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ACS Sens

Title:		N-p-Conductor Transition of Gas Sensing Behaviors in Mo(2)CT(x) MXene
Author(s):		Choi J; Chacon B; Park H; Hantanasirisakul K; Kim T; Shevchuk K; Lee J; Kang H; Cho SY; Kim J; Gogotsi Y; Kim SJ; Jung HT;
Address:		"Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology, 291, Daehak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea. A. J. Drexel Nanomaterials Institute and Department of Materials Science and Engineering, Drexel University, Philadelphia PA 19104, United States. Materials Architecturing Research Center, Korea Institute of Science and Technology, 5, Hwarang-ro 14-gil, Seongbuk-gu, Seoul 02792, Republic of Korea. Department of Materials Science and Engineering, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 02841, Republic of Korea. School of Chemical Engineering, Sungkyunkwan University, 2066 Seobu-ro, Suwon 16419, Republic of Korea. Division of Nanoscience and Technology, KIST School, University of Science and Technology, 5, Hwarang-ro 14-gil, Seongbuk-gu, Seoul 02792, Republic of Korea. Materials Architecturing Research Center and Convergence Research Center for Solutions to Electromagnetic Interference for Future-Mobility, Korea Institute of Science and Technology, 5, Hwarang-ro 14-gil, Seongbuk-gu, Seoul 02792, Republic of Korea"
Journal Title:		ACS Sens
Year:		2022
Volume:		20220715
Issue:		8
Page Number:		2225 - 2234
DOI:		10.1021/acssensors.2c00658
ISSN/ISBN:		2379-3694 (Electronic) 2379-3694 (Linking)
Abstract:		"It is highly important to implement various semiconducting, such as n- or p-type, or conducting types of sensing behaviors to maximize the selectivity of gas sensors. To achieve this, researchers so far have utilized the n-p (or p-n) two-phase transition using doping techniques, where the addition of an extra transition phase provides the potential to greatly increase the sensing performance. Here, we report for the first time on an n-p-conductor three-phase transition of gas sensing behavior using Mo(2)CT(x) MXene, where the presence of organic intercalants and film thickness play a critical role. We found that 5-nm-thick Mo(2)CT(x) films with a tetramethylammonium hydroxide (TMAOH) intercalant displayed a p-type gas sensing response, while the films without the intercalant displayed a clear n-type response. Additionally, Mo(2)CT(x) films with thicknesses over 700 nm exhibited a conductor-type response, unlike the thinner films. It is expected that the three-phase transition was possible due to the unique and simultaneous presence of the intrinsic metallic conductivity and the high-density of surface functional groups of the MXene. We demonstrate that the gas response of Mo(2)CT(x) films containing tetramethylammonium (TMA) ions toward volatile organic compounds (VOCs), NH(3), and NO(2) is approximately 30 times higher than that of deintercalated films, further showing the influence of intercalants on sensing performance. Also, DFT calculations show that the adsorption energy of NH(3) and NO(2) on Mo(2)CT(x) shifts from -0.973, -1.838 eV to -1.305, -2.750 eV, respectively, after TMA adsorption, demonstrating the influence of TMA in enhancing sensing performance"
Keywords:		2D materials MXene Mo2CTx conductivity gas sensors;
Notes:		"PubMed-not-MEDLINEChoi, Junghoon Chacon, Benjamin Park, Hyunsoo Hantanasirisakul, Kanit Kim, Taewoo Shevchuk, Kateryna Lee, Juyun Kang, Hohyung Cho, Soo-Yeon Kim, Jihan Gogotsi, Yury Kim, Seon Joon Jung, Hee-Tae eng 2022/07/16 ACS Sens. 2022 Aug 26; 7(8):2225-2234. doi: 10.1021/acssensors.2c00658. Epub 2022 Jul 15"