physical characteristics of LbL films are investigated by varying different parameters such as number of deposited layer, dipping time in dye solution, pH of PAH solution, concentration of the dye, etc. In addition, the interaction of NB with double tail surfactant Didodecyl dimethyl ammonium bromide (DDAB) at different concentrations is also studied in the light of UV–Vis absorption spectroscopy. Spectroscopic analysis reveals that NB has been successfully anchored to PAH or DDAB through electrostatic self-assembled technique and forms molecular aggregates. The formation of aggregates is further confirmed by atomic force microscopic (AFM) study.