Selective CO gas sensing by Au-decorated WS2-SnO2 core-shell nanosheets on flexible substrates in self-heating mode

The effect of shell thickness and noble metal decoration on the gas-sensing characteristics of two-dimensional (2D) materials has not been reported yet. Herein, we synthesized 2D pristine and Au-decorated WS2-SnO2 core-shell nanosheets (Au NSs). SnO2 shells with various thicknesses (up to 60 nm) were deposited on the WS2 NSs. Subsequently, Au was deposited on the synthesized WS2-SnO2 core-shell NSs (WS2-SnO2 NSs) under UV irradiation. Flexible polyamide substrates were used to fabricate gas sensors, which operated in self-heating mode upon applying different voltages for CO detection. Bare and Au-decorated gas sensors with shell thicknesses of 15 and 30 nm revealed the highest CO sensing performance at a low voltage of 3.4 V. The flexibility of the gas sensors was demonstrated by the negligible degradation of the sensing performance after 10,000 bending cycles. We also evaluated the sensing characteristics under humid conditions. The developed gas sensors with very low applied voltage and high performance for CO gas sensing are very promising for commercial applications.