Liquid metals for tuning gas sensitive layers

Liquid metals can offer extraordinary properties for application in the field of sensors, yet their potential has not been fully realised. In this work, we present a heterostructure mix of eutectic alloy of gallium and two dimensional (2D) flakes of tungsten oxides (WO3) for gas sensing. We show that the eutectic alloy of EGaIn, made of gallium and indium, can be co-sonicated with acid bath synthesised 2D WO3 for chemisorption sensing of H2 gas molecules. We demonstrate that this co-sonication results in extra trap bands within the bandgap of WO3 to enhance the gas sensing properties. Another interesting observation was the effect on reducing the size of the sonicated EGaIn droplets in the presence of 2D WO3 flakes, which is likely due to the increase of shear force during the sonication. Mixes using different ratios of WO3 and EGaIn were synthesised. The optimum gas sensing operation in terms of response factor was seen in the 70% WO3-30% EGaIn mix. This work provides a viable pathway towards a new platform where liquid metals can be used for sensing applications and they offer advantages to augment the capabilities of sensors.