Physical Chemistry Research
Volume:8 Issue: 1, Winter 2020

In this work, we described a cost-effective and environmentally friendly technique for green synthesis of colloidal silver nanoparticles from aqueous extract of fresh leaves of Acacia melanoxylon and its application as a dopamine and hydrogen peroxide sensor. The prepared silver nanoparticles were characterized by UV-Visible absorption spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), zeta-potential analysis, thermogravimetric analysis (TGA), differential scanning calorimeter (DSC), etc. This method was found to be cost-effective, eco-friendly when compared to that of chemical and physical methods of nanoparticle synthesis. Silver nanoparticles modified carbon paste electrode (CPE) was fabricated for the detection of dopamine and hydrogen peroxide. The fabricated electrode showed an excellent sensitivity towards the oxidation of both dopamine (DA) and hydrogen peroxide (H2O2) in 0.1M phosphate buffer (PBS) solution at a pH 7. The effect of the scan rate, the concentration of the modifier and the analyte were studied by the cyclic voltammetric technique. The result exhibits good electrocatalytic activity, diffusion-controlled process and linear increase in peak current with different concentrations of dopamine and hydrogen peroxide.

The effect of different media on the kinetics and mechanism of formation of diethyl (1S, 2S)-3, 3-dibenzoylcyclopropane-1, 2-dicarboxylate was investigated. The reaction was accelerated with changing the medium from non-ionic to ionic. Among the selected ionic salts, NaCl was the best salt to increase the reaction rate of the titled synthesis about 2.5-fold (kobs = 1.295 M-1.min-1 against kobs = 3.105 M-1.min-1). The incremental effect of ionic salts was found to be in this order: NaCl > NaBr > KBr > KCl. Isokinetic plots for the reaction in the presence of different salts were obtained and a linear relationship which indicated an identical mechanism for all reactions, was found. Moreover, the effect of cationic, nonionic, and anionic surfactants on the reaction rate was evaluated. Substantial reduction on the reaction rate and change in the mechanism was observed with the addition of an anionic surfactant such as sodium dodecyl sulfate. The values of activation parameters were also estimated (ΔH‡ = 80.1 ± 0.6 kJ.mol-1, ΔS‡ = 23.9 ± 2.0 J.mol-1.K-1, and ΔG‡ = 72.9 ± 1.1 kJ.mol-1) and the positive value of ΔH‡ confirmed the endothermic process and entropy value referred to an associative mechanism.

Nowadays, one important environmental problem is the pollution from dyes that obtains from industry activities. The adsorption of pollutant by new and useful materials has been studied by scientist. In this research, P-doped graphitic carbon nitride was prepared by the facile strategy with phosphoric acid and melamine. The characterization of the P-doped graphitic carbon nitride (P-g-C3N4) was determined by FT-IR, XRD, SEM, and BET analysis. This preparation method was simple, easy and efficient strategy compared to other methods. The as-synthesized P-doped g-C3N4 was applied for the adsorption of methylene blue. The results were analyzed using the isotherms of Langmuir and Freundlich. The best fit was resulted from Langmuir isotherm having an R2 value of 0.98. The maximum adsorption capacity (qmax) from the Langmuir isotherm was determined 100 mg/g when pH, adsorbent dosage, initial concentration of methylene blue, contact time are 8, 0.07 g, 8 ppm and 60 min at 18 ᴼC. The adsorption on the P-doped graphitic nitride matched pseudo-second order model. These findings suggest it as an efficient material to adsorb methylene blue.

Oil spills and subsequent pollution of marine ecosystems are associated with oil exploitation. The ultimate fate of unrecoverable portion of spilled oil is biodegradation by microorganisms. Rhodococcus sp. Moj-3449 has proven ability of growth on aliphatic hydrocarbons. In this study Response Surface Methodology was employed to optimize the biodegradability of Moj-3449 by changing salinity, pH, temperature and n-C16 concentration. The duplicate experiments conducted were based on a 5-levels rotatable and orthogonal central composite design (CCD) done in 2 separate blocks. The effect of each factor and their interactions on the biodegradation of n-C16 revealed that the optimal conditions for the biodegradation are 0 % salinity at pH= 6.97, T=28°C and 52.98 % wt/V n-C16 concentration. Under these conditions, the maximum biodegraded amount was predicted at 45.52 % wt/V out of 52.98 % wt/V. The experimentally obtained biodegradation amount at the optimum condition was 44.27 ±0.07 % wt/V. The ability of the strain to effectively break down long-chain n-alkanes at concentration up to 55 % wt/V shows at that this strain is an outstanding candidate for industrial bioremediation of crude oil spills in marine environment.

In this study, molecular docking, quantum mechanics and molecular dynamics methods were used to investigate protein-ligand interactions of the epidermal growth factor receptor 2 (HER2 ). The virtual screening was performed by docking among 2000 chemicals derived from the ZINC library to find specific inhibitors. Trastuzumab is the active site in the HER2 extracellular domain and the target area. The scoring function was used to calculate the binding affinity of the found inhibitors to the active site of the HER2. Among the found inhibitors, six ligands were chosen based on suitable electronic structure and energy. The H-bond interaction energies between six ligands and HER2 were investigated and bond critical points were determined for each bond path between the two corresponding atoms by the quantum theory of atoms in molecules. Root mean square deviation, root mean square fluctuation, the radius of gyration and binding free energy were calculated to check and evaluate the stability and mobility of the simulated system using molecular dynamics simulation.

The present study describes the metal chelating ability of 3-Hydroxyflavene, Deferiprone and Maltol with Ni2+ metal ion using density functional theory. Structural analysis indicates that all three chelators bind to Ni2+ ion as a two-dentate chelator. Donor-acceptor interactions show an effective charge transfer from the oxygen atoms of the chelators towards Ni2+. Quantum theory of atoms in molecules analysis shows that the non-covalent interactions, mainly, electrostatic interactions play an important role in the complex formation of the selected chelators and Ni2+ ion. The TD-DFT study was applied in order to investigate the main electron transition. The ELF and LOL analysis was applied to confirm the result obtained from the QTAIM. Interaction energies and metal ion affinity were calculated for the [Ni(L)2] complexes and the results revealed a highly exothermic reaction during the chelation process. Natural bond analysis (NBO) and natural population analysis (NPA) and spin density evaluation were carried out in order to understand the charge transfer in the studied complexes. The NCI–RDG isosurface of the studied complexes show a complete set of electrostatic interactions, which encompass van der Waals interactions. The results verified that the selected chelators could be considered as effective chelating agents for Ni therapy.

In order to find simple, effective and economical methods for dye adsorption, the present work aims at studying the adsorption efficiency of an azo dye “Calcon’’ by polyaniline (PA) films prepared by the electrochemical method. The characterization of these films by X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV–visible spectrophotometer showing an amorphous fibrillary structure of the PA electrodeposited. To find the best conditions for adsorption of Calcon dye, the effect of pH, hydrogen peroxide, contact time and the initial Calcon concentration were studied. These experiments showcased the possibility of increasing the adsorption capacity from 42% to 54% changing pH from 9 to 3. This value increases to 98.6% by the addition of hydrogen peroxide. On the other hand, the effect of Calcon concentration was studied from 15 to 50 mg/L, the results indicated that the discoloration of Calcon dye decreases with the increase of the dye concentration. However, Kinetics and isotherm studies have shown that the adsorption reaction follows the pseudo-second-order model, the adsorption process follows the Langmuir isotherm model, and the PA electrodeposited has a monolayer adsorption capacity of 606mg/g which is considerably high compared to all polyaniline forms prepared chemically.

Pancreatic cancer is an aggressive cancer, usually with poor prognosis, as it is mostly discovered at an advanced stage of development where treatment is challenging. Using principal components analysis (PCA) of variable selection, multiple linear regression (MLR), multiple non-linear regression (MNLR) and the artificial neural network (ANN), 2D-QSAR models for the anti-pancreatic cancer activity are developed from a set of twenty three molecules of 1, 2, 4-triazole derivatives to build the QSAR models. The well generated MLR and MNLR models exhibit the cross validation coefficients Q2 of 0.51 and 0.90, respectively. Moreover, the predictive ability of those models has been evaluated by the external validation using a test set of four compounds with predicted determination coefficients R2test of 0.936 and 0.852, respectively. The artificial neural network (ANN) method has shown a correlation coefficient of 0.896 with an architecture 3-2-1. The obtained results indicate the validation and the good quality of the 2D-QSAR models.

In recent years, there is great attention by researchers in ionic liquid due to the huge potential for separation and reaction technology. Also, the heat capacity of ionic liquids is a substantial parameter for conclusive process designs and engineering calculations. A database for the heat capacity of ionic liquids created by compiling experimental data onto literature covering the period from 1971 to 2016 is reported. In this work, a temperature-dependent equation to the heat capacity for 141 pure ionic liquids is proposed. A database containing 6961 experimental data was used for the development of this model. Finally, a 7-parameter simple equation with the capability for predicting the heat capacity of ionic liquids is presented. The accuracy of the new model has been compared to the most precise models in the literature and the comparison indicates that the proposed method provides more accurate results than other models considered in this work. The average absolute percentage deviation from the new model is only 3.83%.

 Quantum-chemical calculations were performed to study the complexation of drug molecule procaine hydrochloride with beta cyclodextrin (β-CD) in the gas phase and in water. The inclusion process was optimized by the semi empirical method PM3 and the obtained complex structure was further refined by ONIOM method (DFT: PM3). It is found that (B3LYP/6-31G(d,p) : PM3) provides the best energy minimum for the complex, compared to M06-2X and WB97XD functional. Given the energy profile, the configuration of the complex formed indicates that the benzene ring is completely included in the hydrophobic cavity of the β-CD. The thermodynamic parameters analysis has shown that the procaine/β-CD complexation is enthalpically favorable, and the complex is well structured. Natural bond orbital (NBO) analysis indicates that no hydrogen bond interaction exists, and the procaine/β-CD complex is mainly stabilized by Van der Waals forces. 1D 1H NMR spectra analysis shows that the procaine molecule penetrates into the cavity of this CD with the aromatic ring.

In an analytical way effective Debye temperature computations of functional materials are extended to organic liquid mixtures using ultrasonic velocity and density measurements. Thermal properties of organic liquid mixture containing Aniline + Toluene, Aniline + o-Xylene and Aniline + Mesitylene over different mole fractions have been explained using Debye temperature variations and they are scrutinized to bring out the molecular association due to thermal energy changes of binary liquid mixtures. The results including computation of Debye temperatures using standard formula, ideal mixture relation and modified Lorentz-Bertholet combination mixing rule and their deviations are used to explain thermal energy changes of component molecules in liquid mixtures and their association.

Along with the development of science and technology, the attention of researchers has been drawn to the use of the catalysts for removing pollutants from oil. In this research, the oxidative degradation of quinoline using CuO/MCM-41 nanoparticles was optimized, in the presence of ultraviolet radiation without any auxiliary oxidants using Response Surface Methodology (RSM). The CuO/MCM-41 nanocomposite was synthesized by applying a facile method and was investigated using XRD, FESEM, EDS, Mapping, FTIR, and BET/BJH techniques. The degradation efficiency was measured by a UV spectrophotometer, and was evaluated by the use of the GC-MASS technique. The results indicated that the highest removal of quinoline without using auxiliary oxidant and with the help of synthetic catalyst was about 84%.