Recent developments in synthesis and nanofabrication technologies offer the tantalizing prospect of realizing various applications from two-dimensional (2D) materials. A revolutionary development is to flexibly construct many different kinds of heterostructures with a diversity of 2D materials. These 2D heterostructures play an important role in semiconductor and condensed matter physics studies and are promising candidates for new device designs in the fields of integrated circuits and quantum sciences. Theoretical and experimental studies have focused on both vertical and lateral 2D heterostructures; the lateral heterostructures are considered to be easier for planner integration and exhibit unique electronic and photoelectronic properties. In this review, we give a summary of the properties of lateral heterostructures with homogeneous junction and heterogeneous junction, where the homogeneous junctions have the same host materials and the heterogeneous junctions are combined with different materials. Afterward, we discuss the applications and experimental synthesis of lateral 2D heterostructures. Moreover, a perspective on lateral 2D heterostructures is given at the end.

Carbon nitride covalent compounds have emerged as a prominent member of 2D materials beyond graphene. The experimental realizations of 2D graphitic carbon nitride g-C₃N₄, nitrogenated holey graphene C₂N, and polyaniline C₃N have shown their promising potential in energy and environmental applications. In this work, we predict a new type of carbon nitride network with a C₉N₄ stoichiometry from first principles calculations. Unlike common C–N compounds and covalent organic frameworks (COFs), which are typically insulating, surprisingly C₉N₄ is found to be a 2D nodal-line semimetal. The nodal line in C₉N₄ forms a closed ring centered at the Γ point, which originates from the p_z orbitals of both C and N. The linear crossing occurs right at the Fermi level contributed by two sets of dispersive Kagome and Dirac bands, which is robust due to negligible spin–orbit coupling in C and N. Furthermore, it is revealed that the degeneracy along the high-symmetry path is protected by out-of-plane mirror or C₂ rotational symmetry, rather than in-plane mirror symmetry. The chemical potential difference between C and N, as validated by using a single orbital tight-binding model, plays a significant role in forming the nodal ring. Interestingly, a new structure of the nodal line, i.e., a nodal cylinder, is found in momentum space for AA-stacked C₉N₄. Our results indicate possible functionalization for a novel metal-free C–N covalent network with interesting semimetallic properties.

Both wetting and non-wetting tin oxide SnO ₂ were spin-coated and the non-wetting electron transport layer demonstrated a larger perovskite and higher power conversion efficiency.