- Email: [email protected]
Boron nitride nanocones template for adsorbing NO2 and SO2: An ab initio investigation
Physica E: Low-dimensional Systems and Nanostructures 113 (2019) 188–193
Contents lists available at ScienceDirect
Physica E: Low-dimensional Systems and Nanostructures journal homepage: www.elsevier.com/locate/physe
Boron nitride nanocones template for adsorbing NO2 and SO2: An ab initio investigation
T
Mohamed M. Fadlallaha,∗, Ahmed A. Maaroufb, Kamal A. Solimanc,∗∗ a
Department of Physics, Faculty of Science, Benha University, P.O. Box 13518, Benha, Egypt Department of Physics, Institute for Research and Medical Consultations, Imam Abdulrahman Bin Faisal University, Dammam 31441, Saudi Arabia c Department of Chemistry, Faculty of Science, Benha University, P.O. Box 13518, Benha, Egypt b
A R T I C LE I N FO
A B S T R A C T
Keywords: Density functional theory Adsorption NO2 SO2 Boron nitride nanocones Al doped boron nitride nanocones
Many sensing applications depend on molecular adsorption on surfaces. Nanostructured materials have been the focus of many research efforts aimed at developing sensors for toxic gases. In this work, we study the adsorption of NO2 and SO2 molecules on boron nitride nanocones (BNNCs), using first principles calculations. Aluminum doping of BNNCs (Al–BNNCs) significantly increases the adsorption at the apex of the cone, with a minor change upon inclusion of the van der Waals interactions. Adsorption of NO2 and SO2 causes a considerable change in the HOMO-LUMO gap of BNNC/Al-BNNC, suggesting that BNNC can be used as templates for sensing and removal of NO2 and SO2.
1. Introduction The development of gas sensing techniques are important and vital not only for health care but also for environmental protection. Nitrogen dioxide (NO2) and sulfur dioxide (SO2) are toxic gases and common air pollutants. Both gases are natural components of earth's atmosphere produced naturally from the burning of fossil fuels. Breathing these gases may cause many problems such as lung and cardiovascular diseases. Therefore, developing sensing and removal mechanisms of these cases is of great environmental interest. Due to the large surface/volume ratio of nanostructures (as compared to ordinary micro sensors), electronic properties, carrier mobilities, good thermal stabilities, and high adsorption capacities, they are important candidates for gas sensing applications. Nanostructures such as carbon nanocones are free-standing structures, with more curved morphology than carbon nanotube. Carbon nanocones can be synthesized from nanotubes [1,2]. Experimentally, graphene-based sensors can detect NO2 and NH3 because of their high sensitivity [3,4], which is confirmed by theoretical calculations, in contrast to SO2, which reacts only weakly with graphene [5]/carbon nanotube [6]. Boron nitride (BN) nanostructures have high chemical/thermal stability, oxidation inertness, mechanical toughness, and lower toxicity [7–11], which makes them promising candidates for many applications [12–15]. Similar to graphene/carbon nanotubes, the pristine BN
nanosheets [16]/BN nanotubes [17] can not detect the presence of SO2 gas. The methods of fabricating BN nanocones (BNNCs) are the same for preparing the carbon nanocones with different disclination angles [18,19]. The curvature of the apex of nanocones and different covalent bonds (N–N, B–B, and N–B) at the tip of cones are important factors for adsorbing different molecules such as phosgene gas [20], chloropicrin [21], N2O [22], and SO [23]. In addition, Vessally et al. found that BNNCs adsorb the cyanogen chloride better than BN nanosheets [24]. In this work, we use density functional theory to study the adsorption of NO2 and SO2 on BNNC and Al-BNNC. The effects of the adsorption on the electronic properties of the BNNC and Al-BNNC are also investigated. The long range correction to the adsorption energies is considered. Our results indicate that the studied structures can act as effective sensors for NO2 and SO2. 2. Computational methods Density functional theory is employed in all calculations using Gaussian 09 [25]. The calculations of all studied structures are performed using spin-unrestricted/restricted B3LYP hybrid functional and the 6–31g (d,p) level of theory. This functional is successful in explaining some experimental results [26], and is widely used for studying the nanostructures [21,24,27]. The systems are structurally relaxed until the force becomes less than 0.0025 eV/Å with a SCF
∗
Corresponding author. Corresponding author. E-mail addresses: [email protected], [email protected] (M.M. Fadlallah), [email protected], [email protected] (K.A. Soliman). ∗∗
https://doi.org/10.1016/j.physe.2019.05.005 Received 22 February 2019; Received in revised form 26 April 2019; Accepted 5 May 2019 Available online 17 May 2019 1386-9477/ © 2019 Published by Elsevier B.V.
Physica E: Low-dimensional Systems and Nanostructures 113 (2019) 188–193
M.M. Fadlallah, et al.
convergence criteria of 1 × 10−5. The long-range corrected hybrid density functional with dispersion corrections ωB97X-D [27], 100% Hartree-Fock exchange, is utilized in the calculations. The charge transfer is determined by the Mulliken method. The adsorption energy of an adsorbed molecule (Eads) onto BNNC is calculated using:
Eads = Emolecule + BNNC/Al − BNNC − EBNNC/Al − BNNC − Emolecule,
3.2. NO2 and SO2 onto pristine BNNC Since there are three different adsorption orientations for each molecule (Fig. 2a–c), we first determine the orientation with the highest adsorption energy. The apex of nanocones is an active site for the adsorption of different nucleophile agents [31,32]. Three initial configurations are considered. NO2 molecule is initially placed on the exterior surface of BNNC with different orientations as in Fig. 2. We find the configurations in which NO2 molecule attaches to B atom of the cone via any of its O atoms are more energetically favorable than the configuration where the N atom attaches to the B atom. This is due to the higher electronegativity of O atom in comparison to that of N. After relaxation without symmetry constraints, the configuration (a), Fig. 2a, is the most stable complex structure in which one O atom of the NO2 molecule is attached to the B atom of the pentagon in the apex of the cone and the second O atom is attached at the bridge between the N atoms. Calculated B–O distance is 1.51 Å and the adsorption energy is −0.71 eV. The NO2 geometry is deformed: the bond length of N–O is slightly increased from 1.20 Å in free molecule to 1.21 Å and 1.35 Å in the adsorbed molecule, and the angle of O–N–O is decreased from 133.8° to 115.5°. The NO2 gas molecule acts as an electron withdrawing group gaining charge of −0.47e from the cone (see Table 1). As in inset Fig. 2d, the NO2 molecule tends to attack the LUMO site (B atoms) at the base of the cone. Due to the open shell of the NO2 molecule, the DOS/PDOS has two spin components as shown in Fig. 2d. The main contributions of NO2 states appear at −1.4 eV (HOMO+1) and 3.8 eV (LUMO+1) for the two spin components. The N states of BNNC are the majority of HOMO and LUMO (at 1 eV) with very small contributions of B states. The HOMO-LUMO gap is 1.9 eV which is less than the HOMO-LUMO gap of BNNC before the adsorption. The second configuration (b) as depicted in Fig. 2b in which the N atom of the NO2 molecule is closest to the B atom of the pentagon at the apex of the cone, with a distance of 1.62 Å. The geometry of the NO2 molecule is also distorted similar to configuration (a). The adsorption energy is −0.40 eV with a charge transfer of 0.50e to the molecule (Table 1). In the third configuration (c), Fig. 2c, the NO2 molecule is closest to the bridge between B–N atoms via its nitrogen atom with adsorption energy of −0.22 eV and a charge transfer of 0.03e from the BNNC to the molecule. The distance between the N atom of the cone and the N atom of the NO2 molecule is 2.89 Å. Turning to SO2@BNNC, we followed the same procedure for SO2 adsorption on the exterior surface of the BNNC. After relaxation, the SO2 is aligned parallel to the surface of the cone (configuration (a)), the
(1)
where Emolecule+BNNC/Al-BNNC is the total energy of the complex BNNC system, EBNNC/Al-BNNC is the total energy of the BNNC/Al-BNNC, and Emolecule is the total energy of the isolated molecule. The enthalpy/ Gibbs free energy change (ΔH/ΔG) of adsorption at room temperature and 1 atm pressure was evaluated in the same way of Eq. (1) by replacing Eads and E by (ΔH∕ΔG) and (H∕G), respectively, i.e.:
ΔH = Hmolecule + BNNC / Al − BNNC − HBNNC / Al − BNNC − Hmolecule
(2)
and
ΔG = Gmolecule + BNNC / Al − BNNC − G BNNC / Al − BNNC − Gmolecule.
(3)
3. Results and discussion 3.1. Optimized and electronic structures of pristine BNNC The individual NO2 or SO2 molecule in gas phase has a bent structure. Our calculated N–O/S–O bond length of 1.20/1.46 Å and O–N–O/ O–S–O bond angle of 133.8∕119.1° are in good agreement with the experimental values of 1.19/1.43 Å and 134.1 [28]/119.0° [29]. The cone is constructed of 42 N and 38 B atoms and the edge atoms are terminated with hydrogen atoms. The optimized structure of BN nanocone with 60° disclination angle is displayed in Fig. 1a and b. The cone has a pentagonal ring at the apex. There exist two kinds of bonds at the apex of the optimized structure; B–N bond with length of 1.43 Å, and N–N bond with length of 1.45 Å. Fig. 1 shows the density/projected density of states (DOS/PDOS) of pristine BNNC. The energy is offset by the Fermi energy EF. The highest occupied molecular orbital (HOMO), inset Fig. 1c, is localized on the N atoms in N–N bond while the lowest unoccupied molecular orbital (LUMO), inset Fig. 1c, is localized on the B atoms at the base of the cone. The contributions of the H states appear above 4 eV. The HOMOLUMO band gap is 4.6 eV in good agreement with previous work [30]. The molecular electrostatic potential is negative for the N atoms and positive for the B atoms at the apex of the cone.
Fig. 1. (a) Top view of BNNC structure, (b) Side view of BNNC structures, and (c) DOS/PDOS for pristine BNNC. Green, orange, and blue spheres represent H, B, and N atoms in the structures, respectively. 189
Physica E: Low-dimensional Systems and Nanostructures 113 (2019) 188–193
M.M. Fadlallah, et al.
Fig. 2. (a), (b) and (c) are different configurations of NO2@BNNC. (d) DOS/PDOS for more stable adsorbed NO2@pristine BNNC configuration (a). Green, orange, blue, and red spheres represent H, B, N, and O atoms, in the structures, respectively.
where kB and T are Boltzmann's constant and the absolute temperature, respectively. The conductivity of BNNC will change in the presence of NO2 and SO2 gases, due to the gap change, and hence BNNC can be used as a sensor for these toxic gases. The work function of BNNC is affected by the gas adsorption and it depends on the orientation of adsorbate. The work function is evaluated using:
Table 1 Adsorption energies (Eads (eV)) of NO2 and SO2 on BNNC, Mulliken charge (QT (e)) on the adsorbed molecules, the angle (α) of O–N–O and O–S–O, and HOMOLUMO energy gap (Eg (eV)) of BNNC, NO2 and SO2 on BNNC. ΔG (eV) and ΔH (eV) are the changes in Gibbs free energy and enthalpy, respectively, for NO2 and SO2 on BNNC. System
Eads
QT
Eg
α
Φ
ΔG
ΔH
BNNC NO2 (a) NO2 (b) NO2 (c) SO2 (a) SO2 (b) SO2 (c)
– −0.71 −0.40 −0.22 −0.34 −0.27 −0.34
– −0.47 −0.50 −0.03 −0.07 −0.03 −0.08
4.6 1.9 1.9 1.6 2.0 1.7 2.6
5.92 115.5 123.1 133.0 117.7 118.3 118.1
– 6.77 6.82 7.02 6.25 6.26 6.22
– −0.10 – – 0.13 – 0.15
– −0.64 – – −0.25 – −0.41
ϕ = ϕ0 e − EF ,
where ϕ0 is the electrostatic potential of a vacuum level far from the surface. As listed in Table 1, we find that the work function of BNNC increases upon the adsorption of NO2 and SO2. This increase in work function is related the charge transfer between molecule and the cone. For the most stable complexes of NO2 and SO2, we evaluate the Gibbs free energy changes (ΔG) and enthalpy changes (ΔH) to assess the thermodynamics feasibility of the adsorption of the gas molecules on the BNNC. In Table 1, the NO2@BNNC and SO2@BNNC are exergonic. The negative values confirm the spontaneous nature of the adsorption, but for SO2 there is an energy barrier. It is worth mentioning that the value ΔH in comparison with ΔG relates to the entropic effects, e.g. the entropy change is positive in all of studied cases.
O atom of SO2 is linked with the B atom at the apex with a length of 3.41 Å. The calculated adsorption energy of this configuration is −0.34 eV, indicating the weak physisorption nature and little charge transfer of 0.07e from the cone to the SO2 molecule (Table 1). The S is attached with the B of the pentagon at the apex (configuration (b)) with a distance of 3.59 Å. For configuration (c), the S is closest to the N of the pentagon at the apex, with a distance of 2.79 Å, and an adsorption energy of −0.27 eV. The configurations (a) and (c), Fig. 3, have the same Eads (−0.34 eV) which means they are the most stable structures with approximately the same small charge transfer as compared to configuration (b). Negative charge transfer as in Table 1 reveals that the transfer is from the cone to the molecule. The larger distances, as compared to NO2@BNNC, are the result of a weaker interaction and a smaller charge transfer. For SO2, the DOS has only one component due to the closed shell of SO2 molecule, Fig. 3. For complex structure (a), the HOMO and LUMO consist of N and SO2 states, respectively, a HOMO-LUMO gap of 2.0 eV, Fig. 3a. This gap is less than the corresponding BNNC gap before adsorption and higher than the gap of NO2@BNNC. The (c) configuration has a larger HOMO-LUMO gap of 2.6 eV (Fig. 3c). In order to predict the sensitivity of the HOMO-LUMO gap of the BNNC for NO2/SO2 gases, we use the electrical conductivity, σ, defined by Ref. [18]:
σ ∝ exp (−Eg /2kB T ),
(5)
3.3. NO2 and SO2 onto Al doped BNNC The Al dopant increases the adsorption energy for para-nitrophenol [33], glucose and glucosamine [34], SO2 [16] on BN nanosheets, NH3 [35] and CO [36] on BN nanotubes, compared to the corresponding pristine nanostructures. Fig. 4a shows the optimized structure for AlBNNC, where a B atom is replaced by an Al atom at the apex of the cone. Since Al has an atomic radius larger than B (RAl = 1.18 Å, and RB = 0.87 Å), the bond length Al–N of 1.77 Å is larger than the bond length B–N of 1.43 Å. The Al dopant distorts the structure of BNNC, which also happens with BN sheets [34] and graphene [37]. Fig. 4b shows the DOS/PDOS for Al-BNNC. Compared to the pristine cone, the HOMO, inset Fig. 4b, is still dominated by N states. However, the LUMO, inset Fig. 4b, consists of localized Al states which leads to a smaller HOMO-LUMO gap of 2.9 eV. We now discuss our results for the adsorption of NO2 and SO2 on AlBNNC. In this case, and unlike with pristine BNNC, the atom closest to the doped BNNC site is an O atom. The adsorption of NO2 and SO2 on
(4) 190
Physica E: Low-dimensional Systems and Nanostructures 113 (2019) 188–193
M.M. Fadlallah, et al.
Fig. 3. (a), (b) and (c) are different configurations of SO2@BNNC. (d) and (e) are DOS/PDOS for more stable structure (a) and (c), respectively. Green, orange, blue, red, brown spheres represent H, B, N, O, and S atoms, in the structures, respectively.
Al-BNNC elongates the Al–O bond to 1.85 Å for NO2, Figs. 4c, and 1.84/ 1.82 Å for SO2 (a)/(c), Fig. 5a/c. The Al–O bond lengths are 1.83 Å and 1.81/1.84 Å for NO2 and SO2(a)/SO2(c)@Al-BNNC, respectively. The optimized configuration (c) in which SO2 is adsorbed on the Al dopant has a different orientation as compared to configuration (a) where the Al–O–S angle for configuration (c) is larger than configuration (a), Fig. 5a/c. The Mulliken charge analysis indicates that NO2 and SO2(a)/ SO2(c) lose charge locally at the adsorption site; with 0.43e and 0.13/ 0.20e, respectively, transferred to the Al atom. Therefore the work function increases after adsorption. The adsorption energy of the NO2 and SO2(a)/SO2(c) molecules onto Al-BNNC is −3.00 eV and −2.22/1.48 eV, respectively. This means that the Al-BNNC system may be
more sensitive for NO2 than for SO2 (see Table 2). Fig. 4d shows the DOS/PDOS of NO2@Al-BNNC. The HOMO and LUMO of the NO2 molecule are positioned below the HOMO and above the LUMO which is created by the N states of the sheet (see the insets of Fig. 4d). This decreases the HOMO-LUMO gap to 1.9 eV due to the coupling between the NO2 and the Al atoms; the Al 3s state moves away from the HOMO-LUMO gap. Fig. 5b shows the DOS/PDOS of the SO2@Al-BNNC configuration (a). The HOMO/LUMO is occupied by SO2 states and N states and the HOMO-LUMO gap is 0.7 eV. The hybridization between the states in case of (c) configuration for HOMO and LUMO differs from (a) configuration, see Fig. 5d. The HOMO consists of N states only and the LUMO is dominated by SO2 states, with
Fig. 4. (a) the structure of Al-doped BNNC and (b) the corresponding DOS/PDOS. (c) the structure of NO2@Al-doped BNNC and (c) the corresponding DOS/PDOS. Green, orange, blue, and pink spheres represent H, B, N, and Al atoms in the structures, respectively. 191
Physica E: Low-dimensional Systems and Nanostructures 113 (2019) 188–193
M.M. Fadlallah, et al.
Fig. 5. (a) the stable structure of SO2@Al-doped BNNC and (b) the corresponding DOS/PDOS. (c) another stable structure of SO2@Al-doped BNNC and (d) the corresponding DOS/PDOS. Green, orange, blue, pink, and brown spheres represent H, B, N, Al, and S atoms in the structures, respectively.
for NO2 and SO2 (a) on BNNC and increased by ∼ 0.2/0.4 eV on AlBNNC as compared to corresponding values obtained without considering the vdW interactions. The long range corrected results for various structures are shown in Table 3.
Table 2 Adsorption energies (Eads (eV)) of NO2 and SO2 on Al-BNNC, Mulliken charge (QT (e)) on the adsorbed molecules, the angle (α) of O–N–O and O–S–O, and HOMO-LUMO energy gap (Eg (eV)) of Al-BNNC, NO2 and SO2 on Al-BNNC. ΔG (eV) and ΔH (eV) are the changes in Gibbs free energy and enthalpy, respectively, for NO2 and SO2 on Al-BNNC. System
Eads
QT
Eg
α
Φ
ΔG
ΔH
Al-BNNC NO2 (a) SO2 (a) SO2 (c)
– −3.00 −2.22 −1.48
– −0.43 −0.13 −0.09
2.9 1.9 3.4 0.7
– 112.8 110.3 111.3
5.99 6.75 6.47 5.82
– −2.46 −1.55 −0.98
– −2.95 −2.13 −1.45
4. Conclusion Using first principles calculations, we show that the adsorption of NO2 or SO2 on BNNC/Al-BNNC is a spontaneous process. Substitutional doping with Al at the cone apex leads to an enhancement of the adsorption of NO2 or SO2. The work function increases upon the adsorption of NO2 and SO2. Our results of the adsorption energy, HOMOLUMO gap change, and the thermal stability indicate that BNNC may be a good candidate material for an NO2 and SO2 sensor.
Table 3 Adsorption energy (Eads), in eV, using B3LYP, and using ωb97xd (long range corrections (Ed,lr)) for NO2 and SO2 on BNNC/Al-BNNC System
E
NO2
SO2 (a)
SO2 (c)
BNNC
Eads Eads,lr Eads Eads,lr
−0.71 −0.62 −3.00 −3.21
−0.34 −0.22 −2.20 −2.44
−0.34 −0.36 −1.48 −1.14
Al-BNNC
Acknowledgment The authors would like to acknowledge the resources and technical services provided by the Scientific and High Performance Computing Center at Imam Abdulrahman Bin Faisal University, Dammam, Saudi Arabia. References
some N states. The complex structures have work functions larger than Al-doped BNNC because of charge transfer. The NO2 or SO2 on Al-BNNC system is exergonic due to the decrease in the Gibbs free energy and enthalpy compared to the reactants.
[1] S. lijima, T. Ichihashi, Y. Ando, Pentagons, heptagons and negative curvature in graphite microtubule growth, Nature 356 (1992) 776 https://doi.org/10.1038/ 356776a0. [2] G. Maohui, S. Klaus, Observation of fullerene cones, Chem. Phys. Lett. 220 (3) (1994) 192–196 https://doi.org/10.1016/0009-2614(94)00167-7. [3] F. Schedin, S.V. Geim, A.K. andMorozov, P. Hill, E.W. Blake, M.I. Katsnelson, K.S. Novoselov, Detection of individual gas molecules adsorbed on graphene, Nat. Mater. 6 (2007) 652 https://doi.org/10.1038/nmat1967. [4] P. Qi, O. Vermesh, M. Grecu, A. Javey, Q. Wang, H. Dai, S. Peng, K.J. Cho, Toward large arrays of multiplex functionalized carbon nanotube sensors for highly sensitive and selective molecular detection, Nano Lett. 3 (3) (2003) 347–351, https:// doi.org/10.1021/nl034010k. [5] L. Xu-Ying, Z. Jian-Min, X. Ke-Wei, J. Vincent, Improving SO2 gas sensing properties of graphene by introducing dopant and defect: a first-principles study, Appl. Surf. Sci. 313 (2014) 405–410 https://doi.org/10.1016/j.apsusc.2014.05.223. [6] X. Zhang, Z. Dai, Q. Chen, J. Tang, A dft study of so 2 and h 2 s gas adsorption on au-doped single-walled carbon nanotubes, Phys. Scripta 89 (6) (2014) 065803. [7] J. Wu, L. Yin, Platinum nanoparticle modified polyaniline-functionalized boron nitride nanotubes for amperometric glucose enzyme biosensor, ACS Appl. Mater.
3.4. van der Waals corrections We have also investigated the effect of the van der Waals (vdW) interaction between the molecules and the BNNC. Using the vdW functional theory, ωB97X-D [27], the bond lengths of BNNC (B–N) and B–O (nanocones and molecules) are not changed as compared to the results of the B3LYP calculations. For Al-BNNC, there is about 1% decrease in the Al–N bond length upon molecular adsorption and a significant increase in the Al–O bond length (1.91 Å) for both molecules as compared to results obtained by B3LYP (1.83/1.84 Å for NO2 and SO2(c)). The adsorption energy is slightly decreased by ∼ 0.1/0.2 eV 192
Physica E: Low-dimensional Systems and Nanostructures 113 (2019) 188–193
M.M. Fadlallah, et al.
363–369 https://doi.org/10.1016/j.tsf.2017.11.002. [25] M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, G. Scalmani, V. Barone, G. A. Petersson, H. Nakatsuji, X. Li, M. Caricato, A. V. Marenich, J. Bloino, B. G. Janesko, R. Gomperts, B. Mennucci, H. P. Hratchian, J. V. Ortiz, A. F. Izmaylov, J. L. Sonnenberg, D. Williams-Young, F. Ding, F. Lipparini, F. Egidi, J. Goings, B. Peng, A. Petrone, T. Henderson, D. Ranasinghe, V. G. Zakrzewski, J. Gao, N. Rega, G. Zheng, W. Liang, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, T. Vreven, K. Throssell, J. A. Montgomery, Jr, J. E. Peralta, F. Ogliaro, M. J. Bearpark, J. J. Heyd, E. N. Brothers, K. N. Kudin, V. N. Staroverov, T. A. Keith, R. Kobayashi, J. Normand, K. Raghavachari, A. P. Rendell, J. C. Burant, S. S. Iyengar, J. Tomasi, M. Cossi, J. M. Millam, M. Klene, C. Adamo, R. Cammi, J. W. Ochterski, R. L. Martin, K. Morokuma, O. Farkas, J. B. Foresman, D. J. Fox, Gaussian 16 Revision B.01, Gaussian Inc. Wallingford CT. [26] K.-M. Sandor, C.N. Jia, Entropy-driven adsorption of carbon nanotubes on (001) and (111) surfaces of ceo2 islands grown on sapphire substrate, Surf. Sci. 604 (7) (2010) 654–659 https://doi.org/10.1016/j.susc.2010.01.011. [27] J.-D. Chai, M. Head-Gordon, Long-range corrected hybrid density functionals with damped atom–atom dispersion corrections, Phys. Chem. Chem. Phys. 10 (2008) 6615–6620, https://doi.org/10.1039/B810189B. [28] W.F. Schneider, J. Li, K.C. Hass, Combined computational and experimental investigation of sox adsorption on mgo, J. Phys. Chem. B 105 (29) (2001) 6972–6979, https://doi.org/10.1021/jp010747r. [29] D.R. Lide, 78th Edition, Physical Constants of Organic Compounds, CRC Handbook of Chemistry and Physics vol. 2007, Taylor and Francis, 2007. [30] S. Ahmadi, P.D.K. Nezhad, A. Hosseinian, E. Vessally, A computational study on tuning the field emission and electronic properties of bn nanocones by impurity atom doping, Phys. E Low-dimens. Syst. Nanostruct. 100 (2018) 63–68 https://doi. org/10.1016/j.physe.2018.03.010. [31] M.T. Baei, A.A. Peyghan, Z. Bagheri, Carbon nanocone as an ammonia sensor: dft studies, Struct. Chem. 24 (4) (2013) 1099–1103, https://doi.org/10.1007/s11224012-0139-3. [32] M.T. Baei, A.A. Peyghan, Z. Bagheri, M.B. Tabar, B-doping makes the carbon nanocones sensitive towards no molecules, Phys. Lett. 377 (1) (2012) 107–111 https://doi.org/10.1016/j.physleta.2012.11.006. [33] A.A. Peyghan, M. Noei, S. Yourdkhani, Al-doped graphene-like bn nanosheet as a sensor for para-nitrophenol: dft study, Superlattice. Microst. 59 (2013) 115–122 https://doi.org/10.1016/j.spmi.2013.04.005. [34] A.A. Darwish, M.M. Fadlallah, A. Badawi, A.A. Maarouf, Adsorption of sugars on aland ga-doped boron nitride surfaces: a computational study, Appl. Surf. Sci. 377 (2016) 9–16 https://doi.org/10.1016/j.apsusc.2016.03.082. [35] S. Alireza, R. Shima Ghafouri, R. Vahid Joveini, K. Aliakbar Dehno, M. Savar, Ab initio investigation of al- and ga-doped single-walled boron nitride nanotubes as ammonia sensor, Appl. Surf. Sci. 263 (2012) 619–625 https://doi.org/10.1016/j. apsusc.2012.09.122. [36] A.A. Peyghan, A. Soltani, A.A. Pahlevani, Y. Kanani, S. Khajeh, A first-principles study of the adsorption behavior of co on al- and ga-doped single-walled bn nanotubes, Appl. Surf. Sci. 270 (2013) 25–32 https://doi.org/10.1016/j.apsusc.2012. 12.008. [37] A.S. Rad, Al-doped graphene as a new nanostructure adsorbent for some halomethane compounds: dft calculations, Surf. Sci. 645 (2016) 6–12 https://doi.org/ 10.1016/j.susc.2015.10.036.
Interfaces 2 (2011) 4354. [8] J. Beheshtian, A.A. Peyghan, M.B. Tabar, Z. Bagheri, Dft study on the functionalization of a bn nanotube with sulfamide, Appl. Surf. Sci. 266 (2013) 182–187 https://doi.org/10.1016/j.apsusc.2012.11.128. [9] Q. Weng, X. Wang, X. Wang, Y. Bando, D. Golberg, Functionalized hexagonal boron nitride nanomaterials: emerging properties and applications, Chem. Soc. Rev. 45 (2016) 3989–4012, https://doi.org/10.1039/C5CS00869G. [10] G.C. Loh, S. Nigam, G. Mallick, R. Pandey, Carbon-doped boron nitride nanomesh: stability and electronic properties of adsorbed hydrogen and oxygen, J. Phys. Chem. C 118 (41) (2014) 23888–23896, https://doi.org/10.1021/jp508229w. [11] X. Zhi, G. Dmitri, B. Yoshio, Electrical field-assisted thermal decomposition of boron nitride nanotube: experiments and first principle calculations, Chem. Phys. Lett. 480 (1) (2009) 110–112 https://doi.org/10.1016/j.cplett.2009.08.072. [12] A.A. Darwish, M.H. Hassan, M.A.A. Mandour, A.A. Maarouf, Mechanical properties of defective double-walled boron nitride nanotubes for radiation shielding applications: a computational study, Comput. Mater. Sci. 156 (2019) 142–147 https:// doi.org/10.1016/j.commatsci.2018.09.040. [13] M. Sajjad, G. Morell, P. Feng, Advance in novel boron nitride nanosheets to nanoelectronic device applications, ACS Appl. Mater. Interfaces 5 (2013) 5051. [14] Q. Weng, B. Wang, X. Wang, N. Hanagata, X. Li, D. Liu, X. Wang, X. Jiang, Y. Bando, D. Golberg, Highly water-soluble, porous, and biocompatible boron nitrides for anticancer drug delivery, ACS Nano 8 (2014) 6123. [15] H.Z. Zhang, Q. Zhao, J. Yu, D.P. Yu, Y. Chen, Field-emission characteristics of conical boron nitride nanorods, J. Phys. D Appl. Phys. 40 (1) (2007) 144. [16] F. Behmagham, E. Vessally, B. Massoumi, A. Hosseinian, L. Edjlali, A computational study on the SO2 adsorption by the pristine, al, and si doped bn nanosheets, Superlattice. Microst. 100 (2016) 350–357 https://doi.org/10.1016/j.spmi.2016. 09.040. [17] Z.-Y. Deng, J.-M. Zhang, K.-W. Xu, First-principles study of SO2 molecule adsorption on the pristine and mn-doped boron nitride nanotubes, Appl. Surf. Sci. 347 (2015) 485–490 https://doi.org/10.1016/j.apsusc.2015.04.116. [18] L. Bourgeois, Y. Bando, S. Shinozaki, K. Kurashima, T. Sato, Boron nitride cones: structure determination by transmission electron microscopy, Acta Crystallogr. A 55 (2 Part 1) (1999) 168–177, https://doi.org/10.1107/S0108767398008642. [19] L. Bourgeois, Y. Bando, W.Q. Han, T. Sato, Structure of boron nitride nanoscale cones: ordered stacking of 240° and 300° disclinations, Phys. Rev. B 61 (2000) 7686–7691, https://doi.org/10.1103/PhysRevB.61.7686. [20] A. Hosseinian, M. Salary, S. Arshadi, E. Vessally, L. Edjlali, The interaction of phosgene gas with different bn nanocones: dft studies, Solid State Commun. 269 (2018) 23–27 https://doi.org/10.1016/j.ssc.2017.10.011. [21] E. Vessally, R. Moladoust, S.M. Mousavi-Khoshdel, M.D. Esrafili, A. Hosseinian, L. Edjlali, Chloropicrin sensor based on the pristine bn nanocones: dft studies, Struct. Chem. 29 (2) (2018) 585–592, https://doi.org/10.1007/s11224-0171055-3. [22] X. Shi, M. Sarafbidabad, A.Z. Ibatova, R. Razavi, M. Najafi, Potential of doped nanocones as catalysts for n2o+co reaction: theoretical investigation, J. Clust. Sci. (2019), https://doi.org/10.1007/s10876-018-1463-6. [23] X. Zuo, K. Behradfar, J.-B. Liu, M. Lariche, M. Najafi, Theoretical study of ability of boron nitride nanocone to oxidation of sulfur monoxide, Acta Chim. Slov. 65 (2) (2018). [24] E. Vessally, R. Moladoust, S. Mousavi-Khoshdel, M. Esrafili, A. Hosseinian, L. Edjlali, The clcn adsorption on the pristine and al-doped boron nitride nanosheet, nanocage, and nanocone: density functional studies, Thin Solid Films 645 (2018)
193
Contents lists available at ScienceDirect
Physica E: Low-dimensional Systems and Nanostructures journal homepage: www.elsevier.com/locate/physe
Boron nitride nanocones template for adsorbing NO2 and SO2: An ab initio investigation
T
Mohamed M. Fadlallaha,∗, Ahmed A. Maaroufb, Kamal A. Solimanc,∗∗ a
Department of Physics, Faculty of Science, Benha University, P.O. Box 13518, Benha, Egypt Department of Physics, Institute for Research and Medical Consultations, Imam Abdulrahman Bin Faisal University, Dammam 31441, Saudi Arabia c Department of Chemistry, Faculty of Science, Benha University, P.O. Box 13518, Benha, Egypt b
A R T I C LE I N FO
A B S T R A C T
Keywords: Density functional theory Adsorption NO2 SO2 Boron nitride nanocones Al doped boron nitride nanocones
Many sensing applications depend on molecular adsorption on surfaces. Nanostructured materials have been the focus of many research efforts aimed at developing sensors for toxic gases. In this work, we study the adsorption of NO2 and SO2 molecules on boron nitride nanocones (BNNCs), using first principles calculations. Aluminum doping of BNNCs (Al–BNNCs) significantly increases the adsorption at the apex of the cone, with a minor change upon inclusion of the van der Waals interactions. Adsorption of NO2 and SO2 causes a considerable change in the HOMO-LUMO gap of BNNC/Al-BNNC, suggesting that BNNC can be used as templates for sensing and removal of NO2 and SO2.
1. Introduction The development of gas sensing techniques are important and vital not only for health care but also for environmental protection. Nitrogen dioxide (NO2) and sulfur dioxide (SO2) are toxic gases and common air pollutants. Both gases are natural components of earth's atmosphere produced naturally from the burning of fossil fuels. Breathing these gases may cause many problems such as lung and cardiovascular diseases. Therefore, developing sensing and removal mechanisms of these cases is of great environmental interest. Due to the large surface/volume ratio of nanostructures (as compared to ordinary micro sensors), electronic properties, carrier mobilities, good thermal stabilities, and high adsorption capacities, they are important candidates for gas sensing applications. Nanostructures such as carbon nanocones are free-standing structures, with more curved morphology than carbon nanotube. Carbon nanocones can be synthesized from nanotubes [1,2]. Experimentally, graphene-based sensors can detect NO2 and NH3 because of their high sensitivity [3,4], which is confirmed by theoretical calculations, in contrast to SO2, which reacts only weakly with graphene [5]/carbon nanotube [6]. Boron nitride (BN) nanostructures have high chemical/thermal stability, oxidation inertness, mechanical toughness, and lower toxicity [7–11], which makes them promising candidates for many applications [12–15]. Similar to graphene/carbon nanotubes, the pristine BN
nanosheets [16]/BN nanotubes [17] can not detect the presence of SO2 gas. The methods of fabricating BN nanocones (BNNCs) are the same for preparing the carbon nanocones with different disclination angles [18,19]. The curvature of the apex of nanocones and different covalent bonds (N–N, B–B, and N–B) at the tip of cones are important factors for adsorbing different molecules such as phosgene gas [20], chloropicrin [21], N2O [22], and SO [23]. In addition, Vessally et al. found that BNNCs adsorb the cyanogen chloride better than BN nanosheets [24]. In this work, we use density functional theory to study the adsorption of NO2 and SO2 on BNNC and Al-BNNC. The effects of the adsorption on the electronic properties of the BNNC and Al-BNNC are also investigated. The long range correction to the adsorption energies is considered. Our results indicate that the studied structures can act as effective sensors for NO2 and SO2. 2. Computational methods Density functional theory is employed in all calculations using Gaussian 09 [25]. The calculations of all studied structures are performed using spin-unrestricted/restricted B3LYP hybrid functional and the 6–31g (d,p) level of theory. This functional is successful in explaining some experimental results [26], and is widely used for studying the nanostructures [21,24,27]. The systems are structurally relaxed until the force becomes less than 0.0025 eV/Å with a SCF
∗
Corresponding author. Corresponding author. E-mail addresses: [email protected], [email protected] (M.M. Fadlallah), [email protected], [email protected] (K.A. Soliman). ∗∗
https://doi.org/10.1016/j.physe.2019.05.005 Received 22 February 2019; Received in revised form 26 April 2019; Accepted 5 May 2019 Available online 17 May 2019 1386-9477/ © 2019 Published by Elsevier B.V.
Physica E: Low-dimensional Systems and Nanostructures 113 (2019) 188–193
M.M. Fadlallah, et al.
convergence criteria of 1 × 10−5. The long-range corrected hybrid density functional with dispersion corrections ωB97X-D [27], 100% Hartree-Fock exchange, is utilized in the calculations. The charge transfer is determined by the Mulliken method. The adsorption energy of an adsorbed molecule (Eads) onto BNNC is calculated using:
Eads = Emolecule + BNNC/Al − BNNC − EBNNC/Al − BNNC − Emolecule,
3.2. NO2 and SO2 onto pristine BNNC Since there are three different adsorption orientations for each molecule (Fig. 2a–c), we first determine the orientation with the highest adsorption energy. The apex of nanocones is an active site for the adsorption of different nucleophile agents [31,32]. Three initial configurations are considered. NO2 molecule is initially placed on the exterior surface of BNNC with different orientations as in Fig. 2. We find the configurations in which NO2 molecule attaches to B atom of the cone via any of its O atoms are more energetically favorable than the configuration where the N atom attaches to the B atom. This is due to the higher electronegativity of O atom in comparison to that of N. After relaxation without symmetry constraints, the configuration (a), Fig. 2a, is the most stable complex structure in which one O atom of the NO2 molecule is attached to the B atom of the pentagon in the apex of the cone and the second O atom is attached at the bridge between the N atoms. Calculated B–O distance is 1.51 Å and the adsorption energy is −0.71 eV. The NO2 geometry is deformed: the bond length of N–O is slightly increased from 1.20 Å in free molecule to 1.21 Å and 1.35 Å in the adsorbed molecule, and the angle of O–N–O is decreased from 133.8° to 115.5°. The NO2 gas molecule acts as an electron withdrawing group gaining charge of −0.47e from the cone (see Table 1). As in inset Fig. 2d, the NO2 molecule tends to attack the LUMO site (B atoms) at the base of the cone. Due to the open shell of the NO2 molecule, the DOS/PDOS has two spin components as shown in Fig. 2d. The main contributions of NO2 states appear at −1.4 eV (HOMO+1) and 3.8 eV (LUMO+1) for the two spin components. The N states of BNNC are the majority of HOMO and LUMO (at 1 eV) with very small contributions of B states. The HOMO-LUMO gap is 1.9 eV which is less than the HOMO-LUMO gap of BNNC before the adsorption. The second configuration (b) as depicted in Fig. 2b in which the N atom of the NO2 molecule is closest to the B atom of the pentagon at the apex of the cone, with a distance of 1.62 Å. The geometry of the NO2 molecule is also distorted similar to configuration (a). The adsorption energy is −0.40 eV with a charge transfer of 0.50e to the molecule (Table 1). In the third configuration (c), Fig. 2c, the NO2 molecule is closest to the bridge between B–N atoms via its nitrogen atom with adsorption energy of −0.22 eV and a charge transfer of 0.03e from the BNNC to the molecule. The distance between the N atom of the cone and the N atom of the NO2 molecule is 2.89 Å. Turning to SO2@BNNC, we followed the same procedure for SO2 adsorption on the exterior surface of the BNNC. After relaxation, the SO2 is aligned parallel to the surface of the cone (configuration (a)), the
(1)
where Emolecule+BNNC/Al-BNNC is the total energy of the complex BNNC system, EBNNC/Al-BNNC is the total energy of the BNNC/Al-BNNC, and Emolecule is the total energy of the isolated molecule. The enthalpy/ Gibbs free energy change (ΔH/ΔG) of adsorption at room temperature and 1 atm pressure was evaluated in the same way of Eq. (1) by replacing Eads and E by (ΔH∕ΔG) and (H∕G), respectively, i.e.:
ΔH = Hmolecule + BNNC / Al − BNNC − HBNNC / Al − BNNC − Hmolecule
(2)
and
ΔG = Gmolecule + BNNC / Al − BNNC − G BNNC / Al − BNNC − Gmolecule.
(3)
3. Results and discussion 3.1. Optimized and electronic structures of pristine BNNC The individual NO2 or SO2 molecule in gas phase has a bent structure. Our calculated N–O/S–O bond length of 1.20/1.46 Å and O–N–O/ O–S–O bond angle of 133.8∕119.1° are in good agreement with the experimental values of 1.19/1.43 Å and 134.1 [28]/119.0° [29]. The cone is constructed of 42 N and 38 B atoms and the edge atoms are terminated with hydrogen atoms. The optimized structure of BN nanocone with 60° disclination angle is displayed in Fig. 1a and b. The cone has a pentagonal ring at the apex. There exist two kinds of bonds at the apex of the optimized structure; B–N bond with length of 1.43 Å, and N–N bond with length of 1.45 Å. Fig. 1 shows the density/projected density of states (DOS/PDOS) of pristine BNNC. The energy is offset by the Fermi energy EF. The highest occupied molecular orbital (HOMO), inset Fig. 1c, is localized on the N atoms in N–N bond while the lowest unoccupied molecular orbital (LUMO), inset Fig. 1c, is localized on the B atoms at the base of the cone. The contributions of the H states appear above 4 eV. The HOMOLUMO band gap is 4.6 eV in good agreement with previous work [30]. The molecular electrostatic potential is negative for the N atoms and positive for the B atoms at the apex of the cone.
Fig. 1. (a) Top view of BNNC structure, (b) Side view of BNNC structures, and (c) DOS/PDOS for pristine BNNC. Green, orange, and blue spheres represent H, B, and N atoms in the structures, respectively. 189
Physica E: Low-dimensional Systems and Nanostructures 113 (2019) 188–193
M.M. Fadlallah, et al.
Fig. 2. (a), (b) and (c) are different configurations of NO2@BNNC. (d) DOS/PDOS for more stable adsorbed NO2@pristine BNNC configuration (a). Green, orange, blue, and red spheres represent H, B, N, and O atoms, in the structures, respectively.
where kB and T are Boltzmann's constant and the absolute temperature, respectively. The conductivity of BNNC will change in the presence of NO2 and SO2 gases, due to the gap change, and hence BNNC can be used as a sensor for these toxic gases. The work function of BNNC is affected by the gas adsorption and it depends on the orientation of adsorbate. The work function is evaluated using:
Table 1 Adsorption energies (Eads (eV)) of NO2 and SO2 on BNNC, Mulliken charge (QT (e)) on the adsorbed molecules, the angle (α) of O–N–O and O–S–O, and HOMOLUMO energy gap (Eg (eV)) of BNNC, NO2 and SO2 on BNNC. ΔG (eV) and ΔH (eV) are the changes in Gibbs free energy and enthalpy, respectively, for NO2 and SO2 on BNNC. System
Eads
QT
Eg
α
Φ
ΔG
ΔH
BNNC NO2 (a) NO2 (b) NO2 (c) SO2 (a) SO2 (b) SO2 (c)
– −0.71 −0.40 −0.22 −0.34 −0.27 −0.34
– −0.47 −0.50 −0.03 −0.07 −0.03 −0.08
4.6 1.9 1.9 1.6 2.0 1.7 2.6
5.92 115.5 123.1 133.0 117.7 118.3 118.1
– 6.77 6.82 7.02 6.25 6.26 6.22
– −0.10 – – 0.13 – 0.15
– −0.64 – – −0.25 – −0.41
ϕ = ϕ0 e − EF ,
where ϕ0 is the electrostatic potential of a vacuum level far from the surface. As listed in Table 1, we find that the work function of BNNC increases upon the adsorption of NO2 and SO2. This increase in work function is related the charge transfer between molecule and the cone. For the most stable complexes of NO2 and SO2, we evaluate the Gibbs free energy changes (ΔG) and enthalpy changes (ΔH) to assess the thermodynamics feasibility of the adsorption of the gas molecules on the BNNC. In Table 1, the NO2@BNNC and SO2@BNNC are exergonic. The negative values confirm the spontaneous nature of the adsorption, but for SO2 there is an energy barrier. It is worth mentioning that the value ΔH in comparison with ΔG relates to the entropic effects, e.g. the entropy change is positive in all of studied cases.
O atom of SO2 is linked with the B atom at the apex with a length of 3.41 Å. The calculated adsorption energy of this configuration is −0.34 eV, indicating the weak physisorption nature and little charge transfer of 0.07e from the cone to the SO2 molecule (Table 1). The S is attached with the B of the pentagon at the apex (configuration (b)) with a distance of 3.59 Å. For configuration (c), the S is closest to the N of the pentagon at the apex, with a distance of 2.79 Å, and an adsorption energy of −0.27 eV. The configurations (a) and (c), Fig. 3, have the same Eads (−0.34 eV) which means they are the most stable structures with approximately the same small charge transfer as compared to configuration (b). Negative charge transfer as in Table 1 reveals that the transfer is from the cone to the molecule. The larger distances, as compared to NO2@BNNC, are the result of a weaker interaction and a smaller charge transfer. For SO2, the DOS has only one component due to the closed shell of SO2 molecule, Fig. 3. For complex structure (a), the HOMO and LUMO consist of N and SO2 states, respectively, a HOMO-LUMO gap of 2.0 eV, Fig. 3a. This gap is less than the corresponding BNNC gap before adsorption and higher than the gap of NO2@BNNC. The (c) configuration has a larger HOMO-LUMO gap of 2.6 eV (Fig. 3c). In order to predict the sensitivity of the HOMO-LUMO gap of the BNNC for NO2/SO2 gases, we use the electrical conductivity, σ, defined by Ref. [18]:
σ ∝ exp (−Eg /2kB T ),
(5)
3.3. NO2 and SO2 onto Al doped BNNC The Al dopant increases the adsorption energy for para-nitrophenol [33], glucose and glucosamine [34], SO2 [16] on BN nanosheets, NH3 [35] and CO [36] on BN nanotubes, compared to the corresponding pristine nanostructures. Fig. 4a shows the optimized structure for AlBNNC, where a B atom is replaced by an Al atom at the apex of the cone. Since Al has an atomic radius larger than B (RAl = 1.18 Å, and RB = 0.87 Å), the bond length Al–N of 1.77 Å is larger than the bond length B–N of 1.43 Å. The Al dopant distorts the structure of BNNC, which also happens with BN sheets [34] and graphene [37]. Fig. 4b shows the DOS/PDOS for Al-BNNC. Compared to the pristine cone, the HOMO, inset Fig. 4b, is still dominated by N states. However, the LUMO, inset Fig. 4b, consists of localized Al states which leads to a smaller HOMO-LUMO gap of 2.9 eV. We now discuss our results for the adsorption of NO2 and SO2 on AlBNNC. In this case, and unlike with pristine BNNC, the atom closest to the doped BNNC site is an O atom. The adsorption of NO2 and SO2 on
(4) 190
Physica E: Low-dimensional Systems and Nanostructures 113 (2019) 188–193
M.M. Fadlallah, et al.
Fig. 3. (a), (b) and (c) are different configurations of SO2@BNNC. (d) and (e) are DOS/PDOS for more stable structure (a) and (c), respectively. Green, orange, blue, red, brown spheres represent H, B, N, O, and S atoms, in the structures, respectively.
Al-BNNC elongates the Al–O bond to 1.85 Å for NO2, Figs. 4c, and 1.84/ 1.82 Å for SO2 (a)/(c), Fig. 5a/c. The Al–O bond lengths are 1.83 Å and 1.81/1.84 Å for NO2 and SO2(a)/SO2(c)@Al-BNNC, respectively. The optimized configuration (c) in which SO2 is adsorbed on the Al dopant has a different orientation as compared to configuration (a) where the Al–O–S angle for configuration (c) is larger than configuration (a), Fig. 5a/c. The Mulliken charge analysis indicates that NO2 and SO2(a)/ SO2(c) lose charge locally at the adsorption site; with 0.43e and 0.13/ 0.20e, respectively, transferred to the Al atom. Therefore the work function increases after adsorption. The adsorption energy of the NO2 and SO2(a)/SO2(c) molecules onto Al-BNNC is −3.00 eV and −2.22/1.48 eV, respectively. This means that the Al-BNNC system may be
more sensitive for NO2 than for SO2 (see Table 2). Fig. 4d shows the DOS/PDOS of NO2@Al-BNNC. The HOMO and LUMO of the NO2 molecule are positioned below the HOMO and above the LUMO which is created by the N states of the sheet (see the insets of Fig. 4d). This decreases the HOMO-LUMO gap to 1.9 eV due to the coupling between the NO2 and the Al atoms; the Al 3s state moves away from the HOMO-LUMO gap. Fig. 5b shows the DOS/PDOS of the SO2@Al-BNNC configuration (a). The HOMO/LUMO is occupied by SO2 states and N states and the HOMO-LUMO gap is 0.7 eV. The hybridization between the states in case of (c) configuration for HOMO and LUMO differs from (a) configuration, see Fig. 5d. The HOMO consists of N states only and the LUMO is dominated by SO2 states, with
Fig. 4. (a) the structure of Al-doped BNNC and (b) the corresponding DOS/PDOS. (c) the structure of NO2@Al-doped BNNC and (c) the corresponding DOS/PDOS. Green, orange, blue, and pink spheres represent H, B, N, and Al atoms in the structures, respectively. 191
Physica E: Low-dimensional Systems and Nanostructures 113 (2019) 188–193
M.M. Fadlallah, et al.
Fig. 5. (a) the stable structure of SO2@Al-doped BNNC and (b) the corresponding DOS/PDOS. (c) another stable structure of SO2@Al-doped BNNC and (d) the corresponding DOS/PDOS. Green, orange, blue, pink, and brown spheres represent H, B, N, Al, and S atoms in the structures, respectively.
for NO2 and SO2 (a) on BNNC and increased by ∼ 0.2/0.4 eV on AlBNNC as compared to corresponding values obtained without considering the vdW interactions. The long range corrected results for various structures are shown in Table 3.
Table 2 Adsorption energies (Eads (eV)) of NO2 and SO2 on Al-BNNC, Mulliken charge (QT (e)) on the adsorbed molecules, the angle (α) of O–N–O and O–S–O, and HOMO-LUMO energy gap (Eg (eV)) of Al-BNNC, NO2 and SO2 on Al-BNNC. ΔG (eV) and ΔH (eV) are the changes in Gibbs free energy and enthalpy, respectively, for NO2 and SO2 on Al-BNNC. System
Eads
QT
Eg
α
Φ
ΔG
ΔH
Al-BNNC NO2 (a) SO2 (a) SO2 (c)
– −3.00 −2.22 −1.48
– −0.43 −0.13 −0.09
2.9 1.9 3.4 0.7
– 112.8 110.3 111.3
5.99 6.75 6.47 5.82
– −2.46 −1.55 −0.98
– −2.95 −2.13 −1.45
4. Conclusion Using first principles calculations, we show that the adsorption of NO2 or SO2 on BNNC/Al-BNNC is a spontaneous process. Substitutional doping with Al at the cone apex leads to an enhancement of the adsorption of NO2 or SO2. The work function increases upon the adsorption of NO2 and SO2. Our results of the adsorption energy, HOMOLUMO gap change, and the thermal stability indicate that BNNC may be a good candidate material for an NO2 and SO2 sensor.
Table 3 Adsorption energy (Eads), in eV, using B3LYP, and using ωb97xd (long range corrections (Ed,lr)) for NO2 and SO2 on BNNC/Al-BNNC System
E
NO2
SO2 (a)
SO2 (c)
BNNC
Eads Eads,lr Eads Eads,lr
−0.71 −0.62 −3.00 −3.21
−0.34 −0.22 −2.20 −2.44
−0.34 −0.36 −1.48 −1.14
Al-BNNC
Acknowledgment The authors would like to acknowledge the resources and technical services provided by the Scientific and High Performance Computing Center at Imam Abdulrahman Bin Faisal University, Dammam, Saudi Arabia. References
some N states. The complex structures have work functions larger than Al-doped BNNC because of charge transfer. The NO2 or SO2 on Al-BNNC system is exergonic due to the decrease in the Gibbs free energy and enthalpy compared to the reactants.
[1] S. lijima, T. Ichihashi, Y. Ando, Pentagons, heptagons and negative curvature in graphite microtubule growth, Nature 356 (1992) 776 https://doi.org/10.1038/ 356776a0. [2] G. Maohui, S. Klaus, Observation of fullerene cones, Chem. Phys. Lett. 220 (3) (1994) 192–196 https://doi.org/10.1016/0009-2614(94)00167-7. [3] F. Schedin, S.V. Geim, A.K. andMorozov, P. Hill, E.W. Blake, M.I. Katsnelson, K.S. Novoselov, Detection of individual gas molecules adsorbed on graphene, Nat. Mater. 6 (2007) 652 https://doi.org/10.1038/nmat1967. [4] P. Qi, O. Vermesh, M. Grecu, A. Javey, Q. Wang, H. Dai, S. Peng, K.J. Cho, Toward large arrays of multiplex functionalized carbon nanotube sensors for highly sensitive and selective molecular detection, Nano Lett. 3 (3) (2003) 347–351, https:// doi.org/10.1021/nl034010k. [5] L. Xu-Ying, Z. Jian-Min, X. Ke-Wei, J. Vincent, Improving SO2 gas sensing properties of graphene by introducing dopant and defect: a first-principles study, Appl. Surf. Sci. 313 (2014) 405–410 https://doi.org/10.1016/j.apsusc.2014.05.223. [6] X. Zhang, Z. Dai, Q. Chen, J. Tang, A dft study of so 2 and h 2 s gas adsorption on au-doped single-walled carbon nanotubes, Phys. Scripta 89 (6) (2014) 065803. [7] J. Wu, L. Yin, Platinum nanoparticle modified polyaniline-functionalized boron nitride nanotubes for amperometric glucose enzyme biosensor, ACS Appl. Mater.
3.4. van der Waals corrections We have also investigated the effect of the van der Waals (vdW) interaction between the molecules and the BNNC. Using the vdW functional theory, ωB97X-D [27], the bond lengths of BNNC (B–N) and B–O (nanocones and molecules) are not changed as compared to the results of the B3LYP calculations. For Al-BNNC, there is about 1% decrease in the Al–N bond length upon molecular adsorption and a significant increase in the Al–O bond length (1.91 Å) for both molecules as compared to results obtained by B3LYP (1.83/1.84 Å for NO2 and SO2(c)). The adsorption energy is slightly decreased by ∼ 0.1/0.2 eV 192
Physica E: Low-dimensional Systems and Nanostructures 113 (2019) 188–193
M.M. Fadlallah, et al.
363–369 https://doi.org/10.1016/j.tsf.2017.11.002. [25] M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, G. Scalmani, V. Barone, G. A. Petersson, H. Nakatsuji, X. Li, M. Caricato, A. V. Marenich, J. Bloino, B. G. Janesko, R. Gomperts, B. Mennucci, H. P. Hratchian, J. V. Ortiz, A. F. Izmaylov, J. L. Sonnenberg, D. Williams-Young, F. Ding, F. Lipparini, F. Egidi, J. Goings, B. Peng, A. Petrone, T. Henderson, D. Ranasinghe, V. G. Zakrzewski, J. Gao, N. Rega, G. Zheng, W. Liang, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, T. Vreven, K. Throssell, J. A. Montgomery, Jr, J. E. Peralta, F. Ogliaro, M. J. Bearpark, J. J. Heyd, E. N. Brothers, K. N. Kudin, V. N. Staroverov, T. A. Keith, R. Kobayashi, J. Normand, K. Raghavachari, A. P. Rendell, J. C. Burant, S. S. Iyengar, J. Tomasi, M. Cossi, J. M. Millam, M. Klene, C. Adamo, R. Cammi, J. W. Ochterski, R. L. Martin, K. Morokuma, O. Farkas, J. B. Foresman, D. J. Fox, Gaussian 16 Revision B.01, Gaussian Inc. Wallingford CT. [26] K.-M. Sandor, C.N. Jia, Entropy-driven adsorption of carbon nanotubes on (001) and (111) surfaces of ceo2 islands grown on sapphire substrate, Surf. Sci. 604 (7) (2010) 654–659 https://doi.org/10.1016/j.susc.2010.01.011. [27] J.-D. Chai, M. Head-Gordon, Long-range corrected hybrid density functionals with damped atom–atom dispersion corrections, Phys. Chem. Chem. Phys. 10 (2008) 6615–6620, https://doi.org/10.1039/B810189B. [28] W.F. Schneider, J. Li, K.C. Hass, Combined computational and experimental investigation of sox adsorption on mgo, J. Phys. Chem. B 105 (29) (2001) 6972–6979, https://doi.org/10.1021/jp010747r. [29] D.R. Lide, 78th Edition, Physical Constants of Organic Compounds, CRC Handbook of Chemistry and Physics vol. 2007, Taylor and Francis, 2007. [30] S. Ahmadi, P.D.K. Nezhad, A. Hosseinian, E. Vessally, A computational study on tuning the field emission and electronic properties of bn nanocones by impurity atom doping, Phys. E Low-dimens. Syst. Nanostruct. 100 (2018) 63–68 https://doi. org/10.1016/j.physe.2018.03.010. [31] M.T. Baei, A.A. Peyghan, Z. Bagheri, Carbon nanocone as an ammonia sensor: dft studies, Struct. Chem. 24 (4) (2013) 1099–1103, https://doi.org/10.1007/s11224012-0139-3. [32] M.T. Baei, A.A. Peyghan, Z. Bagheri, M.B. Tabar, B-doping makes the carbon nanocones sensitive towards no molecules, Phys. Lett. 377 (1) (2012) 107–111 https://doi.org/10.1016/j.physleta.2012.11.006. [33] A.A. Peyghan, M. Noei, S. Yourdkhani, Al-doped graphene-like bn nanosheet as a sensor for para-nitrophenol: dft study, Superlattice. Microst. 59 (2013) 115–122 https://doi.org/10.1016/j.spmi.2013.04.005. [34] A.A. Darwish, M.M. Fadlallah, A. Badawi, A.A. Maarouf, Adsorption of sugars on aland ga-doped boron nitride surfaces: a computational study, Appl. Surf. Sci. 377 (2016) 9–16 https://doi.org/10.1016/j.apsusc.2016.03.082. [35] S. Alireza, R. Shima Ghafouri, R. Vahid Joveini, K. Aliakbar Dehno, M. Savar, Ab initio investigation of al- and ga-doped single-walled boron nitride nanotubes as ammonia sensor, Appl. Surf. Sci. 263 (2012) 619–625 https://doi.org/10.1016/j. apsusc.2012.09.122. [36] A.A. Peyghan, A. Soltani, A.A. Pahlevani, Y. Kanani, S. Khajeh, A first-principles study of the adsorption behavior of co on al- and ga-doped single-walled bn nanotubes, Appl. Surf. Sci. 270 (2013) 25–32 https://doi.org/10.1016/j.apsusc.2012. 12.008. [37] A.S. Rad, Al-doped graphene as a new nanostructure adsorbent for some halomethane compounds: dft calculations, Surf. Sci. 645 (2016) 6–12 https://doi.org/ 10.1016/j.susc.2015.10.036.
Interfaces 2 (2011) 4354. [8] J. Beheshtian, A.A. Peyghan, M.B. Tabar, Z. Bagheri, Dft study on the functionalization of a bn nanotube with sulfamide, Appl. Surf. Sci. 266 (2013) 182–187 https://doi.org/10.1016/j.apsusc.2012.11.128. [9] Q. Weng, X. Wang, X. Wang, Y. Bando, D. Golberg, Functionalized hexagonal boron nitride nanomaterials: emerging properties and applications, Chem. Soc. Rev. 45 (2016) 3989–4012, https://doi.org/10.1039/C5CS00869G. [10] G.C. Loh, S. Nigam, G. Mallick, R. Pandey, Carbon-doped boron nitride nanomesh: stability and electronic properties of adsorbed hydrogen and oxygen, J. Phys. Chem. C 118 (41) (2014) 23888–23896, https://doi.org/10.1021/jp508229w. [11] X. Zhi, G. Dmitri, B. Yoshio, Electrical field-assisted thermal decomposition of boron nitride nanotube: experiments and first principle calculations, Chem. Phys. Lett. 480 (1) (2009) 110–112 https://doi.org/10.1016/j.cplett.2009.08.072. [12] A.A. Darwish, M.H. Hassan, M.A.A. Mandour, A.A. Maarouf, Mechanical properties of defective double-walled boron nitride nanotubes for radiation shielding applications: a computational study, Comput. Mater. Sci. 156 (2019) 142–147 https:// doi.org/10.1016/j.commatsci.2018.09.040. [13] M. Sajjad, G. Morell, P. Feng, Advance in novel boron nitride nanosheets to nanoelectronic device applications, ACS Appl. Mater. Interfaces 5 (2013) 5051. [14] Q. Weng, B. Wang, X. Wang, N. Hanagata, X. Li, D. Liu, X. Wang, X. Jiang, Y. Bando, D. Golberg, Highly water-soluble, porous, and biocompatible boron nitrides for anticancer drug delivery, ACS Nano 8 (2014) 6123. [15] H.Z. Zhang, Q. Zhao, J. Yu, D.P. Yu, Y. Chen, Field-emission characteristics of conical boron nitride nanorods, J. Phys. D Appl. Phys. 40 (1) (2007) 144. [16] F. Behmagham, E. Vessally, B. Massoumi, A. Hosseinian, L. Edjlali, A computational study on the SO2 adsorption by the pristine, al, and si doped bn nanosheets, Superlattice. Microst. 100 (2016) 350–357 https://doi.org/10.1016/j.spmi.2016. 09.040. [17] Z.-Y. Deng, J.-M. Zhang, K.-W. Xu, First-principles study of SO2 molecule adsorption on the pristine and mn-doped boron nitride nanotubes, Appl. Surf. Sci. 347 (2015) 485–490 https://doi.org/10.1016/j.apsusc.2015.04.116. [18] L. Bourgeois, Y. Bando, S. Shinozaki, K. Kurashima, T. Sato, Boron nitride cones: structure determination by transmission electron microscopy, Acta Crystallogr. A 55 (2 Part 1) (1999) 168–177, https://doi.org/10.1107/S0108767398008642. [19] L. Bourgeois, Y. Bando, W.Q. Han, T. Sato, Structure of boron nitride nanoscale cones: ordered stacking of 240° and 300° disclinations, Phys. Rev. B 61 (2000) 7686–7691, https://doi.org/10.1103/PhysRevB.61.7686. [20] A. Hosseinian, M. Salary, S. Arshadi, E. Vessally, L. Edjlali, The interaction of phosgene gas with different bn nanocones: dft studies, Solid State Commun. 269 (2018) 23–27 https://doi.org/10.1016/j.ssc.2017.10.011. [21] E. Vessally, R. Moladoust, S.M. Mousavi-Khoshdel, M.D. Esrafili, A. Hosseinian, L. Edjlali, Chloropicrin sensor based on the pristine bn nanocones: dft studies, Struct. Chem. 29 (2) (2018) 585–592, https://doi.org/10.1007/s11224-0171055-3. [22] X. Shi, M. Sarafbidabad, A.Z. Ibatova, R. Razavi, M. Najafi, Potential of doped nanocones as catalysts for n2o+co reaction: theoretical investigation, J. Clust. Sci. (2019), https://doi.org/10.1007/s10876-018-1463-6. [23] X. Zuo, K. Behradfar, J.-B. Liu, M. Lariche, M. Najafi, Theoretical study of ability of boron nitride nanocone to oxidation of sulfur monoxide, Acta Chim. Slov. 65 (2) (2018). [24] E. Vessally, R. Moladoust, S. Mousavi-Khoshdel, M. Esrafili, A. Hosseinian, L. Edjlali, The clcn adsorption on the pristine and al-doped boron nitride nanosheet, nanocage, and nanocone: density functional studies, Thin Solid Films 645 (2018)
193