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

Hierarchical flowerlike WO3 nanostructures, assembled from single crystalline WO3 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 PdCl2 in the precursor solution, the surface of the WO3 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 WO3 with 0.1 mmol PdCl2 addition in the precursor solution, while the sample with 0.01 mmol PdCl2 addition always shows fast response and recovery speed (e.g. 27 s/23 s at 200 °C).