Theoretical Studies of the Interaction of an Open-Ended Boron Nitride Nanotube (BNNT) with Gas Molecules

The Journal of Physical Chemistry C (Impact Factor: 4.77). 12/2008; 112(51). DOI: 10.1021/jp805790s


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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    • "For example, BNNTs are highly appropriate to construct insulating nanocables [10] [11] [12] [13], they can be used as an ideal nanosized luminescent material [14] [15] and may be used in nanodevices working at elevated temperature and in hazardous environment. Despite numerous superiorities of BNNTs to CNTs [16] [17] [18] [19] [20], fewer studies have been reported about adsorption of gases on BNNTs, compared to the CNTs. Apparently, an important reason could be the electronic properties of BNNTs partially influenced by the presence of external fields or adsorption of foreign gases [21]. "
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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.
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    ABSTRACT: Whether adsorbates might effectively lower the ionization potential (IP) of open-ended boron nitride nanotubes (BNNTs) in order to design BNNTs based on flat-panel display devices is an unanswered question. In the present work, through density functional theory (DFT) calculations we present the first attempt on the effects of O(2) and H(2)O adsorption on the field-emission properties of an open-ended (8, 0) BNNT. The two adsorbates can chemisorb at the tips of the open-ended BNNT with large adsorption energies and significant charge transfer. An applied electric field of 1 eV A(-1) at the tube tip (a) significantly increases the adsorption energy to stabilize the adsorbates, and (b) alters the emission properties such as ionization potential (IP) or bandgap. The IP of the open N-rich-ended BNNT is lowered, thereby making it easier to lose electrons. However, there is a slight increase of the IP for the open B-rich-end BNNT. Our results would be useful not only to better understand the property of open-ended BNNTs, but also to design more efficient field emitters of molecular electronic devices in experiments.
    Nanotechnology 03/2009; 20(8):085704. DOI:10.1088/0957-4484/20/8/085704 · 3.82 Impact Factor
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    ABSTRACT: In this paper, we explored computationally the feasibility of modulating the bandgap in a single-wall BN nanotube (BNNT) upon noncovalent adsorption of organic molecules, combined with the application of a transverse electric field. Effects of analytes' physisorption on the surface of BNNTs regarding structural and electronic properties were delineated. Relatively large binding energies were calculated, however, with minimal perturbation of the structural framework. Electronic structure calculations indicated that the bandgap of BNNTs can be modified by weak adsorption due to the presence of adsorbate states in the gap of the host system. Furthermore, we have shown that the application of a transverse electric field can tune the bandgap by shifting adsorbate states, consistent with calculated current-voltage characteristics.
    Nanotechnology 10/2009; 20(35):355705. DOI:10.1088/0957-4484/20/35/355705 · 3.82 Impact Factor
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