3D micro-combs self-assembled from 2D N-doped In2S3 for room-temperature reversible NO2 gas sensing

Two-dimensional (2D) metal sulfides have been an emerging material group for high-performance and power-saving gas sensing. However, relatively little attention is paid to developing doping-driven approaches to improve their gas interaction properties, particularly at room temperature. In this work, we realize room-temperature reversible NO2 gas sensing by utilizing the three-dimensional (3D) micro-combs self-assembled from 2D N-doped In2S3. Specifically, hydrothermal synthesized In2S3 microspheres as the initial material are exfoliated down to 2D single-unit-cell-thick (∼3 nm) nanoflakes in the presence of ultrasonic force, while the N dopants are inserted into the crystal lattices simultaneously. The N dopants significantly modify the electronic band structure of In2S3 to facilitate the hybridization with NO2 molecular orbitals, induce an n- to p-type transition, decrease the surface activation energy, and activate the strong excitonic interaction property. The 3D N-doped In2S3 micro-combs exhibit a response magnitude of 15% for 10 ppm NO2 at room temperature with complete recovery, high selectivity, and excellent repeatability, while incorporating blue light excitation further increases the response magnitude and shortens the response/recovery time, which are rarely seen in 2D metal sulfides. This work demonstrates the possibility of implementing 2D doped metal sulfides and their derivatives for high-performance room temperature gas sensors.