[Show abstract][Hide abstract] ABSTRACT: Using density functional theory calculations, the electronic response of a ZnO nanocluster was investigated toward CO, N2, H2, O2, and F2 molecules. The change of enthalpy (at 1 atm and 273 K) upon adsorption of these molecules on the cluster was calculated to be about −168.0, −148.4, −16.3, −8.8, and −51.0 kJ/mol, respectively. It was found that this cluster can selectively detect F2 molecule among the mentioned molecules due to a significant decrease in the HOMO–LUMO gap of the cluster. Our results may help direct experimental explorations of new nanostructured materials for sensor applications.
[Show abstract][Hide abstract] ABSTRACT: We investigated geometric and electronic properties of pristine and Be2O2-decorated carbon nanocones (CNCs) in the presence and absence of an H2S molecule using density functional calculations. It was found that the H2S molecule is physisorbed on the pristine nanocone, but it presents much higher reactivity toward the decorated CNC by Be2O2 cluster. The addition of more H2S molecules has also been considered on the Be2O2/CNC surface. With the increase of H2S coverage, the interaction between H2S molecules and Be2O2/CNC becomes weaker, and up to four H2S molecules can be chemisorbed on the cone, in which adsorption energies ranged from −27.21 to −10.28 kcal/mol at the B3LYP/6-31G(d) level of theory. The results also indicate that decoration of the Be2O2 cluster on the surface of the cone induces some changes in electronic properties of the cone and its Eg is changed after the adsorption of H2S molecule.
Journal of the Iranian Chemical Society 12/2014; 12(6). DOI:10.1007/s13738-014-0570-z · 1.09 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We have investigated the interaction of a COS molecule with a SiC nanotube by means of density functional theory calculations. A carbon or silicon atom of the tube was replaced by an Ag atom, exploring its effect on the interaction. Replacing a carbon and a silicon atom by an Ag atom increases and decreases the adsorption energy, respectively. We found that the carbon doping by Ag atom makes the nanotube a potential chemical sensor to the gaseous COS molecules.
Journal of the Iranian Chemical Society 12/2014; 12(6). DOI:10.1007/s13738-014-0567-7 · 1.09 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The functionalization of pristine and Stone-Wales defected BC3 nanosheets with a pyrene molecule was inves- tigated using density functional theory. Frontier molecular analysis shows that the main interaction is π-π stacking, releasing energies in the range of 143.6 to 169.1 kJ mol −1 . We predicted that after the functionalization process, the elec- trical conductance of the pristine sheet may be increased. Also, it modifies the work function of the pristine sheet and, as a consequence, its field-emission current densities may significantly enhance. However, the pyrene functionalization results in little change in the electronic properties of the defected sheet.
[Show abstract][Hide abstract] ABSTRACT: Adsorption of N2O on pristine and oxygen vacancy defect ZnO and BeO nanotubes was studied at the B3LYP and M06-2X levels of theory. It was found that this molecule can be used to repair the oxygen vacancy defects of these tubes. Adsorption energies of the dissociation of N2O on the defective BeO and ZnO nanotubes were calculated to be about 786.2 and 506.1 kJ/mol at the B3LYP level of theory, respectively. Molecular adsorption is barrierless, while the dissociative adsorptions have to overcome a small activation energy.
[Show abstract][Hide abstract] ABSTRACT: The adsorption of a H2S molecule on the surface of an MgO nanotube was investigated using density functional theory. It was found that H2S molecule can be associatively adsorbed on the tube surface without any energy barrier or it can be dissociated into –H and –SH species overcoming energy barrier of 4.03–7.77 kcal/mol. The associative adsorption is site selective so that the molecule is oriented in such a way that the sulfur atom was linked to an Mg atom. The HOMO–LUMO energy gap of the tube has slightly changed upon associative adsorption, while they were significantly influenced by dissociation process. Especially, the highest occupied molecular orbital of the tube shifts to higher energies which can facilitate electron emission current from the tube surface. Also, energy gap of the tube dramatically decreased by about 0.93–1.05 eV which influences the electrical conductivity of the tube.
[Show abstract][Hide abstract] ABSTRACT: Density functional calculations have been performed on the structural and electronic properties of the pristine and Stone-Wales-defected (SW) carbon nanotubes (CNT) with and without the adsorption of a H2O2 molecule. H2O2 interacts with the pristine CNT weakly, releasing energy of about 2.9 kcal/mol, but it presents a bit higher reactivity toward the SW-defected CNT. However, the adsorption of the H2O2 molecule on the SW-CNT is still very weak because of its small adsorption energy, large binding distance, and small charge transfer. To enhance the reactivity, a Si-Si pair is doped at the center of a SW defect, forming a Si2-SW-CNT. In this case, a strong adsorption is found with a large E ad of 155.6 kcal/mol, and a short bond length in comparison with the SW-CNT. It also was shown that the H2O2 molecule could be reduced into the OH on the Si2-SW-CNT without significant change in the electronic properties of the tube.
[Show abstract][Hide abstract] ABSTRACT: Functionalization of a boron nitride nanotube (BNNT) with 1,2 diaminobenzene (DAB) and its derivatives containing functional groups of -CN, -NO2, -OH, and -NH2 has been investigated using density functional theory in terms of energetic, electronic and geometric properties. DAB prefers to be adsorbed on B atoms of the BNNT via its amine head with the adsorption energy of -16.4 kcal/mol. Calculated density of states show that the HOMO-LUMO energy gap of the BNNT is little changed by chemical modification in the most stable states. The work function of BNNT is significantly decreased upon the functionalization with DAB molecules containing electron-donating groups of -OH and -NH2 which will facilitate the field electron emission from the tube surface.
[Show abstract][Hide abstract] ABSTRACT: Encapsulation of several alkali and alkali earth metals inside a C30B15N15 nanocage was investigated by using density functional calculations at B3LYP and M06-2X levels of theory. It was found that the encapsulation processes are spontaneous at room temperature and 1 atm. pressure. The encapsulation favorability increases in the series: K > Na > Ca > Li > Mg > Be. Alkali earth metals influence the electronic properties of cluster relatively more compared to alkali metals. A tunable HOMO-LUMO energy gap of up to ~ 1.05 eV was predicted for C30B15N15 by the controlled encapsulation of different alkali and alkali earth metals at B3LYP/6-31G (d). Electron emission density from C30B15N15 surface will be significantly increased upon the Ca encapsulation, while in the case of Li capsulation it will be decreased based on work function calculations in our work. The thermodynamic results of B3LYP and M06-2X functionals are somewhat similar, while those of electronic properties are significantly different.
[Show abstract][Hide abstract] ABSTRACT: In this paper, a first-principle investigation of the electronic properties of graphene
on hexagonal boron nitride substrate, and of one-sided and two-sided fully saturated
hydrocarbons with C-H formula derived from a single sheet of graphene, tablelike and
chairlike graphane, are presented within density functional theory (DFT). We obtain the
most stable orientation of graphene on the substrate, the adsorption energy, the charge
transfer and density of states (DOS) for these systems. We discuss the changes in the
density of states as well as the extent of charge transfer, band gap and finally quantum
conductivity and current for graphene due to the presence of the substrate and H atoms. We
show that the band gap of 64 meV induced by the BN substrate can greatly improve the
electrical characteristics of graphene-based field effect transistors (FETs) and its
on/off ratio and decreases the minimum conductance by a factor three. We identify that the
substrate is acting as a donor for graphene layer and graphene is acting as an acceptor
with respect to H atoms after saturation with hydrogen. We show that graphene on h-BN
substrate has higher on/off ratio respect to pristine graphene and higher conductance
respect to tablelike graphane.
[Show abstract][Hide abstract] ABSTRACT: We have investigated the adsorption of hydrogen fluoride (HF) on the AlN nanotube
surface using density functional theory in terms of energetic, structural and electronic
properties. By overcoming energy barriers of 27.90–52.30 kcal/mol, HF molecule is
dissociated into H and F species on the tube surface and its molecular structure is not
preserved after the adsorption process. Dissociation energies have been calculated to be
�52.57 and �70.10 kcal/mol. The process has negligible effect on the electronic and field
emission properties of the AlN nanotube. This process may increase the solubility of AlN
[Show abstract][Hide abstract] ABSTRACT: We have investigated the adsorption of hydrogen fluoride (HF) on the AlN nanotube surface using density functional theory in terms of energetic, structural and electronic properties. By overcoming energy barriers of 27.90–52.30 kcal/mol, HF molecule is dissociated into H and F species on the tube surface and its molecular structure is not preserved after the adsorption process. Dissociation energies have been calculated to be -52.57 and -70.10 kcal/mol. The process has negligible effect on the electronic and field emission properties of the AlN nanotube. This process may increase the solubility of AlN nanotubes.
[Show abstract][Hide abstract] ABSTRACT: By using density functional theory, the electronic response of a BC3 nanotube (BC3NT) to CS2 molecules was investigated. It was found that: (1) the CS2 adsorption on the tube is site-selective and it prefers to be adsorbed on a hexagonal ring of the tube which has six carbon atoms, liberating energy of about 34.36 kcal/mol; (2) the HOMO–LUMO energy gap (Eg) of the tube is significantly decreased from 2.37 to 1.70 eV upon the CS2 adsorption; (3) the Eg of the tube is more decreased by increasing the number of the adsorbed CS2 molecules; (4) the BC3NT may transform the presence of CS2 molecule into an electrical signal, and therefore it may be potentially used in CS2 sensors. Also, the response of the tube may be dependent on the concentration of the CS2 molecules.
[Show abstract][Hide abstract] ABSTRACT: Adsorption of NH 3 molecule on a carbon nanocone (CNC) was investigated using
density functional theory in terms of energetic, structural, and electronic properties. It is
mainly demonstrated that (i) the NH 3 molecule preferentially tends to attach to the apex of
the CNC through its N atom, releasing energy of 54.28 kcal/mol,(ii) the CNC may be a
promising candidate in gas sensor devices in order to detect the NH 3 molecule, and (iii) the
field electron emission current may be enhanced from CNC surface upon the adsorption ...
[Show abstract][Hide abstract] ABSTRACT: We have performed a comparative density functional theory study on adsorption of hydrogen peroxide (H2O2) on the boron nitride and silicon carbide nanotubes (BNNT and SiCNT) in terms of energetic, geometric, and electronic properties. It has been found that the molecule is chemically adsorbed on both of the tubes so that its interaction with SiCNT (adsorption energy ∼−0.97 eV) is much stronger than that with BNNT (adsorption energy ∼−0.47 eV). The H2O2 adsorption on BNNT slightly decreases its work function, increasing the field electron emission from the BNNT surface while it may not affect that of the SiCNT. In addition, the adsorption process may increase the electrical conductivity of SiCNT while does not affect that of the BNNT, significantly. We believe that the SiCNT may be a potential candidate for detection of H2O2.
Physica E Low-dimensional Systems and Nanostructures 02/2013; 48. DOI:10.1016/j.physe.2013.01.007 · 2.00 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Using density functional theory, we have investigated the adsorption of formaldehyde (H2CO) on the interior and exterior walls of a carbon nitride nanotube (CNNT) in terms of energetic, geometric, and electronic properties. It was found that the adsorption is more preferential on the exterior surface of the tube with maximum adsorption energy of −7.4 kcal/mol. It has also been found that the adsorption energy per molecule is increased by increasing the number of adsorbed molecules. The results reveal that the electronic properties of CNNT are very sensitive to the presence of formaldehyde so that the HOMO/LUMO gap is reduced from 4.02 eV in the free tube to 2.44 eV in the most stable configuration of 3H2CO/CNNT complex. Also, we have showed that the response of the tube may depend on concentration of the H2CO molecules, suggesting that the CNNT might produce an electrical signal in the presence of H2CO molecules.