Faculty Publications
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Item Hydrophilicity of the hydrophobic group: Effect of cosolvents and ions(Elsevier B.V., 2019) Dilip, H.N.; Chakraborty, D.Classical molecular dynamics simulations were performed to study the effect of cosolvents and ions on the solvation structure of zwitterionic glycine in liquid water. Simulations were carried out for 2 M and 1 M concentration of TMAO, Urea, KCl and LiCl solutions to observe the changes in liquid structure of water near the glycine molecule. Radial distribution functions and spatial distribution functions showed the presence of protective hydration layer near the C ? in presence of TMAO which gets reduced in case of urea, KCl and minimum in case of LiCl. LiCl is found to disrupt severely the solvation structure near the glycine molecule. For LiCl system, a small hydration layer is found near C ? unit at higher distances which is mainly due to the first hydration shell of lithium ion bonded to the carboxylate group. Presence of these hydration layers gives extra stabilization energy to the glycine water system. Stabilizing and destabilizing effect of water near the glycine molecule is calculated in terms of Potential Mean Force. The anomalous behaviour of lithium salts with respect to Group I cation salts in protein stabilization can be explained on the basis of this behaviour. We found maximum hydrogen bond lifetime for water molecules in presence of TMAO followed by LiCl, KCl and least in case of urea. The higher lifetimes in presence of ions are found mainly due to their electrostatic force. The stabilization of the hydrophobic part of the glycine molecule can be correlated with the stabilization of proteins in presence of these cosolvents. © 2019 Elsevier B.V.Item Effective inhibition of mild steel corrosion by 6-bromo-(2,4-dimethoxyphenyl)methylidene]imidazo [1,2-a]pyridine-2-carbohydrazide in 0.5 M HCl: Insights from experimental and computational study(Elsevier B.V., 2021) Vranda Shenoy, K.; Venugopal, P.P.; Reena Kumari, P.D.; Chakraborty, D.A new inhibitor, 6-bromo-(2,4-dimethoxyphenyl)methylidene]imidazo [1,2-a]pyridine-2-carbohydrazide (DMPIP) was evaluated as a corrosion inhibitor for Mild Steel (MS) in 0.5 M HCl solution at 303–323 K using potentiodynamic polarization and electrochemical impedance spectroscopic (EIS) techniques. Both the techniques confirmed an increase in inhibition efficiency with the concentration of DMPIP but decrease with temperature. The highest inhibitive action (96.7%) was registered at 303 K for 500 ppm of DMPIP concentration. Polarization study revealed mixed inhibition action by DMPIP. Nyquist plot obtained for MS using EIS technique showed two capacitive loops on addition of inhibitor to HCl solution confirmed the inhibitory action of DMPIP via adsorption at the metal/solution interface. The surface morphology analysis was carried out by SEM, EDX and FTIR techniques. The adsorption process was demonstrated using Langmuir's adsorption isotherm model. The thermodynamic parameters (?Goads, ?Hoads) indicated that the adsorption was spontaneous and done by physisorption. Further, quantum chemical studies using Density Functional Theory (DFT) elucidated that the formation of Fe-DMPIP complex presumably due to the interaction of protonated form of DMPIP with the empty d orbitals of the iron atom. © 2021 Elsevier B.V.Item Exploring the potential role of quercetin in corrosion inhibition of aluminium alloy 6063 in hydrochloric acid solution by experimental and theoretical studies(Taylor and Francis Ltd., 2022) Kumari, D.; Venugopal, P.P.; Reena Kumari, P.D.; Chakraborty, D.Quercetin was evaluated as corrosion inhibitor for AA6063 in 0.5 M HCl solution by employing weight-loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Analysis (EDX), Atomic Force Microscopy (AFM), X-Ray photoelectron spectroscopy (XPS) techniques allied to quantum chemical studies. Electrochemical results substantiate that the inhibition efficacy of quercetin increases proportionally with the concentration of the inhibitor. The effect of temperature on the corrosion behavior of the alloy was studied in the range of 30–60 °C. Potentiodynamic polarization study confirms the mixed type of inhibition by quercetin with preferential control of the cathodic reaction. The adsorption of quercetin on alloy surface was explained through the Langmuir adsorption isotherm model. ΔG°ads values and its variation with the temperature ensured spontaneous adsorption through chemisorption and the process was endothermic. Further, quantum chemical parameters calculated from Density Functional Theory (DFT) method for quercetin, proved a perfect correlation between structure and corrosion inhibition efficiency. © 2021 Informa UK Limited, trading as Taylor & Francis Group.Item Anti-corrosion investigation of a new nitro veratraldehyde substituted imidazopyridine derivative Schiff base on mild steel surface in hydrochloric acid medium: Experimental, computational, surface morphological analysis(Elsevier Ltd, 2022) Shenoy K, V.; Venugopal, P.P.; Reena Kumari, P.D.; Chakraborty, D.Intensive research has recently been directed toward synthesizing novel, non-toxic, and cost-effective organic inhibitors against metallic corrosion. In the present investigation, a non-toxic, novel Schiff base inhibitor, 6-bromo-(4,5-dimethoxy-2-nitrophenyl) methylidene] imidazo[1,2-a] pyridine-2-carbohydrazide (NVAIP) was synthesized and tested for its corrosion inhibition performance on Mild Steel (MS) in 1 M HCl at 303–323 K using potentiodynamic polarization study, electrochemical impedance spectroscopy (EIS) measurements, Scanning Electron Microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX), Atomic Force Microscopy (AFM) and X-Ray Photoelectron Spectroscopy (XPS) analyses. The electrochemical results stated the inhibition effectiveness (ƞ%) of NVAIP was dependent on concentration and temperature, with the maximum efficiency (92.3%) recorded at 303 K for 500 ppm. The mixed-type inhibitory effect of NVAIP was substantiated by the polarization test results. The Langmuir adsorption isotherm model accorded with the metal surface evaluated, and Gibbs free energy of adsorption values ranged from - 35.05 to-36.05 kJ/mol, implying a physical and chemical adsorption mechanism. Surface morphological analysis was carried out to characterize the chemical composition of the adsorbed inhibitor on the MS surface, and these techniques confirmed that the inhibitive layer is composed of an iron oxide/hydroxide mixture where NVAIP molecules are incorporated. Further, the physicochemical and electronic properties of the NVAIP were investigated using Density Functional Theory (DFT) and electrostatic potential energy mapping (ESP). ΔEads value of −57.21 kcal/mol obtained from Molecular Dynamic (MD) simulations correlates well with the experimental results. Moreover, the relevance of the molecular structure of NVAIP and its inhibition act was validated by quantum chemical calculations and molecular dynamic (MD) simulation studies. A possible inhibition mechanism was proposed based on the experimental, theoretical, and surface analysis results. The outcomes of all the techniques show consistent agreement with each other. © 2022 Elsevier B.V.