Theoretical Studies of the Interaction of an Open-Ended Boron Nitride Nanotube (BNNT) with Gas Molecules
ABSTRACT We have systematically studied the effects of several gaseous adsorbates (H2, N2, O2, and H2O) on the electronic properties of open edges of boron nitride nanotubes (BNNTs) by using density functional theory calculations. The results indicate that all of the molecules, except N2, dissociate and chemisorb on open BNNT edges with large adsorption energies because the tube edge has either an open or capped structure and thus has dangling bonds or pentagonal defects. The high reactivity of an open-ended BNNT even can be comparable with that of its carbon counterpart, although the wall of the BNNT is chemically more stable than a single-walled carbon nanotube’s wall. Moreover, we note that adsorption of gases at the tips of open BNNTs can modify their electronic properties in various ways. A considerable amount of charge transferred for the adsorption of gases on the open BNNTs may account for the changes of the electronic properties. Interestingly, the open (5,5) BNNT exhibits the properties of wide-band-gap materials when gases are adsorbed at top sites, while a smaller band gap is observed when these gases are adsorbed on seat sites. Additionally, the magnetic moments of gas-adsorbed N atoms in the open N-rich-ended (8,0) are significantly decreased because the dangling bonds are “saturated”. The present results might be helpful in the design of BNNT-based nanomaterials such as field emitters or nanojunctions.
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ABSTRACT: We have performed a comparative study of nine predominant gas molecules (H2, H2O, O2, CO, CO2, NO, NO2, NH3, and CH3OH) adsorption property on the top surface of the (10, 0) zigzag single-walled pristine Carbon nanotube (C-CNT), Boron doped carbon nanotube (B-CNT), and Silicon doped carbon nanotube (Si-CNT) are investigated by using density functional theory (DFT) computations to exploit their potential applications as gas sensors. For the first time, we calculated the optimal equilibrium position, absorption energy (Ead ), Band structure and density of states (DOS) of the considered gas molecules adsorbed on the open end of zigzag single-walled (10, 0) B-CNT and Si-CNT. Our first principle calculations demonstrate that the B-CNT and Si-CNT adsorbent materials are able to adsorb the considered gas molecules with variety of adsorption energy and their electronic structure dramatic changes in the density of states near the Fermi level. The obtained comparative DFT studies results are useful for designing a high-fidelity gas sensor materials and selective adsorbents for a selective gas sensor.Journal of Nanomaterials 12/2013; 2013. · 1.61 Impact Factor
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ABSTRACT: Adsorption of methane (CH4) on inside and outside of aluminum-doped (Al-doped) zigzag single-walled boron nitride nanotubes, BNNTs/Al, has been studied using density-functional theory (DFT) method. The effect of diameter and type of atom of BNNT replaced by the Al atom on the adsorption properties of CH4 were investigated. Our results indicate that, compared to pristine BNNTs, replacing both B atom by Al, BNNT/Al(B) and N atom by Al, BNNT/Al(N), can notably enhance the binding energy of CH4 on BNNTs and the latter case has been more superior. The average binding energy for the most stable configuration of CH4 on BNNTs/Al(N) and BNNTs/Al(B) are about −26.12 and −16.53 kJ mol−1, respectively, which are typical for the physisorption and suitable for technical applications. The results show that while the geometry of BNNT/Al(N or B)–CH4 complexes is determined by weak electrostatic forces, the binding energy mainly determines by dispersion forces. For all complexes, the energy gaps, natural bond orbital (NBO) analysis, dipole moments, natural charge and density of state (DOS) diagrams were extracted. Finally, the applicability of BNNTs/Al(N) both as a medium for storage and gas sensor for methane detection were confirmed.Applied Surface Science 08/2014; 309:54–61. · 2.54 Impact Factor
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ABSTRACT: The interaction of various gas molecules including H2, N2, O2 (in triplet and singlet), and H2O on the geometrical structures, energies, and electronic structures with open edges of zigzag (10, 0) and armchair (6, 6) aluminum nitride nanotubes (AlNNTs) has been systematically studied using density functional theory. It is shown that the σ-type species including H2 and H2O will dissociate when chemisorbed on open AlNNTs, whereas the π-type species including N2 and O2 prefer to form cyclic structures on open AlNNTs; for example, a [2 + 2] cycloaddition configuration is formed when singlet O2 is adsorbed on the Al–N at the armchair edge. The edge of the open N-rich-ended (10, 0) AlNNT generally shows higher reactivity toward gas molecules than that of the open Al-rich-ended (10, 0), open-ended (6, 6) except for O2 (in triplet and singlet) on the Al-rich-ended (10, 0) AlNNT. However, unlike the largest adsorption energy from O2 on B-rich-ended (8, 0) BNNT, that of AlNNT comes from the H2 on the N-rich-ended (10, 0) AlNNT with the Ead of −12.17 eV. Moreover, we note that the adsorbates at the edges of the open AlNNT can modify their electronic properties in various ways. A considerable amount of charge transferred through the adsorption of gas molecules on the open-ended AlNNTs may account for the changes of the electronic properties. Interestingly, the adsorption of open-ended (10, 0) AlNNT will narrow band-gaps, for example, N2 and triplet O2 adsorbed on the Al-rich-ended (10, 0) AlNNT decrease gaps from 1.58 to 0.62 and 0.83 eV, respectively, whereas both triplet and singlet O2 adsorbed on the N-rich-ended (10, 0) AlNNT decrease gaps from 2.71 to 0.30 and 0.31 eV, respectively, which should result from the influence of introduced energy-levels of N2 and O2 on the energy bands of the AlNNT. Accompanied by the change of HOMO–LUMO gaps, the adsorption of H2, N2, and H2O on the N-rich-ended (10, 0) AlNNT lift the Fermi level toward conduction band largely at 15.9, 14.7, and 15.9%, respectively, thus significantly decreasing the work function. The present results may be useful for the design of AlNNT-based nanomaterials devices such as chemical sensor and field emitter.The Journal of Physical Chemistry C 02/2012; 116(8):4957–4964. · 4.84 Impact Factor