Lowerature 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°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 WO₄^2- 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°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.