A Highly Selective NO Sensitivity of Slender Nanoribbon WO3 Prepared by Sulfate-Induced Directional Attachment Growth

Nanostructured WO₃ has excellent NO_x gas-sensing properties, but its selectivity still needs to be further improved. By modulating the concentration of adjuvant H₂C₂O₂ in the hydrothermal method, the morphology of the samples can be dramatically changed from microspheres to nanoribbons. The results also show that, for the growth of WO₃ nanoribbons, the concentration of the structural directing agent, K₂SO₄ , is important and sensitive. Next, we propose a mechanism to explain the growth for different nanostructures of WO₃, which should be a sulfate-induced directional attachment growth in a proper chemical environment by adjuvant H₂C₂O₂. The formation of nanoribbons mainly depends on the competition and balance between the reaction environment and the guiding agents. Furthermore, the NO sensing performance of the WO₃ nanoribbons and microspheres have also been systematically investigated. The results showed that WO₃ nanoribbons has a better NO response, which may originate from their ribbons-like morphology and high crystallinity. At the optimal operating temperature of 140°C, the WO₃ nanoribbon sensor showed a best response to 5 ppm NO (R_g/R_a = 112) and had a good NO response selectivity. Our results demonstrated that WO₃ nanoribbons are a promising gas sensor for NO. It will be helpful to further study the synthesis of different WO₃ nanostructures and their gas-sensing applications.