Physical Chemistry Research
Volume:6 Issue: 2, Spring 2018

In this study graphene oxide (GO) was synthesized by using Hummer’s method. Low dimension graphene quantum dot nanoparticles (GQDs) were synthesized using pulse laser irradiation. Fourier Transform-Infrared Spectroscopy (FTIR), Ultraviolet-Visible (UV-Vis) spectroscopy and photoluminescence (PL) analysis were applied to study the GQDs characteristic. Scanning electron microscopy illustrated the morphology of GQDs and RGQDs. The results showed that the solution’s pH has an effect on the size and bandgap of GQD. We have shown a suitable method to construct GQDs with great bandgap control, which shows a bright horizon for investigating graphene’s potential applications in transparent electronics, transistors, sensors, energy harvesters. The successful attainment was size control by changing pH of solution and low coast synthesis process. The successful achievement was size control by changing pH of solution and low coast synthesis process.

The quantum chemical calculations were performed to investigate the interplay between the anion˗π and intramolecular hydrogen bond (IMHB) interactions in the various complexes of 1,3,5-triamino-2,4,6-trinitrobenzene (ANB) with Hˉ, Fˉ, Clˉ and Brˉ anions. For better understanding the cooperative effects, the parent molecules (ANB) and the corresponding complexes of 1,3,5˗trinitrobenzene with the mentioned anions are also considered, as a set of the reference points. In this regard, the IMHB and anion˗π interactions are comprehensively analyzed by energetic, geometrical, spectroscopic and topological descriptors. It was found that the coexistence of the anion˗π and IMHB increases the strength of both interactions. Furthermore, the influences of the anion-π and IMHB interactions on the significance of the π˗electron delocalization (π˗ED) of the resonance assisted hydrogen bond (RAHB) units and the aromaticity of the benzene ring are evaluated by the harmonic oscillator model of aromaticity (HOMA), as a geometry based index. According to the HOMA values, we concluded that the coexistence of the mentioned interactions decreases the aromaticity of benzene ring and increases the π˗ED of RAHB units. Finally, the strength of the non-covalent interactions and the significance of π˗ED and aromaticity strongly depend on type of the anion.

The molecular properties known to play an essential role in drug-receptor interaction of substructures models of bioactive molecules have been studied using chemical quantum calculations. 1,4-diformyl-piperazine and 1,4-dithionyl-piperazine have been used as models to probe conformational behaviors and some electronic properties of substructure of some tri-substituted piperazine showing dual anti-PAF and anti-HIV-1 activities. The containing sulfur atoms derivatives present different bioactivities than containing oxygen atoms ones. Our results show that the substitution of oxygen atom by sulfur atom induces changes of some activation energies when the conformers have similar structures. This substitution make also changes in the molecular shape, electronic potentials, partial charges distribution and HOMO and LUMO energies.

The ability of a material to supply heat by means of conduction is called thermal conductivity, which is defined by Fourier's equation. Thermodynamic data on environmental refrigerants have attracted considerable interest in the design and optimization of refrigeration equipment, such as heat compressors and exchangers. After analysis of statistical effects, a new simple correlation was developed for the thermal conductivity of refrigerants as a function of temperature. An optimization algorithm was used to obtain the constant parameters of the new equation by fitting them to the source databank. The accuracy of the presented equation was compared with commonly used models. Results indicated that the developed model provides more accurate results than those of other considered equations, with an average absolute percentage deviation of 3.46%.

The modified square well Potential is combined with perturbed-hard-trimer-chain (PHTC) EOS to predict the solubility parameter of several fluids including alkanes, refrigerants and molten polymers. The performance of the proposed model has been evaluated by predicting the solubility parameter of 12 hydrocarbons,3 refrigerants, and 12 polymers. From the 263 data points for hydrocarbons and refrigerants, the average absolute deviations (AAD) of the predicted densities and solubility parameter from the experimental ones were found to be 1.74% and 1.09% respectively. Besides, from 1993 data points of 12 polymers, the AADs of the predicted densities were found to be 0.43%and for 60 data points examined, the AAD of the predicted solubility parameters from the experimental ones were found 0.56%, respectively.

Electron transport properties of pure and Oxygen and/or Methyl substituted pyrene between two semi-infinite Aluminum atomic electrodes have been investigated by means of density functional theory plus the non-equilibrium green’s function method. The electrodes were represented by a slab of Al atoms oriented along the [111] plane. The computations were carried out in the bias voltage range of 0.0 up to 2.0 V under three gate voltages including -3.0, 0.0 and +3.0 V. The results showed negative differential resistance and relatively high rectification. All of the calculations were carried out with Open source Package for Material eXplorer (OPENMX) 3.6 computer code within the generalized gradient approximation for the exchange-correlation energy and Norm-conserving Kleinman–Bylander pseudo potentials. The observed rectifying and the negative differential resistance were justified using the transmission spectrum and its integration in the corresponding bias window. Also, the negative differential resistance behavior has been investigated by studying the density of states of left electrode, central region and right electrode and their overlaps.

This experiment is an investigation of used cooking oil as a sustainable and renewable resource for methyl ester production. with more than 95.5% production yield, thermally activated hydrated cement has been carefully discussed as a catalyst in the transesterification of used cooking oil into methyl ester to use waste cement as a heterogeneous catalyst for methyl ester production through electrolysis method. Acetone as a co-solvent was added to the reaction system for mass transfer-intensification. Theoretically, electrolysis can convert any biodegradable waste into biodiesel, as well as other by-products such as glycerol. In transesterification through electrolysis, OH- ions are produced in the cathode and turn into nucleophile (CH3O-) which lead to the production of biodiesel through attacking carbon UCO. The maximum free fatty methyl ester yield was obtained under the optimized conditions of 7:1 methanol/oil molar ratio, 10wt.% amount of co-solvent, in the range 300rpm, calcination temperature 750℃, 30V, amount of catalyst 12wt.% within 2h. Methyl ester production was done at room temperature in the absence of saponification. The physical and fuel properties contents of the synthetized biodiesel were characterized applying EN standard method.

In this work, we develop a correlative model based on the surface tension data in order to calculate thermodynamic parameters, such as interaction energy between components (Uij), activity coefficients and etc. In the new approach, by using Li et al. (LWW) model, a three-parameter surface tension equation is derived for liquid mixtures. The surface tension data of 54 aqueous and 73 non-aqueous binary mixtures have been correlated as a function of composition using the new model, then the interaction energy between two compounds (Uij) of mixtures and their activity coefficients have been calculated with the results of this model. The average relative error obtained from the comparison of experimental and calculated surface tension values for 127 binary systems is less than 2.8%.In order to evaluate new method, the obtained values using this method were comparable with the results of the UNIFAC group contribution model.

Catalyst activity and performance are the most important factors for selecting a catalyst in different processes. The Fischer-Tropsch synthesis is a very important synthesis that extensive action has been taken place to increase the activity of its catalysts in the recent century. Deactivation of the catalysts of the process is influenced by many factors, among which coking and sintering have come to be considered as key causes of the catalysts deactivation over time. Determination of the deactivation model for catalysts based on empirical data causes the catalyst activity and efficiency to be predictable, for this reason, the cost of construction and processing of various processes reduce significantly at industrial scale up. An Fe-K/Al2O3 catalyst was prepared by using an impregnation method in this research. Experimental data were measured in a fixed-bed tube reactor under low operating pressure (0.2 MPa) and high temperature (310 0C). By comparing the experimental data (in this study), with different models of deactivation, was obtained the best model for the deactivation of Fe-K/Al2O3 catalyst that amounts of kd, aeq and m are 0.425, 0.459 and 1, respectively. Then, the experimental data obtained from this study were evaluated with data of other references to evaluate the effectiveness of potassium promoter and alumina support on the parameters of the deactivation rate equation. It was found that to reduce the deactivation rate of iron catalyst in the presence of K promoter, it is better than the support of alumina is used at high operating pressures and low temperature.

Carbon oxide gaseous species are potentially considered as pollutants of the atmosphere of earth; especially, carbon monoxide and carbon dioxide which are of the well-known carbon oxids, play an effective role in the greenhouse gas emissions. Moreover, these species could initiate or handle some chain reactions in the troposphere that lead to emergence of some secondly air pollutants which may cause ozone to collapse. Due to the ultra-high volume of man-made production of these species which are annually sent into the atmosphere, the effects of them on our environment are much amplified. These concerns led scientists to perform a vast number of precious researches for controlling, eliminating, and detecting those species. In this regard, in the present project, we have made attempts to examine the probability of using the more stable isomers of N4B4 clusters, to find out if these clusters are able to sense, adsorb, or destruct CO, and CO2? The results showed that the N4B4 cluster both in forms (A), and (B), could adsorb (and react with) CO, and CO2 in a very fast and spontaneous process, as well as sensing those two species with clear signals.

Using wet impregnation method, a novel ternary system of silica supported Fe-Co-Ce catalyst was prepared. Preparation conditions such as impregnation time and temperature, drying time and temperature, were optimized by the L9 Taguchi experimental design to achieve a light olefin selective catalyst with maximum CO conversion in a fixed bed micro-reactor. It was found that the best conditions to maximize the responses were obtained at 4h impregnation time, 60°C impregnation temperature, 6h drying time, 90°C drying temperature and 350°C of reaction’s temperature. Characterization of the optimal catalyst precursors and calcined samples before, and after the Fischer-Tropsch reaction was carried out using various techniques.

The SiO2 supported cobalt-iron nano catalysts were prepared by the sol-gel method. This research investigated the effects of (Co/Fe) wt.%, different Co/Fe ratio at different temperature and loading of KCl wt.% for Fisher-Tropsch synthesis (FTS). The results were showed that the catalyst containing 50 wt.% (Co/Fe)/SiO2 (Co/Fe ratio is 70/30) which promoted with 0.6 wt.% KCl is an optimal nano catalyst for conversion CO+H2 to a range of hydrocarbons especially light olefins. Also the results showed that optimal operating conditions for optimal nano catalyst are 250 °C, H2/CO molar ratio 2/1 under 1 bar of pressure. Characterization of catalyst precursors and calcined catalysts were done by different methods such as: powder X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 physisorption and thermal analysis methods such as thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC).

We report highly efficient magnetically recoverable photocatalysts through combination of Fe3O4/ZnO with AgI and Ag2CO3, as narrow band gap semiconductors. The resultant photocatalysts were characterized by XRD, EDX, SEM. TEM, UV–vis DRS, FT-IR, PL, and VSM instruments. Under visible-light illumination, the nanocomposite with 1:6 weight ratio of Fe3O4 to ZnO/AgI/Ag2CO3 exhibited superior activity for degradation of RhB, which is nearly 20 and 11-folds higher than those of the Fe3O4/ZnO/Ag2CO3 and Fe3O4/ZnO/AgI photocatalysts, respectively. Furthermore, activity of this nanocomposite is 99 times higher than that of the Fe3O4/ZnO nanocomposite. The excellent activity of the nanocomposite was attributed to extended absorption in visible region and promoted separation of the charge carriers. Significantly, photocatalytic behavior of the nanocomposite was evaluated using photodegradations of three more organic pollutants and the highly improved activity in comparison to the counterparts was confirmed. Finally, the nanocomposite displayed enough magnetic properties to separate it using an external magnetic field.

Herein, the removal of methyl orange (MO), a monoazo dye, from aqueous solutions was investigated using bimetallic ferromagnetic Fe/Ni nanoparticles (NPs) with the average particle size of 12-16 nm. The effect of contact time, pH, temperature, and Fe/Ni dosage on dye removal process was investigated. The results showed that 60 mg of Fe/Ni NPs at 25 oC and pH= 1 can remove 99.5% of 50 mg/L dye solution within 15 min. The MO removal follows the pseudo-second-order kinetics with the rate constant of 0.4114 g mg-1 min-1. The chromophore structure of the dye was broken down in the presence of Fe/Ni NPs. The Fe/Ni NPs were prepared by simple co-reduction method and characterized by several techniques including X-ray diffraction, scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM, scanning tunneling microscopy, and vibrating sample magnetometer.NPs.

Herein, the application of Carnahan-Starling-vdW-β equation of state (EoS) for 13 refrigerant fluids was investigated. The EoS could predict the saturated liquid densities of these refrigerants over the temperature range of 100-400 K and pressures from zero up to187 MPa with the average absolute deviations of 2.66%. The accuracy of Carnahan-Starling-vdW-β EoS in liquid density prediction was also compared with Peng-Robinson EoS and a perturbed hard-sphere-chain EoS. The surface tension and sound velocity of the saturated refrigerants were also calculated using the Carnahan-Starling-vdW-β EoS within 4.76%. and 5.66%, respectively. Finally, Carnahan-Starling-vdW-β was employed to predict Joule-Thomson inversion curve for some studied refrigerant fluids