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.
- SourceAvailable from: Ernesto Chigo[Show abstract] [Hide abstract]
ABSTRACT: Using the density functional theory (DFT) we study the structural and electronic properties of functionalized (5,5) chirality single wall beryllium oxide nanotubes (SW-BeONTs), i.e. armchair nanotubes. The nanotube surface and ends are functionalized by the hydroxyl (OH) functional group. Our calculations consider the Hamprecht-Cohen-Tozer-Handy functional in the generalized gradient approximation (HCTH-GGA) to deal with the exchange-correlation energies, and the base function with double polarization (DNP). The geometry optimization of both defects free and with point defects nanotubes is done applying the criterion of minimum energy. Six configurations are considered: The OH oriented toward the Be (on the surface and at the end), toward the O (on the surface and at the end) and placed at the nanotube ends. Simulation results show that the nanotube functionalization takes place at the nanotube ends with the BeO bond displaying hydrogen-like bridge bonds. Moreover the nanotube semiconductor behavior remains unchanged. The polarity is high (it shows a transition from covalent to ionic) favoring solvatation. On the other hand, the work function low value suggests this to be a good candidate for the device fabrication. When the nanotube contains surface point defects the work function is reduced which provides excellent possibilities for the use of this material in the electronic industry.Journal of molecular graphics & modelling 04/2013; 42C:115-119. · 2.17 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: The physisorption of methane in homogeneous armchair open-ended SWBNNT triangular arrays was evaluated using grand canonical ensemble Monte Carlo simulation for tubes 11.08, 13.85, 16.62, and 19.41 Å [(8,8), (10,10), (12,12), and (14,14), respectively] in diameter, at temperatures of 273, 298, 323, and 373 K, and at fugacities of 0.5-9.0 Mpa. The intermolecular forces were modeled using the Lennard-Jones potential model. The absolute, excess, and delivery adsorption isotherms of methane were calculated for the various boron nitride nanotube arrays. The specific surface areas and the isosteric heats of adsorption, Q(st), were also studied, different isotherm models were fitted to the simulated adsorption data, and the model parameters were correlated. According to the results, it is possible to reach 108% and 140% of the US Department of Energy's target for CH(4) storage (180 v/v at 298 K and 35 bar) using the SWBNNT array with nanotubes 16.62 and 19.41 Å in diameter, respectively, as adsorbent. The results show that for a van der Waals gap of 3.4 Å, there is no interstitial adsorption except for arrays containing nanotubes with diameters of >15.8 Å. Multilayer adsorption starts to occur in arrays containing nanotubes with diameters of >16.62 Å, and the minimum pressure required for multilayer adsorption is 1.0 MPa. A brief comparison of the methane adsorption capacities of single-walled carbon and boron nitride nanotube arrays was also performed.Journal of Molecular Modeling 11/2011; 18(6):2699-708. · 1.98 Impact Factor
- [Show abstract] [Hide abstract]
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. · 1.55 Impact Factor