Water Structure Modification by Sugars and Its Consequence on Micellization Behavior of Cetyltrimethylammonium Bromide in Aqueous Solution

Water structure modification by d-(+)-glucose at different concentrations and temperatures-effect of mutarotation

Water structure modification by carbohydrates is essential both in chemistry and life processes and in particular, molecular level interaction of glucose with water is very important. With a view to developing a fundamental knowledge base, thermodynamic parameters derived from measurements of density, viscosity, and refractive index have been analyzed to investigate how d-(+)-glucose alters the structure of water at various concentrations and temperatures. The nature and extent of the interactions have been investigated using apparent molar volume, Jones-Dole constants, changes in free energy (ΔG), changes in entropy (ΔS), and changes in enthalpy (ΔH) for viscous flow. Using measurements from dynamic light scattering (DLS), the sizes of the aggregates were studied. The kinetics of mutarotation have been investigated using polarimetry and the structural effect on water during mutarotation between α-d-glucose and β-d-glucose with time has been explored by near-infrared (NIR) spectroscopy. The spectroscopic results were examined using difference spectroscopy and two-dimensional correlation spectroscopy (2DCOS). The absorption bands of water shift to a higher wavenumber irrespective of the concentration of the solution with time due to the enhancement of the cleavage of hydrogen bonding in water. At high temperatures, three bands in the region 7100-7350 cm^-1 are attributed to the first overtones of the hydrogen-bonded -O-H stretching vibration. Refractive index values indicate an increase in the density of the anomer solutions with time, suggesting an increase in free water concentration. These results provide evidence for more than one water molecule being involved in the mechanism of mutarotation and propose a concerted mechanism for proton transfer.

The Influence of Freeze-Dried Alcohol-Water Extracts from Common Yarrow (Achillea millefolium L.) and German Chamomile (Matricaria chamomilla L.) on the Properties of Elastomer Vulcanizates

This research work aimed to investigate the properties of freeze-dried extracts from Matricaria chamomilla L. and Achillea millefolium L. and to perform a characterization of their impact on the natural rubber-based vulcanizates. First, extracts were prepared in three different solvents at selected volume ratios: water (100), water-methanol (50/50), and water-ethanol (50/50). Next, the freeze-drying of extracts was established and then obtained bio-additives were introduced to the rubber mixtures. Freeze-dried extracts were investigated by UV-VIS diffuse reflectance spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), Near-Infrared spectroscopy (NIR) and thermogravimetric analysis (TGA). Antioxidant activity and total phenolic content (TPC) were also defined. Rubber mixtures were examined in a rheometer and after vulcanization they were subjected to accelerated simulated aging by UV radiation and thermo-oxidative aging. To determine the resistance of vulcanizates to the degradation processes, the study of cross-linking density (equilibrium swelling method), mechanical properties (tensile strength, elongation at break) and color change were conducted. Performed studies proved the antioxidant activity of freeze-dried extracts caused by the high content of polyphenols and their beneficial influence on the properties of elastomer vulcanizates.

Molecular level interactions in binary mixtures of 1-ethyl 3-methylimidazolium tetrafluoroborate and water

NIR spectroscopic analysis and DLS measurements were carried out to study hydrogen bonding and aggregation in ionic liquid–water binary mixtures.

Effect of temperature perturbation on hydrogen bonding in aqueous solutions of different urea concentrations

Water structure modifications with urea and temperature have been studied in aqueous solution by analyzing changes in hydrogen bonding and the extent of aggregation.

Temperature perturbed water structure modification by d(−)-fructose at different concentrations

Temperature dependence of water structure modification has been studied at different d(−)-fructose concentrations by near-infrared (NIR) spectroscopy.

An approach towards the synthesis and characterization of ZnO@Ag core@shell nanoparticles in water-in-oil microemulsion

Water-in-oil microemulsions have been found to be good templates for synthesis of ZnO and ZnO@Ag nanoparticles and offered themselves as ideal ‘nanoreactors’ for uniform fabrication of core@shell nanoparticles.