Single-walled Boron Nitride Nanotubes Research Articles

Titanium-decorated boron nitride nanotubes for hydrogen storage: a multiscale theoretical investigation.

A multiscale computational technique from available quantum mechanical and Molecular Dynamics (MD) codes to user-subroutine computational fluid dynamics (CFD) files was applied to the H2 adsorption of Ti-decorated (10,0) single-walled BN nanotubes (BNNTs) with B-N defects. According to density functional theory (DFT), the Ti atom adsorbed in the defect protrudes outward from the surface and does not agglomerate. The Ti/BNNT system possesses excellent affinity towards H2 molecules with thermodynamically favorable binding energies. Up to seven H2 molecules can partially attach near Ti in quasi-molecular form due to the cationic functionalized Ti and heteropolar B-N bonds at the surface. MD simulation further reveals that the seven H2 molecules are indeed physisorbed in two distinct regions near to (at ∼2 Å) and far from (at ∼4 Å) the Ti atom. The thermal properties obtained from MD simulations were utilized in the CFD code to quantify thermal energy transfer. According to CFD, the equilibrium pressure distribution for a type III H2 cylinder is initially low within its locality. The rate of change of pressure increase is quite steep as it rises due to a sudden increase in temperature upon uptake and it eventually slows down when the local temperature reaches its saturation value.

Raman active modes of single-wall boron nitride nanotubes inside carbon nanotubes

The structure of boron–nitride nanotubes (BNNTs) is very similar to that of CNTs, and they exhibit many similar physical and chemical properties. In particular, a single walled boron nitride nanotube (BNNT) and a single walled carbon nanotube (CNT) have been reported. The spectral moment’s method (SMM) was shown to be a powerful tool for determining vibrational spectra (infrared absorption, Raman scattering and inelastic neutron-scattering spectra) of harmonic systems. This method can be applied to very large systems, whatever the type of atomic forces, the spatial dimension, and structure of the material. The calculations of vibrational properties of BNNT@CNT double-walled hybrid nanostructures are performed in the framework of the force constants model, using the spectral moment's method (SMM). A Lennard–Jones potential is used to describe the van der Waals in-teractions between inner and outer tubes in hybrid systems. The calculation of the BNNT@CNT Raman active modes as a function of the diameter and chirality of the inner and outer tubes allows us to derive the diameter dependence of the wave number of the breathing-like modes, intermediate-like modes and tangential-like modes in a large diameter range. These predictions are useful to interpret the experimental data.

Single-walled boron nitride nanotube as nano-sensor

Nowadays, the eye-catching characteristics of boron nitride nanotubes, in particular, the capability of sensing nano-objects, have opened up new prospects to develop the bio-/nano-sensing technologies. This research deals with physically affected single-walled boron nitride nanotubes (SWBNNT) as nano-sensors for sensing attached nanoscale objects. Three different boundary conditions including simply supported at both ends, clamped-free and clamped-clamped are considered to illustrate the vibrational behaviour of SWBNNTs as nano-sensor. The Rayleigh and Timoshenko beam theories are employed to model the SWBNNT. Also, the nonlocal strain gradient model is utilized to capture the size-dependent effects. One of the major factors in the scrutiny of mass nano-sensors is pertinent to the variation in frequency shift magnitudes against the number and mass weight values of attached nanoparticles. Herein, the effects of the nonlocal and material length scale parameters, the number and location of nano-objects, the rotary inertia and mass weight magnitudes of attached nanoparticles, the aspect ratio of SWBNNT, electrical potential and different boundary conditions on the variation in frequency shift and resonant frequency are analysed.

First principles study of structural and electronic properties of BNNTs

In this article the electronic and structural properties of single-walled boron nitride (BN) nanotubes with a diameter range of 4–22 A have been investigated using the generalized gradient approximation with both Perdew, Burke and Ernzerhof (PBE) and Becke–Lee–Yang–Parr (BLYP) functionals based on density functional theory. The variation of radial distribution, bond length, lattice constant, density of states, buckling separation, total energies and the electronic band gap of BN nanotubes have been studied in terms of the diameter of the nanotube. Our results revealed a correlation between the buckling and band gap: the higher the buckling, the lower the band gap, and by decreasing the tube diameter, the buckling separation increases. It is revealed that for both armchair and zigzag boron nitride nanotubes (BNNT) the value of the band gap increases by increasing the nanotube diameter. Moreover, it is concluded that for small BN nanotubes by reducing the radius, the band gap of the armchair nanotube remains almost constant, while the band gap of the zigzag nanotubes has a rapidly decreasing trend. The value of band gap obtained by the BLYP hybrid functional is more accurate than the PBE functional. The PDOS calculations revealed that the VBM comes from the N 2p orbitals, while the CBM is ruled by the B 2p orbitals. According to the obtained results, BNNTs are suggested as good materials for applications in the nanoscale optoelectronic devices.

Hydrogen adsorption of Ti-decorated boron nitride nanotube: a density functional based tight binding molecular dynamics study

The hydrogen adsorption capabilities of Titanium functionalized single-walled BN nanotubes (BNNTs) with B–N defects was assessed by density-functional theory tight binding (DFTB) method. According to the DFTB molecular dynamics simulations, the BNNT structures were thermodynamically stable, the Ti atom once incorporated with the B–N defects present in BNNT (Ti–BNNT) protrudes to the external surface of the BNNT sidewall. The titanium atoms does not agglomerate to form any metal clusters. The results revealed that at 77 K and 10,000 KPa, the H2–Ti–BNNT has a gravimetric hydrogen storage capacity above 7 wt% ideal for department of energy specifications. Further calculations suggest that the Ti–BNNT has a good affinity towards H2 molecules and under low pressure of 500 KPa. The H2 stays close to the Ti metal due to its partially cationic character with some H2 attaching itself at the BNNT surface due to heteropolar bonding. H2 atoms is physisorbed in analogous to or resembling something molecular near the Ti sites which gives rise to a significant storage capacity for H2 in these modified BNNT.

Analysis the electronic properties of the zigzag and armchair single wall boron nitride nanotubes with single Li impurity in the various sites

We utilized the first-principle density functional theory (DFT) calculation to investigate the structural and electronic properties of various diameters for zigzag and armchair single wall boron nitride nanotubes (ZSWBNNTs and ASWBNNTs) with and without single Li impurity in the various sites. Using DFT method, which employed in the Quantum espresso package, to calculate the electronic band structure, band gap, density of states (DOS), total, kinetic, and electrostatic energies. In the pristine case, there are large electronic band gaps, which make all SWBNNTs have insulator behaviors. Also, total, kinetic energies are reduced with increasing the diameter of the tube, but the opposite behavior with the electrostatic energy. By substituting one B atom with single Li impurity, the electronic band gap is reduced. This impurity also changed the shape and reduced the value of the DOS, which confirmed all the obtained results in this report. Similarly, the values of all the above energies are decreased, which make the structure unstable and more reactive. The significant result in this work is that addition of only one lithium atom in the unit cell of SWBNNTs can take the Fermi level down so significantly and result in insulating to semiconducting phase transition. When we replaced one N atom with one Li impurity, all these energies are dependent on the diameter, so the values of energies are reduced with this impurity. The behaviors of these SWBNNTs are altered to P-type. This impurity is converted these SWBNNTs from an insulator to a semimetal state with zero electronic band gap and changing the shape and value of the DOS, which is very important in various applications.

Optical Properties of Armchair Single Wall Boron Nitride Nanotubes

The optical properties of Armchair single wall Boron Nitride Nanotubes (ASWBNNTs) was studied using density functional theory (DFT). In this paper, our calculations focused on the reflectance, absorbance and transmittance. Also, the optical coefficients such as refractive index, extinction coefficient (k), absorption coefficient (α), real (εr) and imaginary (εi) dielectric constant and optical conductivity were. The optical constants are very important parameters because they describe the optical behavior of the materials. The (4,4), (5,5), and (6,6) ASWBNNTs were studied with thicknesses (d= 80.71849, 70.42897, and 64.43785) and the range of wavelength (365.01-1013.98) nm. Additionally, the energy gap was unit calculated for all ASWBNTs and it has direct band gap. The values of optical energy gap are (4.11, 4.4, 4.6) eV. We found out that the (6,6) ASBNNT is the best optical properties. Also, the best average reflection, transmittance, and absorption values for (4,4), (5,5) and (6,6) respectively. These tubes are very useful in various optical applications, such as cover for solar cell, optical window, lenses and green house because these tubes have a transmittance which is greater than other properties like absorption which is small.

Electronic and thermoelectric properties of zigzag and armchair boron nitride nanotubes in the presence of C island

Electronic and thermoelectric properties of zigzag and armchair single wall Boron Nitride Nanotubes (SWBNNTs) are investigated with and without one hexagonal carbon island by using first density functional theory (DFT), which is carried out in the Quantum Espresso packages. The ZSWBNNTs and ASWBNNTs show semiconductor and insulator behaviors, respectively along with a direct bandgap at the Γ point in the pristine cases. The obtained results display that this island is affected and altered to the electronic and thermoelectric properties of all systems. The behaviors of all systems are turning to semiconductor and the electronic band gaps are reduced with the C island which enables to use these doped materials in various applications. Meanwhile, the thermoelectric parameters, such as Seebeck coefficient (S), thermoelectric figure of Merit (ZT), phonon thermal conductance (Kph), electrons thermal conductance (Ke), and thermal conductivity of all systems are calculated and studied with and without the C island. The results show that all these thermoelectric properties are related directly to the diameter of the ZSWBNNTs and ASWBNNTs.

XH3 (X=P or N) Adsorption on Pristine, Pt-Doped and Vacancy-Defective (8,8) Boron Nitride Nanotubes: DFT Calculations

Abstract The adsorption energies (E ad), interaction distances, changes of geometric and electronic structures of XH3 (X=P or N) gas molecule adsorption on pristine, platinum (Pt) doped and vacancy-defected single-walled (8,8) boron nitride nanotubes (BNNTs) have been calculated using the density functional theory (DFT). The effect of the Pt doping on B and N sites (PtB,N-doped) and the B and N vacancy defects (VB,N-defected BNNT) on the sensing behavior of pristine (8,8) BNNTs toward PH3 and NH3 gases have been examined. According to the obtained results, PH3 and NH3 molecules were more likely to be absorbed on the PtB,N-doped and VN-defected BNNT with relatively higher E ad compared with the pristine and VB-defected BNNTs. Therefore the order of the obtained E ad were PtB-doped BNNT/NH3>PtB-doped BNNT/PH3>PtN-doped BNNT/NH3>PtN-doped BNNT/PH3 for the PtB,N-doped BNNTs, and VN-defected BNNT/NH3>VN-defected BNNT/PH3>VB-defected BNNT/NH3>VB-defected BNNT/PH3 for the VB , N-defected BNNTs systems. The partial density of states (PDOS) of the adsorption systems indicated the strong interaction between the adsorbed PH3 and NH3 molecules and the substrates, i.e. PtB,N-doped BNNT and VN-defected BNNT. Therefore, it can concluded that the PtB,N-doped and VN-defected BNNTs have potential applicability in the gas-sensing detection of PH3 and NH3 with good sensitivity.

Hydrogen saturation limit of Ti-doped BN nanotube with B-N defects: An insight from DFT calculations

Ti-decorated (10,0) single-walled BN nanotubes (BNNTs) with B-N defects was fully examined by density functional theory (DFT). According to DFT formalisms, the HOMO-LUMO gap found for the Ti-BNNTs is small compared to that of a wide-gap semiconducting pristine BNNT. The Ti atom does not form any clusters and protrudes to the external surface of the sidewall. The calculations suggest that the Ti-BNNT assembly can attract small molecules and it has a good affinity towards H2 molecules. Up to seven H2 can partially attach to the system in quasi-molecular fashion due to the partially cationic character of the functionalized Ti and heteropolar bonds exhibited at the BNNT surface. The binding energies of H2 with Ti-BNNTs are within the optimal range for H2 storage. The unique electronic structure is barely perturbed upon adsorption and the (H2)7xTixBNNT systems hydrogen storage capacity is in compliance to the specifications mandated by the Department of Energy.

Structure and Raman Spectra of C60 and C70 Fullerenes Encased into Single-Walled Boron Nitride Nanotubes: A Theoretical Study

We report the structures and the nonresonant Raman spectra of hybrid systems composed of carbon fullerenes ( C 60 and C 70 ) encased within single walled boron nitride nanotube. The optimal structure of these systems are derived from total energy minimization using a convenient Lennard-Jones expression of the van der Waals intermolecular potential. The Raman spectra have been calculated as a function of nanotube diameter and fullerene concentration using the bond polarizability model combined with the spectral moment method. These results should be useful for the interpretation of the experimental Raman spectra of boron nitride nanotubes encasing C 60 and C 70 fullerenes.

Effects of Electrostatic Interaction and Chirality on the Friction Coefficient of Water Flow Inside Single-Walled Carbon Nanotubes and Boron Nitride Nanotubes

Water transport through carbon nanotubes (CNTs) and boron nitride nanotubes (BNNTs) has attracted great scientific interest because of their potential applications in water purification and energy conversion. Recent experiments show surprising differences of the water flow friction coefficients in these two types of nanotubes with similar diameters, but the mechanism is yet to be fully understood. We use molecular dynamic simulations to model the transport process of water molecules inside CNTs and BNNTs, and the friction coefficients are calculated by the Green–Kubo formula. Our results show that at similar diameters, water molecules have smaller friction coefficients in zigzag CNTs than in zigzag BNNTs. By analyzing the potential energy landscape inside these nanotubes, we find that in CNTs, the lack of partial charges, and thus the absence of electrostatic interactions with water molecules, leads to a much smoother potential energy landscape and thus smaller water friction coefficient. Although partial charges in armchair BNNTs also lead to electrostatic interactions with water, the atomic arrangement in armchair nanotubes does not create local potential energy traps, and thus the friction coefficient is smaller than the zigzag counterparts. The result helps us understand the distinct behaviors of water flowing through CNTs and BNNTs.

Sensing properties of pristine boron nitride nanostructures towards alkaloids: A first principles dispersion corrected study

To understand the underlying physics behind the interaction of biomolecules with the nanomaterials to use them practically as bio-nanomaterials is very crucial. A first principles calculation under the frame work of density functional theory is executed to investigate the electronic structures and binding properties of alkaloids (Caffeine and Nicotine) over single walled boron nitride nanotube (BNNT) and boron nitride nanoribbon (BNNR) to determine their suitability towards filtration or sensing of these molecules. We have also used GGA-PBE scheme with the inclusion of Van der Waals (vdW) interaction based on DFT-D2. Increase in the accuracy by incorporating the dispersion correction in the calculation is observed for the long range Van der Waals interaction. Binding energy range of BNNT and BNNR with both alkaloids have been found to be −0.35 to −0.76 eV and −0.45 to −0.91 eV respectively which together with the binding distance shows physisorption binding of these molecules to the both nanostructures. The transfer of charge between the BN nanostructures and the adsorbed molecule has also been analysed by using Lowdin charge analysis. The sensitivity of both nanostructures BNNT and BNNR towards both alkaloids is observed through electronic structure calculations, density of states and quantum conductance. The binding of both alkaloids with BNNR is stronger. The analysis of the calculated properties suggests absence of covalent interaction between the considered species (BNNT/BNNR) and alkaloids. The study may be useful in designing the boron nitride nanostructure based sensing device for alkaloids.

Modulating Band Gap and HOCO/LUCO Energy of Boron-Nitride Nanotubes under a Uniform External Electric Field

In this study, spectroscopic properties of the single-walled boron-nitride nanotube (SWBNNT) –a semiconductor channel in molecular diodes and molecular transistors–have been investigated under field-free and various applied electric fields by first principle methods.Our analysis shows that increasing the electric field in boron-nitride nanotube (BNNT) decreases the Highest Occupied Crystal Orbital (HOCO) /Lowest Unoccupied Crystal Orbital (LUCO) gap (HLG) significantly and the nanotube can be a conductor. The observed results suggest that the BNNTs is a useful semiconductor channel as nano-molecular diodes and nano-molecular transistors. Apart from that, the relationship between isotropic chemical shielding as an observable spectroscopic property with atomic charge and magnetizability in the presence and absence of an external electric field was studied. In order to rationalize energy changes, the relationship between the relative energy with the average electron delocalization of nitrogen and boron atoms with a variation of the external electric field is studied.

Can HCCH/HBNH Break B═N/C═C Bonds of Single-Wall BN/Carbon Nanotubes at Their Surface?

The iminoborane (HBNH) molecule selectively breaks a B═N bond of smaller diameter single-wall BN nanotubes (BNNTs) and expands a ring at their surface, either at the edges or at the middle of the tube. Density functional theory is used to test whether its organic counterpart HCCH can do the same with BNNTs. HCCH–BNNT complexes are identified and transition states located for these combination reactions. Also explored are possible reactions of HBNH with single-wall carbon nanotubes (SWNTs) and HCCH with SWNTs. Data suggest that B═N (C═C) bond breaking, followed by ring expansion at the surface, may be possible. Although [2 + 2]cycloaddition reaction seems possible for HBNH–BNNTs, a high energy barrier hinders the process for other combinations of reactants. Introduction of substituents to HBNH/HCCH may allow a facile process. In most cases of HCCH–BNNTs, HBNH–SWNTs, and HCCH–SWNTs, transition states are identified and suggest an electron-rich reactant might lower barrier heights to form stable complexes. R...

Theoretical Prediction of Adsorption Properties of Carmustine Drug on Various Sites of the Outer Surface of the Single-Walled Boron Nitride Nanotube and Investigation of Urea Effect on Drug Delivery by DFT and MD

In this work, the adsorption behavior of Carmustine (BCNU) drug over the (6,0) zigzag single-wall boron nitride nanotube (SWBNNT) is studied by means of density functional theory calculations and molecular dynamics simulations (MD). The calculated adsorption energies proved that the adsorption of BCNU molecule on SWBNNT is a physisorption process. The natural bond orbital calculations demonstrated that existence of a charge transfer from the SWBNNT to the BCNU molecule. Moreover, quantum theory of atoms in molecules showed that the hydrogen bonds and electrostatic interactions are two major factors contributed to the overall stabilities of the complexes. Furthermore, interaction of BCNU with the surface of single wall BNNT at 310 K and 1 bar in the present of water and different concentration of Urea molecules has been studied by MD simulation. The MD results confirm that the highest number of hydrogen bond and the lowest value of Lennard-Jones (L-J) energy between nanotube and drug exist in the simulation system with concentration of 1 mol L−1 Urea.

A DFT study for adsorption of CO on Ni, Pd and Pt atoms doped (7, 0) boron nitride nanotube

ABSTRACTBy using density functional theory calculations, we investigated the structural, electronic and magnetic properties of carbon monoxide (CO) adsorption on the pure, Ni, Pd and Pt doped atoms in zigzag single-walled (7, 0) boron nitride nanotubes (BNNTs). The results indicated that compared to the pure (7, 0) BNNTs, replacing B atom by Ni, Pd and Pt atoms can significantly increase the adsorption energy of CO gas on the BNNTs. The adsorption energies of CO gas on the pure (7, 0) Ni, Pd and Pt doped (7, 0) BNNTs are −0.2013, −1.746, −1.593 and −2.257 eV, respectively. Our results revealed that in comparison with the pure (7, 0) BNNTs, CO gas is chemisorbed on the transition metal doped (7, 0) BNNTs with the appreciable adsorption energy. In addition, it was found that by doping these atoms, band gap energy of the pure (7, 0) BNNTs is considerably decreased. These observations suggested that the Pt doped (7, 0) BNNTs can be introduced as a promising candidate in gas sensor devices for detecting CO gas.

Multitudinous industrialized fabrication of BNNT with high-energy ball milling and arc-discharge-aided template methods

A novel large-scale fabrication technology for single-walled boron nitride nanotube (BNNT) relying on a template of single-walled carbon nanotube (SWCNTs) was introduced. In order to obtain large-scale product, the high-energy ball milling-aided heating technology was used to promote the formation of BNNTs. And arc-discharge methods were used to provide nitrogen ion source. The products were oxidized at 800 °C in air atmosphere to obtain pure BNNTs. The structure and morphology of BNNTs were characterized by X-ray diffraction, transmission electron microscopy, Fourier transformation infrared spectroscopy, and thermogravimetric analysis. The multitudinous industrialized preparation methods for BNNTs were realized as a simple and effective route.

Aluminum doping makes boron nitride nanotubes (BNNTs) an attractive adsorbent of hydrazine (N2H4)

Adsorption of toxic hydrazine (N2H4) at the surface of pristine and Al-doped single-wall boron nitride nanotubes (BNNTs and Al-BNNTs) has been investigated using density functional theory (DFT). Single hydrazine molecule was allowed to interact with Lewis acid center (i.e., B atom) of BNNTs, where most stable gauche conformer of the guest is used. Both zigzag (8,0) and armchair (4,4) variants of BNNTs were considered and to estimate the effect of tube diameter on adsorption energies wider zigzag (9,0) and (10,0), and armchair (5,5) and (6,6), tubes were included in the host list. Estimated adsorption energies of 2–8 kcal/mol do not support strong binding between pristine BNNTs with hydrazine. However, Al doping makes BNNTs an attractive adsorbent of N2H4 with adsorption energy in the range of 32–35 kcal/mol. Stability of such complexes is found less sensitive to the chirality, but nominally decreases with tube diameter. Thus, a large quantity of hydrazine may be adsorbed by Al-BNNT samples. The dative N: → B/Al bond between hydrazine and host tubes is the source of stability of complexes. Molecular electrostatic potentials (MEPs) and frontier molecular orbitals of host and guest were calculated to explain interaction character and strength.

Comb Peculiarities of Dispersion-Managed Solitons in a Hybrid Mode-Locked All-Fiber Ring Laser

We studied the optical comb peculiarities of the ultra-short dispersion-managed soliton generation in an erbium-doped all-fiber ring laser hybrid mode-locked with carbon:boron nitride single-walled nanotubes in the co-action with a nonlinear polarization evolution. A stable low-intensity-noise optical comb was obtained with a narrow single comb linewidth of 18.1 kHz based on dechirped 90-fs pulses with a repetition rate of 42.22 MHz, a spectral pulse width of 56 nm, and an average output power of 16.7 mW corresponding to 4.4-kW maximum peak power and 0.4-nJ pulse energy.