Tailoring Graphene Functionalization with Organic Residues for Selective Sensing of Nitrogenated Compounds: Structure and Transport Properties via QM Simulations

Graphene bearing organic functional groups chemicallytetheredto its surface via covalent bonds can find severalapplications in the sensing of gas, heavy metal ions, and other targetspecies of interest. Herein, we used DFT simulations to study thethermodynamics of graphene functionalization with substituted carbenes,and the use of the resulting adducts to detect gaseous nitrogenatedcompounds focusing on ammonia (NH3), methylamine(MMA), dimethylamine (DMA), and trimethylamine (TMA). We find thatthe modified materials can interact with the amines, selectively alsoin the presence of other gases such as CO2, SO2, H2S, and CH4. Changes in the electronic propertiesof the system upon adsorption such as charge density, Lo''wdinpartial charges, and projected density of states (PDOS) were usedto analyze the interaction. Expected recovery times suggest that thesenanomaterials can be used to detect the nitrogenated compounds hereinvestigated at relatively low temperatures (298 and 373 K). Furthermore,by modeling the conductance of the functionalized graphene bare andin the presence of ammonia, we show that quantum conductance and theintegrated currents are sensitive to functionalization and, importantly,to the presence of ammonia under determined conditions, which in principleallows tuning the sensitivity of the resulting device. Our work thusclarifies the principles governing this phenomenon. Carbene-functionalizedgraphene is concluded to be a potentially good candidate to replacenoble-metal-modified graphene for the detection of ammonia/aminesin chemoresistance or field-effect transistor-based sensors.