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Progress in Chemistry 2021, Vol. 33 Issue (2): 232-242 DOI: 10.7536/PC200506 Previous Articles   Next Articles

• Review •

Application for Exhaled Gas Sensor Based on Novel Mxenes Materials*

Jixiu Zhu1, Qiaofen Chen2, Titong Ni1, Aimin Chen1,*(), Jianmin Wu2,*()   

  1. 1 College of Chemical Engineering, Zhejiang University of Technology,Hangzhou 310014, China
    2 Institute of Analytical Chemistry, Department of Chemistry, Zhejiang University, Hangzhou 310058, China
  • Received: Revised: Online: Published:
  • Contact: Aimin Chen, Jianmin Wu
  • About author:
    * Corresponding author e-mail: (Aimin Chen);
    (Jinmin Wu)
  • Supported by:
    National Natural Science Foundation of China(21575127); Natural Science Foundation of Zhejiang Province(LY19B050004)
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In order to detect, analyze, and identify exhaled gas, electronic-nose combined with artificial intelligence has become a hot spot in the field of non-invasive medical detection. However, gas sensing materials cannot meet the requirements of high sensitivity as well as high selectivity at room temperature, which seriously hinders the application of gas sensors in the field of health care. It is still challenging to find suitable materials for the electronic-nose. With many unique properties: a wide variety, large specific surface area, strong electrical conductivity, rich functional groups on the surface, and adjustable bandwidth, novel two-dimensional MXenes material has become a star candidate for the gas sensor of highly sensitive and low energy consumption. In this review, we summarize the latest research achievements of MXenes based materials with the special structure in gas sensing, focus on the gas sensing mechanism and modification methods, and probe into the problems and challenges still existing in the application of MXenes materials in gas sensing.

Contents

1 Introduction

2 Synthesis of MXenes

3 Structure and properties of MXenes

3.1 Structure of MXenes

3.2 MXenes electronic characteristics for gas sensing

4 Application of MXenes in gas sensing

4.1 Surface adsorption calculation of MXenes

4.2 Gas sensing performance of MXenes

4.3 Gas sensing mechanism of MXenes

5 Conclusion and outlook

Key words: MXenes, gas sensor, gas adsorption, gas sensing mechanism
Fig.1 Schematic crystal structures and electron microscopy images for MXenes.(a) Schematic illustrating evolution from MAX phases to MXenes;(b~d) SEM images of Ti2CTx, Ti3C2Tx and Ta4C3Tx[49]
Table 1 The preparation reaction conditions of HF etched MXenes were partly based on HF etched MXenes
Precursor type Composition Etching method MXene ref
M2AX
211 		Ti2AlC 10% conc.-10 h-RT Ti2CTx 49
V2AlC 50% conc.-90 h-RT V2CTx 53
Nb2AlC 50% conc.-90 h-RT Nb2CTx 53
M3AX2
312 		Ti3AlC2 50% conc.-2 h-RT Ti3C2Tx 48
Ti3SiC2 HF 30% conc. + H2O2 35% conc.-45 h-40 ℃ Ti3C2Tx 62
Ti3AlCN 30% conc.-18 h-RT Ti3CNTx 49
M4AX3
413 		V4AlC3 40% conc.-165 h-RT V4C3Tx 54
Nb4AlC3 49% conc.-140 h-RT Nb4C3Tx 55
Ta4AlC3 50% conc.-72 h-RT Ta4C3Tx 49
Fig.2 Side views of pristine(a) M3X2,(b) M4X3,(c) M'2M″X2, and(d) M'2M″2X3 MXenes, where M, M', and M″ denote transition metals, and X represents C or N[71]
Table 2 Bandgap width for some MXenes
MXene Bandgap(eV) ref
Hf3C2O2 0.16 77
Ti2CO2 0.24 78
Sc2T2(OH)2 0.45 78
Cr2TiC2(OH)2 0.84 79
Zr2CO2 0.88 78
Hf2CO2 1.0 78
Sc2T2F2 1.03 78
Cr2TiC2F2 1.35 79
Cr2C(OH)2 1.43 80
Sc2T2O2 1.8 78
Cr2CF2 3.49 80
Fig.3 (a) Adsorption sites of different gases on Ti2CO2 MXene[81];(b) charge adsorbed density distribution[81];(c) predicted I-V characteristics of Ti2CO2 with NH3 and CO2 molecules[81];(d) predicted I-V characteristics of Sc2CO2 with SO2 molecules[83]
Fig.4 (a) A gas sensor made from Ti3C2Tx drop-cast on an interdigitated circuit[88];(b) Maximal SNR values of sensors upon exposure to 100 ppm of acetone, ethanol, ammonia, and propanal[89];(c) Maximal resistance change upon exposure to 100 ppm of acetone, ethanol, ammonia, propanal, NO2, SO2, and 10 000 ppm of CO2 at room temperature(25 ℃)[89];(d) Resistance variation versus time upon exposure to highly diluted acetone(top), ethanol(middle), and ammonia(bottom) in ppb concentration range(50~1000 ppb)[89]
Table 3 Gas sensing performance of MXene-based gas sensor
Material Gas species LOD Response
((Rg-Ra/Ra)% 		Temperature ref
Ti3C2Tx MXene ammonia 100 ppb 0.1% RT 89
ethanol 100 ppb 0.25%
acetone 50 ppb 0.15%
3D Ti3C2Tx MXene acetone 50 ppb 0.08% RT 97
V2CTx MXene hydrogen 2 ppm 0.04% RT 90
TiO2/Ti3C2Tx ammonia 0.5 ppm 1% 25 ℃ 93
Single-Layer Ti3C2Tx MXene(NaF +HCl etched) ammonia 10 ppm 0.8% 25 ℃ 99
W18O49/Ti3C2Tx acetone 170 ppb 1.6(Ra/Rg) 300 ℃ 92
Alkalized organ-like Ti3C2Tx MXene ammonia 10 ppm — RT 100
V4C3Tx MXene acetone 1 ppm — 25 ℃ 91
Ti3C2Tx/WSe2 hybrids
(n-type sensing behavior) 		ethanol 1 ppm — RT 94
Fe2(MoO4)3/MXene composite n-butanol 5 ppm — 120 ℃ 101
Fig.5 (a) Real-time sensing response of Ti3C2Tx and Ti3C2Tx/WSe2 gas sensors upon ethanol exposure with concentrations ranging from 1 to 40 ppm[94];(b) Enhanced sensing mechanism of Ti3C2Tx/WSe2 heterostructure[94];(c) A multielectrode chip with a film of partially oxidized MXenes flakes prepared by drop-casting[95];(d) LDA diagram of partially oxidized MXenes sensor[95]
Fig.6 (a) Schematic illustration of the spinning process for MXene/GO hybrid fiber;(b) The resistance change of MXene/rGO hybrid fiber exposed to 100 ppm of NH3 at room temperature during fiber cyclic bending;(c) MXene/rGO hybrid fibers were woven in a lab coat and connected to a multimeter;(d) Gas response of 100 ppm of NH3 molecules in MXene/rGO hybrid fibers woven into a lab coat[98]
Fig.7 (a) Minimum binding energies of acetone and ammonia on Ti3C2(OH)2, Ti3C2O2, Ti3C2F2, graphene, MoS2, and BP[89];(b) The(002) peak shift of Ti3C2Tx film during introduction of ethanol(0.1%) for 70 min, followed by N2 purging for 120 min to purge out target gases[106]
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