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Most of water based drilling fluids easily penetrate into shale formations and cause serious problems such as well instability, destruction of the formation, wall pipe folding and pipe adhesion. The present research aims to assess the effects of alumina nano-particles (alpha and gamma) on shale/clay stability due to the unique specifications of alumina (alpha and gamma) nano particles. The SEM, XRD, EDAX and AFM analyses of recovered shale samples indicate that the average size of alpha alumina nano-particles coating the shale surface and the pores existing in the shale is between 25 and 35 nm, whereas the average size of gamma alumina nano-particles coating the shale surface and the pores present in the shale is between 20 and 30 nm. In addition, samples recovered by nano-alpha reveal more porosity remained in the shale sample in comparison with the nano-gamma nano-sample. Furthermore, the results obtained from EDAX illustrate a suitable nano-gamma alumina over the recovered shale. The experiment with five types of drilling fluid without the presence of potassium chloride as an inhibitor salt designed. Thus, the water based drilling fluid containing nano-gamma alumina with less than 1 %wt was chosen as the best sample. Generally, the presence of alumina nano-particles optimizes the stability of formations containing ions like shale.

In this study, the Chicory leaf powder (CLP) was used as a native adsorbent to eliminate the Acid Blue 25 dye from aqueous media. The prepared native adsorbent was characterized by several techniques including the X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform spectroscopy (FTIR), Brunauer–Emmet–Teller essay (BET), and particle size analyzer (PSA). A collection of experiments was performed to distinguish the optimal conditions and to probe the effects of the different parameters such as initial concentration, contact time, adsorbent dosage, pH of solution, and temperature on the sorbent capacity. The attained optimal conditions for removal the Acid Blue 25 dye were pH = 3–4, contact time 50 min, dosage 0.1 g, and initial concentrations 10 (mg/L) at 30 °C. The adsorption data revealed that the adsorption procedure has more match with the Langmuir isotherm than others. The kinetic data were better fitted with the pseudo-second-order pattern with a trusty correlation coefficient. Finally, the thermodynamic parameters illustrated that the adsorption process is exothermal and spontaneous. Based on magnitude of the standard enthalpy change related to the studied adsorption, we may derive that the considered adsorption is physical adsorption.

Ion transport rates of direct forming acid (DFAFC), phosphoric acid (PAFC), alkaline (AFC), proton exchange membrane (PEMFC), direct methanol (DMFC) and solid oxide (SOFC) fuel cells have been studied. AFC which uses an aqueous alkaline electrolyte is suitable for temperature below 90° and is appropriate for higher current applications, while PEMFC is suitable for lower temperature compared to others. Not only are fuel cells clean energy for environment, but they can also have more than two times the efficiency of traditional combustion technologies. However, despite current developments, these technologies are not mature enough to be significantly into the energy market to replace petroleum. Hydrogen is an important energy carrier and a strong candidate for energy storage. It will be a useful tool for storing intermittent energy sources such as solar radiation. Hydrogen is a versatile energy carrier that can be used to power nearly every end-use energy need. By this work, modelling and controlling of ion transport rate efficiencies in PEMFC, AFC, DMFC, PAFC, DFAFC, direct carbon fuel cell (DCFC) and molten carbonate fuel cells (MCFC) have been investigated and compared. Thermodynamic equations have been investigated for those fuel cells from the viewpoint of voltage output data. Effects of operating data including temperature (T), pressure (P), proton exchange membrane water content (λ), and proton exchange membrane thickness (dmem) on the optimal performance of the irreversible fuel cells have been studied. Performance of fuel cells was analysed via simulating polarisation and power curves for a fuel cell operating at various conditions with current densities.

Various composites including (1-x-y) LiNi0.7Co0.3O2, xLi2MnO3and yLiCoO2systems were synthesised using the sol-gel method. Stoichiometric weights of the LiNO3, Mn(Ac)2·4H2O, Co(Ac)2·4H2O, Ni(NO3)2·6H2O for preparing of 28 samples have been used. We found that the sample "Li1.167Ni0.117Co0.699Al0.017Mn0.167O2" with Al doped is the best composition for cathode material in LIBTs. Obviously, the weight of cobalt used in this sample is lower compared to LiCoO2which is an advantage in view point of cost and toxicity. Charge-discharge characteristics of the mentioned cathode materials were investigated by performing cycle tests in the range of 2.4-4.6 V. Our results confirmed that this kind of system can help removing the mentioned disadvantage of cobalt with high efficiency.

Al–Ga surface doped with chromium (Cr) is theoretically studied using first-principles density functional theory (DFT) at the CAM-B3LYP/EPR-III, LANL2DZ, 6-31+G(d,p) level of theory to explore the chemical adsorption and corrosion inhibition of organic carbenes through coating process. Crystal structure of Cr–(Al–Ga) surface was coated by S–&N–heterocyclic carbenes of benzotriazole (BTA), 2-mercaptobenzothiazole (2MBT), 8-hydroxyquinoline (8HQ) and 3-amino-1,2,4-triazole-5-thiol (ATR). The NMR spectroscopy of the adsorption of BTA, 2MBT, 8HQ, and ATR on the Cr-doped Al–Ga nanoalloy surface represents that this surface can be employed as the magnetic S–&N–heterocyclic carbene sensors. In fact, Cr site in Cr–(Al–Ga) nanoalloy surface has bigger interaction energy amount from Van der Waals’ forces with BTA, 2MBT, 8HQ, and ATR that might cause them large stable towards coating data on the nanosurface. It has been estimated that the criterion for choosing the surface linkage of S and N atoms in BTA, 2MBT, 8HQ, and ATR in adsorption sites can be impacted by the existence of close atoms of aluminum and gallium in the Cr–(Al–Ga) surface. The fluctuation of NQR has estimated the inhibiting role of BTA, 2MBT, 8HQ, and ATR for Cr -doped Al–Ga alloy nanosheet due to S and N atoms in the benzene cycle of heterocyclic carbenes being near the monolayer surface of ternary Cr–(Al–Ga) nanoalloy. Moreover, IR spectroscopy has exhibited that Cr-doped Al–Ga alloy nanosheet with the fluctuation in the frequency of intra-atomic interaction leads us to the most considerable influence in the vicinage elements generated due to inter-atomic interaction. Comparison to ΔG∘˙adsamounts versus dipole moment has illustrated a proper accord among measured parameters based on the rightness of the chosen isotherm for the adsorption steps of the formation of BTA @ Cr–(Al–Ga), 2MBT @ Cr–(Al–Ga), 8HQ @ Cr–(Al–Ga), and ATR @ Cr–(Al–Ga) complexes. Thus, the interval between sulfur, nitrogen, and oxygen atoms in BTA, 2MBT, 8HQ, and ATR during interaction with transition metal of Cr in Cr–(Al–Ga) nanoalloy, (N→Cr, O→Cr, S→Cr), has been estimated with relation coefficient of Rˆ2 = 0.9509. Thus, this paper exhibits the influence of Cr doped on the “Al–Ga” surface for adsorption of S–&N–heterocyclic carbenes of BTA, 2MBT, 8HQ, and ATR by using theoretical methods. Furthermore, the partial electron density or PDOS has estimated a certain charge assembly between Cr–(Al–Ga) and S–&N–heterocycles of BTA, 2MBT, 8HQ, and ATR which can remark that the complex dominant of metallic features and an exact degree of covalent traits can describe the augmenting of the sensitivity of Cr–(Al–Ga) surface as a potent sensor for adsorption of BTA, 2MBT, 8HQ, and ATR heterocycles. This work investigates the characteristics, band structure, and projected density of state (PDOS) of Al–Ga nanoalloy doped with Cr element for increasing the corrosion inhibition of the surface through adsorption of organic molecules of carbenes in the surface coatings process. This paper can be helpful in a range of applications which uses Al–Ga alloy for the study of energy storage and adsorption of air pollution or water contamination. Many different approaches such as surface coatings, alloying, and doping can be adopted to protect the surface.

Progress of largely selective and sensitive compounds is essential for removing two toxic gases of hydrogen sulfide (H2S) and sulfur dioxide (SO2).The effect of Iron (Fe), Nickel (Ni), and Zinc (Zn) doping of graphene (Gr) nanosheet (NS) on their adsorption for both H2S and SO2gases has been investigated in this work using first-principles density-functional theory (DFT) computations. In this research, it has been investigated the ability of transition metals of iron, nickel, and zinc doping of Gr@NS for adsorption toxic gas of Sulfur Dioxide and Hydrogen Sulfide Removal. The Langmuir adsorption model with a three-layered ONIOM used CAM-B3LYP functional accompanying LANL2DZ and 6–31 + G (d,p) basis sets due to Gaussian 16 revision C.01 program on the complexes of H2S and SO2→ TM(Fe, Ni, Zn) doping of Gr nanosheet. The changes of charge density have shown the values of ∆QFe-doped= − 0.566 >> ∆QZn-doped= + 0.387 >>> ∆QNi-doped= + 0.605 for H2S adsorption and ∆QFe-doped= − 0.336 >> ∆QZn-doped=  + 0.376 >>> ∆QNi-doped= + 0.618 for SO2adsorption. Based on these amount of changes of charge density, H2S and SO2have exhibited a significant charge transfer for Fe doping of graphene nanosheet compared to Ni- and Zn-doped Gr@NS. Based on NMR spectroscopy, it has been illustrated that the sharp peaks in the adsorption site are due to the Fe, Ni, and Zn doping on the surface of graphene nanosheet through H2S and SO2adsorption. However, it has represented some fluctuations in the chemical shielding of isotropic and anisotropy behaviors around Zn-doped on the H2S/ SO2→ Zn-doped/Gr@NS. Moreover, it has exhibited the fluctuation of occupancy of NBO for H2S/SO2→ Fe-doped, H2S/SO2→ Ni-doped, and H2S/SO2→ Zn-doped graphene nanosheet through the Langmuir adsorption process by indicating the active sulfur atom in hydrogen sulfide (H2S) and sulfur dioxide (SO2) becoming close to the nanosheet. The amounts of ΔGadsothrough IR computations based on polarizability have exhibited that ΔGads,SO2→Fe-Coand ΔGads,H2S→Fe-Cohave exhibited the most energy gap because of charge density transfer from sulfur atom in hydrogen sulfide (H2S) and sulfur dioxide (SO2) to Fe doping of Gr@NS, although, ΔGH2S/SO2→Zn-C0> ΔGH2S/SO2→Ni-C0> ΔGH2S/SO2→Fe-C0. Frontier molecular orbitals of HOMO, LUMO, and band energy gap accompanying some chemical reactivity parameters have represented the attributes of molecular electrical transport of TM (Fe, Ni, Zn) doping of Gr nanosheet for adsorption of H2S and SO2gases. Our results have provided a favorable understanding of the interaction between TM doping of Gr@NS nanosheet and H2S and SO2molecules. A high performance of TM doping of Gr@NS as gas sensor is demonstrated by modeling the material’s transport characteristics by means of the Langmuir adsorption and three-layered ONIOM/DFT method. Furthermore, the results of partial electron density of states (PDOS) have confirmed an obvious charge accumulation between the graphene nanosheet and doped atoms of Fe, Ni, and Zn through adsorption of H2S and SO2molecules on the surface due to the recognition of the conduction band region. Finally, this research can build up our knowledge about the electronic structure, relative stability, and surface bonding of various metal-doped graphene nanosheets, metal alloy surfaces, and other dependent mechanisms, like heterogeneous catalysis, friction lubrication, and biological systems.

The physicochemical attributes of inhibitor → metal & metal alloys nanosheet can be one of the fundamental factors for recognizing determining and selecting the Langmuir adsorption through IR, NMR, NQR, NBO, UV–VIS, HOMO/LUMO, and charge distribution and other quantum attributes. Then, the fluctuation of occupancy of natural bond orbitals has been estimated for pyridine → Al–Al, pyridine → Al–Mg, pyridine → Al–Ga, pyridine → Al–Si; 2-picoline → Al–Al, 2-picoline → Al–Mg, 2-picoline → Al–Ga, 2-picoline → Al–Si; 3-picoline → Al–Al, 3-picoline → Al–Mg, 3-picoline → Al–Ga, 3-picoline →  Al–Si, 4-picoline → Al–Al, 4-picoline → Al–Mg, 4-picoline → Al–Ga, 4-picoline → Al–Si, and 2,4-lutidine → Al–Al, 2,4-lutidine → Al–Mg, 2,4-lutidine → Al–Ga, and 2,4-lutidine → Al–Si through the Langmuir adsorption process due to concerning the nitrogen atom in the benzene ring of related heterocyclic compounds becoming close to the monolayer nanosurface of aluminum and its alloys. Nuclear magnetic resonance has certainly has focused on the aluminum shielding in the intra-atomic interaction with magnesium, gallium, and silicon and simultaneously interatomic interaction with nitrogen atoms in organic heterocyclic inhibitors through variety of high, medium, and low layers of ONIOM method. In addition, on the basis of the computed amounts of UV–VIS spectra for pyridine and its family adsorbing on the Al alloy surface, there are maximum adsorption bands between 150 and 240 nm. Two maximum adsorption bands for pyridine, 2-picoline, 3-picoline, and 4-picoline are at 200 nm and 250 nm. Besides, it has been observed two maximum adsorption bands for 2,4-lutidine around 170 nm and 210 nm, respectively.

The molecular dynamics simulation method was used to investigate the structural details for human prion protein (PrPN) and its D178N mutant (PrPM). Root-mean-square fluctuations (RMSFs) and the root-mean-square deviations (RMSDs) showed an increase in the flexibility and high dynamic plasticity of PrPM. Average Total energy for PrPM and PrPN sequentially was -2.975 x105 (kJmol-1) and -3.193 x 105 (kJmol-1). The results showed conformational rearrangement susceptibility for PrPM. For PrPM, highly surface-exposed Glu196 and Arg136 caused hydrogen bond weakening and electrostatic interactions changes in salt bridges. Hydrogen bond weakening under mutation can be mentioned as the leader of conformational changes and disease-related conversions. Contrary to some reports, the contributions of electrostatic interactions of Glu146–Arg208 and Arg156–Glu196 salt bridges for PrPN is less than of these interactions for PrPM. These interactions can pave the way to conformational changes in PrPM. The results showed that the role of the hydrogen bonds in the stability of human prion protein is more important than these salt bridges. The calculation of the solvent accessible surface area showed that the conformational plasticity in PrPM is mainly due to Asn residues that were solvent exposed. Conformational changes in the specific amino acids can affect metal-ion occupancy and function. The secondary structure has also showed that the structural transition arose from D178N mutation and occurs in specific residues. Our studies support the large scale effects of electrostatic forces at key position 178 of prion. As a result, the conformational rearrangements happen by eliminating only a single negative charge because of the mutation induced global forces in the prion structure. These rearrangements can be considered as a molecular switch, which triggers the initial stages of the conformational transition.

The reaction of electrochemically generated o-benzoquinones from the oxidation of catechol derivatives as Michael acceptors with dimethyl phosphite as nucleophile has been studied using cyclic voltammetry. The reaction mechanism is believed to be EC comprising oxidation of catechol moiety of these antioxidants followed by Michael addition of dimethyl phosphite. The observed homogeneous rate constants (kobs) for the reactions were estimated by comparing the experimental voltammetric responses with the digitally simulated results based on the proposed mechanism. In addition, the effects of nucleophile concentration and of substitutent group of the catechols on the voltammetric behaviour and the rate constants of the chemical reactions are described.

Ab initiocalculations are applied in order to explore metalation of the exocyclic amino group of cytosine by the elements of group IIA (Be, Mg, Ca, Sr and Ba).

Ab initiocalculations indicate that metalation of the exocyclic amino group of cytosine by the elements of Group IA (Li, Na, K, Rb and Cs) induces protonation of a nucleobase ring nitrogen atom, and hence causes a proton shift from an exocyclic to an endocyclic nitrogen atom. Thus, this metal‐assisted process leads to the generation of rare nucleobase tautomers. The calculations suggest that this kind of metalation increases the protonation energies of the aromatic ring of the nucleobase. The present study reports the quantum chemistry analysis of the metal‐assisted tautomerization. The calculations clearly demonstrate that metalation of the exocyclic amino group of the nucleobase significantly increases the protonation energy of the aromatic rings of the nucleobase. Also, absolute anisotropy shift, molecular orbital and natural bond orbital calculations are compatible with these results. Copyright © 2003 John Wiley & Sons, Ltd.

Ab initio calculations indicate that metalation of the exocyclic amino group of cytosine by the elements of Group IA (Li, Na, K, Rb and Cs) induces protonation of a nucleobase ring nitrogen atom, and hence causes a proton shift from an exocyclic to an endocyclic nitrogen atom. Thus, this metal-assisted process leads to the generation of rare nucleobase tautomers. The calculations suggest that this kind of metalation increases the protonation energies of the aromatic ring of the nucleobase. The present study reports the quantum chemistry analysis of the metal-assisted tautomerization. The calculations clearly demonstrate that metalation of the exocyclic amino group of the nucleobase significantly increases the protonation energy of the aromatic rings of the nucleobase. Also, absolute anisotropy shift, molecular orbital and natural bond orbital calculations are compatible with these results. Copyright © 2003 John Wiley & Sons, Ltd.

The structure and relative energies of the tautomers of 5-methylcytosine in the gasphase and in different solvents are predicted using MP2 and density functional theory methods. The order of stability for these tautomers is C3>C1>C2>C4>C5>C6 calculated by MP2 and C1>C3>C2>C4>C5>C6 calculated by the B3LYP method. Relative energy calculations are performed in wide range of solvent dielectrics and in all solvents the oxo-amino C1 is predicted as the most stable tautomer. The infrared spectra of two dominant tautomers are calculated in the gas phase using HF and density functional theory. Good agreement between calculated (DFT) and experimental harmonic vibrational frequencies is found.

The internal rotational barriers for formamide are calculated in gas and solution phases (acetonitrile) at the HF/6-31G*(16.64 and 16.18 kcal/mol, respectively) and MP2/6-31G*(16.86 and 16.71 kcal/ mol, respectively) level of theory. Calculated parameters are compared with experimental data and there is a good agreement between them. Orbital populations are obtained by MPA (mulliken population analysis) and NPA (natural population analysis) methods and bond energies are calculated by the NBO method (natural bond orbitals). The distribution of atomic charges are also given. These calculation indicate that the internal rotational barrier is produced because of change in the distribution of orbital populations of 2py, 2pz, dyz, dy2and dz2orbitals of the nitrogen atom.

Solvent effects on rotational barriers of 2-amino-3-mercapto-propionamide, an amide derived from cysteine, have been investigated at HF and MP2 levels of theory using a polarisable continuum model (PCM) of solvent. The predicted barrier in the gas phase increases by increasing the polarity of solvents. It was shown that the observed solvent-induced shielding variation is more strongly related to the intensity of the solvent reaction field rather than to the change of molecular geometry induced by the solvent.