Carbon-doped Boron Nitride Nanotubes Research Articles

Engineering the thermodynamic properties of carbon doped boron nitride nanotubes by impurity concentration and electric field

The effects of the impurity concentration and electric field strength on the electronic and thermal properties of carbon doped boron nitride nanotubes are investigated by the tight binding model, Kubo-Greenwood formula and Green function approach. The position, intensity and number of the density of sate peaks are affected by electric field strength F and dopant concentration which leads to band gap reduction in the doped boron nitride nanotubes compared to the pure boron nitride nanotubes. The thermal functions of the doped boron nitride nanotubes are zero first in very low temperature due to existing the large band gap and become zero by increasing the temperature until reach their maximum values at TM and finally decrease significantly in higher temperature above the TM. The increasing (decreasing) pattern in low (high) temperature region occurs due to the band gap modifications (scattering and collision between charge carriers) and for all selected structures, they are related to the electric field strength and doping concentration. The Lorenz number of the doped boron nitride nanotubes with and without the electric field has a peak with LMax intensity at TM which in the presence of the external electric field, it moves to lower temperature with decreasing intensity. By increasing the nanotube radius, the thermal properties of the doped boron nitride nanotubes increase in terms of the temperature and this behavior becomes valid in the presence of the electric field.

Computational Study of Carbon-Doped Boron Nitride Nanotubes Loaded with Pd Atoms as Single-Atom Catalysts for Heck Reactions

This work was supported by the National Natural Science Foundation of China (21406039 and 21506174), the Guangdong Natural Science Foundation (2020A1515010490), and the Sichuan Provincial Science and Technology Project (2018GZ0313).

C-doped boron nitride nanotubes for the catalysis of acetylene hydrochlorination: A density functional theory study

The mechanism of a novel mercury-free catalyst, carbon-doped boron nitride nanotubes (BNNTs), for acetylene hydrochlorination reaction was investigated by density function theory (DFT) calculations. Two types of carbon-doped BNNTs with different diameters, boron substituted and nitride substituted with carbon, were studied in detail as the catalyst of the acetylene hydrochlorination reaction. Results show the adsorption of C2H2 on carbon-doped BNNTs is dominant in the adsorption process due to the stronger interaction of C2H2 with carbon-doped BNNTs. HCl can be dissociated on carbon-doped BNNTs with small diameter during the adsorption process. The C2H2 is chemically adsorbed on the doped impurity C atom where it is activated to continue the addition reaction with the gaseous HCl molecule. The rate-limiting step is the splitting of HCl molecule and the attack of H and Cl atoms on CC bond of the activated C2H2 to form the transition state. The reaction can take place easily on carbon-doped BNNTs and a low energy barrier of 28.47 kcal/mol is found. The doping site and curvature have a slight impact on the catalytic performance in the reaction based on the comparison of energy barrier. The study reveals that the doped impurity C atom can largely improve the activity of BNNTs, and carbon-doped BNNTs can be an effective non-metal catalyst in the acetylene hydrochlorination reaction.

Effect of substitutional carbon-doping in BNNTs on HF adsorption: DFT study

We employed density functional calculations to investigate the adsorption behavior of HF gas on the side walls of pure and carbon-doped boron nitride nanotubes (BNNTs). The HF adsorption over the pure BNNT opens a door for its functionalization without causing significant changes in its electronic properties. The substitutional doping of carbon atom on the BNNT considerably enhances its affinity towards HF where the effect of the dopant concentration plays a vital role. The change in electronic properties of the doped BNNT on HF adsorption is significant enough to consider it a potential sensor for HF detection.

Electric field effect on the electronic properties of double-walled carbon-doped boron-nitride nanotubes

Carbon (C) doped zigzag (8, 0)@(16, 0) and armchair (5, 5)@(10, 10) double-walled boron-nitride nanotubes (DWBNNTs), under the influence of external electric fields applied in different directions are studied through first-principles calculations. We have considered the substitution of a B and a N (one species at each wall—inner or outer) by C atoms, generating a type-n inside a type-p semiconductor ((type-n)@(type-p)) and vice-versa. The resulting doped DWBNNT can be thought as a p–n junction. The obtained formation energies and structural properties results indicate that these structures present good stability and are not affected by the electric field application. For the electronic structure, it was observed that external fields can be used to modulate these systems energy gaps. Also, there is a preferred field direction which minimizes the gap values, and the gap increase or decrease is related to the reverse and direct polarization of the p–n junction, respectively.

Can trans-polyacetylene be formed on single-walled carbon-doped boron nitride nanotubes?

Recently, the grafting of polymer chains onto nanotubes has attracted increasing attention as it can potentially be used to enhance the solubility of nanotubes and in the development of novel nanotube-based devices. In this article, based on density functional theory (DFT) calculations, we report the formation of trans-polyacetylene on single-walled carbon-doped boron nitride nanotubes (BNNTs) through their adsorption of a series of C(2)H(2) molecules. The results show that, rather than through [2 + 2] cycloaddition, an individualmolecule would preferentially attach to a carbon-doped BNNT via "carbon attack" (i.e., a carbon in the C(2)H(2) attacks a site on the BNNT). The adsorption energy gradually decreases with increasing tube diameter. The free radical of the carbon-doped BNNT is almost completely transferred to the carbon atom at the end of the adsorbed C(2)H(2) molecule. When another C(2)H(2) molecule approaches the carbon-doped BNNT, it is most energetically favorable for this C(2)H(2) molecule to be adsorbed at the end of the previously adsorbed C(2)H(2) molecule, and so on with extra C(2)H(2) molecules, leading to the formation of polyacetylene on the nanotube. The spin of the whole system is always localized at the tip of the polyacetylene formed, which initiates the adsorption of the incoming species. The present results imply that carbon-doped BNNT is an effective "metal-free" initiator for the formation of polyacetylene.

SiC-doped boron nitride nanotubes: computations of 11B and 14N quadrupole coupling constants

Density-functional theory calculations have been performed to investigate the properties of the electronic structures of silicon–carbon-doped boron nitride nanotubes (BNNTs). The geometries of zigzag and armchair BNNTs were initially optimized and the quadrupole coupling constants subsequently calculated. The results indicate that doping of B and N atoms by C and Si atoms has more influence on the electronic structure of the BNNTs than does doping of B and N atoms by Si and C atoms. The changes of the electronic sites of the N atoms are also more significant than those of the B atoms.

Calculation of chemical shielding in C-doped zigzag BN nanotubes

Chemical shielding tensors at the sites of various 11B and 15N nuclei were calculated to study the electronic structure properties of carbon-doped boron nitride nanotubes. The chemical shielding tensors were converted to isotropic and anisotropic chemical shielding parameters. The results reveal the significant effect of C-doping on the chemical shielding tensors at the sites of those 11B and 15N nuclei located in the nearest neighborhood of the C-doped ring. The isotropic and anisotropic chemical shielding tensors of those B atoms directly bonded to C atoms reach values observed for B atoms placed at the B-mouth of the nanotube.

Contrast in the Electronic and Magnetic Properties of Doped Carbon and Boron Nitride Nanotubes: A First-Principles Study

We determine atomic and electronic structures of boron- and/or nitrogen-doped carbon nanotubes (CNTs) and carbon-doped boron nitride nanotubes (BN-NTs) of armchair and zigzag types using first-principles pseudopotential-based density functional theory calculations. For comparison, we also determine the atomic and electronic structures of two-dimensional honeycomb lattices of carbon (graphene) and boron nitride. Although carbon doping at either the B or N site in BN-NTs results in anti-ferromagnetically ordered semiconducting state, B or N doping in CNTs gives a simple shift in the Fermi energy and a nonmagnetic state.

Adsorption of CO and NO molecules on carbon doped boron nitride nanotubes

Using first principles calculations, we have investigated the electronic and structural properties of CO and NO molecules adsorbed on boron nitride nanotubes (BNNTs) and carbon doped BNNTs. Our results indicate that for non defective nanotubes, small binding energies (around 150 meV) are obtained. When a carbon substitution impurity is present in the BNNT the binding energies are substantially increased and a chemical adsorption is observed. The calculated band structures show that the defect electronic levels inside the band gap are sensitive to the presence of the adsorbed molecules. This increasing of the functionalization capacity of the tubes due to carbon doping is an important mechanism to open up new possibilities for nanodevices applications.

Hydrogen Adsorption on Carbon-Doped Boron Nitride Nanotube

The adsorption of atomic and molecular hydrogen on carbon-doped boron nitride nanotubes is investigated within the ab initio density functional theory. The binding energy of adsorbed hydrogen on carbon-doped boron nitride nanotube is substantially increased when compared with hydrogen on nondoped nanotube. These results are in agreement with experimental results for boron nitride nanotubes (BNNT) where dangling bonds are present. The atomic hydrogen makes a chemical covalent bond with carbon substitution, while a physisorption occurs for the molecular hydrogen. For the H(2) molecule adsorbed on the top of a carbon atom in a boron site (BNNT + C(B)-H(2)), a donor defect level is present, while for the H(2) molecule adsorbed on the top of a carbon atom in a nitrogen site (BNNT + C(N)-H(2)), an acceptor defect level is present. The binding energies of H(2) molecules absorbed on carbon-doped boron nitride nanotubes are in the optimal range to work as a hydrogen storage medium.

Spin-unrestricted linear-scaling electronic structure theory and its application to magnetic carbon-doped boron nitride nanotubes

We present an extension of the density-matrix-based linear-scaling electronic structure theory to incorporate spin degrees of freedom. When the spin multiplicity of the system can be predetermined, the generalization of the existing linear-scaling methods to spin-unrestricted cases is straightforward. However, without calculations it is hard to determine the spin multiplicity of some complex systems, such as many magnetic nanostuctures and some inorganic or bioinorganic molecules. Here we give a general prescription to obtain the spin-unrestricted ground state of open-shell systems. Our methods are implemented into the linear-scaling trace-correcting density-matrix purification algorithm. The numerical atomic-orbital basis, rather than the commonly adopted Gaussian basis functions, is used. The test systems include O2 molecule and magnetic carbon-doped boron nitride (BN)(5,5) and BN(7,6) nanotubes. Using the newly developed method, we find that the magnetic moments in carbon-doped BN nanotubes couple antiferromagnetically with each other. Our results suggest that the linear-scaling spin-unrestricted trace-correcting purification method is very powerful to treat large magnetic systems.