QM/MM Studies on Cyclodextrin-Alcohol Interaction

The main objective of this study is to provide an insight into the interactions involved during adsorption of the alcohols on β-CD composite nanostructured membrane. Interactions between β-cyclodextrin (β-CD) and alcohols (methanol, ethanol and butanol) are studied using the QM/MM method. Magnitude of interaction energies show that the alcohols are adsorbed on the membrane. In addition, the thermochemical analysis suggests that the formation of these host-guest complexes is enthalpy driven.     

Fluorogenic ratiometric dipodal optode containing imine-amide linkages: Exploiting subtle thorium (IV) ion sensing

The (13E,19E)-N1′,N3′-bis[4-(diethylamino)-2-hydroxybenzylidene]malonohydrazide (L) has been developed for the detection of Th⁴⁺ ions using dual channel signalling system. The UV–vis absorbance and fluorescence spectroscopic data revealed the formation of L–Th⁴⁺ complex in 1:1 equilibrium. The density functional theory (DFT) also confirms the optimum binding cavity for the recognition of metal ion. The binding constant computed from different mathematical models for an assembly of L–Th⁴⁺. The detection limit of L for Th⁴⁺ recognition is to a concentration down to 0.1 μM (0.023 μg g⁻¹). The present sensing system is also successfully applied for the detection of Th⁴⁺ ion present in soil near nuclear atomic plants.     

Effective Behavior Near Clogging in Upscaled Equations for Non-isothermal Reactive Porous Media Flow

For a non-isothermal reactive flow process, effective properties such as permeability and heat conductivity change as the underlying pore structure evolves. We investigate changes of the effective properties for a two-dimensional periodic porous medium as the grain geometry changes. We consider specific grain shapes and study the evolution by solving the cell problems numerically for an upscaled model derived in Bringedal et al. (Transp Porous Media 114(2):371–393, 2016. doi: 10.1007/s11242-015-0530-9). In particular, we focus on the limit behavior near clogging. The effective heat conductivities are compared to common porosity-weighted volume averaging approximations, and we find that geometric averages perform better than arithmetic and harmonic for isotropic media, while the optimal choice for anisotropic media depends on the degree and direction of the anisotropy. An approximate analytical expression is found to perform well for the isotropic effective heat conductivity. The permeability is compared to some commonly used approaches focusing on the limiting behavior near clogging, where a fitted power law is found to behave reasonably well. The resulting macroscale equations are tested on a case where the geochemical reactions cause pore clogging and a corresponding change in the flow and transport behavior at Darcy scale. As pores clog the flow paths shift away, while heat conduction increases in regions with lower porosity.     

Effect of time dependent morphological parameters of nanoclusters on perikinetic heat conduction and induced micro-convection mechanisms of oxide based nanofluids

The article represents an experimentally supported quantitative analysis to observe the effect of time, temperature, nanoclusters’ morphology, and instantaneous volume fractions on perikinetic heat conduction and Brownian motion-based induced convection mechanisms of oxide (Al₂O₃ and TiO₂, size 25–30 nm) based nanofluids. The appropriate models of thermal conductivity have been introduced to study the effect of various parameters such as; varying volume fractions, suspensions’ stabilities, nanoclusters’ growth, temperature, and the liquid layering. The developed model could predict the thermal conductivity enhancements of nanofluids within the accuracy of ± 0.5% to ± 4.5.0% in the temperature range from 20°C to 50°C.

Abbreviations: DI: De-ionized water; DLS: Dynamic light scattering; XRD: X-rays diffraction; TEM: Transmission electronic microscope; SDBS:Sodium dodecyl benzene sulphonate.

Figure Effect of temperature on the Brownian Reynold number for Al₂O₃-H₂O and TiO₂-H₂O nanofluids.     

A new lawsone azo-dye for optical sensing of Fe3+ and Cu2+ and their DFT study

A new lawsone-based azo-dye 2-hydroxy-3-((pyridin-2-ylmethyl)diazenyl)naphthalene-1,4-dione (1) was synthesized and applied for sensing of metal ions. Receptor 1 showed selective fluorescent and colorimetric response for the detection of Cu²⁺ and Fe³⁺ over other tested metal ions. The fluorescence intensity of 1 was significantly quenched allowing detection of Fe³⁺ and Cu²⁺ down to 0.61 and 6.06 μM, respectively. The binding has been established by fluorescence spectroscopic method. Receptor 1 provided a 1?:?1 binding scaffold for recognition of Fe³⁺ and Cu²⁺ ions with the association constant of 3.33 × 10⁶ and 3.33 × 10⁵ M^?1, respectively. The B3LYP/6-31G/LANL2DZ method was employed for the optimization of 1 and 1·Fe³⁺ and 1·Cu²⁺.     

Temperature-dependent volumetric and viscometric properties of amino acids in aqueous solutions of an antibiotic drug

Volumetric and viscometric properties of glycine and methionine (amino acids) in a 0.2 vol. % amikacin sulphate (antibiotic drug) aqueous solution with the molality range of 0.025 mol kg^?1–0.25 mol kg^?1 were measured over the temperature range of 20°C–40°C at the interval of 5°C. Different parameters like apparent molar volume (? _V), apparent molar adiabatic compression (? _κ ), isentropic compression (κ _S) along with other acoustical parameters were calculated. Parameters like viscous relaxation time (τ), free volume (V _F), internal pressure (Π _I), and molar cohesive energy (MCE) were calculated from dynamic viscosity measurements. The ? _V values are positive in both cases, but with higher magnitude observed in methionine. These positive values of ? _V are indicative of strong solute-solvent interactions at all temperatures. In case of methionine there is a sharp initial increase in the ? _V values which become almost constant with further additions of the amino acid. Structural differences in the two amino acids studied are clearly reflected in the different nature of the plots of different parameters. In case of an amino acid-drug system, dynamic viscosity increase has been attributed to the increase in the hydrophilic-ionic and hydrophilic-hydrophilic interactions with the increase in the amino acid concentration which in turn may cause more frictional resistance to the flow of the solution. All other parameters are discussed in terms of solute-solvent and solvent-solvent interactions.     

Volumetric and Conductance Studies of Cetyltrimethyl Ammonium Bromide in Aqueous Glycine

Apparent molar volumes (? _v ), apparent molar adiabatic compressions (? _κ) and thermodynamic parameters of cetyltrimethyl ammonium bromide (CTAB) in 0.001, 0.01, 0.05 and 0.1 mol·dm^?3 aqueous solution of glycine in the temperature range 25–40 °C (at an interval of 5 °C) have been determined from density, speed of sound and conductometric measurements, respectively. The above calculated parameters were found to be sensitive to the interactions prevailing in the glycine–CTAB–water system. The analysis of the data was found to suggest that the ? _v and ? _κ values decrease sharply in the pre-micellar region and thereafter the decrease is almost linear at all concentrations of glycine, showing the dominance of hydrophobic interactions and facilitating the process of micellization. The ? _v and ? _κ values of these surfactants are found to be completely consistent with temperature over the entire concentration range. From conductance studies, the value of critical micelle concentration has been calculated, which shows dependence on the concentration of glycine as well as on temperature. A reasonably good qualitative correlation is found to exist with regard to CTAB–glycine interactions obtained from the conductance measurements and those from density and sound velocity measurements. All these observations demonstrate that this amino acid–surfactant system behaves in a different manner as compared to amino acid–electrolyte systems.     

First Dual Responsive “Turn-On” and “Ratiometric” AIEgen Probe for Selective Detection of Hydrazine Both in Solution and the Vapour Phase

A new dual responsive “turn-on” and “ratiometric” aggregation-induced emission luminogen (AIEgen) 3-formyl-5-(piperidin-1-yl)biphenyl-4-carbonitrile 6 a (FPBC 6 a ) for selective detection of hydrazine in solution as well as in vapour phase is described. At a low concentration of 2.5 μm , the probe FPBC 6 a is non-fluorescent (turn-off) but remarkably lights up (turn-on with blue emission) in the presence of hydrazine solution (0.25–25 μm ). Interestingly, at higher concentrations, the nanoaggregates of FPBC 6 a (>25 μm , 99 % HEPES in DMSO) displayed ratiometric response in the presence of hydrazine with a remarkable hypsochromic shift from the green (500–550 nm) to blue regions (440–480 nm). Furthermore, a real application of FPBC 6 a was successfully demonstrated through the detection and visualization of hydrazine in live cervical cancer cells as well as using portable test strips.