Skip to main content
NCBI home page
ACS Omega logoLink to ACS Omega
. 2023 Jan 19;8(4):4261–4269. doi: 10.1021/acsomega.2c07492

Highly NH3 Sensitive and Selective Ti3C2O2-Based Gas Sensors: A Density Functional Theory-NEGF Study

Kaiyi Weng †,‡, Jiahe Peng †,‡, Zuhao Shi †,‡, Arramel Arramel §, Neng Li †,‡,∥,*
PMCID: PMC9893262  PMID: 36743015

Abstract

graphic file with name ao2c07492_0009.jpg

Ammonia (NH3) detection at the early stage is an important precaution for human health and agricultural production. However, conventional sensing materials are difficult to achieve all the targeted operational performances such as low power consumption and high selectivity. MXenes are a type of graphene-like emergent material equipped with abundant surface sites benefiting gas-sensing applications. In the work, we discuss the sensing performance of Ti3C2O2 to anticipate harmful and polluting NH3 gases by density functional theory and nonequilibrium Green’s function. The adsorption geometry, charge difference density, and partial density of states are discussed to understand the nature of interactions between gas molecules and Ti3C2O2. The theoretical results show that only NH3 adsorbs onto the nanosheet through chemisorption. Then, a two-electrode Ti3C2O2-based gas sensor device is built to unravel the transport properties. Current under different bias voltages indicates the Ti3C2O2-based sensor could maintain extremely high sensitivity, demonstrating that Ti3C2O2 has great potential for the NH3 sensor with high selectivity, excellent sensitivity, and low energy consumption. Upon external electric fields, the adsorption energy and charge transfer can be tuned effectively, suggesting that Ti3C2O2 is a versatile agent as an ammonia-sensing material.

Introduction

Ammonia is a colorless, water-soluble gas with strong pungent odors. When NH3 is combined with particulate matter in the atmosphere, the formation of ammonium salts and haze particulate matter will accelerate causing acidification of the ecosystem and eutrophication of water. Moreover, ammonia is harmful to the human body. Therefore, it is vital to detect the presence of ammonia in the ambient environment. Gas sensors are devices capturing environmental changes and output readable signals by postprocessing. In practice, the physical function gas sensors should possess depend on specific purposes and service environments. However, among all the requirements, sensing performance-related ones (sensitivity, selectivity, and rate of response) and reliability-related ones (drift, stability, and interfering gases) are of importance.1−3 Diverse classes of materials such as semiconducting metal oxides,4−7 carbon nanotubes,8,9 and conducting polymers10,11 are used in research and application of gas sensing. However, achieving the ideal combination of high sensitivity, low cost, and wide operating temperate is still challenging. For example, nanotubes possess great sensitivity but are difficult to manufacture and require a long recovery time.8 Metal oxide-based gas sensors are low cost but have poor selectivity and require high operating temperature due to the wide band gap and their sensing mechanics.12,13

In recent years, MXenes have attracted the attention of worldwide scientists owing to their graphene-like structure. They can be obtained by etching A layers from the MAX phase. The general formula of MXenes is Mn+1XnTx, where M, X, T, and A stand for early transition metal, carbon or/and nitrogen, the functional group obtained during the preparation process, and IIIA or IVA elements, respectively. Ti3C2Tx is the first MXene to be discovered and widely investigated throughout their early discoveries.14 Several superior chemical and physical properties such as good conductivity, large specific surface area, high stability, highly adjustable metal composition, and surface functional groups made Ti3C2Tx an excellent material in supercapacitors,15−17 catalysis,18−20 optoelectronic devices,21,22 water purification,23,24 and gas sensors.25,26

In this paper, we explore the possibility of Ti3C2 covered with different functional groups (−O, −OH, −F, −Cl) as an ammonia sensor by DFT-NEGF. Here, we assess the respective sensing performances by investigating their interactions with toxic and greenhouse gases. We take CO, CO2, CH4, HCHO, H2S, SO2, SO3, NO2, NO, and NH3 gases into consideration. Based on the analysis of electronic structures like adsorption geometry, charge density difference, and partial density of states, we find moderate adsorption energy and charge transfer amount of NH3 on Ti3C2O2, verifying the selectivity and sensitivity of Ti3C2O2 toward NH3. Furthermore, the transport properties of Ti3C2O2 under bias voltages ranging from 0 to 1 V are evaluated. The dramatic current change of Ti3C2O2 with NH3 adsorption shows Ti3C2O2 is a very promising ammonia sensor material. The satisfactory results show the adsorption strength can be tuned effectively by applying external electric fields and offer an effective way to realize the capture and release of ammonia.

Computational Methods

The density functional theory (DFT) was used in structural optimizations and performance analyses by Vienna Ab Initio Simulation Package (VASP).27 Projector augmented wave (PAW) pseudopotentials28 are used to describe the electron–ion interaction. For the exchange and correlation functionals, we use the Perdew–Burke–Ernzerhof method from the generalized gradient approximation (GGA-PBE).28 A 15 Å vacuum region was added along the Z-direction and a 3 × 3 × 1 supercell structural model was built to eliminate the interaction between adjacent layers and gas molecules, respectively. The K-point was set as 5 × 5 × 1, and the cutoff energy for wave function expansion was 500 eV. Meanwhile, the energy and force convergence criteria were less than 10–5 eV and 0.01 eV/Å, respectively. The van der Waals interactions between MXenes and gas were described by empirical dispersion correction (DFT-D3).29

The adsorption energy (Ead) is defined as follows:

graphic file with name ao2c07492_m001.jpg

where ETi3C2Tx + gas is the total energy of Ti3C2Tx with adsorbate, ETi3C2Tx and Egas are the energy of pure Ti3C2Tx and isolated gas molecule.

The electron transport calculations were performed by first principles package NANODCAL based on the density functional theory and nonequilibrium Green’s function (NEGF-DFT) method.30 The GGA-PBE and double-zeta polarized (DZP) basis sets were used in these calculations. A larger vacuum slab (20 Å) and three atomic layers along the transport direction in each side (Figure S1) were applied to ensure the potential along the transport direction is smooth. The cutoff energy and K-point for devices and electrodes were 80 Hartree, 1 × 8 × 1, and 100 × 6 × 1, respectively.

The current I at bias voltage Vb can be obtained using the Landauer–Butiker formula:31

graphic file with name ao2c07492_m002.jpg
graphic file with name ao2c07492_m003.jpg

where T(E, Vb) is the transmission coefficient, f and u refer to the Fermi–Dirac distribution function and electrochemical potential, respectively, the subscript L/R is used to distinguish the left/right electrode.

The sensitivity S of the gas sensor is defined as:32

graphic file with name ao2c07492_m004.jpg

where I0 is the current of the clean device and I represents the current of the device with different gas molecules.

The optimized geometric conditions of Ti3C2 with functional groups are predetermined to be perpendicular with respect to the middle layer Ti atoms that are considered as the most stable structure.33−35 Therefore, the sequence calculations discussed in this study are based on these approaches. The Ti3C2Tx surfaces and gas adsorption sites are shown in Figures 1a and S2.

Figure 1.

Figure 1

Open in a new tab

A schematic illustration of Ti3C2O2 surface and gas adsorption. (a) Adsorption sites on Ti3C2O2, (b) distance between gas and Ti3C2O2, and (c) side and top views of gas adsorption configuration. Red: O, blue: Ti; brown: C; white: H, yellow: S, purple: N.

Results and Discussion

The possible adsorption sites and orientations like vertical and horizontal directions of CO, CO2, CH4, HCHO, SO2, SO3, H2S, NO2, NO, and NH3 on Ti3C2O2 are considered. The corresponding adsorption energy, charge transfer amount, and adsorption distance (schematic diagram shown in Figure 1b) of the most stable configurations are summarized in Table 1 and Tables S1–3.

Table 1. Calculated Adsorption Energy (Ead), Bader Charge (ΔQ) of Different Gas Molecule on the Ti3C2O2 Supercell, and Interfacial Spacing (dTi3C2O2 – gas) (Positive ΔQ Value Represents Substrate as an Electron Acceptor).

gas molecule Ead (eV) dTi3C2O2 – gas (Å) ΔQ (e)
NH3 –0.420 1.730 0.181
NO –0.348 2.300 0.226
SO3 –0.340 2.875 –0.017
SO2 –0.285 2.876 –0.013
H2S –0.254 2.362 0.024
HCHO –0.233 2.547 –0.004
CH4 –0.207 2.536 0.004
CO –0.162 2.761 0.002
CO2 –0.201 3.010 –0.007
NO2 –0.185 2.632 –0.003
Open in a new tab

The negative sign of adsorption energy indicates that the gas molecules can adsorb on the Ti3C2T2 surface spontaneously. According to Yang et al.,13 a suitable gas-sensing material should capture the target gas by weak chemical interactions or strong physical interactions. Too small adsorption energy and large charge transfer (Table S2) often accompany with the gas molecule adsorptions on Ti3C2(OH)2, which lead to bond-breaking reactions and poison the sensor so that the sensor cannot be reused.36 While for −F and −Cl terminated Ti3C2, the small charge transfer and relatively large adsorption energy (Tables S1, S3) after adsorption lead to low sensitivity and long response time,37 which disadvantage to rapid detection. Ti3C2O2 exhibits the best selectivity and moderate adsorption energy and charge transfer to NH3. Therefore, subsequent analytical calculations are based on Ti3C2O2.The most stable adsorption geometries are shown in Figure 1c. Based on these results, we find that all interacting gases can realize spontaneous adsorption and maintain their molecule forms. Interestingly, a local structural deformation appears when NH3 was adsorbed onto the Ti3C2O2 surface.

In detail, the Ti atoms at the close proximity of NH3 slightly move outward, indicating a strong interaction between NH3 and Ti3C2O2. Meanwhile, the adsorption distance between Ti3C2O2 and NH3 is the smallest compared with the others, and we find that this value is slightly smaller than the sum of the covalent radii of O and N, which suggests that NH3 gas may adsorb on Ti3C2O2 by chemical adsorption. While for other gas adsorptions, the distances between gas and Ti3C2O2 are still larger than the sum of their covalent radii, inferring the presence of physical adsorptions between the adsorbent and the gas molecules. It is worth mentioning that CO, CO2, CH4, and NO2 occur with few charge transfer and large adsorption energy, indicating poor interaction between the substrate and the adsorbate, that is, Ti3C2O2 cannot detect them effectively. Thus, we choose HCHO, SO2, SO3, H2S, NO, and NH3 as the target gases for the following research.

To further analyze the charge redistribution of the adsorption systems, the charge density difference was calculated. As shown in Figure 2, NO and NH3 act as strong electron donors. Especially, NH3 overlaps a lot with the Ti3C2O2 surface, indicating the existence of a bond between the gas molecule and Ti3C2O2. Compared with NH3 adsorption, the charge density difference of NO/Ti3C2O2 is more localized which leads to weaker interaction and no appreciable atomic displacement. In contrast, there are minor charge redistributions between other gas molecules and Ti3C2O2, manifesting the Ti3C2O2 monolayers capture these gas molecules by physical adsorption.

Figure 2.

Figure 2

Open in a new tab

Charge density difference of molecule/Ti3C2O2. (a) NH3/Ti3C2O2, (b) NO/Ti3C2O2; (c) SO2/Ti3C2O2;(d) SO3/Ti3C2O2; (e) HCHO/Ti3C2O2; (f) H2S/Ti3C2O2. Yellow: charge accumulation, cyan: charge depletion. The isosurface value was set to 0.0002 e Å–3.

To analyze the nature of the interactions between gas molecules and Ti3C2O2 sheets more intuitively, the partial density of states (PDOS) of the atom with the most charge transfer in each of gas molecule (Figure S3) and the nearby Ti atom and O atom in Ti3C2O2 are presented (Figure 3). When the NH3 adsorbed on the Ti3C2O2, the dispersion of N p states overlapped significantly with the d states of Ti and the p states of O from −4 to −1.5 eV, indicating that the N p states are strongly hybridized with the d states of Ti and the p states of O atoms. At the meantime, a slight shift toward Ef was observed in the PDOS of Ti. As for NO/Ti3C2O2, the adsorption of NO induced few small peaks of O p states around the Fermi level, demonstrating minute interactions between the N p states and the O p states. However, this character allows more charge transfers between NO and Ti3C2O2.38 For the remaining systems, the PDOS of Ti and O are hardly changed after adsorption, representing that these gases are physically adsorbed on the Ti3C2O2 sheets which are consistent with the charge density difference analysis.

Figure 3.

Figure 3

Open in a new tab

Partial density of states of molecule/Ti3C2O2. (a) NH3/Ti3C2O2, (b) NO/Ti3C2O2, (c) SO2/Ti3C2O2; (d) SO3/Ti3C2O2;(e) HCHO/Ti3C2O2; (f) H2S/Ti3C2O2.

To simulate the electronic transport properties, a Ti3C2O2-based sensor consisting of a Ti3C2O2 sheet and two Ti3C2O2 electrodes is proposed in this investigation. Three atomic layers in each side along the transport direction are added to realize the shielding effect between the central region and the electrodes. Both electrodes and the scattering regions are periodically perpendicular to the transport direction (Figure 4). By applying bias voltages ranging from 0 to 1 V, the current values are depicted in Figure 5a. In general, devices with gases except NH3 exhibit similar I–V trends with the clean device. After NH3 adsorption, the device shows a drastic current change, suggesting that Ti3C2O2 is a promising ammonia-sensitive material, which is consistent with the experimental results.25,26

Figure 4.

Figure 4

Open in a new tab

Scheme of the Ti3C2O2-based gas sensor. Gray cuboid represents the electrodes. Two distinct downward arrows represent different physical interactions of gases with the Ti3C2O2 surfaces.

Figure 5.

Figure 5

Open in a new tab

(a) Current–voltage (I–V) relations before and after the adsorption of the gas molecule on Ti3C2O2, (b) sensitivity of the device to gas molecule, and transmission coefficient at (c) Vb = 0.1 V, (d) Vb = 1 V. Dashed lines represent the bias windows.

The device with NH3 demonstrates a rapid and linear current increment when the bias voltages increase from 0 to 0.4 V, then the current gradually decreases as the voltage increases. In other words, negative differential resistance (NDR) occurs. However, the current value is still about 50% higher than other gas-induced currents. The current increases again when the voltage is continuously increased above 0.8 V, but the slope of the curve is smaller than that at low bias. To describe the current change before and after adsorption quantitatively, we present the sensitivity S of the gas sensor in Figure 5b. For NH3 adsorption, S could reach 1.8 at Vb = 0.3 V and even the minimum value could reach 0.4. It is worth pointing out that the sensitivity remains higher than 0.8 when the bias voltages are applied ranging from 0.2 to 0.8 V, which shows that Ti3C2O2 has a great sensing performance and stability. On the contrary, when SO2, SO3, and H2S adsorb on the surface, the Ti3C2O2-based gas sensor is completely insensitive as the values of S are close to 0. The sensitivities to HCHO and NO are slightly higher than the above gases, but the highest value is about 0.2, still much less than that of NH3, which verifies the sensitivity of Ti3C2O2 to NH3.

Transmission coefficients plotted in Figure 5c,d are calculated to uncover the microscopic mechanisms of the gas sensor. Under different bias voltages, the current is determined by the integral of the transmission coefficient in the bias window. At Vb = 0.1 V, the coefficient of NH3 near the Fermi level is always higher than that of other gases and clean sensors, indicating more ballistic transports in NH3/Ti3C2O2. At Vb = 1 V, the bias window is from −0.5 to 0.5 eV. Although the coefficient of every system decreases the current still increases due to the expansion of the integration range. Gases except NH3 show similar coefficient values with the clean device, leading to low sensitivity. While for NH3, when the energy ranges from −0.5 to about −0.1 eV, the coefficient is the smallest, then it becomes largest and starts to pull away from other gases and lead to the highest current than the other systems.

To figure out the physical origin of NDR, we plotted the transmission spectrum mapping under different bias is illustrated in Figure 6a. The black lines represent different bias windows under different Vb. When the initial voltage increases, a peak gradually shifts into the bias window, making the current increase rapidly. Then, the peak changes its course and gradually moves away. Most of the coefficients in the bias window are close to zero. Consequently, the current is dramatically reduced. To further understand the microscopic image, scattering states are also analyzed. In this work, the scattering states at the initial voltage (0.1 V) and 0.4, 0.8 V are calculated.

Figure 6.

Figure 6

Open in a new tab

(a) Transmission spectra of NH3/Ti3C2O2 under a bias range from 0 to 1 V. Black lines represent bias windows, (b) the scattering states of NH3/Ti3C2O2 at Vb = 0.1, 0.4, 0.8 V, respectively.

It turns out that these bias regions exhibited the minimum current and the current inflection point. As shown in Figure 6b, three Bloch states exist in the left and right electrodes in all cases, indicating the presence of 3 transport channels. However, at Vb = 0.1 V, only 1 state is delocalized and the other two states are local which imply that most of the transmission channels are blocked. When the bias increases to 0.4 V, 3 states are all delocalized, facilitating the transfer of electrons. At Vb = 0.8 V, the second state is localized; hence, this electronic transmission channel is blocked again, resulting in a current reduction. Consequently, we propose that the current in this observation could be associated to the localization of scattering states. We note that the scattering states are gradually delocalized at a small bias. Then, the scattering states localize again and thus NDR occurs.

In general, lower adsorption energy means higher sensitivity and shorter sensing response time. Here, we revisit the results mentioned above that have shown the adsorption energy of ammonia adsorbed on Ti3C2O2 equals −0.42 eV. In the light of Guo et al.,39,40 adsorption smaller than −0.5 eV could facilitate the solid capture of the gas more efficiently on the surface. The external E-field which is a useful method to control the adsorption energy38,41 is introduced to improve the sensing performance of Ti3C2O2 to NH3. To ensure that the geometric configuration of NH3 adsorbed on the Ti3C2O2 sheet is the most stable, here, we assign the electric field direction perpendicular to the MXene sheet. The positive (negative) direction is up (down), the electric field strength applied is from −0.5 to 0.5 V/Å, and the interval is 0.1 V/Å.

Figure 7a depicts the adsorption energy and the charge transfer amount of NH3 adsorbed on Ti3C2O2 under different electric fields. It is obvious that the adsorption process of NH3 on the Ti3C2O2 is greatly affected by the E-fields strength. When the E-fields increase negatively, as a consequence, the adsorption energy of ammonia gradually decreases. The adsorption energy can be smaller than −0.50 eV when the E-fields range from −0.5 to −0.2 V/Å. However, when the positive value of E-fields is applied, the adsorption energy of NH3 increases first and then decreases. The largest adsorption energy achieves −0.34 eV when the E-field is 0.1 eV. The above results indicate that more effective adsorption and desorption of NH3 can be achieved by regulating the external E-fields, which is beneficial to improve the sensing performance and facilitate the recycling of the devices.

Figure 7.

Figure 7

Open in a new tab

Electric field effects on NH3-adsorbed Ti3C2O2 monolayers. Variation of (a) adsorption energy and (b) charge transfer profiles.

Furthermore, we discuss the evolution of charge transfers between gases and nanosheets which is vital for sensing performance. Thus, we investigate the influence of applied electric fields on the charge transfers, as shown in Figure 7b. As the electric fields were increased from −0.5 to 0.5 V/Å, the amount of charge transfer was decreased gradually. For instance, charge transfer between NH3 and Ti3C2O2 could reach 0.2 e when the electric field is −0.5 V/Å, while there are 0.14 e charges transfer when the E-field is 0.5 V/Å. That is, as the E-field increases along the positive direction, the charge transfer from the gas molecule to Ti3C2O2 decreases. The effect could be driven from to the dipole moment of NH3 and Ti3C2O2 and the electronegativity among H, N, Ti, C, and O atoms.42,43 Considering that NH3 molecules have permanent dipoles, whereas Ti3C2O2 nanosheets have net dipole moments in zero fields, the dipole changes induced by the electric field could influence the interaction between the gas molecules and the nanosheets.

Conclusions

In summary, we investigated the physical interactions between Ti3C2O2 and several toxic gases to elucidate their electronic structures and transport properties by DFT and NEGF. The results have shown that Ti3C2O2 has a great promise for NH3-sensing materials. The calculated adsorption energy of NH3 on Ti3C2O2 yields an appropriate value (−0.42 eV), and the charge transfer rate of 0.18 e. Then, the PDOS and charge difference density were calculated to analyze the nature of the bond between gas molecules and Ti3C2O2.

It turns out that NH3 molecules chemisorb on the surface and thereby trigger a substantial electronic structure variation. Although NDR appeared when NH3 was absorbed on Ti3C2O2, the sensitivity of Ti3C2O2 to NH3 was always higher than 0.4 and NH3 showed the highest current amount of all the tested gases. The sensing performance under bias voltages ranging from 0 to 1 V revealed Ti3C2O2-enabled stable and reliable sensing of NH3 with small power consumption. Transmission coefficient spectra and the scattering states under different bias voltages were used to explain the reason for the emergence of NDR from the displacements of the transmission peak and the local degree of the transport channels. The adsorption energy and charge transfer upon applying external electric fields could be tuned effectively, and this facilitated the gas detection and the device recovery. Generally, Ti3C2O2 is a promising sensing material for ammonia, and this work paves the way for designing high-yield, low-power, and high-selectivity gas sensors.

Acknowledgments

We gratefully acknowledge HZWTECH for providing computation facilities and technical communication support. This work was supported by the Natural Science Fund for Distinguished Young Scholars of Hubei Province (No. 2020CFA087), Basic and Applied Basic Research Foundation of Guangdong Province (No. 2022A1515011303), the Basic Research Program of Shenzhen (No. JCYJ20190809120015163), the Central Government Guides Local Science and Technology Development Funds to Freely Explore Basic Research Projects (2021Szvup106), and the Fundamental Research Funds for the Central Universities (No. WUT35401053-2022).

Supporting Information Available

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsomega.2c07492.

  • Bader charge and adsorption energy of Ti3C2Tx; convergence test of the device potential; schematic diagram of adsorption sites; and charge transfer amount of gas molecules (PDF)

The authors declare no competing financial interest.

Supplementary Material

ao2c07492_si_001.pdf (423.4KB, pdf)

References

  1. Yamazoe N. Toward Innovations of Gas Sensor Technology. Sens. Actuators, B 2005, 108, 2–14. 10.1016/j.snb.2004.12.075. [DOI] [Google Scholar]
  2. Xu Q.; Liu Y.; Su R.; Cai L.; Li B.; Zhang Y.; Zhang L.; Wang Y.; Wang Y.; Li N.; Gong X.; Gu Z.; Chen Y.; Tan Y.; Dong C.; Sreeprasad T. S. Highly Fluorescent Zn-Doped Carbon Dots as Fenton Reaction-Based Bio-Sensors: An Integrative Experimental–Theoretical Consideration. Nanoscale 2016, 8, 17919–17927. 10.1039/C6NR05434J. [DOI] [PubMed] [Google Scholar]
  3. Zou J.; Mao D.; Arramel; Li N.; Jiang J. Reliable and Selective Lead-Ion Sensor of Sulfur-Doped Graphitic Carbon Nitride Nanoflakes. Appl. Surf. Sci. 2020, 506, 144672 10.1016/j.apsusc.2019.144672. [DOI] [Google Scholar]
  4. Imawan C.; Solzbacher F.; Steffes H.; Obermeier E. Gas-Sensing Characteristics of Modified-MoO3 Thin Films Using Ti-Overlayers for NH3 Gas Sensors. Sens. Actuators, B 2000, 64, 193–197. 10.1016/S0925-4005(99)00506-7. [DOI] [Google Scholar]
  5. Aslam M.; Chaudhary V. A.; Mulla I. S.; Sainkar S. R.; Mandale A. B.; Belhekar A. A.; Vijayamohanan K. A Highly Selective Ammonia Gas Sensor Using Surface-Ruthenated Zinc Oxide. Sens. Actuators, A 1999, 75, 162–167. 10.1016/S0924-4247(99)00050-3. [DOI] [Google Scholar]
  6. Thai N. X.; Van Duy N.; Van Toan N.; Hung C. M.; Van Hieu N.; Hoa N. D. Effective Monitoring and Classification of Hydrogen and Ammonia Gases with a Bilayer Pt/SnO2 Thin Film Sensor. Int. J. Hydrogen Energy 2020, 45, 2418–2428. 10.1016/j.ijhydene.2019.11.072. [DOI] [Google Scholar]
  7. Xu K.; Li N.; Zeng D.; Tian S.; Zhang S.; Hu D.; Xie C. Interface Bonds Determined Gas-Sensing of SnO2–SnS2 Hybrids to Ammonia at Room Temperature. ACS Appl. Mater. Interfaces 2015, 7, 11359–11368. 10.1021/acsami.5b01856. [DOI] [PubMed] [Google Scholar]
  8. Gilbertson L. M.; Busnaina A. A.; Isaacs J. A.; Zimmerman J. B.; Eckelman M. J. Life Cycle Impacts and Benefits of a Carbon Nanotube-Enabled Chemical Gas Sensor. Environ. Sci. Technol. 2014, 48, 11360. 10.1021/es5006576. [DOI] [PubMed] [Google Scholar]
  9. Jung H. Y.; Kim Y. L.; Park S.; Datar A.; Lee H.; Huang J.; Somu S.; Busnaina A.; Jung Y. J.; Kwon Y. High-Performance H2S Detection by Redox Reactions in Semiconducting Carbon Nanotube-Based Devices. Analyst 2013, 138, 7206. 10.1039/c3an01762a. [DOI] [PubMed] [Google Scholar]
  10. Li Y.; Zheng Y.; Pionteck J.; Pötschke P.; Voit B. Tuning the Structure and Performance of Bulk and Porous Vapor Sensors Based on Co-Continuous Carbon Nanotube-Filled Blends of Poly(Vinylidene Fluoride) and Polycarbonates by Varying Melt Viscosity. ACS Appl. Mater. Interfaces 2020, 12, 45404–45419. 10.1021/acsami.0c15184. [DOI] [PubMed] [Google Scholar]
  11. Virji S.; Huang J.; Kaner R. B.; Weiller B. H. Polyaniline Nanofiber Gas Sensors: Examination of Response Mechanisms. Nano Lett. 2004, 4, 491–496. 10.1021/nl035122e. [DOI] [Google Scholar]
  12. Mutschall D.; Holzner K.; Obermeier E. Sputtered Molybdenum Oxide Thin Films for NH3 Detection. Sens. Actuators, B 1996, 36, 320–324. 10.1016/S0925-4005(97)80089-5. [DOI] [Google Scholar]
  13. Yang S.; Jiang C.; Wei S. Gas Sensing in 2D Materials. Appl. Phys. Rev. 2017, 4, 021304 10.1063/1.4983310. [DOI] [Google Scholar]
  14. Zou J.; Wu J.; Wang Y.; Deng F.; Jiang J.; Zhang Y.; Liu S.; Li N.; Zhang H.; Yu J.; Zhai T.; Alshareef H. N. Additive-Mediated Intercalation and Surface Modification of MXenes. Chem. Soc. Rev. 2022, 51, 2972–2990. 10.1039/D0CS01487G. [DOI] [PubMed] [Google Scholar]
  15. Hu M.; Cheng R.; Li Z.; Hu T.; Zhang H.; Shi C.; Yang J.; Cui C.; Zhang C.; Wang H.; Fan B.; Wang X.; Yang Q.-H. Interlayer Engineering of Ti3C2Tx MXenes towards High Capacitance Supercapacitors. Nanoscale 2020, 12, 763–771. 10.1039/C9NR08960H. [DOI] [PubMed] [Google Scholar]
  16. Wen Y.; Rufford T.; Chen X.; Li N.; Lyu M.; Dai L.; Wang L. Nitrogen-Doped Ti3C2Tx MXene Electrodes for High-Performance Supercapacitors. Nano Energy 2017, 38, 368. 10.1016/j.nanoen.2017.06.009. [DOI] [Google Scholar]
  17. Ma R.; Chen Z.; Zhao D.; Zhang X.; Zhuo J.; Yin Y.; Wang X.; Yang G.; Yi F. Ti3C2Tx MXene for Electrode Materials of Supercapacitors. J. Mater. Chem. A 2021, 9, 11501–11529. 10.1039/D1TA00681A. [DOI] [Google Scholar]
  18. Zhang Y.; Zhou Z.; Lan J.; Zhang P. Prediction of Ti3C2O2 MXene as an Effective Capturer of Formaldehyde. Appl. Surf. Sci. 2019, 469, 770–774. 10.1016/j.apsusc.2018.11.018. [DOI] [Google Scholar]
  19. Qian X.; Ma C.; Shahid U. B.; Sun M.; Zhang X.; Tian J.; Shao M. Synergistic Enhancement of Electrocatalytic Nitrogen Reduction over Few-Layer MoSe2-Decorated Ti3C2Tx MXene. ACS Catal. 2022, 12, 6385–6393. 10.1021/acscatal.2c01172. [DOI] [Google Scholar]
  20. Sun Y.; Jin D.; Sun Y.; Meng X.; Gao Y.; Dall’Agnese Y.; Chen G.; Wang X.-F. g-C3N4/Ti3C2Tx (MXenes) Composite with Oxidized Surface Groups for Efficient Photocatalytic Hydrogen Evolution. J. Mater. Chem. A 2018, 6, 9124–9131. 10.1039/C8TA02706D. [DOI] [Google Scholar]
  21. Ebrahimi M.; Mei C.-T. Optoelectronic Properties of Ti3C2Tx MXene Transparent Conductive Electrodes: Microwave Synthesis of Parent MAX Phase. Ceram. Int. 2020, 46, 28114–28119. 10.1016/j.ceramint.2020.07.307. [DOI] [Google Scholar]
  22. Chen K.; Cai P.; Peng H.; Xue X.; Wang Z.; Sun L. Ti3C2Tx MXene for Organic/Perovskite Optoelectronic Devices. J. Cent. South Univ. 2021, 28, 3935–3958. 10.1007/s11771-021-4846-z. [DOI] [Google Scholar]
  23. Ding L.; Li L.; Liu Y.; Wu Y.; Lu Z.; Deng J.; Wei Y.; Caro J.; Wang H. Effective Ion Sieving with Ti3C2Tx MXene Membranes for Production of Drinking Water from Seawater. Nat. Sustainability 2020, 3, 296–302. 10.1038/s41893-020-0474-0. [DOI] [Google Scholar]
  24. Wang J.; Zhang Z.; Zhu J.; Tian M.; Zheng S.; Wang F.; Wang X.; Wang L. Ion Sieving by a Two-Dimensional Ti3C2Tx Alginate Lamellar Membrane with Stable Interlayer Spacing. Nat. Commun. 2020, 11, 3540. 10.1038/s41467-020-17373-4. [DOI] [PMC free article] [PubMed] [Google Scholar]
  25. Wu M.; He M.; Hu Q.; Wu Q.; Sun G.; Xie L.; Zhang Z.; Zhu Z.; Zhou A. Ti3C2 MXene-Based Sensors with High Selectivity for NH3 Detection at Room Temperature. ACS Sens. 2019, 4, 2763–2770. 10.1021/acssensors.9b01308. [DOI] [PubMed] [Google Scholar]
  26. Kim S. J.; Koh H.-J.; Ren C. E.; Kwon O.; Maleski K.; Cho S.-Y.; Anasori B.; Kim C.-K.; Choi Y.-K.; Kim J.; Gogotsi Y.; Jung H.-T. Metallic Ti3C2Tx MXene Gas Sensors with Ultrahigh Signal-to-Noise Ratio. ACS Nano 2018, 12, 986–993. 10.1021/acsnano.7b07460. [DOI] [PubMed] [Google Scholar]
  27. Kresse G.; Furthmüller J. Efficient Iterative Schemes for Ab Initio Total-Energy Calculations Using a Plane-Wave Basis Set. Phys. Rev. B 1996, 54, 11169–11186. 10.1103/PhysRevB.54.11169. [DOI] [PubMed] [Google Scholar]
  28. Kresse G.; Joubert D. From Ultrasoft Pseudopotentials to the Projector Augmented-Wave Method. Phys. Rev. B 1999, 59, 1758–1775. 10.1103/PhysRevB.59.1758. [DOI] [Google Scholar]
  29. Grimme S.; Antony J.; Ehrlich S.; Krieg H. A Consistent and Accurate Ab Initio Parametrization of Density Functional Dispersion Correction (DFT-D) for the 94 Elements H-Pu. J. Chem. Phys. 2010, 132, 154104 10.1063/1.3382344. [DOI] [PubMed] [Google Scholar]
  30. Taylor J.; Guo H.; Wang J. Ab Initio Modeling of Quantum Transport Properties of Molecular Electronic Devices. Phys. Rev. B 2001, 63, 245407 10.1103/PhysRevB.63.245407. [DOI] [Google Scholar]
  31. Büttiker M.; Imry Y.; Landauer R.; Pinhas S. Generalized Many-Channel Conductance Formula with Application to Small Rings. Phys. Rev. B 1985, 31, 6207–6215. 10.1103/PhysRevB.31.6207. [DOI] [PubMed] [Google Scholar]
  32. Ayesh A. I.; Abu-Hani A. F. S.; Mahmoud S. T.; Haik Y. Selective H2S Sensor Based on CuO Nanoparticles Embedded in Organic Membranes. Sens. Actuators, B 2016, 231, 593–600. 10.1016/j.snb.2016.03.078. [DOI] [Google Scholar]
  33. Tang Q.; Zhou Z.; Shen P. Are MXenes Promising Anode Materials for Li Ion Batteries? Computational Studies on Electronic Properties and Li Storage Capability of Ti3C2 and Ti3C2X2 (X = F, OH) Monolayer. J. Am. Chem. Soc. 2012, 134, 16909–16916. 10.1021/ja308463r. [DOI] [PubMed] [Google Scholar]
  34. Li L. Lattice Dynamics and Electronic Structures of Ti3C2O2 and Mo2TiC2O2 (MXenes): The Effect of Mo Substitution. Comput. Mater. Sci. 2016, 124, 8–14. 10.1016/j.commatsci.2016.07.008. [DOI] [Google Scholar]
  35. Jayan R.; Islam M. M. Functionalized MXenes as Effective Polyselenide Immobilizers for Lithium–Selenium Batteries: A Density Functional Theory (DFT) Study. Nanoscale 2020, 12, 14087–14095. 10.1039/D0NR02296A. [DOI] [PubMed] [Google Scholar]
  36. Abdulkader Tawfik S.; Cui X. Y.; Carter D. J.; Ringer S. P.; Stampfl C. Sensing Sulfur-Containing Gases Using Titanium and Tin Decorated Zigzag Graphene Nanoribbons from First-Principles. Phys. Chem. Chem. Phys. 2015, 17, 6925–6932. 10.1039/C4CP05919K. [DOI] [PubMed] [Google Scholar]
  37. He C.; Zhang M.; Li T. T.; Zhang W. X. Electric Field-Modulated High Sensitivity and Selectivity for NH3 on α-C2N2 Nanosheet: Insights from DFT Calculations. Appl. Surf. Sci. 2020, 505, 144619 10.1016/j.apsusc.2019.144619. [DOI] [Google Scholar]
  38. Ma S.; Yuan D.; Jiao Z.; Wang T.; Dai X. Monolayer Sc2CO2: A Promising Candidate as a SO2 Gas Sensor or Capturer. J. Phys. Chem. C 2017, 121, 24077–24084. 10.1021/acs.jpcc.7b07921. [DOI] [Google Scholar]
  39. Guo H.; Zhang W.; Lu N.; Zhuo Z.; Zeng X. C.; Wu X.; Yang J. CO2 Capture on h-BN Sheet with High Selectivity Controlled by External Electric Field. J. Phys. Chem. C 2015, 119, 6912–6917. 10.1021/acs.jpcc.5b00681. [DOI] [Google Scholar]
  40. Yu X.; Li Y.; Cheng J.; Liu Z.; Li Q.; Li W.; Yang X.; Xiao B. Monolayer Ti2CO2 : A Promising Candidate for NH3 Sensor or Capturer with High Sensitivity and Selectivity. ACS Appl. Mater. Interfaces 2015, 7, 13707–13713. 10.1021/acsami.5b03737. [DOI] [PubMed] [Google Scholar]
  41. Wu Y.; Chen X.; Weng K.; Arramel; Jiang J.; Ong W.; Zhang P.; Zhao X.; Li N. Highly Sensitive and Selective Gas Sensor Using Heteroatom Doping Graphdiyne: A DFT Study. Adv. Electron. Mater. 2021, 7, 2001244 10.1002/aelm.202001244. [DOI] [Google Scholar]
  42. Tang S.; Cao Z. Adsorption of Nitrogen Oxides on Graphene and Graphene Oxides: Insights from Density Functional Calculations. J. Chem. Phys. 2011, 134, 044710 10.1063/1.3541249. [DOI] [PubMed] [Google Scholar]
  43. Li L. Effects of the Interlayer Interaction and Electric Field on the Band Gap of Polar Bilayers: A Case Study of Sc2CO2. J. Phys. Chem. C 2016, 120, 24857–24865. 10.1021/acs.jpcc.6b08300. [DOI] [Google Scholar]

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

ao2c07492_si_001.pdf (423.4KB, pdf)

Articles from ACS Omega are provided here courtesy of American Chemical Society

RESOURCES