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In Situ Self-Oxidation of Few-Layered Nb2CTx Nanosheets in Aqueous Solution for Achieving Improved Humidity Sensitivity and Selectivity
journal contributionposted on 2023-09-19, 04:13 authored by Xiong Yu, Hao Li, Min Li, Xiaoyan Wen, Shuo Deng, Sisi Liu, Ming-Yu Li, Haifei Lu
MXenes with numerous superior properties have great potential for portable and conformal humidity sensing, which can meet the ever-increasing requirements for noncontact medical diagnosis, noninvasive epidermal detection, and environmental monitoring. Due to the ambiguous mechanism, the absence of an efficient approach for improving the sensitivity and selectivity remains a big obstacle for realization of MXene-based humidity sensing. In this work, the evolution of humidity sensing mechanisms of few-layered Nb2CTx nanosheets before and after self-oxidation in aqueous solutions are clarified depending on a systematic comparison. The evolution of structure and chemical bonds in few-layered Nb2CTx nanosheets after different incubation durations has been investigated to understand the in situ self-oxidation process and establish the relationship between the oxidation degree and humidity sensing performance. Meanwhile, the humidity sensing mechanism of sensors for different few-layered Nb2CTx nanosheets has been also clarified, and the humidity sensitivity has been optimized to −2.3 × 104 with a relative humidity of 53%. Compared with the sensor prepared from as-prepared few-layered Nb2CTx nanosheets, the humidity sensing selectivity from oxidized few-layered Nb2CTx nanosheets has been improved, contributed to by the transformation of the sensing mechanism from electronic conduction to ionic conduction. Finally, the oxidized few-layered Nb2CTx nanosheets have been prepared on a PI substrate to demonstrate its application in a flexible humidity sensor, providing a facile solution for ultrasensitive wearable gas sensing.
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