Stepless IR Chromism in Ti<sub>3</sub> C<sub>2</sub> T<sub>x</sub> MXene Tuned by Interlayer Water Molecules.

Li, Keqiao; Lin, Chongjia; Liu, Gongze; Wang, Guang; Ma, Wei; Li, Meng; Li, Yang; Huang, Baoling · Adv Mater · 2024

basic_science · Level V

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Abstract

Real-time control over infrared (IR) radiation of objects is highly desired in a variety of areas such as personal thermal regulation and IR camouflage. This requires the dynamic modulation of IR emissivity in a stepless manner over a wide range (>50%), which remains a daunting challenge. Here, an emissivity modulation phenomenon is reported in stacked 2D Ti<sub>3</sub> C<sub>2</sub> T<sub>x</sub> MXene nanosheets, from 12% to 68% as the intercalation/discharging of water molecules within the interlayers. The intercalation of water molecules dynamically changes the electronic properties and the complex permittivity in IR frequencies of Ti<sub>3</sub> C<sub>2</sub> T<sub>x</sub> . This emissivity modulation is a stepless and reversible process without the assistance of any external energy input. Further, intercalating cellulose nanofibers into the Ti<sub>3</sub> C<sub>2</sub> T<sub>x</sub> interlayers makes this dynamic process highly repeatable. Last, a sweat-responsive adaptive textile that can improve thermal comfort of human body under changes in metabolic rates and environmental conditions is demonstrated, showing great potential of this mechanism in passive on-demand radiation modulation.