Majid Hashemianzadeh | Iran University of Science and Technology (IUST) (original) (raw)

Papers by Majid Hashemianzadeh

Research paper thumbnail of First-principles study of hydrogen storage on Si atoms decorated C6o

International Journal of Hydrogen Energy, 2009

a b s t r a c t Hydrogen storage capacity of Si n C 60 is studied via first-principles theory bas... more a b s t r a c t Hydrogen storage capacity of Si n C 60 is studied via first-principles theory based on DFT and Canonical Monte Carlo Simulation (CMCS). It is shown that Si atoms strongly prefer D-site rather than other sites and in these structures maximum number of hydrogen molecule onto any Si atom is one. Each Si atom adsorbs one hydrogen molecule in molecular form and with proper binding energies when Si atom is placed in any D-site of C 60 . Si atoms enhance remarkably hydrogen storage capability in fullerene. ª (M. Hashemianzadeh). A v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / h e

Research paper thumbnail of First-principles study of hydrogen storage on Si atoms decorated C60

International Journal of Hydrogen Energy, 2009

a b s t r a c t Hydrogen storage capacity of Si n C 60 is studied via first-principles theory bas... more a b s t r a c t Hydrogen storage capacity of Si n C 60 is studied via first-principles theory based on DFT and Canonical Monte Carlo Simulation (CMCS). It is shown that Si atoms strongly prefer D-site rather than other sites and in these structures maximum number of hydrogen molecule onto any Si atom is one. Each Si atom adsorbs one hydrogen molecule in molecular form and with proper binding energies when Si atom is placed in any D-site of C 60 . Si atoms enhance remarkably hydrogen storage capability in fullerene. ª (M. Hashemianzadeh). A v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / h e

Research paper thumbnail of Quantum chemical investigation of structural and electronic properties of trans- and cis-structures of some azo dyes for dye-sensitized solar cells

Computational and Theoretical Chemistry, 2017

Research paper thumbnail of Tuning of Elastic Properties of Nanotubes by Imposing a Transverse Electric Field: Computational Approach

The Journal of Physical Chemistry C, 2016

Research paper thumbnail of Molecular Interactions of Cationic and Anionic Surfactants in Mixed Monolayers and Aggregates

The Journal of Physical Chemistry B, Nov 1, 2008

The properties of anionic-rich and cationic-rich mixtures of CTAB (cetyltrimethylammonium bromide... more The properties of anionic-rich and cationic-rich mixtures of CTAB (cetyltrimethylammonium bromide) and SDS (sodium dodecyl sulfate) were investigated with conductometry and surface tension measurements and by determining the surfactant NMR self-diffusion coefficients. The critical aggregate concentration (CAC), surface tension reduction effectiveness(γ CAC ), surface excess(Γ max ), and mean molecular surface area (A min ) were determined from plots of the surface tension (γ) as a function of the total surfactant concentration. The compositions of the adsorbed films (Z) and aggregates ( ) were estimated by using regular solution theory, and then the interaction parameters in the aggregates ( ) and the adsorbed film phases ( σ ) were calculated. The results showed that the synergism between the surfactants enhances the formation of mixed aggregates and reduces the surface tension. Further, the nature and strength of the interaction between the surfactants in the mixtures were obtained by calculating the values of the following parameters: the interaction parameter, , the size parameter, F, and the nonrandom mixing parameter,P*. These results indicate that in ionic surfactant mixtures the optimized packing parameter has the highest value and that the size parameter can be used to account for deviations from the predictions of regular solution theory. It was concluded that, for planar air/ aqueous interfaces and aggregation systems, this nonideality increases as the temperature increases. This trend is attributed to the increased dehydration of the surfactant head groups that results from increases in temperature. Further, our conductometry measurements show that the counterion binding number of mixed micelles formed in mixtures with a high CTAB content is different to those with a high SDS content. This difference is due to either their different aggregation sizes or the different interactions between the head groups and the counterions.

Research paper thumbnail of Role of Interaction Energies in the Behavior of Mixed Surfactant Systems: A Lattice Monte Carlo Simulation

Langmuir, Sep 7, 2010

We have investigated micellization in systems containing two surfactant molecules with the same s... more We have investigated micellization in systems containing two surfactant molecules with the same structure using a lattice Monte Carlo simulation method. For the binary systems containing two surfactants, we have varied the head-head interactions or tail-tail repulsions in order to mimic the nonideal behavior of mixed surfactant systems and to manipulate the net interactions between surfactant molecules. The simulation results indicate that interactions between headgroups or tailgroups have an effect on thermodynamic properties such as the mixed critical micelle concentration (cmc), distribution of aggregates, shape of the aggregates, and composition of the micelles formed. Moreover, we have compared the simulation results with estimates based on regular solution theory, a mean-field theory, to determine the applicability of this theory to the nonideal mixed surfactant systems. We have found that the simulation results agree reasonable well with regular solution theory for the systems with attractions between headgroups and repulsions between tailgroups. However, the large discrepancies observed for the systems with head-head repulsions could be attributed to the disregarding of the correlation effect on the interaction among surfactant molecules and the nonrandom mixing effect in the theory.

Research paper thumbnail of Can Nitride-boron Nanocage Sense or Capture Carbon Monoxide? A Density Functional Theory Study

Research paper thumbnail of Effect of the adsorption of oxygen on electronic structures and geometrical parameters of armchair single-wall carbon nanotubes: A density functional study

Journal of Colloid and Interface Science, Apr 1, 2009

We investigated the effect of atomic and molecular oxygen adsorption on the geometries and electr... more We investigated the effect of atomic and molecular oxygen adsorption on the geometries and electronic properties of small and large armchair single-walled carbon nanotubes (SWCNTs) by means of the density functional theory (DFT). We calculated the equilibrium geometries, energetics, and electronic properties of the nanotubes as well as the tube-molecules. Global indices such as electronic chemical potential and hardness were calculated using the Kopmann's theorem. Our investigation involved the physisorption of molecular oxygen, chemisorption of atomic oxygen, and formation of epoxide-like structures. The adsorption energies of the oxygen molecules physisorbed to different sites were determined by calculating the short-range interactions. The effect of the tube diameter on the stability of the tube-O 2 system was studied for the different sites. Also we considered the orientation of O 2 molecule during adsorption of O 2 molecule on the outer surface of tubes. Adsorption of oxygen atom on top of the carbon atom of the tubes was also considered. We found out that O atoms bind to the outer surface of the SWCNTs to give stable epoxide-like structures. The most stable epoxide-like structure on the outer surface of the nanotubes was the (4, 4)-O system with a calculated adsorption energy of À2.944 eV.

Research paper thumbnail of Modeling the adsorptive selectivity of carbon nanotubes for effective separation of CO 2 /N 2 mixtures

J Mol Model, 2011

Canonical Monte Carlo (CMC) simulations were carried out to investigate the behavior of CO 2 and ... more Canonical Monte Carlo (CMC) simulations were carried out to investigate the behavior of CO 2 and N 2 mixtures upon adsorption on single walled carbon nanotubes (CNTs). In the simulation, all the particle-particle interactions between CO 2 , N and C were modeled using Lennard-Jones (LJ) potential. To provide deep insight into the effect of pore width, temperature, pressure and bulk composition on the adsorption behavior of CO 2 /N 2 mixtures, five different CNTs [(6,6), (7,7), (8,8) (9,9) and (10,10) CNT] with diameters ranging from 0.807 to 1.35 nm, three temperatures (300 323 and 343 K), six pressures (0.15, 2, 4, 6, 8 and 10 MPa), and three bulk mole compositions of carbon dioxide (0.3 0.5 and 0.7) were tested. The results from all the simulation conditions investigated in this work show that CNTs preferentially adsorb carbon dioxide relative to nitrogen in a binary mixture. The results are consistent with the hypothesis that stronger interaction of one component with the nanotube surface results in a higher adsorption capacity compared to the other component. An optimized pore size of D= 8.07 nm corresponding to (6, 6) CNT, at T=300 K and P=0.15 MPa at a bulk mole composition of y CO2 =0.3 was identified in which carbon nanotubes demonstrate the greatest selectivity for separation of carbon dioxide relative to nitrogen. In addition, it is worth pointing out that, under similar simulation conditions, CNTs exhibit higher selectivity compared to other carbon-based materials [carbon membrane polyimide (PI) and PI/multi-wall carbon nanotubes (MWCNTs)] for CO 2 adsorption. As a prototype, the selectivity of an equimolar mixture of CO 2 /N 2 for adsorption on (6, 6) CNTs at 300 K and 0.15 MPa reaches 9.68, which is considerably larger than that reported in carbon membrane. Therefore, it can be concluded that carbon nanotubes can act as a capable adsorbent for adsorption/desorption of CO 2 in comparison with other carbon-based materials in the literature.

Research paper thumbnail of Computational investigation of low band gap dyes based on 2-styryl-5-phenylazo-pyrrole for dye-sensitized solar cells

Current Applied Physics, 2014

ABSTRACT In this work, the geometry, electronic properties and absorption spectra of low band gap... more ABSTRACT In this work, the geometry, electronic properties and absorption spectra of low band gap organic dyes based on 2-styryl-5-phenylazo-pyrrole, C1, C2 and S dyes were theoretically investigated via DFT and TD-DFT in the gas phase and in solution. Theoretical calculations have been also carried out on the adsorption of these dyes on the TiO2 anatase (101) surface that show bidentate bridging is preferred adsorption mode in these dyes. Highest charge populated in the acceptor group, longest lifetime of the first excited state, highest electronic coupling constant (|VRP|) of the S dye and the most negative shift of the conduction band of TiO2 due to the adsorption of the S dye on TiO2 (ΔECB) show that these parameters are favorable to increase Voc. The calculated results of these dyes demonstrate that theoretical calculations are useful not only in the description of these properties, but also in the design of new sensitizers.

Research paper thumbnail of The Effect of Amino Substituents on the Interactions of Quinazolone Derivatives with c-KIT G-Quadruplex: Insight from Molecular Dynamics Simulation Study to Rational Design of Ligands

Research paper thumbnail of Investigation of thermodynamic and structural properties of drug delivery system based on carbon nanotubes as a carboplatin drug carrier by molecular dynamics simulations

Journal of Inclusion Phenomena and Macrocyclic Chemistry, 2015

Research paper thumbnail of Density functional theory study of new azo dyes with different π-spacers for dye-sensitized solar cells

Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy, Jan 15, 2015

Some of new azo-based metal-free dyes with different π-conjugation spacers, such as carbazole, fl... more Some of new azo-based metal-free dyes with different π-conjugation spacers, such as carbazole, fluorene, pyrrole, thiophene, furan and thiazole, have been investigated with density functional theory (DFT) and time-dependent DFT (TDDFT) calculations. Theoretical calculations allow us to quantify factors such as light harvesting efficiency (LHE), electron injection driving force (ΔG(inject)) and the weight of the LUMO orbital on the carboxylic group (QLUMO) related to the short-circuit photocurrent density (Jsc), and to evaluate both charge recombination between the semiconductor conduction band electrons and the oxidized dyes and/or electrolyte, and also the shift of the conduction band of the semiconductor as a result of the adsorption of the dyes onto the semiconductor surface, associated with the open-circuit photovoltage (Voc). According to the results, we could predict that how the π-conjugation spacers influence the Jsc as well as the Voc of DSSCs. Among these dyes, the carbazo...

Research paper thumbnail of Mixed micellization of gemini and conventional surfactant in aqueous solution: A lattice Monte Carlo simulation

Journal of Molecular Graphics and Modelling, 2014

In the current study, we have investigated the micellization of pure gemini surfactants and a mix... more In the current study, we have investigated the micellization of pure gemini surfactants and a mixture of gemini and conventional surfactants using a 3D lattice Monte Carlo simulation method. For the pure gemini surfactant system, the effects of tail length on CMC and aggregation number were studied, and the simulation results were found to be in excellent agreement with the experimental results. For a mixture of gemini and conventional surfactants, variations in the mixed CMC, interaction parameter β, and excess Gibbs free energy G(E) with composition revealed synergism in micelle formation. Simulation results were compared to estimations made using regular solution theory to determine the applicability of this theory for non-ideal mixed surfactant systems. A large discrepancy was observed between the behavior of parameters such as the activity coefficients fi and the excess Gibbs free energy G(E) and the expected behavior of these parameters as predicted by regular solution theory. Therefore, we have used the modified version of regular solution theory. This three parameter model contains two parameters in addition to the interaction parameters: the size parameter, ρ, which reflects differences in the size of components, and the packing parameter, P*, which reflects nonrandom mixing in mixed micelles. The proposed model provides a good description of the behavior of gemini and conventional surfactant mixtures. The results indicated that as the chain length of gemini surfactants in mixture is increased, the size parameter remains constant while the interaction and packing parameters increase.

Research paper thumbnail of Hydrogen adsorption on SiC nanotube under transverse electric field

Physics Letters A, 2014

Using density functional theory, we present a model to illustrate that under a transverse electri... more Using density functional theory, we present a model to illustrate that under a transverse electric field the overall amount of hydrogen storage can be increased on the SiC nanotube. Due to the cylindrical shape of the nanotube, an electric field does not have the similar effects on the different adsorption sites. Although it has the desired effects on some sites, the electric field may lead the binding energy to decrease on some other sites. We demonstrate that the binding energy decreases slightly just on the two small areas and increases significantly on the largest part of the nanotube surface.

Research paper thumbnail of Molecular Interactions of Cationic and Anionic Surfactants in Mixed Monolayers and Aggregates

The Journal of Physical Chemistry B, 2008

The properties of anionic-rich and cationic-rich mixtures of CTAB (cetyltrimethylammonium bromide... more The properties of anionic-rich and cationic-rich mixtures of CTAB (cetyltrimethylammonium bromide) and SDS (sodium dodecyl sulfate) were investigated with conductometry and surface tension measurements and by determining the surfactant NMR self-diffusion coefficients. The critical aggregate concentration (CAC), surface tension reduction effectiveness(γ CAC ), surface excess(Γ max ), and mean molecular surface area (A min ) were determined from plots of the surface tension (γ) as a function of the total surfactant concentration. The compositions of the adsorbed films (Z) and aggregates ( ) were estimated by using regular solution theory, and then the interaction parameters in the aggregates ( ) and the adsorbed film phases ( σ ) were calculated. The results showed that the synergism between the surfactants enhances the formation of mixed aggregates and reduces the surface tension. Further, the nature and strength of the interaction between the surfactants in the mixtures were obtained by calculating the values of the following parameters: the interaction parameter, , the size parameter, F, and the nonrandom mixing parameter,P*. These results indicate that in ionic surfactant mixtures the optimized packing parameter has the highest value and that the size parameter can be used to account for deviations from the predictions of regular solution theory. It was concluded that, for planar air/ aqueous interfaces and aggregation systems, this nonideality increases as the temperature increases. This trend is attributed to the increased dehydration of the surfactant head groups that results from increases in temperature. Further, our conductometry measurements show that the counterion binding number of mixed micelles formed in mixtures with a high CTAB content is different to those with a high SDS content. This difference is due to either their different aggregation sizes or the different interactions between the head groups and the counterions.

Research paper thumbnail of Complexation between a Macromolecule and an Amphiphile by Monte Carlo Technique

The Journal of Physical Chemistry B, 2006

Using a simple modified version of Larson's model, we stu... more Using a simple modified version of Larson's model, we studied the complexation between a macromolecule and an amphiphile in a dilute range of concentrations. The main characteristic of amphiphile molecules, that is, the hydrophobicity of the tails and hydrophilicity of the heads, is used to model the self-assembling process. Contrary to the molecular thermodynamics approaches, no prior shape was considered for the aggregates and the system was allowed to choose the most stable structure. For true ensemble averaging, without any synthetic results, configurational bias Monte Carlo and reptation moves are used to produce a Markov chain of configurations. From the results, it is found that the macromolecule causes the clusters of surfactants to be formed at a concentration much lower than the critical micelle concentration. Furthermore, the shape of the clusters tends to be more spherical, which is in line with theory and experiments. From the results, it is learned how a polymer can change the behavior of an amphiphilic molecule. All of the results are in good qualitative agreement with experimental and molecular thermodynamics results. Furthermore, the model predicts network formation between bound clusters at high concentrations of the surfactant.

Research paper thumbnail of Theoretical Study of the Interactions between Isolated DNA Bases and Various Groups IA and IIA Metal Ions by Ab Initio Calculations

Monatshefte für Chemie - Chemical Monthly, 2008

Interactions of the DNA bases adenine (A), guanine (G), cytosine (C), and thymine (T) with variou... more Interactions of the DNA bases adenine (A), guanine (G), cytosine (C), and thymine (T) with various metal ions (M) of groups IA and IIA of the periodic table of the elements were studied at the HF, MP2, and DFT levels of theory. The structures and thermodynamic stabilities of these species were studied at the gas phase. The calculations uphold that there exist two active sites in G and one in A, C, and T. The calculations also show that the O 2 atom in T is a more active site for metal ion bindings than that in C. The stability energies for G . . . M complexes are larger than those for A . . . M complexes and the stability energies for T . . . M complexes are larger than those for C . . . M complexes. As z=r ratio for the metal ion increases, the interaction energy for the complex increases systematically. Thermodynamic quantities such as ÁH, ÁG, ÁS, and ln K were determined for each complexation reaction, [Base þ M nþ ! (Base . . . M) nþ ]. A, G, and C complexation reactions except for C . . . Rb þ are exothermic. The situation is quite different for T complexation reactions and all except for T . . . Be 2þ and T . . . Mg 2þ are endothermic.

Research paper thumbnail of DFT-Based QSAR Study of Valproic Acid and its Derivatives

QSAR & Combinatorial Science, 2008

... Majid Hashemianzadeha, Mohammad Ali Safarpoura*, Kiana Gholamjani-Moghaddama and Ahmad Reza M... more ... Majid Hashemianzadeha, Mohammad Ali Safarpoura*, Kiana Gholamjani-Moghaddama and Ahmad Reza Mehdipourb a Department of Physical Chemistry, Faculty of Chemistry, Iran University of ... We also gratefully acknowledge Ms. M. Jamali and Ms. F. Taghavi for their help. ...

Research paper thumbnail of Role of Interaction Energies in the Behavior of Mixed Surfactant Systems: A Lattice Monte Carlo Simulation

Langmuir, 2010

We have investigated micellization in systems containing two surfactant molecules with the same s... more We have investigated micellization in systems containing two surfactant molecules with the same structure using a lattice Monte Carlo simulation method. For the binary systems containing two surfactants, we have varied the head-head interactions or tail-tail repulsions in order to mimic the nonideal behavior of mixed surfactant systems and to manipulate the net interactions between surfactant molecules. The simulation results indicate that interactions between headgroups or tailgroups have an effect on thermodynamic properties such as the mixed critical micelle concentration (cmc), distribution of aggregates, shape of the aggregates, and composition of the micelles formed. Moreover, we have compared the simulation results with estimates based on regular solution theory, a mean-field theory, to determine the applicability of this theory to the nonideal mixed surfactant systems. We have found that the simulation results agree reasonable well with regular solution theory for the systems with attractions between headgroups and repulsions between tailgroups. However, the large discrepancies observed for the systems with head-head repulsions could be attributed to the disregarding of the correlation effect on the interaction among surfactant molecules and the nonrandom mixing effect in the theory.

Research paper thumbnail of First-principles study of hydrogen storage on Si atoms decorated C6o

International Journal of Hydrogen Energy, 2009

a b s t r a c t Hydrogen storage capacity of Si n C 60 is studied via first-principles theory bas... more a b s t r a c t Hydrogen storage capacity of Si n C 60 is studied via first-principles theory based on DFT and Canonical Monte Carlo Simulation (CMCS). It is shown that Si atoms strongly prefer D-site rather than other sites and in these structures maximum number of hydrogen molecule onto any Si atom is one. Each Si atom adsorbs one hydrogen molecule in molecular form and with proper binding energies when Si atom is placed in any D-site of C 60 . Si atoms enhance remarkably hydrogen storage capability in fullerene. ª (M. Hashemianzadeh). A v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / h e

Research paper thumbnail of First-principles study of hydrogen storage on Si atoms decorated C60

International Journal of Hydrogen Energy, 2009

a b s t r a c t Hydrogen storage capacity of Si n C 60 is studied via first-principles theory bas... more a b s t r a c t Hydrogen storage capacity of Si n C 60 is studied via first-principles theory based on DFT and Canonical Monte Carlo Simulation (CMCS). It is shown that Si atoms strongly prefer D-site rather than other sites and in these structures maximum number of hydrogen molecule onto any Si atom is one. Each Si atom adsorbs one hydrogen molecule in molecular form and with proper binding energies when Si atom is placed in any D-site of C 60 . Si atoms enhance remarkably hydrogen storage capability in fullerene. ª (M. Hashemianzadeh). A v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / h e

Research paper thumbnail of Quantum chemical investigation of structural and electronic properties of trans- and cis-structures of some azo dyes for dye-sensitized solar cells

Computational and Theoretical Chemistry, 2017

Research paper thumbnail of Tuning of Elastic Properties of Nanotubes by Imposing a Transverse Electric Field: Computational Approach

The Journal of Physical Chemistry C, 2016

Research paper thumbnail of Molecular Interactions of Cationic and Anionic Surfactants in Mixed Monolayers and Aggregates

The Journal of Physical Chemistry B, Nov 1, 2008

The properties of anionic-rich and cationic-rich mixtures of CTAB (cetyltrimethylammonium bromide... more The properties of anionic-rich and cationic-rich mixtures of CTAB (cetyltrimethylammonium bromide) and SDS (sodium dodecyl sulfate) were investigated with conductometry and surface tension measurements and by determining the surfactant NMR self-diffusion coefficients. The critical aggregate concentration (CAC), surface tension reduction effectiveness(γ CAC ), surface excess(Γ max ), and mean molecular surface area (A min ) were determined from plots of the surface tension (γ) as a function of the total surfactant concentration. The compositions of the adsorbed films (Z) and aggregates ( ) were estimated by using regular solution theory, and then the interaction parameters in the aggregates ( ) and the adsorbed film phases ( σ ) were calculated. The results showed that the synergism between the surfactants enhances the formation of mixed aggregates and reduces the surface tension. Further, the nature and strength of the interaction between the surfactants in the mixtures were obtained by calculating the values of the following parameters: the interaction parameter, , the size parameter, F, and the nonrandom mixing parameter,P*. These results indicate that in ionic surfactant mixtures the optimized packing parameter has the highest value and that the size parameter can be used to account for deviations from the predictions of regular solution theory. It was concluded that, for planar air/ aqueous interfaces and aggregation systems, this nonideality increases as the temperature increases. This trend is attributed to the increased dehydration of the surfactant head groups that results from increases in temperature. Further, our conductometry measurements show that the counterion binding number of mixed micelles formed in mixtures with a high CTAB content is different to those with a high SDS content. This difference is due to either their different aggregation sizes or the different interactions between the head groups and the counterions.

Research paper thumbnail of Role of Interaction Energies in the Behavior of Mixed Surfactant Systems: A Lattice Monte Carlo Simulation

Langmuir, Sep 7, 2010

We have investigated micellization in systems containing two surfactant molecules with the same s... more We have investigated micellization in systems containing two surfactant molecules with the same structure using a lattice Monte Carlo simulation method. For the binary systems containing two surfactants, we have varied the head-head interactions or tail-tail repulsions in order to mimic the nonideal behavior of mixed surfactant systems and to manipulate the net interactions between surfactant molecules. The simulation results indicate that interactions between headgroups or tailgroups have an effect on thermodynamic properties such as the mixed critical micelle concentration (cmc), distribution of aggregates, shape of the aggregates, and composition of the micelles formed. Moreover, we have compared the simulation results with estimates based on regular solution theory, a mean-field theory, to determine the applicability of this theory to the nonideal mixed surfactant systems. We have found that the simulation results agree reasonable well with regular solution theory for the systems with attractions between headgroups and repulsions between tailgroups. However, the large discrepancies observed for the systems with head-head repulsions could be attributed to the disregarding of the correlation effect on the interaction among surfactant molecules and the nonrandom mixing effect in the theory.

Research paper thumbnail of Can Nitride-boron Nanocage Sense or Capture Carbon Monoxide? A Density Functional Theory Study

Research paper thumbnail of Effect of the adsorption of oxygen on electronic structures and geometrical parameters of armchair single-wall carbon nanotubes: A density functional study

Journal of Colloid and Interface Science, Apr 1, 2009

We investigated the effect of atomic and molecular oxygen adsorption on the geometries and electr... more We investigated the effect of atomic and molecular oxygen adsorption on the geometries and electronic properties of small and large armchair single-walled carbon nanotubes (SWCNTs) by means of the density functional theory (DFT). We calculated the equilibrium geometries, energetics, and electronic properties of the nanotubes as well as the tube-molecules. Global indices such as electronic chemical potential and hardness were calculated using the Kopmann's theorem. Our investigation involved the physisorption of molecular oxygen, chemisorption of atomic oxygen, and formation of epoxide-like structures. The adsorption energies of the oxygen molecules physisorbed to different sites were determined by calculating the short-range interactions. The effect of the tube diameter on the stability of the tube-O 2 system was studied for the different sites. Also we considered the orientation of O 2 molecule during adsorption of O 2 molecule on the outer surface of tubes. Adsorption of oxygen atom on top of the carbon atom of the tubes was also considered. We found out that O atoms bind to the outer surface of the SWCNTs to give stable epoxide-like structures. The most stable epoxide-like structure on the outer surface of the nanotubes was the (4, 4)-O system with a calculated adsorption energy of À2.944 eV.

Research paper thumbnail of Modeling the adsorptive selectivity of carbon nanotubes for effective separation of CO 2 /N 2 mixtures

J Mol Model, 2011

Canonical Monte Carlo (CMC) simulations were carried out to investigate the behavior of CO 2 and ... more Canonical Monte Carlo (CMC) simulations were carried out to investigate the behavior of CO 2 and N 2 mixtures upon adsorption on single walled carbon nanotubes (CNTs). In the simulation, all the particle-particle interactions between CO 2 , N and C were modeled using Lennard-Jones (LJ) potential. To provide deep insight into the effect of pore width, temperature, pressure and bulk composition on the adsorption behavior of CO 2 /N 2 mixtures, five different CNTs [(6,6), (7,7), (8,8) (9,9) and (10,10) CNT] with diameters ranging from 0.807 to 1.35 nm, three temperatures (300 323 and 343 K), six pressures (0.15, 2, 4, 6, 8 and 10 MPa), and three bulk mole compositions of carbon dioxide (0.3 0.5 and 0.7) were tested. The results from all the simulation conditions investigated in this work show that CNTs preferentially adsorb carbon dioxide relative to nitrogen in a binary mixture. The results are consistent with the hypothesis that stronger interaction of one component with the nanotube surface results in a higher adsorption capacity compared to the other component. An optimized pore size of D= 8.07 nm corresponding to (6, 6) CNT, at T=300 K and P=0.15 MPa at a bulk mole composition of y CO2 =0.3 was identified in which carbon nanotubes demonstrate the greatest selectivity for separation of carbon dioxide relative to nitrogen. In addition, it is worth pointing out that, under similar simulation conditions, CNTs exhibit higher selectivity compared to other carbon-based materials [carbon membrane polyimide (PI) and PI/multi-wall carbon nanotubes (MWCNTs)] for CO 2 adsorption. As a prototype, the selectivity of an equimolar mixture of CO 2 /N 2 for adsorption on (6, 6) CNTs at 300 K and 0.15 MPa reaches 9.68, which is considerably larger than that reported in carbon membrane. Therefore, it can be concluded that carbon nanotubes can act as a capable adsorbent for adsorption/desorption of CO 2 in comparison with other carbon-based materials in the literature.

Research paper thumbnail of Computational investigation of low band gap dyes based on 2-styryl-5-phenylazo-pyrrole for dye-sensitized solar cells

Current Applied Physics, 2014

ABSTRACT In this work, the geometry, electronic properties and absorption spectra of low band gap... more ABSTRACT In this work, the geometry, electronic properties and absorption spectra of low band gap organic dyes based on 2-styryl-5-phenylazo-pyrrole, C1, C2 and S dyes were theoretically investigated via DFT and TD-DFT in the gas phase and in solution. Theoretical calculations have been also carried out on the adsorption of these dyes on the TiO2 anatase (101) surface that show bidentate bridging is preferred adsorption mode in these dyes. Highest charge populated in the acceptor group, longest lifetime of the first excited state, highest electronic coupling constant (|VRP|) of the S dye and the most negative shift of the conduction band of TiO2 due to the adsorption of the S dye on TiO2 (ΔECB) show that these parameters are favorable to increase Voc. The calculated results of these dyes demonstrate that theoretical calculations are useful not only in the description of these properties, but also in the design of new sensitizers.

Research paper thumbnail of The Effect of Amino Substituents on the Interactions of Quinazolone Derivatives with c-KIT G-Quadruplex: Insight from Molecular Dynamics Simulation Study to Rational Design of Ligands

Research paper thumbnail of Investigation of thermodynamic and structural properties of drug delivery system based on carbon nanotubes as a carboplatin drug carrier by molecular dynamics simulations

Journal of Inclusion Phenomena and Macrocyclic Chemistry, 2015

Research paper thumbnail of Density functional theory study of new azo dyes with different π-spacers for dye-sensitized solar cells

Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy, Jan 15, 2015

Some of new azo-based metal-free dyes with different π-conjugation spacers, such as carbazole, fl... more Some of new azo-based metal-free dyes with different π-conjugation spacers, such as carbazole, fluorene, pyrrole, thiophene, furan and thiazole, have been investigated with density functional theory (DFT) and time-dependent DFT (TDDFT) calculations. Theoretical calculations allow us to quantify factors such as light harvesting efficiency (LHE), electron injection driving force (ΔG(inject)) and the weight of the LUMO orbital on the carboxylic group (QLUMO) related to the short-circuit photocurrent density (Jsc), and to evaluate both charge recombination between the semiconductor conduction band electrons and the oxidized dyes and/or electrolyte, and also the shift of the conduction band of the semiconductor as a result of the adsorption of the dyes onto the semiconductor surface, associated with the open-circuit photovoltage (Voc). According to the results, we could predict that how the π-conjugation spacers influence the Jsc as well as the Voc of DSSCs. Among these dyes, the carbazo...

Research paper thumbnail of Mixed micellization of gemini and conventional surfactant in aqueous solution: A lattice Monte Carlo simulation

Journal of Molecular Graphics and Modelling, 2014

In the current study, we have investigated the micellization of pure gemini surfactants and a mix... more In the current study, we have investigated the micellization of pure gemini surfactants and a mixture of gemini and conventional surfactants using a 3D lattice Monte Carlo simulation method. For the pure gemini surfactant system, the effects of tail length on CMC and aggregation number were studied, and the simulation results were found to be in excellent agreement with the experimental results. For a mixture of gemini and conventional surfactants, variations in the mixed CMC, interaction parameter β, and excess Gibbs free energy G(E) with composition revealed synergism in micelle formation. Simulation results were compared to estimations made using regular solution theory to determine the applicability of this theory for non-ideal mixed surfactant systems. A large discrepancy was observed between the behavior of parameters such as the activity coefficients fi and the excess Gibbs free energy G(E) and the expected behavior of these parameters as predicted by regular solution theory. Therefore, we have used the modified version of regular solution theory. This three parameter model contains two parameters in addition to the interaction parameters: the size parameter, ρ, which reflects differences in the size of components, and the packing parameter, P*, which reflects nonrandom mixing in mixed micelles. The proposed model provides a good description of the behavior of gemini and conventional surfactant mixtures. The results indicated that as the chain length of gemini surfactants in mixture is increased, the size parameter remains constant while the interaction and packing parameters increase.

Research paper thumbnail of Hydrogen adsorption on SiC nanotube under transverse electric field

Physics Letters A, 2014

Using density functional theory, we present a model to illustrate that under a transverse electri... more Using density functional theory, we present a model to illustrate that under a transverse electric field the overall amount of hydrogen storage can be increased on the SiC nanotube. Due to the cylindrical shape of the nanotube, an electric field does not have the similar effects on the different adsorption sites. Although it has the desired effects on some sites, the electric field may lead the binding energy to decrease on some other sites. We demonstrate that the binding energy decreases slightly just on the two small areas and increases significantly on the largest part of the nanotube surface.

Research paper thumbnail of Molecular Interactions of Cationic and Anionic Surfactants in Mixed Monolayers and Aggregates

The Journal of Physical Chemistry B, 2008

The properties of anionic-rich and cationic-rich mixtures of CTAB (cetyltrimethylammonium bromide... more The properties of anionic-rich and cationic-rich mixtures of CTAB (cetyltrimethylammonium bromide) and SDS (sodium dodecyl sulfate) were investigated with conductometry and surface tension measurements and by determining the surfactant NMR self-diffusion coefficients. The critical aggregate concentration (CAC), surface tension reduction effectiveness(γ CAC ), surface excess(Γ max ), and mean molecular surface area (A min ) were determined from plots of the surface tension (γ) as a function of the total surfactant concentration. The compositions of the adsorbed films (Z) and aggregates ( ) were estimated by using regular solution theory, and then the interaction parameters in the aggregates ( ) and the adsorbed film phases ( σ ) were calculated. The results showed that the synergism between the surfactants enhances the formation of mixed aggregates and reduces the surface tension. Further, the nature and strength of the interaction between the surfactants in the mixtures were obtained by calculating the values of the following parameters: the interaction parameter, , the size parameter, F, and the nonrandom mixing parameter,P*. These results indicate that in ionic surfactant mixtures the optimized packing parameter has the highest value and that the size parameter can be used to account for deviations from the predictions of regular solution theory. It was concluded that, for planar air/ aqueous interfaces and aggregation systems, this nonideality increases as the temperature increases. This trend is attributed to the increased dehydration of the surfactant head groups that results from increases in temperature. Further, our conductometry measurements show that the counterion binding number of mixed micelles formed in mixtures with a high CTAB content is different to those with a high SDS content. This difference is due to either their different aggregation sizes or the different interactions between the head groups and the counterions.

Research paper thumbnail of Complexation between a Macromolecule and an Amphiphile by Monte Carlo Technique

The Journal of Physical Chemistry B, 2006

Using a simple modified version of Larson's model, we stu... more Using a simple modified version of Larson's model, we studied the complexation between a macromolecule and an amphiphile in a dilute range of concentrations. The main characteristic of amphiphile molecules, that is, the hydrophobicity of the tails and hydrophilicity of the heads, is used to model the self-assembling process. Contrary to the molecular thermodynamics approaches, no prior shape was considered for the aggregates and the system was allowed to choose the most stable structure. For true ensemble averaging, without any synthetic results, configurational bias Monte Carlo and reptation moves are used to produce a Markov chain of configurations. From the results, it is found that the macromolecule causes the clusters of surfactants to be formed at a concentration much lower than the critical micelle concentration. Furthermore, the shape of the clusters tends to be more spherical, which is in line with theory and experiments. From the results, it is learned how a polymer can change the behavior of an amphiphilic molecule. All of the results are in good qualitative agreement with experimental and molecular thermodynamics results. Furthermore, the model predicts network formation between bound clusters at high concentrations of the surfactant.

Research paper thumbnail of Theoretical Study of the Interactions between Isolated DNA Bases and Various Groups IA and IIA Metal Ions by Ab Initio Calculations

Monatshefte für Chemie - Chemical Monthly, 2008

Interactions of the DNA bases adenine (A), guanine (G), cytosine (C), and thymine (T) with variou... more Interactions of the DNA bases adenine (A), guanine (G), cytosine (C), and thymine (T) with various metal ions (M) of groups IA and IIA of the periodic table of the elements were studied at the HF, MP2, and DFT levels of theory. The structures and thermodynamic stabilities of these species were studied at the gas phase. The calculations uphold that there exist two active sites in G and one in A, C, and T. The calculations also show that the O 2 atom in T is a more active site for metal ion bindings than that in C. The stability energies for G . . . M complexes are larger than those for A . . . M complexes and the stability energies for T . . . M complexes are larger than those for C . . . M complexes. As z=r ratio for the metal ion increases, the interaction energy for the complex increases systematically. Thermodynamic quantities such as ÁH, ÁG, ÁS, and ln K were determined for each complexation reaction, [Base þ M nþ ! (Base . . . M) nþ ]. A, G, and C complexation reactions except for C . . . Rb þ are exothermic. The situation is quite different for T complexation reactions and all except for T . . . Be 2þ and T . . . Mg 2þ are endothermic.

Research paper thumbnail of DFT-Based QSAR Study of Valproic Acid and its Derivatives

QSAR & Combinatorial Science, 2008

... Majid Hashemianzadeha, Mohammad Ali Safarpoura*, Kiana Gholamjani-Moghaddama and Ahmad Reza M... more ... Majid Hashemianzadeha, Mohammad Ali Safarpoura*, Kiana Gholamjani-Moghaddama and Ahmad Reza Mehdipourb a Department of Physical Chemistry, Faculty of Chemistry, Iran University of ... We also gratefully acknowledge Ms. M. Jamali and Ms. F. Taghavi for their help. ...

Research paper thumbnail of Role of Interaction Energies in the Behavior of Mixed Surfactant Systems: A Lattice Monte Carlo Simulation

Langmuir, 2010

We have investigated micellization in systems containing two surfactant molecules with the same s... more We have investigated micellization in systems containing two surfactant molecules with the same structure using a lattice Monte Carlo simulation method. For the binary systems containing two surfactants, we have varied the head-head interactions or tail-tail repulsions in order to mimic the nonideal behavior of mixed surfactant systems and to manipulate the net interactions between surfactant molecules. The simulation results indicate that interactions between headgroups or tailgroups have an effect on thermodynamic properties such as the mixed critical micelle concentration (cmc), distribution of aggregates, shape of the aggregates, and composition of the micelles formed. Moreover, we have compared the simulation results with estimates based on regular solution theory, a mean-field theory, to determine the applicability of this theory to the nonideal mixed surfactant systems. We have found that the simulation results agree reasonable well with regular solution theory for the systems with attractions between headgroups and repulsions between tailgroups. However, the large discrepancies observed for the systems with head-head repulsions could be attributed to the disregarding of the correlation effect on the interaction among surfactant molecules and the nonrandom mixing effect in the theory.