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摘要: 随着柔性电子学的快速发展,有望实现具有高灵敏度和宽检测范围的柔性传感器。近年来,二维层状过渡金属碳氮材料MXene由于具有高导电性、高比表面积、优异的亲水性及良好的机械性能等特点,且能够与包括炭材料(碳纳米管、炭纤维、石墨烯等)在内的多种材料形成性能优异的复合材料,在柔性传感器领域受到众多研究者们的关注。本综述首先介绍MXene材料的结构、合成等内容,随后总结MXene柔性传感器的结构、性能指标和常用制备工艺。在此基础上,回顾了多种MXene柔性传感器,详细介绍其传感机制和制备技术。最后,总结MXene材料用于柔性传感器的研究趋势。Abstract: The rapid development of flexible electronics has made it possible to realize flexible sensors with high sensitivity and a wide detection range. In recent years, the two-dimensional MXene layer materials composed of transition metals, carbon and/or nitrogen have attracted the attention of many researchers in the field of flexible sensors, because of their high conductivity, high specific surface area, outstanding hydrophilicity, excellent mechanical properties and other characteristics. They can be composited with other materials, such as carbon nanotubes, carbon fibers and graphene, to form a variety of materials. Here, the structure and synthesis of MXene materials are introduced, followed by a summary of their preparation methods, structures, performance and sensing mechanisms as flexible sensors. Finally, research trends for flexible sensors using MXene materials are discussed.
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Key words:
- MXene /
- Flexible sensor /
- Composite materials /
- Sensor performance
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图 3 通过改变外部过渡金属M层元素改变MXene电学性质[41]:(a)Mo2TiC2Tx(红色)、Mo2Ti2C3Tx(蓝色)和Ti3C2Tx(黑色)的电阻率随温度的变化,(b)电阻率比较结果,电阻率曲线下面的彩色三角形(红色和黑色)说明了dρ/dT的差异
Figure 3. The electrical properties of MXene changed by changing the external transition metal M layer elements [41]: (a) Temperature dependence of resistivity for a Mo2TiC2Tx (red), Mo2Ti2C3Tx (blue), and Ti3C2Tx (black). (b) Comparison of resistivity. The colored triangles (red and black) below each resistivity curve illustrate the differences in dρ/dT. Reprinted with permission.
图 5 MXene薄膜的机械强度[47]:(a)不同Ti3C2Tx含量的Ti3C2Tx/PVA混合薄膜的应力应变曲线,(b)Ti3C2Tx薄膜制成的圆柱体支撑起自身重量4000倍的重量,(c)90%含量的Ti3C2Tx/PVA混合薄膜制成的圆柱体支撑起自身重量15000倍的重物
Figure 5. Mechanical strength of MXene films [47]: (a) Stress–strain curves for Ti3C2Tx/PVA films with different Ti3C2Tx contents. (b) The cylinder made from Ti3C2Tx films can support 4000 times its own weight. (c) The cylinder made from 90% Ti3C2Tx/PVA can support 15000 times its own weight. Reprinted with permission.
图 9 MXene/PANIF柔性传感器用于应变检测[75]:(a-f) MXene/PANIF应变传感器检测喉部发声、扬声器声波手腕处脉搏、皱眉、手指弯曲及肘部弯曲,(g)无线传输示意图:通过与手机的无线通信实现的遥感性能,(h)在手机上获得的检测10%应变的感测性能
Figure 9. Strain measurement of the MXene/PANIF flexible sensor [75]: (a-f) The MXene/PANIF strain sensor detects throat during speaking, sound waves of the loudspeaker, human wrist pulse, frowning, finger bending and elbow bending. (g) The concept of wireless transmission: remote sensing performance by wireless communication to the mobile phone. (h) The sensing performance obtained on the mobile phone for detecting 10% strain. Reprinted with permission.
图 10 Ti3C2Tx/PDMS 柔性传感器用于距离检测和温度检测[86]:(a)手指与Ti3C2Tx膜之间的不同距离使温度传感器的电阻发生变化,(b)温度传感器的可重复性,循环三次接近至0.3 cm,(c)随着装有冰、温水和热水的小瓶的接近,温度传感器的电阻变化,(d)使用不同功率的红外激光持续照射温度传感器得到的电阻变化
Figure 10. Distance and temperature measurement of Ti3C2Tx/PDMS flexible sensor [86]: (a) Resistance variation of the temperature sensor at different distances between the finger and the Ti3C2Tx film. (b) The repeatability of the proximity temperature sensor for 0.3 cm with 3 circles. (c) Resistance variation of the temperature sensor with the approach of vials containing ice, warm and hot water. (d) Resistance variation of the temperature sensor using infrared lasers with different powers. Reprinted with permission.
图 11 MXene-PDMAEMA薄膜(绿色)和原始MXene薄膜(橙色)以及MXene-PDMAEMA悬浮液的电导率随温度变化曲线[99]. 蓝色和红色点分别标记了25至40 °C之间的测量温度范围. 测量循环了至少3次,并且每次测量产生的变化的误差相对较小
Figure 11. Conductivity results measured on thin films of hybrid MXene (green) and pristine MXene (orange) as well as a suspension of hybrid MXene (black) [99]. Blue and red dots mark the temperature range for the measurement between 25 and 40 °C, respectively. The measurements have been repeated at least three times, and the resulting variations from measurement to measurement (error bars) are relatively small. Reprinted with permission.
图 12 柔性传感器的汗液监测实验,用于检测pH值、乳酸和葡萄糖浓度[100]:(a)柔性汗液传感器贴片连接到便携式电化学分析仪,该分析仪可供电并控制柔性传感器,并可以通过蓝牙进行无线通信;(b)柔性汗液传感器贴片连接到皮肤上的便携式电化学分析仪;(c)骑行强度变化曲线;(d)用3种不同的葡萄糖传感器在饭前和饭后测得的葡萄糖传感器的电流响应和pH值变化;(e)pH传感器在运动过程中的不同时间测得的pH值;(f)乳酸传感器在运动过程中的不同时间测得的电流响应;(g)用3种不同的葡萄糖和pH传感器比较饭前和饭后的葡萄糖浓度和pH值;(h)使用3种不同的pH传感器比较运动过程中不同时间的pH值;(i)使用3种不同的乳酸传感器比较运动过程中不同时间的乳酸水平
Figure 12. The sweat monitoring of flexible sensor, to detect pH, lactate and glucose concentrations[100]: (a) The flexible sweat-monitoring patch is connected to a portable electrochemical analyzer that supplies power and controls the patch and can wirelessly communicate with commercial mobile phones via Bluetooth. (b) The flexible sweat-monitoring patch is connected to a portable electrochemical analyzer on the skin. (c) Cycling resistance profile for on-body tests. (d) Measured chronoamperometric responses of glucose sensors and pH changes before and after meals with 3 different glucose sensors. (e) Measured pH level of pH sensor at different times during the exercise. (f) Measured chronoamperometric responses of lactate sensor at different times during the exercise. (g) Comparison of glucose and pH levels before and after meals with 3 different glucose and pH sensors. (h) Comparison of pH levels at different times during the exercise with 3 different pH sensors. (i) Comparison of lactate levels at different times during the exercise with lactate sensors. Reprinted with permission.
图 13 V2CTx传感器在室温(23 ℃)下的气敏特性[108]:(a)传感器暴露于不同气体中的电阻变化,(b)传感器对100 ×10−6的氢气、乙醇、丙酮、甲烷、氨气和硫化氢的气体响应,(c-f)V2CTx气体传感器在不同浓度下的氢气、丙酮、甲烷和硫化氢的气体响应
Figure 13. Gas sensing properties of a V2CTx sensor at RT (23 ℃) [108]: (a) The resistance variation of the sensor when exposed to different gases. (b) Gas response toward 100 ppm of hydrogen, ethanol, acetone, methane, ammonia, and hydrogen sulfide. (c-f) Sensing response of V2CTx gas sensors at varying concentrations of hydrogen, acetone, methane and hydrogen sulfide. Reprinted with permission.
图 14 MXene/GO杂化纤维合成及实物展示[109]:(a)MXene/GO杂化纤维的合成示意图,(b)MXene/GO凝胶状纤维从喷头到凝固浴的状态,(c)超过1.2米长的MXene/GO杂化纤维绕成的线轴,(d)MXene/GO杂化纤维(40%MXene)的柔韧性
Figure 14. The synthesis and photograph of MXene/GO hybrid fiber [109]: (a) Schematic illustration of the spinning process for MXene/GO hybrid fibers. (b) Photograph of MXene/GO gel fiber states from the nozzle to the bath. (c) A bobbin of wound MXene/GO hybrid fibers over 1.2 m long. (d) The flexibility and bendability of MXene/GO fiber (40% MXene). Reprinted with permission.
表 1 一些已报道的柔性应变传感器:材料、制备方法和性能
Table 1. Some of the reported flexible strain sensors: materials, production methods and performances.
Materials Substrates Production methods Detection range(%) Sensitive(GF) Ref. MXene/SWCNT PI Layer-by-layer spray 30~130 64.6~772.6 [74] MXene/PANIF Elastic rubber Layer-by-layer spray 0~80 97.6~2369.1 [75] SWCNT PDMS CVD 0~280 0.06~0.82 [76] Graphene Stretchable latex CVD 0~70 0.76~2.55 [77] Graphene PDMS CVD 0~30 35~106 [78] rGO Elastic tape Layer-by-layer adhere 0~82 16.2~150 [79] CB/CMC Paper Dip-coating 0~0.6 4.3 [80] AgNPs XSBR Mix to form film 0~100 0.0025~0.01 [81] VN/CNT \ In situ catalytic aerogel 0~10 135~386 [82] ZnO Nanowire/Polystyrene PDMS Electrospinning 0~50 116 [83] 表 2 一些已报道的柔性温度传感器:材料、制备方法和性能
Table 2. Some of the reported flexible temperature sensors: materials, production methods and performances.
Materials Substrates Production methods Detection range(°C) Sensitivity(%/°C) Ref. MXene PDMS Vacuum filtration 20~140 98600 [86] MXene/graphene PI Ink jet printing 50~100 53.6 μV·°C−1 [87] PEDOT:PSS PDMS Drop-casting 30~55 4.2 [88] Graphene nanowalls PDMS CVD 25~120 0.214 [89] Graphene/P(VDF-TrFE) \ Drop-casting −20~300 2.5 [90] CNT PET Screen printing/gravure printing −40~100 −0.4 [91] Nickel -CNT Flax fabric Dip-coating/electroless deposition 25~45 −2.96 [92] FG/CNT/PDMS PET Screen printing 40~80 2.8 [93] rGO Parylene Spray-coating 22~70 0.83%·K−1 [94] AgNPs Paper Ink jet printing −20~60 0.11 [95] AgNW PI spray-coating 25~60 0.332 [96] NiO nanoparticles PET Drop-casting/laser-induced reductive sintering 25~70 −9.2 [97] 表 3 一些已报道的柔性生物传感器:材料、制备方法和性能
Table 3. Some of the reported flexible biosensors: materials, production methods and performances.
Materials Substrates Production methods Target substance Sensitivity Ref. Enzyme/MXene/CNT/PB CFM Mix to vacuum filtration Glucose/lactic acid/pH value 35.3 μA·mM−1·cm−2(Glucose)
11.4 μA·mM−1·cm−2(Lactic acid)
−70 mV·pH−1(pH value)[100] Enzyme/GO PA Vacuum assisted diffusion/
evaporation depositionLactic acid 71.3%(1~100 mM) [101] Enzyme/Pt-graphite/chitosan PU Screen printing Glucose 105 μA·mM−1·cm−2 [102] Enzyme/SPP-PEDOT:PSS PDMS Spin-coating/
photolithographyDopamine/
ascorbic acid/
glucose113 nA·μM−1·cm−2(Dopamine)
25 nA·μM−1·cm−2(Ascorbic acid)
5.06 μA·mM−1·cm−2(Glucose)[103] Antibody/PEDOT:PSS Fibroin Spin-coating/photolithography Vascular endothelial growth factor 11.84%±4.44%(0.1~1 ng·ml−1) [104] MoS2 Al foil Hydrothermal method Uric Acid 98.1±1 μA·μM−1 [105] PtCo alloy nanoparticles/
nanoporous goldGraphene paper Electrodeposition Glucose 7.84 μA·mM−1·cm−2 [106] Note: M—mol L−1 表 4 一些已报道的柔性气体传感器:材料、制备方法和性能
Table 4. Some of the reported flexible gas sensors: materials, production methods and performances.
Materials Substrates Production methods Target gas Detection range (×10−6) Sensitivity Ref. MXene PI Drop-casting H2 2~100 0.2435(100×10−6, 23 °C) [108] MXene/rGO \ Wet spinning NH3 10~50 0.0677(50×10−6,23 °C) [109] CNT Paper Ink jet printing NO2/Cl2 10~100 0.35(10×10−6, NO2)
0.16(10×10−6, Cl2)[110] Graphene PET CVD NO2 \ 0.2276(200×10−6, 23 °C) [111] MoS2/Graphene \ Wet spinning/
hydrothermal methodNO2/NH3 2~1000 \ [112] Graphene/PEDOT:PSS Flexible transparent film Ink jet printing NH3 25~1000 0.096(500×10−6, 23 °C) [113] PANI PET In situ polymerization NH3 5~1000 0.3(200×10−6, 23 °C) [114] PANI/FWMCNT PET In situ polymerization/
depositionNH3 1~100 0.24(100×10−6, 23 °C) [115] Flower-like palladium nanoclusters/graphene PEN Electrodeposition H2 0.1~100 0.05(10×10−6, 23 °C) [116] SnO PI Ink jet printing CO/CO2 1~50(CO)
0.6~20(CO2)1.8(20×10−6, 300 °C)
35(20×10−6, 300 °C)[117] ZnO PI Themolysis assisted
solution methodEthanol 10~100 3.11(100×10−6, 300 °C) [118] -
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