Search

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 C 3 B/graphene (Gra) and C 3 N/Gra vdW heterojunctions. Calculations show the metallic properties of C 3 B/Gra and C 3 N/Gra after the formation of heterojunctions. Interestingly, the heterojunctions C 3 B/Gra (C 3 N/Gra) for the adsorption of small organic molecules (C 2 H 2 , C 2 H 4 , CH 3 OH, CH 4 , and HCHO) at the C 3 B (C 3 N) side are sensitive to the chemisorption of C 2 H 2 and C 2 H 4 . Similarly, the Gra/C 3 B is chemisorbed for both C 2 H 2 and C 2 H 4 when adsorbed on Gra side, while it is only chemisorbed for C 2 H 2 in Gra/C 3 N. Interestingly, all heterojunctions on different sides are physisorbed for CH 3 OH, CH 4 , and HCHO. Furthermore, the calculated I-V curves demonstrate that the devices based on the adsorption of C 2 H 2 and C 2 H 4 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 C 2 H 2 adsorbed on the Gra side, the sensitivity along the armchair direction is up to 85.0% for Gra/C 3 B and close to 100% for Gra/C 3 N. This study reveals that C 3 B/Gra (C 3 N/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.

The highly sensitive gas sensors used to monitor the decomposition of toxic gases in the dielectric materials of electrical equipment are vital in preventing safety problems arising from corrosion of the equipment. Recently, biphenylene (BPN) has been prepared through surface interpolymer hydrofluorination (HF zipper) reaction, whereas potential gas-sensitive devices based on the BPN monolayer have lacked in-depth investigation. The stable geometries, adsorption energies, interlayer distances, and charge transfers of small molecules of toxic gases (H 2 S, SO 2 , SOF 2 , SO 2 F 2 ) produced by SF 6 chalcogenide molecules of decomposition adsorbed on the original BPN monolayer are systematically researched by using nonequilibrium Green's function methods and density functional theory. The results indicated that all small molecules adsorbed on the BPN monolayer are physisorbed, while the type of adsorption turned from physisorption to chemisorption when BPN carried out adsorption with adsorbing a transition metal atom (TMA). In addition, the characteristics of current-voltage ( I - V ) curves of H 2 S and SO 2 based on the TMA-BPN gas sensors revealed that the currents in BPN-based gas sensors displayed an obvious anisotropy, and the currents in the zigzag direction are larger than that in the armchair orientation regardless of the molecular adsorption cases. Moreover, the difference of currents for TMA-decorated BPN sensors changed more remarkably before and after the adsorption of H 2 S and SO 2 in the zigzag direction. This work offers insights into the design of gas-sensitive devices through the adsorption of small molecules on the TMA-decorated BPN monolayer.