Multi-modal, ultrasensitive, wide-range humidity sensing with Ti3C2 film.

Gravimetric, direct-current electrical, and electrical impedance sensing modes were used to measure response of high surface area 2D Ti3C2 MXene film to water vapor pressures spanning 3 orders of magnitude (20 mTorr-20 Torr). The Ti3C2 film exhibited reproducible reversible response in 0.1%-95% relative humidity (RH) range with a detection limit of <20 mTorr H2O partial pressure (<0.1% RH). DC electrical current-based sensing with 3 mV operating voltage and 0.8 pW power consumption was demonstrated. The highest normalized sensitivity was shown for gravimetric sensing modalities which scale with the overtone number, reaching highest sensitivity of about 12 Hz/% RH at the 9th crystal overtone (45 MHz oscillation).