Quasicrystal Nanosheet/α-Fe₂O₃ Heterostructure-Based Low Power NO₂ Sensors: Experimental and DFT Studies

Industrial emissions, environmental monitoring, and medical fields have put forward huge demands for high-performance and low power consumption sensors. Two-dimensional quasicrystal (2D QC) nanosheets of metallic multicomponent Al₇₀Co₁₀Fe₅Ni₁₀Cu₅ have emerged as a promising material for gas sensors due to their excellent catalytic and electronic properties. Herein, we demonstrate highly sensitive and selective NO₂ sensors developed by low-cost and scalable fabrication techniques using 2D QC nanosheets and α-Fe₂O₃ nanoparticles. The sensitivity (ΔR/R%) of the optimal amount of 2D QC nanosheet-loaded α-Fe₂O₃ sensor was 32%, which is significantly larger about 3.5 times than bare α-Fe₂O₃ sensors for 1 ppm of NO₂ at 150 °C operating temperature. The sensors exhibited p-type conduction, and resistance was reduced when exposed to NO₂, an oxidizing gas. The enhanced sensing characteristics are a result of the formation of nanoheterojunctions between 2D QC and α-Fe₂O₃, which improved the charge transport and provided a large sensing signal. In addition, the heterojunction sensor demonstrated excellent NO₂ selectivity over other oxidizing and reducing gases. Furthermore, density functional theory calculation examines the adsorption energy and charge transfer between NO₂ molecules on the α-Fe₂O₃(110) and QC/α-Fe₂O₃(110) heterostructure surfaces, which coincides well with the experimental results.