Pankaj Bharmoria

Complexation of chitosan with surfactant like ionic liquids: Molecular interactions and preparation of chitosan nanoparticles

Interactions and behavior of chitosan (Ch) with surface active ionic liquids (ILs)- 1-butyl-3-methylimidazolium octylsulfate, [C4mim][C8OSO3] or 3-methyl-1-octylimidazolium chloride, [C8mim][Cl]-have been probed at the air solution interface and in the bulk in aqueous media at pH 3.0 using a multi-technique approach, viz. tensiometry, conductometry, turbidimetry, dynamic light scattering (DLS), and atomic force microscopy (AFM). At the interface, a strong complexation is observed in Ch-[C4mim][C8OSO3] system. Bulk [C4mim][C8OSO3] interacts with Ch to form Ch-[C4mim][C8OSO3] complexes which precipitate out at higher IL concentrations, whereas comparatively weaker Ch-[C8mim][Cl] complexes remain solubilized in the solution. DLS measurements showed that the Ch chains contract before the cmc and expands after the cmc upon interaction with both the ILs. Interaction of ILs with Ch resulted in facile preparation of uniformly distributed Ch nanoparticles with good sphericity and control which have been verified using DLS, SEM, AFM, and fluorescence microscopy. The present study provides an understanding of forces governing the complexation behavior of Ch with surface active ILs and their efficacy to produce Ch nanoparticles.

Interactional behaviour of surface active ionic liquids with gelling biopolymer agarose in aqueous medium

Interactions of surfactant-like ionic liquids (ILs), 1-butyl-3-methylimidazolium octylsulfate [C4mim][C8OSO3] and 3-methyl-1-octylimidazolium chloride [C8mim][Cl] with the neutral biopolymer agarose (Ag) has been investigated in aqueous media through an array of techniques, viz. tensiometry, isothermal titrimetric calorimetry (ITC), turbidimetry, dynamic light scattering (DLS), conductometry, scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Tensiometric and calorimetric profiles of the studied systems showed three transitions corresponding to the critical aggregation concentration C1(cac), the saturation concentration C2(sc), and the critical micelle concentration C3(cmc). The tensiometric behaviour of both the systems is found to be more like charged polymer–surfactant systems because of the large number of electron rich oxygens in the Ag chain. Interactions in the Ag–[C4mim][C8OSO3] system were found to be weaker when compared with the Ag–[C8mim][Cl] system because of higher cation–anion interactions in the former as evidenced by low a van’t Hoffs factor (∼1.0) of [C4mim][C8OSO3] in the studied concentration regime. ITC measurements showed that both the ILs interact exothermically below 6 mmol kg−1 with Ag and endothermically thereafter until C3(cmc) is reached. Turbidimetric and DLS profiles have shown coacervate formation of Ag with both the ILs. The complex formation has been verified by SEM images, which have shown that Ag nanoplates change into spherical complexes upon interaction with the ILs. FTIR spectra indicated hydrogen bonding between IL ions and Ag in various concentration regimes. The study can be useful in understanding the importance of ion–dipole, hydrogen bonding and hydrophobic interactions in Ag sol–gel systems, which are often used as matrices for electrophoresis of charged molecules.

A reciprocal binary mixture of protic/aprotic ionic liquids as a deep eutectic solvent: physicochemical behaviour and application towards agarose processing

Apart from structural tuning, the desired properties of ionic liquids (IL) can be achieved through judicious mixing of two or more ionic liquids. Herein we have investigated the alterations in the physicochemical properties of protic/aprotic ILs, (2-hydroxyethylammonium formate/1-butyl-3-methylimidazolium chloride) upon reciprocal binary mixing. Melting point analysis of the mixtures at various mole fractions showed their deep eutectic solvent nature. The variation in physical properties like density, speed of sound, and viscosity have been measured and utilized to derive the volume of mixing, isentropic compressibility, and activation energy of the viscous flow. Unlike the binary mixtures of ILs having common cations or anions, the investigated reciprocal binary mixture showed significant non-ideality, normally desired to take advantage of improved solvent properties. The polarity and ion–ion interactions have been studied through solvatochromic parameters (normalized Reichardts parameter, dipolarity/polarizability, and hydrogen bond donor and acceptor coefficients) derived using solvatochromic probes. The prepared binary mixtures have been utilized for the dissolution of a gelling biopolymer agarose and formation of ionogels. Dissolution of agarose has been correlated with the solvatochromic parameters and the viscoelastic behaviour of ionogels is discussed in light of rheological measurements. The work gives fundamentally useful insights into tuning the properties of ILs for a specific application purpose.

Generalized synthesis and evaluation of formation mechanism of metal oxide/sulphide@C hollow spheres

Herein, we report a generalized novel soft-template approach for the synthesis of a variety of uniform metal oxide (MoO2, Fe3O4, V2O3) and sulphide (MoS2, ZnS)@C hollow spheres using sucrose and cetyl trimethylammonium bromide (CTAB) as a soft template. The synthesized hollow spheres are uniform in size, with a size range of 800 nm to 1.3 μm. The developed methodology allows for altering the carbon content by just varying the amount of sucrose in the precursor solution. The formation mechanism of the soft template was also studied by using isothermal titration calorimetry (ITC), infrared (IR) spectroscopic analysis and scanning electron microscopy (SEM) of the intermediate. The strategy was developed based on the in situ formation of the spherical soft template by the interaction of sucrose and CTAB under the experimental conditions, formation of an inorganic shell by the interaction of a metal salt and template surface, carbonization of sucrose under hydrothermal conditions, and finally formation of the desired metal oxide/sulphide@C through calcination under 5% H2 in a flow of N2. Using the synthesized MoS2@C hollow sphere as a typical representative of such hollow spheres, its performance was examined as an anode for a lithium-ion battery to determine the applicability of the developed procedure; it exhibited a high specific capacity (∼1100 mA h g−1 at 150 mA g−1) as a lithium-ion battery (LiB) anode.

Modulation of Micellization Behavior of Cetyltrimethylammonium Bromide (CTAB) by Organic Anions in Low Concentration Regime

Micellization of the cationic surfactant cetyltrimethylammonium bromide (CTAB) in dilute aqueous solutions of sodium butyrate (Na-Bu), sodium benzoate (Na-Ben) and sodium salicylate (Na-Sal) at different concentrations, viz. 0.005, 0.01, and 0.05xa0mol·L−1, has been investigated. Conductivity, steady-state fluorescence, dynamic light scattering (DLS), atomic force microscopy (AFM), and 1H NMR techniques shed light on different aspects of micellization. Various micellization parameters such as critical micelle concentration (cmc), degree of ionization of micelle (α), and standard Gibbs energy of micellization (

Ionic liquid-induced all-α to α + β conformational transition in cytochrome c with improved peroxidase activity in aqueous medium

Delta G_{text{m}}^{text{o}}

Illuminating microemulsions: ionic liquid–CdS quantum dots hybrid materials as potential white light harvesting systems

ΔGmo) have been obtained from conductivity measurements. Steady-state fluorescence has provided useful information about the cmc, polarity of cybotactic region and aggregation number of micelles of CTAB using pyrene as fluorescent probe in various aqueous salt solutions. The data have been analyzed in terms of hydrophobicity/hydrophilicity and polarizability of the anions of the added electrolytes. The content and nature of organic anions governs the shape and size of the micelles as revealed by DLS and AFM measurements. In the dilute concentration regime of added electrolytes, contrary to most of the reported studies pertaining to very high concentration of added electrolyte, no worm like micelles forming a gel like structure have been observed. 1H NMR experiments provided information about the sites of interaction of anions of added electrolytes with the surfactant head group.Graphical abstract