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Atomic defects, being the most prevalent zero-dimensional topological defects, are ubiquitous in a wide range of 2D transition-metal dichalcogenides (TMDs). They could be intrinsic, formed during the initial sample growth, or created by postprocessing. Despite the majority of TMDs being largely unaffected after losing chalcogen atoms in the outermost layer, a spectrum of properties, including optical, electrical, and chemical properties, can be significantly modulated, and potentially invoke applicable functionalities utilized in many applications. Hence, controlling chalcogen atomic defects provides an alternative avenue for engineering a wide range of physical and chemical properties of 2D TMDs. In this article, we review recent progress on the role of chalcogen atomic defects in engineering 2D TMDs, with a particular focus on device performance improvements. Various approaches for creating chalcogen atomic defects including nonstoichiometric synthesis and postgrowth treatment, together with their characterization and interpretation are systematically overviewed. The tailoring of optical, electrical, and magnetic properties, along with the device performance enhancement in electronic, optoelectronic, chemical sensing, biomedical, and catalytic activity are discussed in detail. Postformation dynamic evolution and repair of chalcogen atomic defects are also introduced. Finally, we offer our perspective on the challenges and opportunities in this field.

The major limitation of current engineered myocardial patches for the repair of heart defects is that insulating polymeric scaffold walls hinder the transfer of electrical signals between cardiomyocytes. This loss in signal transduction results in arrhythmias when the scaffolds are implanted. We report that small, subtoxic concentrations of single-walled carbon nanotubes, on the order of tens of parts per million, incorporated in a gelatin–chitosan hydrogel act as electrical nanobridges between cardiomyocytes, resulting in enhanced electrical coupling, synchronous beating, and cardiomyocyte function. These engineered tissues achieve excitation conduction velocities similar to native myocardial tissue (22 ± 9 cm/s) and could function as a full-thickness patch for several cardiovascular defect repair procedures, such as right ventricular outflow track repair for Tetralogy of Fallot, atrial and ventricular septal defect repair, and other cardiac defects, without the risk of inducing cardiac arrhythmias.

We have succeeded in the production of defect-free and spatially organized individual one-dimensional peptide nanofilaments by real-time control of the self-assembly process on a solid substrate. Using a unique mechanical manipulation method based on atomic force microscopy, we are able to introduce mechanical stimuli to generate active ends at designated positions on an existing peptide nanofilament previously formed. By doing so, defects in the filament were removed, and self-repairing occurred when the active ends extended along the direction of the supporting lattice, resulting in the closure of the broken filament. Furthermore, new active ends of the nanofilaments can be specifically generated to guide the self-assembly of new filaments at designated positions with selected orientations. The mechanism of defect repair and guided epitaxial growth is also discussed.