Hierarchical flowerlike WO3 nanostructures assembled by porous nanoflakes for enhanced NO gas sensing

Abstract Hierarchical flowerlike WO 3 nanostructures, assembled from single crystalline WO 3 nanoflakes, were prepared on patterned FTO substrates via a solvothermal technique. The flowerlike nanostructures provide large area of active surfaces, and the interconnected nanoflakes are continuous paths for the electrical conduction. With the addition of PdCl 2 in the precursor solution, the surface of the WO 3 nanoflakes was etched and became rough and porous, which is advantageous for gas sensing. A response value of 203 to 20 ppm NO was achieved at 200 °C by the flowerlike WO 3 with 0.1 mmol PdCl 2 addition in the precursor solution, while the sample with 0.01 mmol PdCl 2 addition always shows fast response and recovery speed (e.g. 27 s/23 s at 200 °C).