MXenes are a promising class of two-dimensional materials with several potential applications, including energy storage, catalysis, electromagnetic interference shielding, transparent electronics, and sensors. Here, we report a novel Mo2CTx MXene sensor for the successful detection of volatile organic compounds (VOCs). The proposed sensor is a chemi-resistive device fabricated on a Si/SiO2 substrate using photolithography. The impact of various MXene process conditions on the performance of the sensor is evaluated. The VOCs toluene, benzene, ethanol, methanol, and acetone are studied at room temperature with varying concentrations. Under optimized conditions, the sensor demonstrates a detection limit of 220 ppb and a sensitivity of 0.0366 Ohm/ppm at a toluene concentration of 140 ppm. It exhibits an excellent selectivity toward toluene against the other VOCs. Ab initio simulations demonstrate selectivity toward toluene in line with the experimental results.

Two-dimensional materials can be utilized to detect gas molecules in low concentration due to their high surface-to-volume ratios. In this respect, we investigate in the present work recently fabricated borophene, two-dimensional B, which has buckled and line-defective phases. Both are systematically studied for four gas molecules: NH3, NO, NO2, and CO. In each case, the adsorption energy is found to be high and borophene develops distinct wrinkles. Our results provide a thorough understanding of the interaction between borophene and the gas molecules. An excellent performance of borophene as gas sensor is demonstrated by simulating the material’s transport characteristics by means of the nonequilibrium Green’s function method.

First principles calculations are performed to compare the adsorption of CO, NH 3 , NO, and NO 2 molecules on monolayer, bilayer, and heterobilayer MoS 2 and WS 2 , using van der Waals corrected density functional theory. Only minor differences are demonstrated for the adsorption behaviors of the monolayer and bilayer systems despite fundamental differences in the electronic structure (direct versus indirect band gap). We also show that NO 2 binds stronger to the sensor materials than the other gas molecules, resulting in enhanced charge transfer. Adsorption of paramagnetic NO and NO 2 has significant impact on the electronic states, in contrast to adsorption of nonmagnetic CO and NH 3 .

We demonstrate that the thermal conductivity is massively reduced in monolayer C3N as compared to isostructural graphene.

A self-folding approach inspired by the origami technique is developed to form complex three-dimensional graphene structures using pattern-based surface functionalization.