Outstanding Performance of Transition-Metal-Decorated Single-Layer Graphene-like BC6N Nanosheets for Disease Biomarker Detection in Human Breath

In the present work, we report highly sensitive and selective nanosensors constructed with metal-decorated graphenelike BC6N employing nonequilibrium Green's function (NEGF) formalism combined by density functional theory (DFT) toward multiple inorganic and sulfur-containing gas molecules (NO, NO2, NH3, CO, CO2, H2S, and SO2) as disease biomarkers from human breath. Monolayer sheets of pristine BC6N and Pd-decorated BC6N were evaluated for their gas adsorption properties, electronic property changes, sensitivity, and selectivity toward disease biomarkers. The pristine BC6N nanosheets exhibited sharp drops in the bandgap when interacted with gases such as NO2 while barely affected by other gases. However, the nanosecond recovery time and low adsorption energies limit the gas sensing applications of the pristine BC6N sheet. On the other hand, the Pddecorated BC6N-based sensor underwent a semiconductor to metal transition upon the adsorption of NOx gas molecules. The conductance change of the sensor's material in terms of I-V characteristics revealed that the Pd-decorated BC6N sensor is highly sensitive (98.6-134%) and selective (12.3-74.4 times) toward NOx gas molecules with a recovery time of 270 s under UV radiation at 498 K while weakly interacting with interfering gases in exhaled breath such as CO2 and H2O. The gas adsorption behavior suggests that metal-decorated BC6N sensors are excellent candidates for analyzing pulmonary disease and cardiovascular biomarkers, among other ailments of the stomach, kidney, and intestine.