Susceptible Detection of Organic Molecules Based on CB/Graphene and CN/Graphene van der Waals Heterojunction Gas Sensors.

Constructing van der Waals (vdW) heterostructures is a prospective approach that is essential for developing a new generation of functional two-dimensional (2D) materials and designing new conceptual nanodevices. Using density-functional theory combined with a nonequilibrium Green's function approach allows for the theoretical and systematic exploration of the electronic structure, transport properties, and sensitivity of organic small molecules adsorbed on 2D CB/graphene (Gra) and CN/Gra vdW heterojunctions. Calculations show the metallic properties of CB/Gra and CN/Gra after the formation of heterojunctions. Interestingly, the heterojunctions CB/Gra (CN/Gra) for the adsorption of small organic molecules (CH, CH, CHOH, CH, and HCHO) at the CB (CN) side are sensitive to the chemisorption of CH and CH. Similarly, the Gra/CB is chemisorbed for both CH and CH when adsorbed on Gra side, while it is only chemisorbed for CH in Gra/CN. Interestingly, all heterojunctions on different sides are physisorbed for CHOH, CH, and HCHO. Furthermore, the calculated curves demonstrate that the devices based on the adsorption of CH and CH at each side of the heterojunction have remarkable anisotropy, in with the current being considerably greater in the zigzag direction than in the armchair direction. More specifically, with CH adsorbed on the Gra side, the sensitivity along the armchair direction is up to 85.0% for Gra/CB and close to 100% for Gra/CN. This study reveals that CB/Gra (CN/Gra) heterojunctions with high selectivity, high anisotropy, and excellent sensitivity are highly prospective 2D materials for applications, which further contributes new insights into the development of future electronic nanodevices.