Elemental 2D Materials: Progress and Perspectives Toward Unconventional Structures

Abstract

Elemental 2D materials have attracted a great deal of interest due to their excellent properties for various applications in catalysis, sensing, photonics, intracellular gene regulation, magnetism, superconductivity, and so on. It is broadly accepted that the physicochemical properties are highly associated with their atomic arrangements and coordination. Recent studies have demonstrated that unconventional structures of elemental 2D materials exhibit unexpected physicochemical properties and innovative applications beyond conventional structures. Those unconventional structures bring new life to elemental 2D materials and deserve special attention. However, there are considerable challenges to controllably prepare them due to their metastable characters. Herein, their synthetic strategies are focused on to shed light on the reasonable design of new structures with special atomic arrangements to open up tremendous opportunities for expanding their functionalities and potential applications. In addition, the correlations among the types of unconventional structures, the element types, and corresponding synthetic strategies are uncovered. Finally, based on the achievements in the representative studies, some prospects and potential opportunities for extending the scope of elemental 2D materials with unconventional structures and potentially distinctive applications are provided.

Recent Progress on Two-Dimensional Materials

“…61,62 , elemental 2D materials (e.g., black phosphorus (BP), tellurium, silicene, germanene, borophene, etc.) [63][64][65] , layered metal oxides 66,67 , layered double hydroxides (LDHs) 68,69 , graphitic carbon nitride (g-C3N4) 70,71 , MXenes 72 , metals 73 , organics/polymers 74,75 , metal-organic frameworks (MOFs) 76,77 , covalent-organic frameworks (COFs) 78,79 , organic-inorganic hybrid perovskites [80][81][82] , and transition metal halides 83,84 , have been synthesized by various synthetic methods in the last decade. It is worth pointing out that the number of materials in the family of 2D materials is still continuously growing every year.…”

Ta2Ni3Se8: 1D van der Waals Material with Ambipolar Behavior

“…[18][19][20][21] Moreover, it was theoretically confirmed that some of the 1D vdW materials exhibit thickness-dependent properties, such as the bandgap expansion with the indirect-to-direct transition as the number of unit chains decrease from their bulk crystal, similar to well-studied transition metal dichalcogenides (TMDs). [22][23][24][25] Based on this aspect, numerous studies have been conducted to utilize 1D nanowires in functional electronic devices such as FET [26][27][28][29] and photodetectors, [30][31][32][33] but diversity among promising materials is still limited. Therefore, it is necessary to discover new types of 1D materials, verify their electronic properties, and expand the potential candidates for future electronic device applications.…”

Borophene as an emerging 2D flatland for biomedical applications: current challenges and future prospects

“…Borophene manifested improved tunable properties among chemically similar structures described by anisotropy and polymorphism. 99 In a general sense, numerous common aspects are shown by these polymorphs. Particularly, most of the structural prototypes of borophene are found to be metallic and have excellent optical transparency and mechanical strength.…”