JOURNAL OF PHYSICAL AND THEORETICAL CHEMISTRY
Year:2015 | Volume:12 | Issue:2|Papers Count:8

Recently titanium oxide nanotubes (TiO2) are obtained by hydrothermal alkaline synthesis; where synthesis temperature and pressure, concentrations of NaOH and HCl, and annealing temperature are important parameters in the formation, purification and stability of the nanotubes structure. In this work, the effect of the hydrothermal treatment, the purification and the annealing temperature on the formation process, structure and morphology of TiO2 nanotubes was investigated. X-Ray diffraction (XRD), transmission electron microscopy (TEM), and EDS (energy dispersive X-ray spectroscopy) analysis were conducted to describe the formation and characterization of the structure and morphology of the nanotubes. From the analysis of results it was found that the hydrothermal treatment of the precursor nanoparticles of TiO2 and the purification with a HCl solution are essential to form and define the structure of the nanotubes. The hydrothermal treatment induces a change in the crystalline structure of the precursor nanoparticles from anatase phase to an orthorhombic phase which characterizes the titanate structure. The purification contributes to the formation of high purity nanotubes due to a Na exchange from the titanate structure to the HCl solution. The annealing temperature affects the morphology and the dimensions of the nanotubes structure. Annealing temperatures in the range of 400oC and 600oC are optimum to maintain a very stable tubular morphology of nanotubes. Temperatures greater than 600oC change the morphology of nanotubes from tubular to an irregular structure of nanoparticles with a size bigger than that of the precursor material, i.e., the crystalline structure changes from anatase phase to rutile phase causing the destruction of the nanotubes.

The reduction of electron transfer distance leads to an electronic communication between the electrode and redox proteins. This study elaborates upon the relationship between the number of carbon atoms in the fullerenes and the four free energies of electron transfer (DGet(1) to DGet(4)) between the fullerenes Cn (n=60, 70, 76, 82 and 86) and the six most well –known enzyme molecular systems: Laccase Coriolus hirsutus (LCh), Tyrosinase, Laccase Rhus vernicifera (LRv), Cytochrome c peroxidase, Ascorbate oxidase and Cytochrome c oxidase, numbered 1-6, respectively, in the text. The free energies of electron transfer are based on the four reduction potentials (Red.E1 to Red.E4) of the fullerenes, as assessed by applying the electron transfer (ET) equation to create [Laccase Coriolus hirsutus (LCh)].Cn, A-1 to A-5; [Tyrosinase].Cn, B-1 to B-5; [Laccase Rhus vernicifera (LRv)].Cn, C- 1 to C-5; [Cytochrome c peroxidase].Cn, D-1 to D-5; [Ascorbate oxidase].Cn, E-1 to E-5; and [Cytochrome c oxidase].Cn, F-1 to F-5. The results were extended to calculate the four free energies of the electron transfer (DGet(1) to DGet(4)) of other supramolecular complexes of each enzyme 1-6, as a class of electron transfer species, with fullerenes C60 to C120 ([(R)].Cn supramolecular complexes. The study also calculated the first to fourth activation free energies of electron transfer, DG# et(n) (n=1- 4), respectively, as assessed using the Marcus theory and the above equations on the basis of the first to fourth reduction potentials (Red.E1 to Red.E4) of fullerenes Cn (n=60, 70, 76, 82 and 86) for the predicted supramolecular complexes [Laccase Coriolus hirsutus (LCh)].Cn, A-1 to A-5; [Tyrosinase].Cn, B-1 to B-5; [Laccase Rhus vernicifera (LRv)].Cn, C-1 to C-5; [Cytochrome c peroxidase].Cn, D-1 to D-5; [Ascorbate oxidase].Cn, E-1 to E-5; and [Cytochrome c oxidase].Cn, F-1 to F-5. Furthermore, this study determined the wavelengths (l(n); n=1-4; in nm) of the electromagnetic photons for the electron transfer processes and in the nanostructure supramolecular complexes.

In the present study, all possible nitro and amino-substituted 1,2,3,4-tetrazine molecules have been investigated as potential candidates for high energy density materials (HEDMs) by using quantum chemical treatment. All compounds were designed and optimized to obtain molecular geometries and electronic structures at ab-initio and density functional theory (DFT, B3LYP) at the levels of 6- 31G (d, p), 6-31+G (d, p), 6-311G (d, p), 6-311+G (d,p) and cc-pvDZ. Moreover, thermal stabilities have been evaluated from the hemolytic bond dissociation energies (BDEs). Other important properties such as bond dissociation density, frontier orbital energy, nucleus-independent chemical shifts (NICSs), and heat of formation and detonation parameters were then calculated. Also, IR and NMR spectra of the structures were obtained. According to the results of the calculations, the introduction of nitro group can improve the detonation properties of the structures. The calculation results revealed that these molecules exhibit excellent performance, and the all compounds are viable candidate of high energy density materials (HEDMs). Comparing the detonation properties of molecules with standards (RDX and HMX) shows 5,6-dinitro-1, 2, 3, 4-tetrazine can be an explosive.

The present study aimed at investigating the chemical properties of the solvents playing the key role in CO2 absorption process from the exhaust stream of power plants or other industrial sources. For this purpose, energy computations were performed using a DFT-based quantum chemistry method at B3LYP/6-311++G (d, p) level of theory. Furthermore, the solvent effect was taken into account by means of a dielectric constant in SMD continuum model at HF/6-31G (d) level of theory. With this approach, the relative stability of carbamate ion versus bicarbonate ion as the main products of CO2 absorption into the aqueous alkanolamine solvents was evaluated and the results were discussed in terms of various factors such as types of alkanolamine, carbon chain length in alkanolamine and steric hindrance. This study revealed that increasing both carbon chain length and steric hindrance leads to a decrease in carbamate stability. Moreover, DEA as a secondary alkanolamine demonstrated a lower carbamate stability.

A series of exohedrally functionalized derivatives of D3-symmetrical fullerene interaction with Glycine (NFG) have been investigated by using a DFT approach at the B3LYP/3-21G* basis sets. In the present investigation relative and formation energies of compounds, the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), the Homo-Lumo band gap, chemical potential (m), global softness (S), global electrophilicity index (w), electro negativity (c), hardness (h), were calculated for the title compound. In order to find the stable conformer, conformational analysis was performed based on Density Functional Theory B3LYP methods in 3-21G* basis set. The optical properties, thermodynamic properties and Mulliken charges of the NFG are calculated. A study of the electronic properties such as HOMO and LUMO energies, are performed by time – dependent DFT (TD-DFT) approach. The nuclear magnetic resonance (NMR) chemical shifts of the molecule is calculated by the gauge independent atomic orbital (GIAO) method. Moreover, their corresponding Homo-Lumo orbits are mainly associated with the surface of the cage. Surface modification and functionalization of nano-materials are very useful so that it could extend their applications in many fields especially metal ion adsorption, and catalytic process. It was concluded that it would be possible to produce novel specifically for bio-medical application.

The complexive ability of p-sulphonato-calix[6]arene towards dioxovanadium(V) has been evaluated in acidic aqueous solution (pH 1.7) using UV–Vis spectrophotometric technique. The result showed that the ligand is capable to complex with the oxo-cations by 1: 1 cation to ligand ratios. Formation constant of the system has been determined at different temperatures (25 to 40oC). Considering the formation constant values, the binding selectivity of the ligand towards the oxo-cations at 25 oC is in the order VO2+. The thermodynamic parameters have evaluated and are interpreted in terms of the importance of the various interactions responsible for the complexation. A roughly linear relationship between DHo and TDSo has been observed for the studied systems and those were reported in the literature. Finally, the host and guest desolvation involved in the complexation processes are discussed. In conclusion, this study demonstrated the efficiency of the calixarene emulsion, which can be regarded as a promising treatment for dioxovanadium cutaneous contamination.

Poly (vinylidene chloride) (PVDC) is a barrier polymer which has a wide scope in food packaging industries. A comprehensive study of the normal modes and their dispersion in PVDC using Wilson’s GF matrix method as modified by Higgs is reported. It provides a detailed interpretation of IR and Raman spectra. Characteristic feature of dispersion curves, such as regions of high density-of-states, repulsion, and character mixing of dispersion modes, are discussed. Heat capacity has been calculated in the range 50–500 K via density-of-states using Debye relation. It is in fairly good agreement with the experimental data. Heat capacity behavior of PVDC with temperature was observed nearly linear in nature. Heat capacity provides a relationship between microscopic behavior and a macroscopic property. The thermal stability of a polymeric system and its interactive nature with other properties, such as phonon-phonon coupling is also related to thermodynamic behavior. The present study provides a theoretical framework to understand experimental measurements.

The interamolecular hydrogen bond (IMHB) of the neutral, cationic, and anionic cis-urocanic acid (cis-UCA, (Z)-3-(I’H-imidazol-4’ (5’)-yl)propenoic acid) were investigated in the gas phase within ab-initio calculations. To determine the energy and molecular structures, all the compounds were initially optimized at B3LYP and MP2 methods by use of 6-31G* and 6-31G** level of theory. Suitable single-point calculations have been subsequently done. Two dimensional energy curves have been obtained, and by adding a geometrical parameter, the potential energy surface is also plotted. The three-dimensional potential energy surface for proton motion within the molecule in the direction posses the lowest possible energy has been determined. These results show that the properties of hydrogen bonds are significantly different in the three forms of the investigated cis-urocanic acid. For instance, the bond strength in ionic molecules (cationic and anionic) is about twice of that of the neutral molecule. Evaluation of the potential energy versus distance curve is performed by mentioned methods and a single potential barrier curve which is relatively symmetrical is gained. The removal of potential barrier can be attributed to the high magnitude of hydrogen bonding strength.