1T-Phase Titanium Disulfide Nanosheets for Sensing H<inf>2</inf>S and O<inf>2</inf>

A chemiresistive, 1T-TiS2 nanosheet (TNS) based gas sensor has been developed, and its ultrahigh sensitivity toward hydrogen sulfide (H2S) and oxygen (O2) gas at room temperature has been experimentally demonstrated. The sensor displayed room-temperature detection with a maximum response of 395% to 4 ppm H2S (reducing gas) in dry air and a response of 234% to 100% oxygen (oxidizing gas) in ambient conditions. The H2S and O2 sensing in humid environment (40% and 80%) has also been demonstrated so as to ensure the reliable operation of sensor in real-time applications. The ultrasensitive nature and linear behavior of the sensor enable it to operate reliably in the wide range of 300 ppb to 4 ppm H2S and 1% to 100% oxygen. Density functional theory (DFT) simulations were carried out to study the structural and electronic properties of TNS. Adsorption behavior of these gas molecules on TNS nanosheets was also studied theoretically. A plausible sensing mechanism based on the theoretical model has been detailed, and interestingly, it suggests physisorption phenomena between the adsorbate and adsorbent which enables fast recovery of the sensor without any external stimulation. The rather low lower limit of detection (LLoD) for H2S and O2 reported here, specifically at room temperature, is unique and competes favorably with reported studies. This outstanding sensor performance can be attributed to small adsorption energy and van der Waals interaction between analyte and the receptor.