1T and 2H mixed phase WS2 nanoflakes decorated with quasicrystal nanosheets for NO2 sensors

Abstract

The development of new nanomaterials is immensely important for real-world sensing applications to improve the sensitivity, selectivity, and stability of the sensors devices. Herein, we explore the gas sensing properties of two-dimensional quasicrystal (2D QC) nanosheets and WS₂ nanoflakes. The decoration of chemically exfoliated QC nanosheets on WS2 nanoflakes significantly enhances their NO₂ sensing performance. This approach allows for detecting target gas molecules with exceptionally high sensitivity. For 20 ppm NO₂ at 125 °C the ΔR/R_a% value for optimal amount of 2D QC nanosheets decorated WS₂ nanoflakes based sensors reaches 52%, which is a 233% higher response than that of bare WS₂ nanoflakes sensors. The increased sensitivity of the 2D QC decorated device is due to the increased carrier concentration in WS₂ caused by the Fermi level alignment and the high affinity of the QC towards NO₂. Furthermore, the density functional theory (DFT) study revealed atomic insight into increasing the gas sensing response due to the presence of transition metals in 2D QCs, drastically enhancing the active sites for NO₂ adsorption; therefore, adsorption energy is boosted manifold compared to the WS₂ monolayer. This experimental and DFT study of NO₂ gas sensors provides detailed insight into gas sensors, and it would be very useful for the design of highly efficient NO₂ gas sensors.