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

Nanostructured WO3 has excellent NOx 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 degrees 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.