Room-Temperature,\nFlexible Formaldehyde Gas Sensors\nUsing Titanium-Incorporated 1T/2H MoS<sub>2</sub>

The\ndevelopment of room-temperature (RT) formaldehyde sensors is\nsignificant for indoor air quality monitoring. In this contribution,\ntitanium (Ti)-incorporated 1T/2H molybdenum disulfide (MoS<sub>2</sub>) phase heterostructures were prepared via a facile hydrothermal\nmethod. Compared with 1T/2H MoS<sub>2</sub>, the as-prepared 1T/2H\nMo<sub>1–<i>x</i></sub>Ti<sub><i>x</i></sub>S<sub>2</sub> nanosheets showed a boosted RT formaldehyde sensing\nperformance, which was attributed to the enhanced gas adsorption and\ncharge transfer processes induced by Ti incorporation and could be\nregulated by tuning the Mo/Ti ratio in Mo<sub>1–<i>x</i></sub>Ti<sub><i>x</i></sub>S<sub>2</sub>. In addition,\nthe Ti-incorporated phase heterostructures with an optimized 1T concentration\nshowed further improved gas-sensing properties compared to the highly\nmetallic or semiconducting nanosheets with the same chemical composition,\nwhich exhibited an obvious response of 0.035% to 1 ppm formaldehyde\nwith an excellent limit of detection as low as 39 ppb, good repeatability,\nand short response and recovery times. Moreover, flexible gas sensors\nbased on the optimized nanosheets showed well-maintained responses\nunder moderately bent conditions. Our findings demonstrate that the\ncreation of phase heterostructures with tunable compositions and phases\nmay provide more opportunities to tailor their sensing properties.