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DFT analysis of H2S adsorbed zigzag and armchair graphene nanoribbons
Chemical Physics Letters 745 (2020) 137280
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Chemical Physics Letters journal homepage: www.elsevier.com/locate/cplett
Research paper
DFT analysis of H2S adsorbed zigzag and armchair graphene nanoribbons Harshika Suman C.S. Malvid
a,b
, Reena Srivastava
b,c,⁎
b
c
T a
, Sadhna Shrivastava , Anurag Srivastava , A.P. Jacob ,
a
Department of Chemical Engineering, Madhav Institute of Technology and Science, Gwalior 474005, India Department of Chemistry, Government S L P College, Morar, Gwalior, M.P. 474010, India Advanced Material Research Group, CNT Lab, Atal Bihari Vajpayee-Indian Institute of Information Technology and Management, Gwalior 474015, India d Department of Mechanical Engineering, Madhav Institute of Technology and Science, Gwalior 474005, India b c
H I GH L IG H T S
analysis of zigzag and armchair GNR as H S gas sensing element. • DFT transport properties have been analysed as sensing parameters. • Electronic process found exothermic and H S physisorbed to Z/A GNR, defends its reusable property. • Adsorption • H S gas sensitivity of ZGNRs is better than Armchair GNR, however suffers in recovery time. 2
2
2
A R T I C LE I N FO
A B S T R A C T
Keywords: GNR Armchair Zigzag Adsorption H2S Conductance I-V Sensitivity Recovery time
Armchair (A) and zigzag (Z) type graphene nanoribbons (GNR) have been investigated for its suitability to sense the toxic H2S gas, by using density functional theory (DFT) based ab-initio approach. On adsorption of H2S, the variations in original metallic behaviour of ZGNR and semiconducting behaviour of AGNR has further been analysed by observing the conductance and bandgap variation as a function of H2S distance from GNR surface. The HOMO-LUMO profiles have also been analysed to understand the chemistry of GNRs and H2S molecule. Further, the current-voltage characteristics in presence of H2S near the nanoribbon surface, also shows the sensing of H2S, discussed in terms of that the current in both the nanoribbons increases due to H2S presence. The computed sensitivity confirms the zigzag GNR as better sensor than its armchair counterpart however, relatively with less recovery time than its zigzag counterpart.
1. Introduction The two dimensional monolayer of graphite, known as graphene has been reported first [1] in 2004 and used in variety of applications [2], reason being its unique electronic, mechanical, optical, chemical and electrical properties. In the last one decade, number of experimental and computational studies have been reported on the use of graphene as sensing element [3–21]. The one dimension counterpart of graphene is the nanoribbon, simply the strips of a graphene [22–29]. Depending on its edge morphology, the grapheme nanoribbons are of two types Zigzag Graphene Nanoribbon (ZGNR) and Armchair Graphene Nanoribbon (AGNR). Where, it has been observed that the ZGNRs are always metallic and AGNR’s band structure changes with its width, hence, may be semiconducting or metallic. Environmental pollution has become a big challenge in the last one decade and needs attention of scientific
⁎
community in large. The gas sensors are required in industry as well as for domestic purposes as an important part of the safety system. Besides the graphene and carbon nanotubes, its one dimension counterpart graphene nanoribbons have also been tested for sensing element [30–32] but still needs attention due to its better suitability in device applications. For the present study, the considered gas for sensing is H2S [33,34], a highly explosive and flammable gas, burn readily and form other toxic products. Hydrogen sulfide (H2S) is a flammable, extremely toxic, colorless, irritating and transparent gas with a sweet odor in high concentrations and the odor of rotten egg in low concentrations. H2S is commonly found in sour, natural gas, coal and oil companies. Exposure to very small concentration of it (e.g. 10 ppm for 5 h) can cause death. The high risk and abundance of this gas in the current petrochemical and petroleum industry makes its monitoring a number one priority. Various efforts have been made for H2S sensing using
Corresponding author. E-mail address: [email protected] (R. Srivastava).
https://doi.org/10.1016/j.cplett.2020.137280 Received 22 August 2019; Received in revised form 21 February 2020; Accepted 24 February 2020 Available online 25 February 2020 0009-2614/ © 2020 Elsevier B.V. All rights reserved.
Chemical Physics Letters 745 (2020) 137280
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Fig. 1.1. Optimized geometries of (a) pristine and (b) H2S adsorbed Zigzag GNR and (c) Optimized bond parameters of (c) pristine and (d) H2S adsorbed Zigzag GNR.
3. Results and discussion
variety of materials, from one dimension nanotubes [35,36] to two dimensional sheets [37], however, seems insufficient and needs to be addressed again. The present study reports the investigation of sensing ability of 10-AGNR and 12-ZGNR for H2S gas sensing, using DFT based ab-initio approach, discussed in terms of variations in the electronic and transport properties of GNRs due to presence of H2S in its surrounding.
In the present work, 10-AGNR and 12-ZGNR have been considered as a channel material of a modelled device to sense the H2S gas molecule. For the computation, the nanoribbons have C84H14 and C80H16 atoms for the ZGNR and AGNR, respectively. These graphene nanoribbons are passivated with hydrogen atoms to satisfy the dangling bonds and avoid interaction with the surrounding environment. The best site has been analysed by computing the lowest total energies, with different molecular orientations, like centre of the ring, bridge and on edge atom. The optimized structure confirms the edge site as the best site for gas molecule in both Zigzag and Armchair GNRs shown in Figs. 1.1 (a,b) and 1.2(a,b). The variations in the bond lengths and bond angles due to H2S molecule adsorption in ZGNR as well as AGNR have also been analysed and reported in Figs. 1.1(c,d) and 1.2(c,d). The H2S molecule has been optimized for its bond parameters and also on its adsorption with ZGNR and AGNR, its orientation as well as variation in bond parameters (angle and lengths) has been analysed, shown in Fig. 1.3(i–k) and reported in Table 2. Initially, the H2S molecule was placed at a distance of 1.176 Å and 1.108 Å for zigzag and armchair nanoribbon, respectively, which on optimization, shows physisorption and changes its bond parameters, reported in Table 2. The adsorption energy (for zigzag nanoribbon is −0.159 eV and for armchair nanoribbon, −0.269 eV) has been computed for H2S adsorbed 10-AGNR and 12-ZGNR systems, using Eq. (1). The computed negative adsorption energy confirms the interaction process as exothermic. On optimizing the H2S adsorbed Z/A GNR system, the orientation of H2S molecule become almost parallel to the GNR surface in both the cases with binding distance of 3.36 Å and 3.5 Å for zigzag and armchair nanoribbon, respectively, shown in Figs. 1.1 and 1.2 and tabulated in Table 1. The variations in the bond parameters of H2S molecule after adsorption
2. Computational methods The adsorption of H2S gas through two different morphologies of graphene nanoribbons, has been analysed by using a Density functional theory (DFT) [38] based Atomistic toolkit in Virtual nano lab (ATKVNL) environment [39]. To compute the structural and electronic properties of armchair and zigzag graphene nanoribbons with and without H2S gas, near to its surface, the k-point sampling of (1 × 1 × 10) has been considered for Brillouin-zone integration via Monkhorst Pack grid scheme. Generalized gradient approximation (GGA) has been considered to define the exchange correlation function, parameterized with revised Perdew Burke-Ernzerhof (PBE) [40,41]. For each configuration, density mesh cut-off is opted as 150 Rydberg while the process of optimization is continued until the forces on each atom becomes less than 0.05 eV/Å. The adsorption energy for the systems includes the armchair/zigzag graphene nanoribbon and H2S molecule has been calculated using
Eads = ET (GNR + H2 S ) − ET (GNR) − ET (H2 S )
(1)
where ET (GNR + H2 S ) and ET (GNR) are the total energies of geometrically optimized structure of GNRs with the adsorbed molecule and pristine GNR subsequently. While ET (H2 S ) is the total energy of an isolated H2S molecule. 2
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Fig. 1.2. Optimized geometries of (a) pristine and (b) H2S adsorbed Armchair GNR and (c) Optimized bond parameters of (c) pristine and (d) H2S adsorbed Armchair GNR. Fig. 1.3. Optimized geometries of H2S molecule as (i) isolated molecule (j) after adsorption with AGNR (k) after adsorption with ZGNR.
have also been analysed and reported in Table 2. Recovery time (τ), is an important parameter for a good sensor, defined as the time required for a sensor to return to 90% of the original baseline signal upon removal the target gas, and has been computed with the knowledge of adsorption energy (Eads ) using following equation reported elsewhere [42]
Table 1 Adsorption energy and Band structure of gas molecule adsorbed on the A/Z GNRs. H2S adsorbed system
Initial distance (Å)
Optimized distance (Å)
Adsorption energy (eV)
Band gap (eV)
ZGNR AGNR
1.176 1.108
3.36 3.50
−0.1594 −0.269
Metallic 1.187
τ = ν−1exp(−Eads / kB T )
where (ν ) is the attempt frequency, (kB ) the Boltzmann constant and (T ) operational temperature of the sensor. Here, for H2S molecule, the computed recovery time is faster in AGNR (1.27 ns) in comparison to that of ZGNR (0.0183 ns), which is better than the reported recovery time of 16.9–49 s (at 350 °C), using CuO thick film reported elsewhere [43]. To understand the adsorption better, the chemistry of the interaction between A/Z GNR and H2S molecule has been analysed through computation of HOMO-LUMO profiles with isosurface value of 0.02 electrons/(bohr)3, shown in Fig. 2(a–d), calculated using Gaussian 09 [44] also confirms the physisorption and show no overlap of orbitals. The HOMO LUMO profiles clearly show a strong edge effect in both the systems. The presence of H2S molecule near the surface of Z/AGNR can easily be analysed in terms of spreading (shifting) of charges in HOMO
Table 2 Bond angle (A1) and bond lengths (S1 and S2) of H2S molecule structure before and after adsorption on ZGNR/AGNR. H2S molecule parameters
Original Molecule
After Adsorption on ZGNR
After Adsorption on AGNR
A1 (Angle in °) S1 (Distance in Å) S2 (Distance in Å)
91.549° 1.368 Å 1.368 Å
92.124° 1.356 Å 1.355 Å
91.038° 1.357 Å 1.357 Å
(2)
3
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Fig. 2. HOMO- LUMO profiles of optimized systems of pristine (a) zigzag, (c) armchair and H2S adsorbed (b) zigzag, (d) armchair Graphene Nanoribbons.
near −2.0 eV in valance band and enhanced peak near 1.75 eV due to H2S molecule confirms the variations in comparison to its pristine counterpart. As the molecule shows physisorption with Z/A GNRs, there is no significant change observed on its band structures of optimized system. To further analyse these interactions between A/Z GNR and H2S molecule, the charge transfer analysis has also been performed using Mulliken population computation. The variations in the charge on the carbon atoms of A/ZGNR due to presence of Hydrogen and Sulphur atoms of H2S gas molecule has been computed and marked as charge transfer. The computed charge transfer between zigzag nanoribbon and H2S is −0.002e, whereas for armchair nanoribbon it is −0.014e. These variations in electronic properties have further been examined through electron transport analysis discussed in next section.
as well as LUMO profiles of pristine and H2S adsorbed systems. The electronic properties of the optimized geometries have been investigated in terms of band structure, electron difference density, molecular energy level (HOMO-LUMO energies) and density of state profiles of both the systems (H2S adsorbed ZGNR and AGNR), shown in Fig. 3.1(a,b) and Fig. 3.2(a,b). The AGNR observes a minor change in band gap from 1.2 eV to 1.1 eV, due to presence of H2S, whereas the metallic behaviour of ZGNR seems unchanged even with the presence of H2S. The careful analysis of band structures of ZGNR in its pristine as well as H2S adsorbed (Fig. 3.1a) shows a very slight change with an additional band appearance around −1.5 eV, whereas in case of AGNR (Fig. 3.2a), an additional band can be seen near −2.0 eV. To understand these minute changes, molecular energy levels of these GNR systems have also been marked along with its band structure and electron difference density, that confirms the H2S sensing. Both the cases have further been analysed through their DOS profiles reported in Figs. 3.1(b) and 3.2(b). In case of pristine ZGNR, at the Fermi level the decrease in the size of the peak and appearance of large peak near the −1.5 eV confirms the variation due to H2S molecule near to its surface. Similarly, in case AGNR DOS, the appearance of large additional peak
4. Electron transport analysis To further investigate the H2S sensitivity of Z/A graphene nanoribbons, the transport properties have been computed for the zigzag as well as armchair nanoribbons in its pristine and H2S adsorbed form. For 4
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Fig. 3.1. (a,b) Electron Difference Density, Band structure, Molecular energy level and density of states (DOS) profiles of Pristine and H2S adsorbed ZGNR.
To analyse the variation in the computed current of the nanoribbons, with and without molecule as a function of voltage, a large kpoint sampling of 1 × 1 × 100 has been used, using Landauer formula [45,46]. The conductance of each system (ZGNR and AGNR) with and
the same, optimized geometries of each system has been introduced to the two probe device model as shown in the Fig. 4(a,b), have three parts, left, right electrode and central region. Where the left and right electrode size of ZGNR are 5.0 Å and in case of AGNR, it is 4.38 Å. 5
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a AGNR
b AGNR+H2S Fig. 3.2. (a,b) Electron Difference Density, Band structure, Molecular energy level and density of states (DOS) profiles of Pristine and H2S adsorbed AGNR. (E − EF )/ kB T
without H2S molecule can be expressed in terms of energy band gap, exhibit the following relation:
G=
−Eg
⎞ σ = σ0 exp ⎛ ⎝ 2kT ⎠ ⎜
∫ dET (E ) (1 +e e(E−E )/k T )2 F
B
(4)
where EF is the Fermi energy and kB, the Boltzmann constant. The computed transmission probability generated the transmission spectrums for Pristine and H2S adsorbed ZGNR (Fig. 5a,b) and AGNR (Fig. 5c,d) respectively. The transmission peaks matches well with the density of states profile reported in Figs. 3.1 and 3.2(b), where the
⎟
(3)
To verify it further, the conductance G has been computed using Eq. (4) through its transmission probability T (E ) for ZGNR as well as AGNR in its pristine as well as H2S adsorbed form. 6
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Fig. 4. Two probe model of I-V analysis for H2S adsorbed (a) ZGNR (b) AGNR system.
G − G0 ⎞ S=⎛ ∗ 100 ⎝ G0 ⎠ ⎜
(a)
ZGNR
(b)
⎟
(5)
To visualize the range of detection for H2S molecule in case of ZGNR as well as AGNR, the two methods have been adopted, one, the conductance variation as a function of H2S molecule distance from the Z/A GNR surface shown in Fig. 6.1(a,b) along with bandgap variation shown in Fig. 6.2, and the other, current as a function of bias voltage with and without molecule, shown in Fig. 7(a,b) respectively. The calculated conductance at various distances between GNR surfaces to H2S molecule shows the range of detection of the GNR’s surface for the gas molecule. The analysis shows that in case of zigzag nanoribbon, the conductance increases linearly in almost whole range, however, becomes saturated at around 3.0 Å, whereas in case of armchair GNR the conductance shows a drop between 2.7 and 2.9 Å and beyond this invariable. Further, the current passing through the material in terms of transmission probability can be expressed as
ZGNR+ H2S
I=
2e h
∫μ
μR
L
[T (E ){fL (E ) − fR (E )}] dE
T (E ) = Tr (ΓL (E , V ) G R (E , V )ΓR (E , V ) G A (E , V )
(c)
AGNR
where T (E ) is the total transmission probability of channels at applied voltage V and energy E. μR and μL represents the chemical potentials of left and right electrodes, respectively with Fermi distribution functions fL(E) and fR(E). GR and GA are retarded and advanced Green’s function with ГL and ГR as coupling functions of left and right electrode selfenergies [47]. The computed current-voltage characteristics of the given configurations of ZGNR and AGNR (Fig. 4) in its pristine as well as H2S adsorbed form, shown in Fig. 7(a,b), have been analyzed by applying the bias voltage of upto1.5 V to the electrodes. It is inferred from the Fig. 7(a,b), representing the current-voltage characteristics, that the current increases as gas molecule approaches to the proposed armchair and zigzag graphene nanoribbon surface and this change in the current due to introduction of gas molecule confirms the sensing ability of the material. Further, the comparative currentvoltage analysis of two proposed GNRs, shows that, the difference in current on applying the voltage in the zigzag GNR is relatively large than that observed in its armchair counterpart in presence of H2S molecule near the GNR surface. In case of zigzag nanoribbon, when H2S interact with its surface, it shows a minor difference from pristine nanoribbon, at around 0.25 V, thereafter the current increases linearly as a function of voltage. At around 1 V, the pristine zigzag nanoribbon has very low current than the gas adsorbed surface. Whereas, the armchair ribbon has almost no change from 0 to 0.5 V, and beyond that the current increases linearly, shown in Fig. 7(b). In both the cases, the
(d) AGNR + H2S
Fig. 5. Transmission spectrums of (a,c) Pristine and (b,d) H2S adsorbed ZGNR and AGNR, respectively.
energy, reaches to zero, the transmission peak mimic the same drop at that point, however, when in density of state profile, it doesn’t reach to zero, the transmission doesn’t get affected much. The sensitivity (S) is another important parameter to analyse the suitability of any material as sensing element for any specific gas. This has also been analysed through the knowledge of conductance (G) of nanoribbons with gas (G) and without gas (G0) and confirms that the H2S sensitivity is remarkably better in case of Zigzag GNR (80.16%) in comparison to its Armchair counterpart (60.79%) calculated using following equation
7
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Fig. 6.1. Zero bias conductance of (a) ZGNR and (b) AGNR as a function of H2S distance from GNR surface.
current changes due to presence of H2S gas molecule confirm the sensing ability of the nanoribbons for gas molecule.
5. Conclusion The present study reports the H2S sensing ability of Zigzag and Armchair nanoribbons, by analysing their structural, electronic and transport properties. In structural properties, the stability of system has been confirmed through its total energy and variation in bond parameters due to H2S adsorption. Both the cases show the adsorption mechanism as physisorption, confirms the reusability of sensing material, whereas the negative adsorption energy, conveys the process as exothermic and hence gives a guess of low operational temperature. In electronic properties, the band gap of the Armchair nanoribbon slightly changes from 1.2 eV to 1.1 eV due to adsorption of H2S, whereas ZGNR retain its metallic nature. Besides the variation in band structure and DOS, the I-V analysis confirms that the ZGNR surface is more sensitive for H2S gas molecule in its surrounding, in comparison to its armchair counterpart. Computed current of the GNR systems drastically change with the gas adsorption. The range of detection also confirms the sensing ability of zigzag as well as armchair graphene nanoribbons. However, the recovery time of Armchair graphene nanoribbon based device is relatively better than its zigzag counterpart.
Fig. 6.2. Bandgap variation of AGNR as a function of H2S distance from GNR surface.
Fig. 7. Current- Voltage characteristics of (a) ZNGR and (b) AGNR before and after H2S adsorption. 8
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CRediT authorship contribution statement
[18] S. Dandeliya, A. Srivastava, Defected graphene as ammonia sensor: theoretical insight, IEEE Sens. J. 19 (6) (2018) 2031–2038, https://doi.org/10.1109/JSEN.2018. 2884971. [19] J. Dai, J. Yuan, P. Giannozzi, Gas adsorption on graphene doped with B, N, Al, and S: Atheoretical study, Appl. Phys. Lett. 95 (2009) 232105. [20] O. Faye, A. Raj, V. Mittal, A.C. Beye, H2S adsorption on graphene in the presence of sulfur: a density functional theory study, Comput. Mater. Sci. 117 (2016) 110–119. [21] J. Cai, P. Ruffieux, R. Jaafar, M. Bieri, T. Braun, S. Blankenburg, M. Muoth, A.P. Seitsonen, M. Saleh, X. Feng, K. Müllen, R. Fasel, Atomically precise bottom-up fabrication of graphene nanoribbons, Nature 466 (2010) 470. [22] D.V. Kosynkin, A.L. Higginbotham, A. Sinitskii, J.R. Lomeda, A. Dimiev, K. Price, J.K. Tour, Longitudinal unzipping of carbon nanotubes to form graphene nanoribbons, Nature 458 (2009) 872. [23] S. Duttaa, S.K. Pati, Novel properties of graphene nanoribbons: a review, J. Mater. Chem. 20 (2010) 8207–8223. [24] M. Berahman, M. Sanaee, R. Ghayour, A theoretical investigation on the transport properties of overlapped graphene nanoribbons, Carbon 75 (2014) 411. [25] M. Berahman, M.H. Sheikhi, Transport properties of zigzag graphene nanoribbon decorated with copper clusters, J. Appl. Phys. 116 (2014) 093701. [26] M. Berahman, M.H. Sheikhi, A. Zarifkar, H. Nadgaran, Structural and electronic properties of zigzag graphene nanoribbon decorated with copper cluster, J. Comput. Elec. 14 (1) (2015) 270–279. [27] A. Celis, Manuscript version: graphene nanoribbons: fabrication, properties and devices, J. Phys. D Appl. Phys. Top. 49 (2016) 1–26. [28] A. Srivastava, A. Jain, R. Kurchania, N. Tyagi, Width dependent electronic properties of graphene nanoribbons: an ab-initio study, J. Comput. Theor. Nanosci. 9 (7) (2012) 1008–1013. [29] M. Berahman, M.H. Sheikhi, Hydrogen Sulfide gas sensor based on decorated zigzag graphene nanoribbon with copper, Sensors Actuat. B: Chem. 219 (2015) 338–345. [30] A.H. Pourasl, M. Taghi, R. Ismail, N. Gharaei, Gas adsorption effect on the graphene nanoribbon band structure and quantum capacitance, Adsorption 23 (6) (2017) 767–777. [31] L. Shao, et al., Sulfur dioxide molecule sensors based on zigzag graphene nanoribbons with and without Cr dopant, Phys. Lett. Sect. A Gen. At. Solid State Phys. 378 (7–8) (2014) 667–671. [32] B. Huang, et al., Adsorption of gas molecules on graphene nanoribbons and its implication for nanoscale molecule sensor, J. Phys. Chem. C 112 (35) (2008) 13442–13446. [33] T.W. Lambert, V.M. Goodwin, D. Stefani, L. Strosher, Hydrogen sulfide (H2S) and sour gas effects on the eye. A historical perspective, Sci. Total Environ. 367 (1) (2006) 1–22. [34] Hydrogen Sulfide (H2S). Available: www.osha.gov. [Accessed: 20-Apr-2019]. [35] M. Berahman, M. Asad, M.H. Sheikhi, M. Fathi pur, Hydrogen Sulfide gas sensor based on carbon Nanotubes, IR-PATENT NO 75680 (2012). [36] R. Srivastava, H. Suman, S. Shrivastava, A. Srivastava, DFT analysis of pristine and functionalized zigzag CNT: a case of H2S sensing, Chem. Phys. Lett 731 (2019) 136575. [37] A.H. Reshak, S. Auluck, Adsorbing H2S onto a single graphene sheet: A possible gas sensor, J. App. Phys. 116 (2014) 103702. [38] E. E., R.M. Dreizler, Density Functional Theory: An Advanced Course, Springer Science & Business Media. [39] Virtual NanoLab Tutorial. Atomistix Toolkit, Quantum Wise A/S (www. quantumwise.com). [40] J.P. Perdew, K. Burke, M. Ernzerhof, Generalized gradient approximation made simple, 3 (1996) 3865–3868. [41] Y. Zhang, W. Yang, Comment on Generalized Gradient Approximation Made Simple 80 (1998) 890. [42] S. Peng, K. Cho, P. Qi, H. Dai, Ab initio study of CNT NO2 gas sensor, Chem. Phys. Lett. 387 (2004) 271–276. [43] B. Urasinska-Wojcik, J.W. Gardner, H2S Sensing in dry and humid H2 environment with p-Type CuO thick-film gas sensors, IEEE Sens. J. 18 (9) (2018) 3502–3508. [44] M.J. Frisch, et al., Gaussian09, Revision A.02, Gaussian, Inc., Wallingford CT, 2009. [45] S. Datta, Exclusion principle and the Landauer-Buttiker formalism, Phys. Rev. B 45 (3) (Jan. 1992) 1347–1362. [46] M. Büttiker, Y. Imry, R. Landauer, S. Pinhas, Generalized many-channel conductance formula with application to small rings, Phys. Rev. B 31 (10) (1985) 6207–6215, https://doi.org/10.1103/PhysRevB.31.6207. [47] H.H.B. Sørensen, P.C. Hansen, D.E. Petersen, S. Skelboe, K. Stokbro, Efficient wavefunction matching approach for quantum transport calculations, Phys. Rev. B 79 (20) (May 2009) 205322.
Harshika Suman: Investigation, Validation. Reena Srivastava: Conceptualization, Methodology, Software, Writing - original draft. Sadhna Shrivastava: Supervision. Anurag Srivastava: Supervision, Writing - review & editing. A.P. Jacob: Visualization, Investigation. C.S. Malvi: Visualization, Investigation. Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgement Authors are thankful to Computational Nanoscience and Technology lab of ABV-IIITM, Gwalior for extending the infrastructure support. References [1] A.K. Geim, K.S. Novoselov, The rise of graphene, Nat. Mater. 6 (2007) 183. [2] Z. Zhen, H. Zhu, Structure and properties of graphene, Graphene 1–12 (2018), https://doi.org/10.1016/b978-0-12-812651-6.00001-x. [3] Shengli Zhang, Shiying Guo, Zhongfang Chen, Yeliang Wang, Hongjun Gao, Julio Gomez-Herrero, Pablo Ares, Felix Zamora, Zhen Zhu, Haibo Zeng, Recent progress in 2D group-VA semiconductors: from theory to experiment, Chem. Soc. Rev. 47 (2018) 982–1021. [4] X.Y. Liu, J.M. Zhang, K.W. Xu, V. Ji, Improving SO2gas sensing properties of graphene by introducing dopant and defect: a first-principles study, Appl. Surf. Sci. 313 (2014) 405–410. [5] E. Llobet, Gas sensors using carbon nanomaterials: a review, Sensors Actuators, B Chem. 179 (2013) 32–45. [6] S. Aslam, T.H. Bokhari, T. Anwar, U. Khan, A. Nairan, K. Khan, Graphene oxide coated graphene foam based chemical sensor, Materials Letters 235 (2019) 66–70. [7] V. Nagarajan, R. Chandiramouli, Investigation on probing explosive nitroaromatic compound vapors using graphyne nanosheet: a first-principle study, Struct. Chem. 30 (2019) 657. [8] T. Wang, et al., A review on graphene-based gas/vapor sensors with unique properties and potential applications, Nano-Micro Lett. 8 (2016) 95–119. [9] C.K. Ho, A. Robinson, D.R. Miller, M.J. Davis, Overview of sensors and needs for environmental monitoring, Sensors 5 (1–2) (2005) 4–37. [10] F. Schedin, et al., Detection of individual gas molecules adsorbed on graphene, Nat. Mater. 6 (Jul. 2007) 652. [11] Xiaoxing Zhang, Hao Cuiand, Yingang Gui, Synthesis of graphene-based sensors and application on detecting SF6 decomposing products: a review, Sensors 17 (2017) 363. [12] W. Yuana, W.G. Shi, Graphene-based gas sensors, J. Mater. Chem. A. 1 (2013) 10078. [13] F. Yavari, N. Koratkar, Graphene-based chemical sensors, J. Phys. Chem. Lett. 3 (2012) 1746. [14] B.C. Wood, S.Y. Bhide, D. Dutta, V.S. Kandagal, A.D. Pathak, S.N. Punnathanam, K.G. Ayappa, S. Narasimhan, Methane and carbon dioxide adsorption on edgefunctionalized graphene: a comparative DFT study, J. Chem. Phys. 137 (2012) 054702. [15] P. Lazar, F. Karlický, P. Jurečka, M. Kocman, E. Otyepková, K. Šafářová, M. Otyepka, Adsorption of small organic molecules on graphene, J. Am. Chem. Soc. 135 (2013) 6372–6377. [16] O. Leenaerts, B. Partoens, F.M. Peeters, Adsorption of small molecules on graphene, Microelectron. J. 40 (4–5) (2009) 860–862. [17] S. Dandeliya, A. Srivastava, Electron transport in ethanol & methanol absorbed defected graphene, AIP Conference Proceedings 1953 (2018) 140140, https://doi. org/10.1063/1.5033315.
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Chemical Physics Letters journal homepage: www.elsevier.com/locate/cplett
Research paper
DFT analysis of H2S adsorbed zigzag and armchair graphene nanoribbons Harshika Suman C.S. Malvid
a,b
, Reena Srivastava
b,c,⁎
b
c
T a
, Sadhna Shrivastava , Anurag Srivastava , A.P. Jacob ,
a
Department of Chemical Engineering, Madhav Institute of Technology and Science, Gwalior 474005, India Department of Chemistry, Government S L P College, Morar, Gwalior, M.P. 474010, India Advanced Material Research Group, CNT Lab, Atal Bihari Vajpayee-Indian Institute of Information Technology and Management, Gwalior 474015, India d Department of Mechanical Engineering, Madhav Institute of Technology and Science, Gwalior 474005, India b c
H I GH L IG H T S
analysis of zigzag and armchair GNR as H S gas sensing element. • DFT transport properties have been analysed as sensing parameters. • Electronic process found exothermic and H S physisorbed to Z/A GNR, defends its reusable property. • Adsorption • H S gas sensitivity of ZGNRs is better than Armchair GNR, however suffers in recovery time. 2
2
2
A R T I C LE I N FO
A B S T R A C T
Keywords: GNR Armchair Zigzag Adsorption H2S Conductance I-V Sensitivity Recovery time
Armchair (A) and zigzag (Z) type graphene nanoribbons (GNR) have been investigated for its suitability to sense the toxic H2S gas, by using density functional theory (DFT) based ab-initio approach. On adsorption of H2S, the variations in original metallic behaviour of ZGNR and semiconducting behaviour of AGNR has further been analysed by observing the conductance and bandgap variation as a function of H2S distance from GNR surface. The HOMO-LUMO profiles have also been analysed to understand the chemistry of GNRs and H2S molecule. Further, the current-voltage characteristics in presence of H2S near the nanoribbon surface, also shows the sensing of H2S, discussed in terms of that the current in both the nanoribbons increases due to H2S presence. The computed sensitivity confirms the zigzag GNR as better sensor than its armchair counterpart however, relatively with less recovery time than its zigzag counterpart.
1. Introduction The two dimensional monolayer of graphite, known as graphene has been reported first [1] in 2004 and used in variety of applications [2], reason being its unique electronic, mechanical, optical, chemical and electrical properties. In the last one decade, number of experimental and computational studies have been reported on the use of graphene as sensing element [3–21]. The one dimension counterpart of graphene is the nanoribbon, simply the strips of a graphene [22–29]. Depending on its edge morphology, the grapheme nanoribbons are of two types Zigzag Graphene Nanoribbon (ZGNR) and Armchair Graphene Nanoribbon (AGNR). Where, it has been observed that the ZGNRs are always metallic and AGNR’s band structure changes with its width, hence, may be semiconducting or metallic. Environmental pollution has become a big challenge in the last one decade and needs attention of scientific
⁎
community in large. The gas sensors are required in industry as well as for domestic purposes as an important part of the safety system. Besides the graphene and carbon nanotubes, its one dimension counterpart graphene nanoribbons have also been tested for sensing element [30–32] but still needs attention due to its better suitability in device applications. For the present study, the considered gas for sensing is H2S [33,34], a highly explosive and flammable gas, burn readily and form other toxic products. Hydrogen sulfide (H2S) is a flammable, extremely toxic, colorless, irritating and transparent gas with a sweet odor in high concentrations and the odor of rotten egg in low concentrations. H2S is commonly found in sour, natural gas, coal and oil companies. Exposure to very small concentration of it (e.g. 10 ppm for 5 h) can cause death. The high risk and abundance of this gas in the current petrochemical and petroleum industry makes its monitoring a number one priority. Various efforts have been made for H2S sensing using
Corresponding author. E-mail address: [email protected] (R. Srivastava).
https://doi.org/10.1016/j.cplett.2020.137280 Received 22 August 2019; Received in revised form 21 February 2020; Accepted 24 February 2020 Available online 25 February 2020 0009-2614/ © 2020 Elsevier B.V. All rights reserved.
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Fig. 1.1. Optimized geometries of (a) pristine and (b) H2S adsorbed Zigzag GNR and (c) Optimized bond parameters of (c) pristine and (d) H2S adsorbed Zigzag GNR.
3. Results and discussion
variety of materials, from one dimension nanotubes [35,36] to two dimensional sheets [37], however, seems insufficient and needs to be addressed again. The present study reports the investigation of sensing ability of 10-AGNR and 12-ZGNR for H2S gas sensing, using DFT based ab-initio approach, discussed in terms of variations in the electronic and transport properties of GNRs due to presence of H2S in its surrounding.
In the present work, 10-AGNR and 12-ZGNR have been considered as a channel material of a modelled device to sense the H2S gas molecule. For the computation, the nanoribbons have C84H14 and C80H16 atoms for the ZGNR and AGNR, respectively. These graphene nanoribbons are passivated with hydrogen atoms to satisfy the dangling bonds and avoid interaction with the surrounding environment. The best site has been analysed by computing the lowest total energies, with different molecular orientations, like centre of the ring, bridge and on edge atom. The optimized structure confirms the edge site as the best site for gas molecule in both Zigzag and Armchair GNRs shown in Figs. 1.1 (a,b) and 1.2(a,b). The variations in the bond lengths and bond angles due to H2S molecule adsorption in ZGNR as well as AGNR have also been analysed and reported in Figs. 1.1(c,d) and 1.2(c,d). The H2S molecule has been optimized for its bond parameters and also on its adsorption with ZGNR and AGNR, its orientation as well as variation in bond parameters (angle and lengths) has been analysed, shown in Fig. 1.3(i–k) and reported in Table 2. Initially, the H2S molecule was placed at a distance of 1.176 Å and 1.108 Å for zigzag and armchair nanoribbon, respectively, which on optimization, shows physisorption and changes its bond parameters, reported in Table 2. The adsorption energy (for zigzag nanoribbon is −0.159 eV and for armchair nanoribbon, −0.269 eV) has been computed for H2S adsorbed 10-AGNR and 12-ZGNR systems, using Eq. (1). The computed negative adsorption energy confirms the interaction process as exothermic. On optimizing the H2S adsorbed Z/A GNR system, the orientation of H2S molecule become almost parallel to the GNR surface in both the cases with binding distance of 3.36 Å and 3.5 Å for zigzag and armchair nanoribbon, respectively, shown in Figs. 1.1 and 1.2 and tabulated in Table 1. The variations in the bond parameters of H2S molecule after adsorption
2. Computational methods The adsorption of H2S gas through two different morphologies of graphene nanoribbons, has been analysed by using a Density functional theory (DFT) [38] based Atomistic toolkit in Virtual nano lab (ATKVNL) environment [39]. To compute the structural and electronic properties of armchair and zigzag graphene nanoribbons with and without H2S gas, near to its surface, the k-point sampling of (1 × 1 × 10) has been considered for Brillouin-zone integration via Monkhorst Pack grid scheme. Generalized gradient approximation (GGA) has been considered to define the exchange correlation function, parameterized with revised Perdew Burke-Ernzerhof (PBE) [40,41]. For each configuration, density mesh cut-off is opted as 150 Rydberg while the process of optimization is continued until the forces on each atom becomes less than 0.05 eV/Å. The adsorption energy for the systems includes the armchair/zigzag graphene nanoribbon and H2S molecule has been calculated using
Eads = ET (GNR + H2 S ) − ET (GNR) − ET (H2 S )
(1)
where ET (GNR + H2 S ) and ET (GNR) are the total energies of geometrically optimized structure of GNRs with the adsorbed molecule and pristine GNR subsequently. While ET (H2 S ) is the total energy of an isolated H2S molecule. 2
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Fig. 1.2. Optimized geometries of (a) pristine and (b) H2S adsorbed Armchair GNR and (c) Optimized bond parameters of (c) pristine and (d) H2S adsorbed Armchair GNR. Fig. 1.3. Optimized geometries of H2S molecule as (i) isolated molecule (j) after adsorption with AGNR (k) after adsorption with ZGNR.
have also been analysed and reported in Table 2. Recovery time (τ), is an important parameter for a good sensor, defined as the time required for a sensor to return to 90% of the original baseline signal upon removal the target gas, and has been computed with the knowledge of adsorption energy (Eads ) using following equation reported elsewhere [42]
Table 1 Adsorption energy and Band structure of gas molecule adsorbed on the A/Z GNRs. H2S adsorbed system
Initial distance (Å)
Optimized distance (Å)
Adsorption energy (eV)
Band gap (eV)
ZGNR AGNR
1.176 1.108
3.36 3.50
−0.1594 −0.269
Metallic 1.187
τ = ν−1exp(−Eads / kB T )
where (ν ) is the attempt frequency, (kB ) the Boltzmann constant and (T ) operational temperature of the sensor. Here, for H2S molecule, the computed recovery time is faster in AGNR (1.27 ns) in comparison to that of ZGNR (0.0183 ns), which is better than the reported recovery time of 16.9–49 s (at 350 °C), using CuO thick film reported elsewhere [43]. To understand the adsorption better, the chemistry of the interaction between A/Z GNR and H2S molecule has been analysed through computation of HOMO-LUMO profiles with isosurface value of 0.02 electrons/(bohr)3, shown in Fig. 2(a–d), calculated using Gaussian 09 [44] also confirms the physisorption and show no overlap of orbitals. The HOMO LUMO profiles clearly show a strong edge effect in both the systems. The presence of H2S molecule near the surface of Z/AGNR can easily be analysed in terms of spreading (shifting) of charges in HOMO
Table 2 Bond angle (A1) and bond lengths (S1 and S2) of H2S molecule structure before and after adsorption on ZGNR/AGNR. H2S molecule parameters
Original Molecule
After Adsorption on ZGNR
After Adsorption on AGNR
A1 (Angle in °) S1 (Distance in Å) S2 (Distance in Å)
91.549° 1.368 Å 1.368 Å
92.124° 1.356 Å 1.355 Å
91.038° 1.357 Å 1.357 Å
(2)
3
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Fig. 2. HOMO- LUMO profiles of optimized systems of pristine (a) zigzag, (c) armchair and H2S adsorbed (b) zigzag, (d) armchair Graphene Nanoribbons.
near −2.0 eV in valance band and enhanced peak near 1.75 eV due to H2S molecule confirms the variations in comparison to its pristine counterpart. As the molecule shows physisorption with Z/A GNRs, there is no significant change observed on its band structures of optimized system. To further analyse these interactions between A/Z GNR and H2S molecule, the charge transfer analysis has also been performed using Mulliken population computation. The variations in the charge on the carbon atoms of A/ZGNR due to presence of Hydrogen and Sulphur atoms of H2S gas molecule has been computed and marked as charge transfer. The computed charge transfer between zigzag nanoribbon and H2S is −0.002e, whereas for armchair nanoribbon it is −0.014e. These variations in electronic properties have further been examined through electron transport analysis discussed in next section.
as well as LUMO profiles of pristine and H2S adsorbed systems. The electronic properties of the optimized geometries have been investigated in terms of band structure, electron difference density, molecular energy level (HOMO-LUMO energies) and density of state profiles of both the systems (H2S adsorbed ZGNR and AGNR), shown in Fig. 3.1(a,b) and Fig. 3.2(a,b). The AGNR observes a minor change in band gap from 1.2 eV to 1.1 eV, due to presence of H2S, whereas the metallic behaviour of ZGNR seems unchanged even with the presence of H2S. The careful analysis of band structures of ZGNR in its pristine as well as H2S adsorbed (Fig. 3.1a) shows a very slight change with an additional band appearance around −1.5 eV, whereas in case of AGNR (Fig. 3.2a), an additional band can be seen near −2.0 eV. To understand these minute changes, molecular energy levels of these GNR systems have also been marked along with its band structure and electron difference density, that confirms the H2S sensing. Both the cases have further been analysed through their DOS profiles reported in Figs. 3.1(b) and 3.2(b). In case of pristine ZGNR, at the Fermi level the decrease in the size of the peak and appearance of large peak near the −1.5 eV confirms the variation due to H2S molecule near to its surface. Similarly, in case AGNR DOS, the appearance of large additional peak
4. Electron transport analysis To further investigate the H2S sensitivity of Z/A graphene nanoribbons, the transport properties have been computed for the zigzag as well as armchair nanoribbons in its pristine and H2S adsorbed form. For 4
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Fig. 3.1. (a,b) Electron Difference Density, Band structure, Molecular energy level and density of states (DOS) profiles of Pristine and H2S adsorbed ZGNR.
To analyse the variation in the computed current of the nanoribbons, with and without molecule as a function of voltage, a large kpoint sampling of 1 × 1 × 100 has been used, using Landauer formula [45,46]. The conductance of each system (ZGNR and AGNR) with and
the same, optimized geometries of each system has been introduced to the two probe device model as shown in the Fig. 4(a,b), have three parts, left, right electrode and central region. Where the left and right electrode size of ZGNR are 5.0 Å and in case of AGNR, it is 4.38 Å. 5
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a AGNR
b AGNR+H2S Fig. 3.2. (a,b) Electron Difference Density, Band structure, Molecular energy level and density of states (DOS) profiles of Pristine and H2S adsorbed AGNR. (E − EF )/ kB T
without H2S molecule can be expressed in terms of energy band gap, exhibit the following relation:
G=
−Eg
⎞ σ = σ0 exp ⎛ ⎝ 2kT ⎠ ⎜
∫ dET (E ) (1 +e e(E−E )/k T )2 F
B
(4)
where EF is the Fermi energy and kB, the Boltzmann constant. The computed transmission probability generated the transmission spectrums for Pristine and H2S adsorbed ZGNR (Fig. 5a,b) and AGNR (Fig. 5c,d) respectively. The transmission peaks matches well with the density of states profile reported in Figs. 3.1 and 3.2(b), where the
⎟
(3)
To verify it further, the conductance G has been computed using Eq. (4) through its transmission probability T (E ) for ZGNR as well as AGNR in its pristine as well as H2S adsorbed form. 6
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Fig. 4. Two probe model of I-V analysis for H2S adsorbed (a) ZGNR (b) AGNR system.
G − G0 ⎞ S=⎛ ∗ 100 ⎝ G0 ⎠ ⎜
(a)
ZGNR
(b)
⎟
(5)
To visualize the range of detection for H2S molecule in case of ZGNR as well as AGNR, the two methods have been adopted, one, the conductance variation as a function of H2S molecule distance from the Z/A GNR surface shown in Fig. 6.1(a,b) along with bandgap variation shown in Fig. 6.2, and the other, current as a function of bias voltage with and without molecule, shown in Fig. 7(a,b) respectively. The calculated conductance at various distances between GNR surfaces to H2S molecule shows the range of detection of the GNR’s surface for the gas molecule. The analysis shows that in case of zigzag nanoribbon, the conductance increases linearly in almost whole range, however, becomes saturated at around 3.0 Å, whereas in case of armchair GNR the conductance shows a drop between 2.7 and 2.9 Å and beyond this invariable. Further, the current passing through the material in terms of transmission probability can be expressed as
ZGNR+ H2S
I=
2e h
∫μ
μR
L
[T (E ){fL (E ) − fR (E )}] dE
T (E ) = Tr (ΓL (E , V ) G R (E , V )ΓR (E , V ) G A (E , V )
(c)
AGNR
where T (E ) is the total transmission probability of channels at applied voltage V and energy E. μR and μL represents the chemical potentials of left and right electrodes, respectively with Fermi distribution functions fL(E) and fR(E). GR and GA are retarded and advanced Green’s function with ГL and ГR as coupling functions of left and right electrode selfenergies [47]. The computed current-voltage characteristics of the given configurations of ZGNR and AGNR (Fig. 4) in its pristine as well as H2S adsorbed form, shown in Fig. 7(a,b), have been analyzed by applying the bias voltage of upto1.5 V to the electrodes. It is inferred from the Fig. 7(a,b), representing the current-voltage characteristics, that the current increases as gas molecule approaches to the proposed armchair and zigzag graphene nanoribbon surface and this change in the current due to introduction of gas molecule confirms the sensing ability of the material. Further, the comparative currentvoltage analysis of two proposed GNRs, shows that, the difference in current on applying the voltage in the zigzag GNR is relatively large than that observed in its armchair counterpart in presence of H2S molecule near the GNR surface. In case of zigzag nanoribbon, when H2S interact with its surface, it shows a minor difference from pristine nanoribbon, at around 0.25 V, thereafter the current increases linearly as a function of voltage. At around 1 V, the pristine zigzag nanoribbon has very low current than the gas adsorbed surface. Whereas, the armchair ribbon has almost no change from 0 to 0.5 V, and beyond that the current increases linearly, shown in Fig. 7(b). In both the cases, the
(d) AGNR + H2S
Fig. 5. Transmission spectrums of (a,c) Pristine and (b,d) H2S adsorbed ZGNR and AGNR, respectively.
energy, reaches to zero, the transmission peak mimic the same drop at that point, however, when in density of state profile, it doesn’t reach to zero, the transmission doesn’t get affected much. The sensitivity (S) is another important parameter to analyse the suitability of any material as sensing element for any specific gas. This has also been analysed through the knowledge of conductance (G) of nanoribbons with gas (G) and without gas (G0) and confirms that the H2S sensitivity is remarkably better in case of Zigzag GNR (80.16%) in comparison to its Armchair counterpart (60.79%) calculated using following equation
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Fig. 6.1. Zero bias conductance of (a) ZGNR and (b) AGNR as a function of H2S distance from GNR surface.
current changes due to presence of H2S gas molecule confirm the sensing ability of the nanoribbons for gas molecule.
5. Conclusion The present study reports the H2S sensing ability of Zigzag and Armchair nanoribbons, by analysing their structural, electronic and transport properties. In structural properties, the stability of system has been confirmed through its total energy and variation in bond parameters due to H2S adsorption. Both the cases show the adsorption mechanism as physisorption, confirms the reusability of sensing material, whereas the negative adsorption energy, conveys the process as exothermic and hence gives a guess of low operational temperature. In electronic properties, the band gap of the Armchair nanoribbon slightly changes from 1.2 eV to 1.1 eV due to adsorption of H2S, whereas ZGNR retain its metallic nature. Besides the variation in band structure and DOS, the I-V analysis confirms that the ZGNR surface is more sensitive for H2S gas molecule in its surrounding, in comparison to its armchair counterpart. Computed current of the GNR systems drastically change with the gas adsorption. The range of detection also confirms the sensing ability of zigzag as well as armchair graphene nanoribbons. However, the recovery time of Armchair graphene nanoribbon based device is relatively better than its zigzag counterpart.
Fig. 6.2. Bandgap variation of AGNR as a function of H2S distance from GNR surface.
Fig. 7. Current- Voltage characteristics of (a) ZNGR and (b) AGNR before and after H2S adsorption. 8
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CRediT authorship contribution statement
[18] S. Dandeliya, A. Srivastava, Defected graphene as ammonia sensor: theoretical insight, IEEE Sens. J. 19 (6) (2018) 2031–2038, https://doi.org/10.1109/JSEN.2018. 2884971. [19] J. Dai, J. Yuan, P. Giannozzi, Gas adsorption on graphene doped with B, N, Al, and S: Atheoretical study, Appl. Phys. Lett. 95 (2009) 232105. [20] O. Faye, A. Raj, V. Mittal, A.C. Beye, H2S adsorption on graphene in the presence of sulfur: a density functional theory study, Comput. Mater. Sci. 117 (2016) 110–119. [21] J. Cai, P. Ruffieux, R. Jaafar, M. Bieri, T. Braun, S. Blankenburg, M. Muoth, A.P. Seitsonen, M. Saleh, X. Feng, K. Müllen, R. Fasel, Atomically precise bottom-up fabrication of graphene nanoribbons, Nature 466 (2010) 470. [22] D.V. Kosynkin, A.L. Higginbotham, A. Sinitskii, J.R. Lomeda, A. Dimiev, K. Price, J.K. Tour, Longitudinal unzipping of carbon nanotubes to form graphene nanoribbons, Nature 458 (2009) 872. [23] S. Duttaa, S.K. Pati, Novel properties of graphene nanoribbons: a review, J. Mater. Chem. 20 (2010) 8207–8223. [24] M. Berahman, M. Sanaee, R. Ghayour, A theoretical investigation on the transport properties of overlapped graphene nanoribbons, Carbon 75 (2014) 411. [25] M. Berahman, M.H. Sheikhi, Transport properties of zigzag graphene nanoribbon decorated with copper clusters, J. Appl. Phys. 116 (2014) 093701. [26] M. Berahman, M.H. Sheikhi, A. Zarifkar, H. Nadgaran, Structural and electronic properties of zigzag graphene nanoribbon decorated with copper cluster, J. Comput. Elec. 14 (1) (2015) 270–279. [27] A. Celis, Manuscript version: graphene nanoribbons: fabrication, properties and devices, J. Phys. D Appl. Phys. Top. 49 (2016) 1–26. [28] A. Srivastava, A. Jain, R. Kurchania, N. Tyagi, Width dependent electronic properties of graphene nanoribbons: an ab-initio study, J. Comput. Theor. Nanosci. 9 (7) (2012) 1008–1013. [29] M. Berahman, M.H. Sheikhi, Hydrogen Sulfide gas sensor based on decorated zigzag graphene nanoribbon with copper, Sensors Actuat. B: Chem. 219 (2015) 338–345. [30] A.H. Pourasl, M. Taghi, R. Ismail, N. Gharaei, Gas adsorption effect on the graphene nanoribbon band structure and quantum capacitance, Adsorption 23 (6) (2017) 767–777. [31] L. Shao, et al., Sulfur dioxide molecule sensors based on zigzag graphene nanoribbons with and without Cr dopant, Phys. Lett. Sect. A Gen. At. Solid State Phys. 378 (7–8) (2014) 667–671. [32] B. Huang, et al., Adsorption of gas molecules on graphene nanoribbons and its implication for nanoscale molecule sensor, J. Phys. Chem. C 112 (35) (2008) 13442–13446. [33] T.W. Lambert, V.M. Goodwin, D. Stefani, L. Strosher, Hydrogen sulfide (H2S) and sour gas effects on the eye. A historical perspective, Sci. Total Environ. 367 (1) (2006) 1–22. [34] Hydrogen Sulfide (H2S). Available: www.osha.gov. [Accessed: 20-Apr-2019]. [35] M. Berahman, M. Asad, M.H. Sheikhi, M. Fathi pur, Hydrogen Sulfide gas sensor based on carbon Nanotubes, IR-PATENT NO 75680 (2012). [36] R. Srivastava, H. Suman, S. Shrivastava, A. Srivastava, DFT analysis of pristine and functionalized zigzag CNT: a case of H2S sensing, Chem. Phys. Lett 731 (2019) 136575. [37] A.H. Reshak, S. Auluck, Adsorbing H2S onto a single graphene sheet: A possible gas sensor, J. App. Phys. 116 (2014) 103702. [38] E. E., R.M. Dreizler, Density Functional Theory: An Advanced Course, Springer Science & Business Media. [39] Virtual NanoLab Tutorial. Atomistix Toolkit, Quantum Wise A/S (www. quantumwise.com). [40] J.P. Perdew, K. Burke, M. Ernzerhof, Generalized gradient approximation made simple, 3 (1996) 3865–3868. [41] Y. Zhang, W. Yang, Comment on Generalized Gradient Approximation Made Simple 80 (1998) 890. [42] S. Peng, K. Cho, P. Qi, H. Dai, Ab initio study of CNT NO2 gas sensor, Chem. Phys. Lett. 387 (2004) 271–276. [43] B. Urasinska-Wojcik, J.W. Gardner, H2S Sensing in dry and humid H2 environment with p-Type CuO thick-film gas sensors, IEEE Sens. J. 18 (9) (2018) 3502–3508. [44] M.J. Frisch, et al., Gaussian09, Revision A.02, Gaussian, Inc., Wallingford CT, 2009. [45] S. Datta, Exclusion principle and the Landauer-Buttiker formalism, Phys. Rev. B 45 (3) (Jan. 1992) 1347–1362. [46] M. Büttiker, Y. Imry, R. Landauer, S. Pinhas, Generalized many-channel conductance formula with application to small rings, Phys. Rev. B 31 (10) (1985) 6207–6215, https://doi.org/10.1103/PhysRevB.31.6207. [47] H.H.B. Sørensen, P.C. Hansen, D.E. Petersen, S. Skelboe, K. Stokbro, Efficient wavefunction matching approach for quantum transport calculations, Phys. Rev. B 79 (20) (May 2009) 205322.
Harshika Suman: Investigation, Validation. Reena Srivastava: Conceptualization, Methodology, Software, Writing - original draft. Sadhna Shrivastava: Supervision. Anurag Srivastava: Supervision, Writing - review & editing. A.P. Jacob: Visualization, Investigation. C.S. Malvi: Visualization, Investigation. Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgement Authors are thankful to Computational Nanoscience and Technology lab of ABV-IIITM, Gwalior for extending the infrastructure support. References [1] A.K. Geim, K.S. Novoselov, The rise of graphene, Nat. Mater. 6 (2007) 183. [2] Z. Zhen, H. Zhu, Structure and properties of graphene, Graphene 1–12 (2018), https://doi.org/10.1016/b978-0-12-812651-6.00001-x. [3] Shengli Zhang, Shiying Guo, Zhongfang Chen, Yeliang Wang, Hongjun Gao, Julio Gomez-Herrero, Pablo Ares, Felix Zamora, Zhen Zhu, Haibo Zeng, Recent progress in 2D group-VA semiconductors: from theory to experiment, Chem. Soc. Rev. 47 (2018) 982–1021. [4] X.Y. Liu, J.M. Zhang, K.W. Xu, V. Ji, Improving SO2gas sensing properties of graphene by introducing dopant and defect: a first-principles study, Appl. Surf. Sci. 313 (2014) 405–410. [5] E. Llobet, Gas sensors using carbon nanomaterials: a review, Sensors Actuators, B Chem. 179 (2013) 32–45. [6] S. Aslam, T.H. Bokhari, T. Anwar, U. Khan, A. Nairan, K. Khan, Graphene oxide coated graphene foam based chemical sensor, Materials Letters 235 (2019) 66–70. [7] V. Nagarajan, R. Chandiramouli, Investigation on probing explosive nitroaromatic compound vapors using graphyne nanosheet: a first-principle study, Struct. Chem. 30 (2019) 657. [8] T. Wang, et al., A review on graphene-based gas/vapor sensors with unique properties and potential applications, Nano-Micro Lett. 8 (2016) 95–119. [9] C.K. Ho, A. Robinson, D.R. Miller, M.J. Davis, Overview of sensors and needs for environmental monitoring, Sensors 5 (1–2) (2005) 4–37. [10] F. Schedin, et al., Detection of individual gas molecules adsorbed on graphene, Nat. Mater. 6 (Jul. 2007) 652. [11] Xiaoxing Zhang, Hao Cuiand, Yingang Gui, Synthesis of graphene-based sensors and application on detecting SF6 decomposing products: a review, Sensors 17 (2017) 363. [12] W. Yuana, W.G. Shi, Graphene-based gas sensors, J. Mater. Chem. A. 1 (2013) 10078. [13] F. Yavari, N. Koratkar, Graphene-based chemical sensors, J. Phys. Chem. Lett. 3 (2012) 1746. [14] B.C. Wood, S.Y. Bhide, D. Dutta, V.S. Kandagal, A.D. Pathak, S.N. Punnathanam, K.G. Ayappa, S. Narasimhan, Methane and carbon dioxide adsorption on edgefunctionalized graphene: a comparative DFT study, J. Chem. Phys. 137 (2012) 054702. [15] P. Lazar, F. Karlický, P. Jurečka, M. Kocman, E. Otyepková, K. Šafářová, M. Otyepka, Adsorption of small organic molecules on graphene, J. Am. Chem. Soc. 135 (2013) 6372–6377. [16] O. Leenaerts, B. Partoens, F.M. Peeters, Adsorption of small molecules on graphene, Microelectron. J. 40 (4–5) (2009) 860–862. [17] S. Dandeliya, A. Srivastava, Electron transport in ethanol & methanol absorbed defected graphene, AIP Conference Proceedings 1953 (2018) 140140, https://doi. org/10.1063/1.5033315.
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