Advances in precision synthesis and synergistic applications of Janus nanostructures

Janus nanostructures, named after the two-faced Roman god, represent a class of novel materials that integrate two or more distinct properties within a single micro-or nanoscale entity. In contrast to traditional homogeneous materials, Janus structures achieve the spatial segregation and integration of functionalities across distinct regions of a single particle by breaking symmetry. While numerous reviews over the past three decades have chronicled the morphological evolution of Janus particles, a comprehensive understanding bridging precise atomic-level topological engineering and multifunctional synergy remains scarce. To transcend conventional descriptive summaries, this review systematically categorizes the interactions within asymmetric architectures into series, parallel, and regulatory synergy modes. Through this lens, recent advancements in precision synthesis were critically evaluated, emphasizing the mode shift from random macroscopic segregation to programmable atomic-level control (e.g., built-in electric fields and strain engineering). Subsequently, the unique physicochemical properties emerging from structural asymmetry are explored. Based on these fundamental properties, specific application examples in frontier fields, including energy catalysis, biomedicine, environmental remediation, and intelligent sensing, are highlighted. The discussion clarifies how distinct functional components achieve synergistic enhancements superior to single-component materials through a "division of labor" mechanism. Finally, the challenges facing this field, such as large-scale low-cost fabrication and the precise characterization of dynamic behaviors, are summarized. Future trends toward more complex and intelligent designs are also prospected to provide a reference for the development of next-generation high-performance nanomaterials.