Low-temperature solvothermal synthesis of hierarchical flower-like WO3 nanostructures and their sensing properties for H2S

In this work, hierarchical flower-like tungsten trioxide (WO3) nanostructures assembled by needle-like single-crystalline nanosheets were fabricated. These were synthesized via a facile and simple solvothermal method at a rather low temperature (100 degrees C) without any surfactants or templates. Time-dependent experiments were carried out to understand the formation process, which undergoes four stages: polymerizing, nucleating, assembling and growing from WO42- to the flower-like WO3. The as-prepared WO3 microflowers exhibit a good reversibility, fast response time (0.9 s) and recovery time (19 s) and good sensing selectivity at a relatively low working temperature (160 degrees C) after exposing to hydrogen sulfide (H2S). Such excellent performance can be attributed to the highly exposed surface area and the assembling of single-crystalline nanosheets. The sensing process is tentatively explained in terms of the adsorption-desorption mechanism and chemical kinetics theories are discussed in detail.