Room-Temperature, Flexible Formaldehyde Gas Sensors Using Titanium-Incorporated 1T/2H MoS₂

The development of room-temperature (RT) formaldehyde sensors is significant for indoor air quality monitoring. In this contribution, titanium (Ti)-incorporated 1T/2H molybdenum disulfide (MoS₂) phase heterostructures were prepared via a facile hydrothermal method. Compared with 1T/2H MoS₂, the as-prepared 1T/2H Mo_1-<i>x</i>Ti_<i>x</i>S₂ nanosheets showed a boosted RT formaldehyde sensing performance, which was attributed to the enhanced gas adsorption and charge transfer processes induced by Ti incorporation and could be regulated by tuning the Mo/Ti ratio in Mo_1-<i>x</i>Ti_<i>x</i>S₂. In addition, the Ti-incorporated phase heterostructures with an optimized 1T concentration showed further improved gas-sensing properties compared to the highly metallic or semiconducting nanosheets with the same chemical composition, which exhibited an obvious response of 0.035% to 1 ppm formaldehyde with an excellent limit of detection as low as 39 ppb, good repeatability, and short response and recovery times. Moreover, flexible gas sensors based on the optimized nanosheets showed well-maintained responses under moderately bent conditions. Our findings demonstrate that the creation of phase heterostructures with tunable compositions and phases may provide more opportunities to tailor their sensing properties.