Room-temperature High-performance Gas Sensors Based on Grafting of Functional Groups on MXene

Project: Research

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Air pollution from emissions of hazardous gases has been one of the most crucial problems that human beings are facing. NO2 and volatile organic compounds such as benzene, toluene, ethanol, and formaldehyde are major pollutants. They often participate in photochemical reaction, yielding toxic products, which is currently a main challenge to public health and environmental preservation. Therefore, to effectively monitor air pollution, advanced sensors that can analyze environmental gases are indispensable in modern society, especially in heavily urbanized areas such as Hong Kong and many parts of China.A variety of gas sensor types have been reported in the last decade including cantilever, thermoelectric, acoustic, bioluminescent, chemiresistive, polymer-based and chemical field effect transistor gas sensors. Amongst the various types, chemiresistive gas sensors, whose resistance changes upon exposure to targeting gases, have attracted great attention due to their high sensitivity, short response time, and ease of fabrication. Oxide semiconductors have been widely employed as the sensing materials in chemiresistive sensors. However, as is well-known, oxide gas sensors typically need high working temperatures to achieve high sensitivity, which requires extra circuits for heating. The heating process not only leads to additional high power consumption and system complexity, but also results in aggregation and coarsening of grains in the sensing material, which adversely causes long-term signal drift.In this project, we propose an investigation based on the engineering of functional groups through plasma treatment of MXene, for enhanced hazardous gas sensing performance. The target gases are primarily NO2 and VOCs, released mainly from the burning of fossil fuel such as vehicle emission and industrial processes. We propose to design, fabricate, and experimentally characterize various MXenes with a layered structure for maximal gas sensing surface area. We will graft various suitable functional groups on the surface of MXene for enhancement in gas sensing. Then, we will assemble sensors based on various architectures and process parameters. Experimental verification and performance assessment will be performed both in the lab and practical environments with common gas pollutants. We will gain suitable field-test locations via partnering with industry and registered architects. Quantitative analysis and modelling of the gas sensing mechanism will be formulated into a design methodology, forming the basis for subsequent developments.The proposed functional group engineering approach stands out as an innovative and highly advantageous method for tuning MXene sensing properties. Firstly, surface functional groups on MXene, e.g. -O, and -OH, provide sites for selective absorption of the target gas, as well as expanding the MXene nanosheet interlayer space, thus leading to tunable sensing properties. Secondly, the use of plasma treatment for the grafting of function groups open doors to a gentle route that does not degrade the material, which preserves the inherent merits of MXene, e.g., its layered structure and high conductivity. Thirdly, the use of plasma is highly controllable, i.e. the working atmosphere (O2, H2, N2, and Ar), pressure, power, and irradiation duration are all parameters that can be readily tuned.The successful completion of the project will lead to an effective approach to developing gas sensor based on MXene and other layered materials that are highly selective towards specific target gases, sensitivity, fast, and recovers well. Most importantly, the ability to operate at room temperature will eliminate the power consumption and system complexity associated with heating. The high performance achievable will give rise to advanced products and new applications in environmental protection and healthcare.   


Project number9043348
Grant typeGRF
Effective start/end date1/01/23 → …