Nitrogen-Doped Graphyne as a Promising Material for Sensing Volatile Organic Compounds in Human Breath

Using density functional theory and the nonequilibrium Green function method, the interaction between two-dimensional nitrogen-doped graphyne (N-GY) and volatile organic compounds (ethanol, ethylene glycol, acetone, and toluene) was investigated, and the potential application of N-GY for sensing volatile biomarkers exhaled by human breath was explored. The N-GY is a direct band gap semiconductor with a band gap width of 0.408 eV. The bottom of the conduction band and the top of the valence band are both located at the Γ point. All target volatile organic compounds (VOCs) are in physical adsorption states. In order to verify the sensing mechanism of VOCs, Bader charge transfer, adsorption distance, work function, electron localization function, charge density difference, energy band structure, and density of states were analyzed. At the same time, the I-V relationship of VOCs molecules before and after adsorption was calculated by using the NEGF method. The results show that at 0.5 V bias voltage under the armchair direction, N-GY can well distinguish four gas molecules and has the highest sensitivity for acetone with a sensitivity of 81%. Therefore, the N-GY monolayer is a potential candidate material for analyzing VOCs exhaled by the human body as well as for early screening of diabetes.