3D substoichiometric MoO3−x/EGaln framework for room temperature NH3 gas sensing

Though conventional metal oxide-based NH3 gas sensors possess the advantage of simplicity and high sensitivity, their relatively high operating temperature still limits their widespread applications. Therefore, it is essential to develop a reliable NH3 sensor that operated at room temperature. In this context, we employ the ultrasonic method to coat the sonication-prepared substoichiometric molybdenum trioxide (MoO3−x) nanosheets upon the eutectic gallium indium (EGaIn) microdroplets, thus forming a three-dimensional (3D) MoO3−x/EGaIn semiconducting liquid metal framework. Due to the high surface-reducing properties of EGaIn, the concentration of oxygen vacancies in MoO3−x is further increased, presenting enhanced surface plasmon resonance in the visible light range. Such a plasmonic oxide framework (POF) exhibits a response magnitude of 1.22 for 50 ppm NH3 at room temperature with almost complete recovery, high selectivity, and excellent repeatability under the blue light excitation. It is remarkable that room temperature optoelectronic gas sensing performance is rarely seen in pure metal oxides. This work not only provides a promising NH3 gas sensing material but also demonstrates the great potential of liquid metal/semiconductor contacts for room temperature reversible gas sensing.