Chemical Gibbs Energy Research Articles

Effect of the Al Doping on the Sensing Behaviour of Carbon Nanotubes Toward Carbazochrome: a Computational Study

In the current report, the interaction of Al-doped carbon nanotubes (CNT) with carbazochrome, an anti-hemorrhagic or hemostatic agent, was investigated with the M06-2X functional and 6-31G* basis set. The global index including frontier molecular orbital energies, hardness, softness, chemical Gibbs energies and some parameters and NLO properties of Carbazochrome, Al doped CNT and complexes formed between their were calculated and evaluated. Electron localization function (ELF) calculations were performed to validate the essence of the formed bonding model progress along the interaction. It is obtained that polarizability of the complex are bigger than those of Carbazochrome and Al doped CNT. According to the maximum electron flow index, the electrophilicity power is increased by increasing the chemical potential, the decreasing chemical hardness. All obtained complexes are exergonic and thus thermodynamically favorable

Carbazochrome carbon nanotube as drug delivery nanocarrier for anti-bleeding drug: quantum chemical study.

The interaction between drugs and single-walled carbon nanotubes is proving to be of fundamental interest for drug system of delivery and nano-bio-sensing. In this study, the interaction of pristine CNT with carbazochrome, an anti-hemorrhagic or hemostatic agent, was investigated with M06-2X functional and 6-31G* basis set. All probable positions of related adsorption for these kind drugs were thought-out to find out which one is energetically suitable. Based on the achieved data, the stronger interactions appeared the oxygen atom of C = O group and nitrogen atom of imine groups. The topology analysis of QTAIM (quantum theory of atoms in a molecule) method was accomplished to understand the properties of interactions between the CNT and carbazochrome. Frontier molecular orbital energies of all systems, global index including stiffness, softness, chemical Gibbs energies, and electrophilicity parameters, as well as some other important physical data such as dipole moment, polarizability, anisotropy polarisibility, and hyperpolaribility were calculated, evaluated, and then compared together. The essence of the formed bonding model progress along the reaction roots was further validated using electron localization function (ELF) calculations. The highest values of adsorption energies were determined in the range of 18.24 up to 22.12kcalmol-1 for these kind systems. The acceptable recovery time of 849s was obtained for the desorption of carbazochrome from the CNT surface under UV-light. The final results exhibit that carbazochrome can serve as a promising carrier and also as sensitive sensors in any kind of practical application.

Chemisorption model of electrochemical passivity of metals and thermodynamic calculation of the flade potential of metals Ni and Cr taking into account their surface Gibbs energy

A model of the chemisorption passivity of metals based on the consideration of equality of the electrochemical potentials of the metal ion at the interfaces between the bulk of a metal, the monoatomic surface layer (SL) of a metal, and the surface metal oxide has been proposed. Thereby, unlike the Vetter model, this approach takes into account the occurrence of the Galvani potential of the metal atoms (ions) in the SL in the form of the surface Gibbs energy ΔGS(hkl) of a particular crystal face. On this basis, a formula of the Flade potential EF(S) of a metal has been derived; this formula, along with the chemical Gibbs energy of formation of oxides, makes allowance for the ΔGS(hkl) value (of a low-index face of the metal). Normal potential EF(S)0(a pH of 0) has been calculated using the data of the first-principle calculation of the surface energy of metals. The calculated EF(S)0 values of 0.46 and−0.19 V for Ni and Cr, respectively, are in good agreement with the literature data. The calculated EF(S) values and the critical points in the anodic curves of passivation and activation of nickel in a 0.5 M H2SO4 solution and in the presence of KSCN additives have been compared.

Phase field simulation of microstructure evolution in Fe–Cr–Co alloy during thermal magnetic treatment and step aging

The evolution of modulated structures in Fe–Cr–Co alloys during isothermal aging under an external magnetic field and multiple step aging was simulated based on a phase field method. In this simulation, the magnetic configuration during the decomposition was calculated by a micromagnetic method, and the chemical Gibbs energy function was calculated by the CALPHAD approach based on the experimental equilibrium phase diagram. The calculation results provide a quantitative microstructure change directly linked to the phase diagram and demonstrate obvious microstructure difference between isothermal aging and multiple aging. The ferromagnetic precipitates elongate along the direction of the external magnetic field. The simulated evolution and microstructure are in good agreement with the experimental results.

Ionic components of the real and chemical Gibbs energy of transport of potassium and chloride ions from water to water-methanol mixtures

With the method of volta-potential differences at 298.15 K the ionic components of the standard real and chemical thermodynamic properties of the resolvation of potassium and chloride ions were determined in mixtures of water and methanol (MeOH). The value of the surface potential at the methanol/gas phase boundary (ΔχMeOH = −0.18 V) is obtained. The characteristics of the solvation of these ions in a water-methanol medium are identified, and a comparison with literature data for other nonaqueous mixtures is carried out.

Application of Volta chains to determine ionic components of real and chemical Gibbs energies of transfer of individual ions from water to aqueous-organic solvents

The state of individual ions in individual and mixed solvents was described from the thermodynamic point of view using the method of Volta potential differences. This methodology provides a way of solving the problem of determination of thermodynamic characteristics of individual ions in solutions. The possibility of using the method of Volta potential differences to determine the ionic components of the real and chemical thermodynamic properties of individual ions in solutions and the surface potentials at gas-solution interface is substantiated.

Thermodynamic characteristics of the resolvation of K + and Cl – ions in mixtures of water with aprotic solvents

The solvation of K + and Cl – ions in water mixtures with aprotic solvents (acetone, acetonitrile, dimethylsulfoxide and dimethylformamide) was studied based on the analysis of primary effects of the medium of K + and Cl – and the chemical Gibbs energies of transfer of these ions from water to the mixed solvents at 298.15 K obtained from Volta potential differences.

Kinetics of the abnormal austenite–ferrite transformation behaviour in substitutional Fe-based alloys

The kinetics of the recently discovered abnormal austenite (γ)–ferrite (α) transformation of substitutional Fe–Co and Fe–Mn alloys were measured by dilatometry and compared with the, also measured, corresponding normal transformation behaviour. A phase transformation model, involving site saturation, interface-controlled continuous growth and incorporating an impingement correction, has been employed to extract the migration velocity of the γ/α interface. It was found that the normal transformation process could be well described assuming a constant nucleus density and interface migration velocity. The thus assessed misfit-accommodation, deformation Gibbs energy is of the same order of magnitude as the chemical Gibbs energy change driving the transformation. A large austenite grain size was shown to be the precondition for the occurrence of abnormal kinetics. The abnormal transformation process involves the occurrence of additional peaks in the transformation rate for the first stage of the transformation. An autocatalytic type of nucleation was successfully incorporated in the above model to describe the occurrence of the repeated nucleation during the abnormal transformation.

Mechanism for metastable phase formation in undercooled Ti–Al peritectic alloys

Melt undercooling technique has been proved to be a powerful tool to investigate the formation of metastable phase in rapid solidification processing. Here, the recently observed phase evolution behaviour of the near equal atomic percent Ti–Al alloys was analyzed, as a function of melt undercooling, by thermodynamic and kinetic calculation. It was found that the formation of metastable phase is lightly predicted by the chemical Gibbs energy difference among competing phase but strongly controlled by kinetic effects arising from the competition of nucleation. The transient nucleation theory, with a consideration of incubation time, was proved to be an effective tool to explain the metastable phase formation in the undercooled near equal atomic percent Ti–Al alloys.

Thermodynamics of Na + ion solvation in water–organic mixtures studied by the method of Volta potential differences

The features of the solvation of the Na+ ion compared with the Cl– ion in mixtures of water with various organic solvents have been elucidated on the basis of the analysis of chemical Gibbs energies of Na+ transfer from water to mixed solvents.

The kinetics of the austenite–ferrite phase transformation of Fe-Mn: differential thermal analysis during cooling

Differential thermal analysis (DTA) has been employed to study the austenite–ferrite phase transformation of Fe-1.89at% Mn upon cooling. The transformation has been shown to occur in two stages. The first stage is not thermally activated; the second stage is thermally activated. A phase transformation model, incorporating a new impingement correction, has been used for the extraction, from the DTA experiments, of data for the velocity of the austenite–ferrite interface. It follows that the interface velocity does not only depend on temperature, but also on transformed fraction. This has been interpreted as the consequence of the (non-neglectable) dissipation of energy by the volume misfit of the austenite and ferrite phases during the transformation. This misfit accommodation Gibbs energy has been assessed quantitatively; it has been shown to be of the same order of magnitude as the chemical Gibbs energy.

SYNTHESIS OF A SELF‐CONTAINED CONCEPT OF THE MOLECULAR MECHANISM OF ENERGY INTERCONVERSION BY H+‐TRANSPORTING ATP SYNTHASE

The original aim of the review has been to probe into the validity of the paradigm on the high energy-carrier function of ATP. It seemed to be called into question on the basis of findings with H(+)-transporting ATP synthase suggesting the formation of ATP from ADP and Pi without energy input. Thus, ATP appeared as a low-energy compound. Starting from the current, rich knowledge of the molecular structure and the inviting thinking on the mechanism of H(+)-transporting ATP synthase, we have endeavoured to freshly interpret and integrate the pertinent observations in the light of the comprehensively derived model of the molecular mechanism of energy interconversion by Na+/K(+)-transporting ATPase. In this way, we have uncovered the common mechanistic elements of the two energy-interconverting enzymes. The emerging purpose of the present paper has been the 'synthesis' of a self-contained concept of the molecular mechanism of the interconversion of electrochemical and chemical Gibbs energies by H(+)-transporting ATP synthase. The outcome is reflected in the following tentative evaluations. 1. In ATP hydrolysis, the great Gibbs energy change which is observed in solution, is largely conserved by the F1 sector of ATP synthase as mechanical Gibbs energy in the enzyme's protein fabric, so that it can be utilized in the resynthesis of ATP from enzyme-bound ADP and Pi. The plainly measured low Gibbs energy change results from large compensating enthalpy and entropy changes that reflect the underlying changes in protein conformation. 2. In stoichiometric ATP synthesis by F1 sector from ADP and Pi bound to the catalytic centre, their intrinsic binding energy brings about a loss of peptide chain entropy that makes possible an entropy-driven ATP formation. 3. The driving force for ATP synthesis cannot be the high Gibbs energy change on binding of product ATP; the tight ATP-enzyme complex rather is a low Gibbs energy intermediate from which escape is difficult. 4. The catalytic centre exists either in an open state unable to firmly bind the substrate-product couple, or in a closed state protecting formed ATP from facile hydrolysis by ambient water. 5. The cleft closure, induced by binding of Pi and ADP or ATP, does not necessarily need external energy supply, because the cleft closure proceeds from rigid domain rotations which can occur rather spontaneously. In further analogy to adenylate kinase, the driving force of this domain movement presumably comes from the electrostatic interactions between phosphate moieties and arginine side chains in the catalytic centre.(ABSTRACT TRUNCATED AT 400 WORDS)

The real and chemical Gibbs energies of silver ion transfer from water to some organic solvents

The real Gibbs energy, Δ s wα Ag + , and the chemical Gibbs energy, Δ s w G Ag + , of silver ion transfer from water to γ-butyrolactone, isobutyl methyl ketone and ethylene glycol have been determined experimentally as well as those for methanol and, in part, for acetone, which were considered to be test solvents. The Δ s wα Ag + measurements were carried out by the dynamic condenser method and the Δ s w G Ag + measurements were made using transfer cells in which tetraethylammonium picrate (TEAPi) solutions were used to eliminate the diffusion potentials, mainly in dipolar solvents. The Δ s wα Ag + data were used to calculate the surface potential differences between the studied solvents and water, Δ s w χ . These values were compared with the Δ s wχ values measured directly by the dynamic condenser method. The salt bridge containing TEAPi was used in those measurements, also, on the organic phase side. The effect of mutual saturation of water and isobutyl methyl ketone on the Δ s w G Ag + and Δ s wα Ag + and Δ s wχ was studied.