Te@Se Core–Shell Heterostructures with Tunable Shell Thickness for Ultra-Stable NO2 Detection

An effective long-term nitrogen dioxide (NO₂) monitoring at trace concentration is critical for protecting the ecological environment and public health. Tellurium (Te), as a recently discovered 2D elemental material, is promising for NO₂ detection because of its suitable band structure for gas adsorption and charge mobility. However, the high activity of Te leads to poor stability in ambient and harsh conditions, limiting its application as a gas-sensitive material. Herein, 2D single-elemental Te@Se heterostructures with a core–shell structure are prepared using a solvothermal method. The Te@Se heterostructures demonstrate an extremely high response of 622% to 1 ppm of NO₂ at room temperature, with ultrafast response/recovery times of 10 s/30 s. Moreover, the core–shell heterostructures exhibit excellent stability in NO₂ sensing performance over a period of 90 days. The success relies on the ultrathin Se shell with a thickness of 4–6 nm on Te, which enables the efficient redistribution and transport of interfacial charges. These findings reveal the potential of single-element core–shell heterojunctions to achieve high-performance gas sensing, paving the way for advancements in NO₂ detection materials.