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Layer-Dependent Gas Sensing Mechanism of 2D Titanium Carbide (Ti3C2Tx) MXene
ACS Nano ( IF 15.8 ) Pub Date : 2024-09-13 , DOI: 10.1021/acsnano.4c08225 Michael J Loes 1 , Saman Bagheri 1 , Alexander Sinitskii 1
ACS Nano ( IF 15.8 ) Pub Date : 2024-09-13 , DOI: 10.1021/acsnano.4c08225 Michael J Loes 1 , Saman Bagheri 1 , Alexander Sinitskii 1
Affiliation
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Monolayers of Ti3C2Tx MXene and bilayer structures formed by partially overlapping monolayer flakes exhibit opposite sensing responses to a large scope of molecular analytes. When exposed to reducing analytes, monolayer MXene flakes show increased electrical conductivity, i.e., an n-type behavior, while bilayer structures become less conductive, exhibiting a p-type behavior. On the contrary, both monolayers and bilayers show unidirectional sensing responses with increased resistivity when exposed to oxidizing analytes. The sensing responses of Ti3C2Tx monolayers and bilayers are dominated by entirely different mechanisms. The sensing behavior of MXene monolayers is dictated by the charge transfer from adsorbed molecules and the response direction is consistent with the donor/acceptor properties of the analyte and the intrinsic n-type character of Ti3C2Tx. In contrast, the bilayer MXene structures always show the same response regardless of the donor/acceptor character of the analyte, and the resistivity always increases because of the intercalation of molecules between the Ti3C2Tx layers. This study explains the sensing behavior of bulk MXene sensors based on multiflake assemblies, in which this intercalation mechanism results in universal increase in resistance that for many analytes is seemingly inconsistent with the n-type character of the material. By scaling MXene sensors down from multiflake to single-flake level, we disentangled the charge transfer and intercalation effects and unraveled their contributions. In particular, we show that the charge transfer has a much faster kinetics than the intercalation process. Finally, we demonstrate that the layer-dependent gas sensing properties of MXenes can be employed for the design of sensor devices with enhanced molecular recognition.
中文翻译：
二维碳化钛 (Ti3C2TX) MXene 的层相关气体传感机制
Ti 3 C 2 T x MXene 的单层和由部分重叠的单层薄片形成的双层结构对大范围的分子分析物表现出相反的传感响应。当暴露于还原性分析物时，单层 MXene 薄片表现出更高的电导率，即 n 型行为，而双层结构的导电性变得较低，表现出 p 型行为。相反，当暴露于氧化分析物时，单层和双层都表现出单向传感响应，电阻率增加。 Ti 3 C 2 T x单层和双层的传感响应由完全不同的机制主导。 MXene 单层的传感行为由吸附分子的电荷转移决定，响应方向与分析物的供体/受体特性以及 Ti 3 C 2 T x的固有 n 型特征一致。相比之下，无论分析物的供体/受体特性如何，双层MXene结构总是表现出相同的响应，并且由于Ti 3 C 2 T x层之间分子的插入，电阻率总是增加。这项研究解释了基于多层组件的块状 MXene 传感器的传感行为，其中这种插入机制导致电阻普遍增加，对于许多分析物来说，这似乎与材料的 n 型特性不一致。 通过将 MXene 传感器从多层缩小到单层，我们解开了电荷转移和嵌入效应，并揭示了它们的贡献。特别是，我们表明电荷转移的动力学比嵌入过程快得多。最后，我们证明了 MXene 的层相关气体传感特性可用于设计具有增强分子识别功能的传感器设备。
更新日期：2024-09-13
中文翻译：
二维碳化钛 (Ti3C2TX) MXene 的层相关气体传感机制
Ti 3 C 2 T x MXene 的单层和由部分重叠的单层薄片形成的双层结构对大范围的分子分析物表现出相反的传感响应。当暴露于还原性分析物时，单层 MXene 薄片表现出更高的电导率，即 n 型行为，而双层结构的导电性变得较低，表现出 p 型行为。相反，当暴露于氧化分析物时，单层和双层都表现出单向传感响应，电阻率增加。 Ti 3 C 2 T x单层和双层的传感响应由完全不同的机制主导。 MXene 单层的传感行为由吸附分子的电荷转移决定，响应方向与分析物的供体/受体特性以及 Ti 3 C 2 T x的固有 n 型特征一致。相比之下，无论分析物的供体/受体特性如何，双层MXene结构总是表现出相同的响应，并且由于Ti 3 C 2 T x层之间分子的插入，电阻率总是增加。这项研究解释了基于多层组件的块状 MXene 传感器的传感行为，其中这种插入机制导致电阻普遍增加，对于许多分析物来说，这似乎与材料的 n 型特性不一致。 通过将 MXene 传感器从多层缩小到单层，我们解开了电荷转移和嵌入效应，并揭示了它们的贡献。特别是，我们表明电荷转移的动力学比嵌入过程快得多。最后，我们证明了 MXene 的层相关气体传感特性可用于设计具有增强分子识别功能的传感器设备。
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