songul guryel | Vrije Universiteit Brussel (original) (raw)

Papers by songul guryel

Chemical Physics Letters, Mar 1, 2013

Journal of Physical Chemistry C, Oct 15, 2012

In this study, the Young's and flexural moduli of single-and double-layer graphene have been theo... more In this study, the Young's and flexural moduli of single-and double-layer graphene have been theoretically investigated using periodic boundary condition (PBC) density functional theory (DFT) with the PBE, HSE06 H , and M06L functionals in conjunction with the 6-31G* and the 3-21G basis sets. The unit-cell size and shape dependence as well as the directional dependencies of the mechanical properties have also been investigated. Additionally, the calculated stretching and flexural strain−stress curves are reported. Finally, finiteelement simulations have been performed so as to find a homogeneous equivalent isotropic transverse material for single-layer graphene, in order to reproduce mechanical behavior in both tensile and bending sollicitations.

Journal of the American Chemical Society, Sep 3, 2019

We report the preparation of triazatruxenefaced tetrahedral cage 1, which exhibits two diastereom... more We report the preparation of triazatruxenefaced tetrahedral cage 1, which exhibits two diastereomeric configurations (T1 and T2) that differ in the handedness of the ligand faces relative to that of the octahedrally coordinated metal centers. At lower temperatures, T1 is favored, whereas T2 predominates at higher temperatures. Host−guest studies show that T1 binds small aliphatic guests, whereas T2 binds larger aromatic molecules, with these changes in binding preference resulting from differences in cavity size and degree of enclosure. Thus, by a change in temperature the cage system can be triggered to eject one bound guest and take up another.

Physical Chemistry Chemical Physics, 2013

Due to its unique mechanical properties, graphene can be applied for reinforcement in nanocomposi... more Due to its unique mechanical properties, graphene can be applied for reinforcement in nanocomposites. We analyse the Young's modulus of graphene at the semi-empirical PM6 level of theory. The internal forces are calculated and the Young's modulus is predicted for a finite graphene sheet when external strain is applied on the system. These results are in a good agreement with theoretical and experimental results from the literature giving values of about 1 TPa for the Young's modulus. Stress-strain curves are computed for elongation up to 20%. In addition, the influence of the presence of a single vacancy, as well as for oxygenation of a vacancy, on the mechanical properties of graphene has been analysed. Our results indicate that when applying the deformation locally onto the system, higher local stress can be induced, as confirmed by Finite Element Analysis. Also, the presence of structural defects in the system will stiffen the system upon low strain, but reduces the elastic limit from more than 20% strain for pristine graphene to less than 10% strain when defects are present.

Physical Chemistry Chemical Physics, 2017

The structure and morphology of three polymer/graphene nanocomposites have been studied using cla... more The structure and morphology of three polymer/graphene nanocomposites have been studied using classical molecular dynamics (MD) simulations. The simulations use 10-monomer oligomeric chains of three polymers: polyethylene (PE), polystyrene (PS) and polyvinylidene fluoride (PVDF). The structure of the polymer chains at the graphene surface have been investigated and characterized by pair correlation functions (PCF), g(r), g(θ) and g(r,θ). In addition, the influence of the temperature on the graphene/polymer interactions has been analysed for each of the three polymer/graphene nanocomposite systems. The results indicate that graphene induces order in both the PE and PVDF systems by providing a nucleation site for crystallisation, steering the growth of oligomer crystals according to the orientation of the graphene sheet, whereas the PS system remains disordered in the presence of graphene. The overall results are in line with the findings in a recent quantumchemical study by some of the present authors.

Journal of Molecular Modeling, Feb 1, 2017

Understanding the interaction between graphene and polymers is of essential interest when designi... more Understanding the interaction between graphene and polymers is of essential interest when designing novel nanocomposites with reinforced mechanical and electrical properties. In this computational study, the interaction of pristine graphene (PG) and graphene oxide (GO) with a series of functional groups, representative of the functionalised buildings blocks occurring in different polymers, and attached to aliphatic and aromatic chains, is analyzed using dispersioncorrected semi-empirical methods (PM6-D3H4X) and density functional theory calculations with empirical dispersion corrections. Functional groups include alkyl, hydroxyl, aldehyde, carboxyl, amino and nitro groups, and the binding energies of these groups with graphene derivatives (PG and GO) are determined. Nitro-and carbonyl groups display stronger interactions in both aliphatic and aromatic chains. The importance of dispersion-type and non-covalent interactions (NCI) in general, which typically, double the interaction energies, is revealed. The results are interpreted in an extensive NCI analysis in order to characterize the different types of NCI, providing a better understanding of the nature of the interaction (π-π stacking, CH-π bonding, H-bonding and lone pair-π interaction) at stake. In order to highlight the influence of polymer structure/conformation on top of that of their functional groups, the binding of three polymers, polyethylene (PE), polystyrene (PS) and polyvinylidene fluoride (PVDF), on pristine graphene is also investigated. Our calculations indicate that, although all polymers exhibit evident attractive interactions with the graphene sheet, the overall interaction is strongly influenced by the specific polymer structure. Thus, three main conformations of PVDF (the so-called α, β and γ, ε conformations) are analyzed and we find that, although the α-conformer with a trans-gauche-trans-gauche (TGTG') conformation is the lowest energy conformer, the β-conformation of PVDF with the hydrogen atoms facing the graphene (BF-up^) has the strongest interaction with the graphene surface among the polymers under consideration. Taken together, our computational approach sheds light on the character and importance of non-covalent graphene-polymer functional group interactions combined with the structural/conformational properties of the polymer, which are at stake in the design of novel nanocomposites with reinforced mechanical and electrical properties.

Thermodynamic stability of graphene against stacking in the gas phase and in different solvents (... more Thermodynamic stability of graphene against stacking in the gas phase and in different solvents (N-methyl-2-pyrrolidone), dimethyl sulfoxide, and water) has been investigated using the semi-empirical PM6 method combined with supermolecular approach, and with Periodic Boundary Conditions using Density Functional Theory in conjunction with the Perdew-Burke-Erzernhof functional. In the case of a supermolecular approach, the effect of the ratio of the edge and the center part on the solvation enthalpy has also been investigated.

The Journal of Physical Chemistry C, 2012

Phys. Chem. Chem. Phys., 2013

Due to its unique mechanical properties, graphene can be applied for reinforcement in nanocomposi... more Due to its unique mechanical properties, graphene can be applied for reinforcement in nanocomposites. We analyse the Young's modulus of graphene at the semi-empirical PM6 level of theory. The internal forces are calculated and the Young's modulus is predicted for a finite graphene sheet when external strain is applied on the system. These results are in a good agreement with theoretical and experimental results from the literature giving values of about 1 TPa for the Young's modulus. Stress-strain curves are computed for elongation up to 20%. In addition, the influence of the presence of a single vacancy, as well as for oxygenation of a vacancy, on the mechanical properties of graphene has been analysed. Our results indicate that when applying the deformation locally onto the system, higher local stress can be induced, as confirmed by Finite Element Analysis. Also, the presence of structural defects in the system will stiffen the system upon low strain, but reduces the elastic limit from more than 20% strain for pristine graphene to less than 10% strain when defects are present.

Chemical Physics Letters, 2013

In this Letter we predict the out-of-plane Young's modulus (perpendicular to the basal plane) and... more In this Letter we predict the out-of-plane Young's modulus (perpendicular to the basal plane) and the out-of-plane shear modulus of double-layer graphene using density functional theory calculations with periodic boundary conditions using the GAUSSIAN 09 program package. These values are discussed in the context of the corresponding values of graphite.

Chemical Physics Letters, Mar 1, 2013

Journal of Physical Chemistry C, Oct 15, 2012

In this study, the Young's and flexural moduli of single-and double-layer graphene have been theo... more In this study, the Young's and flexural moduli of single-and double-layer graphene have been theoretically investigated using periodic boundary condition (PBC) density functional theory (DFT) with the PBE, HSE06 H , and M06L functionals in conjunction with the 6-31G* and the 3-21G basis sets. The unit-cell size and shape dependence as well as the directional dependencies of the mechanical properties have also been investigated. Additionally, the calculated stretching and flexural strain−stress curves are reported. Finally, finiteelement simulations have been performed so as to find a homogeneous equivalent isotropic transverse material for single-layer graphene, in order to reproduce mechanical behavior in both tensile and bending sollicitations.

Journal of the American Chemical Society, Sep 3, 2019

We report the preparation of triazatruxenefaced tetrahedral cage 1, which exhibits two diastereom... more We report the preparation of triazatruxenefaced tetrahedral cage 1, which exhibits two diastereomeric configurations (T1 and T2) that differ in the handedness of the ligand faces relative to that of the octahedrally coordinated metal centers. At lower temperatures, T1 is favored, whereas T2 predominates at higher temperatures. Host−guest studies show that T1 binds small aliphatic guests, whereas T2 binds larger aromatic molecules, with these changes in binding preference resulting from differences in cavity size and degree of enclosure. Thus, by a change in temperature the cage system can be triggered to eject one bound guest and take up another.

Physical Chemistry Chemical Physics, 2013

Due to its unique mechanical properties, graphene can be applied for reinforcement in nanocomposi... more Due to its unique mechanical properties, graphene can be applied for reinforcement in nanocomposites. We analyse the Young's modulus of graphene at the semi-empirical PM6 level of theory. The internal forces are calculated and the Young's modulus is predicted for a finite graphene sheet when external strain is applied on the system. These results are in a good agreement with theoretical and experimental results from the literature giving values of about 1 TPa for the Young's modulus. Stress-strain curves are computed for elongation up to 20%. In addition, the influence of the presence of a single vacancy, as well as for oxygenation of a vacancy, on the mechanical properties of graphene has been analysed. Our results indicate that when applying the deformation locally onto the system, higher local stress can be induced, as confirmed by Finite Element Analysis. Also, the presence of structural defects in the system will stiffen the system upon low strain, but reduces the elastic limit from more than 20% strain for pristine graphene to less than 10% strain when defects are present.

Physical Chemistry Chemical Physics, 2017

The structure and morphology of three polymer/graphene nanocomposites have been studied using cla... more The structure and morphology of three polymer/graphene nanocomposites have been studied using classical molecular dynamics (MD) simulations. The simulations use 10-monomer oligomeric chains of three polymers: polyethylene (PE), polystyrene (PS) and polyvinylidene fluoride (PVDF). The structure of the polymer chains at the graphene surface have been investigated and characterized by pair correlation functions (PCF), g(r), g(θ) and g(r,θ). In addition, the influence of the temperature on the graphene/polymer interactions has been analysed for each of the three polymer/graphene nanocomposite systems. The results indicate that graphene induces order in both the PE and PVDF systems by providing a nucleation site for crystallisation, steering the growth of oligomer crystals according to the orientation of the graphene sheet, whereas the PS system remains disordered in the presence of graphene. The overall results are in line with the findings in a recent quantumchemical study by some of the present authors.

Journal of Molecular Modeling, Feb 1, 2017

Understanding the interaction between graphene and polymers is of essential interest when designi... more Understanding the interaction between graphene and polymers is of essential interest when designing novel nanocomposites with reinforced mechanical and electrical properties. In this computational study, the interaction of pristine graphene (PG) and graphene oxide (GO) with a series of functional groups, representative of the functionalised buildings blocks occurring in different polymers, and attached to aliphatic and aromatic chains, is analyzed using dispersioncorrected semi-empirical methods (PM6-D3H4X) and density functional theory calculations with empirical dispersion corrections. Functional groups include alkyl, hydroxyl, aldehyde, carboxyl, amino and nitro groups, and the binding energies of these groups with graphene derivatives (PG and GO) are determined. Nitro-and carbonyl groups display stronger interactions in both aliphatic and aromatic chains. The importance of dispersion-type and non-covalent interactions (NCI) in general, which typically, double the interaction energies, is revealed. The results are interpreted in an extensive NCI analysis in order to characterize the different types of NCI, providing a better understanding of the nature of the interaction (π-π stacking, CH-π bonding, H-bonding and lone pair-π interaction) at stake. In order to highlight the influence of polymer structure/conformation on top of that of their functional groups, the binding of three polymers, polyethylene (PE), polystyrene (PS) and polyvinylidene fluoride (PVDF), on pristine graphene is also investigated. Our calculations indicate that, although all polymers exhibit evident attractive interactions with the graphene sheet, the overall interaction is strongly influenced by the specific polymer structure. Thus, three main conformations of PVDF (the so-called α, β and γ, ε conformations) are analyzed and we find that, although the α-conformer with a trans-gauche-trans-gauche (TGTG') conformation is the lowest energy conformer, the β-conformation of PVDF with the hydrogen atoms facing the graphene (BF-up^) has the strongest interaction with the graphene surface among the polymers under consideration. Taken together, our computational approach sheds light on the character and importance of non-covalent graphene-polymer functional group interactions combined with the structural/conformational properties of the polymer, which are at stake in the design of novel nanocomposites with reinforced mechanical and electrical properties.

Thermodynamic stability of graphene against stacking in the gas phase and in different solvents (... more Thermodynamic stability of graphene against stacking in the gas phase and in different solvents (N-methyl-2-pyrrolidone), dimethyl sulfoxide, and water) has been investigated using the semi-empirical PM6 method combined with supermolecular approach, and with Periodic Boundary Conditions using Density Functional Theory in conjunction with the Perdew-Burke-Erzernhof functional. In the case of a supermolecular approach, the effect of the ratio of the edge and the center part on the solvation enthalpy has also been investigated.

The Journal of Physical Chemistry C, 2012

Phys. Chem. Chem. Phys., 2013

Due to its unique mechanical properties, graphene can be applied for reinforcement in nanocomposi... more Due to its unique mechanical properties, graphene can be applied for reinforcement in nanocomposites. We analyse the Young's modulus of graphene at the semi-empirical PM6 level of theory. The internal forces are calculated and the Young's modulus is predicted for a finite graphene sheet when external strain is applied on the system. These results are in a good agreement with theoretical and experimental results from the literature giving values of about 1 TPa for the Young's modulus. Stress-strain curves are computed for elongation up to 20%. In addition, the influence of the presence of a single vacancy, as well as for oxygenation of a vacancy, on the mechanical properties of graphene has been analysed. Our results indicate that when applying the deformation locally onto the system, higher local stress can be induced, as confirmed by Finite Element Analysis. Also, the presence of structural defects in the system will stiffen the system upon low strain, but reduces the elastic limit from more than 20% strain for pristine graphene to less than 10% strain when defects are present.

Chemical Physics Letters, 2013

In this Letter we predict the out-of-plane Young's modulus (perpendicular to the basal plane) and... more In this Letter we predict the out-of-plane Young's modulus (perpendicular to the basal plane) and the out-of-plane shear modulus of double-layer graphene using density functional theory calculations with periodic boundary conditions using the GAUSSIAN 09 program package. These values are discussed in the context of the corresponding values of graphite.