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. 2022 Mar 29;12(16):9828-9835.
doi: 10.1039/d2ra00442a. eCollection 2022 Mar 25.

Exploring a silicene monolayer as a promising sensor platform to detect and capture NO and CO gas

Duy Khanh Nguyen  1 , Duc-Quang Hoang  2 , D M Hoat  3   4
Affiliations

Exploring a silicene monolayer as a promising sensor platform to detect and capture NO and CO gas

Duy Khanh Nguyen et al. RSC Adv. .

Abstract

Searching for new two-dimensional (2D) materials for the early and efficient detection and capture of toxic gas has received special attention from researchers. In this work, we investigate the adsorption of NO and CO molecules onto a silicene monolayer using first-principles calculations. Different numbers of adsorbates, as well as adsorption configurations, have been considered. The results show that up to four NO molecules can be chemically adsorbed onto the pristine monolayer with adsorption energies varying between -0.32 and -1.22 eV per molecule. In these cases, the gas adsorption induces feature-rich electronic behaviors, including magnetic semiconducting and half-metallicity, where the magnetic properties are produced mainly by the adsorbates. Except for two CO molecules adsorbing onto two adjacent Si atoms with an adsorption energy of -0.26 eV per molecule, other adsorption configurations show weak physisorption of CO molecules onto the pristine silicene platform. However, the sensitivity can be enhanced considerably by doping with Al atoms, drastically reducing the adsorption energy to between -0.19 and -0.71 eV per molecule. The doping and adsorption process may lead to either band gap opening or metallization, depending on its configuration. This study reveals the promising applicability of pristine and Al doped silicene monolayers as sensors for more than one single NO and CO molecule.

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Conflict of interest statement

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.

Figures

Fig. 1
Fig. 1. (a) A 5 × 5 × 1 supercell (blue balls: Si) and (b) phonon dispersion curves of the silicene monolayer.
Fig. 2
Fig. 2. (a) Electronic band structure, (b) projected density of states (DOS – states per eV) (black bubble and line: s state; blue bubble and line: px state; red bubble and line: py state; green bubble and line: pz state) and (c) charge density difference (yellow surface: charge accumulation; blue surface: charge depletion; iso-surface value: 0.01) of the silicene monolayer.
Fig. 3
Fig. 3. (a) Spin density (yellow surface: spin-up; iso-surface value: 0.005), (b) electronic band structure (black line: spin-up; red line: spin-down), (c) projected density of states and (d) charge density difference (yellow surface: charge accumulation; blue surface: charge depletion; iso-surface value: 0.004) of the NO-adsorbed silicene monolayer.
Fig. 4
Fig. 4. (a) Spin density (yellow surface: spin-up; iso-surface value: 0.005) (a) 2NO2-, (b) 2NO3-, (c) 2NO4-, (d) 3NO-, and (e) 4NO-adsorbed silicene monolayer.
Fig. 5
Fig. 5. Electronic band structure (black line: spin-up; red line: spin-down) (a) 2NO1-, (b) 2NO2-, (c) 2NO3-, (d) 2NO4-, (e) 3NO- and (f) 4NO-adsorbed silicene monolayer.
Fig. 6
Fig. 6. (a) Electronic band structure, (b) projected density of states, and (c) charge density difference (yellow surface: charge accumulation; blue surface: charge depletion; iso-surface value: 0.004) of the CO-adsorbed silicene monolayer.
Fig. 7
Fig. 7. Electronic band structure of the 2CO1-adsorbed silicene monolayer.
Fig. 8
Fig. 8. (a) Electronic band structure, (b) projected density of states, and (c) charge density difference (yellow surface: charge accumulation; blue surface: charge depletion; iso-surface value: 0.004) of the CO-adsorbed Al-doped silicene monolayer.
Fig. 9
Fig. 9. Electronic band structure (black line: spin-up; red line: spin-down) (a) 2CO1-, (b) 2CO2-, (c) 2CO3-, (d) 2CO4-, (e) 3CO- and (f) 4CO-adsorbed Al-doped silicene monolayer.
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