WO₃ Nanosheet/W₁₈O₄₉ Nanowire Composites for NO₂ Sensing

Herein, a strategy is proposed for the self-assembly hybrid hierarchical structure of a WO3 nanosheets/W18O49 nanowires (HHW) composite via a one-step hydrothermal method. The method requires only H2O and surfactants to regulate the hydrolysis rate of tungsten ions to yield the desired morphology. The self-assembled growth of the hierarchical structures is principally governed by the competition and equilibrium between the surfactant concentration, precipitation coefficient, and hydrolysis rate of tungsten ions. The hybrid hierarchical HHW material exhibits an ultrahigh-sensitive response, up to 1678 upon exposure to 10 ppm of NO2, which demonstrates a significant enhancement over that of conventional hierarchical gas-sensitive nanosheet or nanowire materials. The ultrahigh-sensitive response and excellent selectivity toward NO2 by HHW is considered to derive from the synergistic effect of rapid electron separation and transport by the W18O49 nanowires and the abundance of adsorption sites offered by the WO3 nanosheets. This low-cost and rapid synthesis of self-assembled hybrid hierarchical materials provides an effective strategy for high-performance gas sensors or catalysts.