2D Nonlayered Selenium Nanosheets: Facile Synthesis, Photoluminescence, and Ultrafast Photonics

Abstract

nearly 100%) with low-dimensional effect, thus having specific physical features that offer a wealth of potential to both scientific and industrial communities. [1][2][3][4][5] Extensive investigations have demonstrated that layered materials are the most common precursors to produce 2D nanostructures because these materials are constructed from stacked layers wherein weak van der Waals interactions hold together each interplane layer and strong chemical covalent bonding governs each individual in-plane layer. [5][6][7] Interestingly, 2D nanoplates can be readily prepared through two main well-established strategies, namely, the "top-down method" (mechanical cleavage, liquid-phase exfoliation, etc.) [1,[7][8][9][10][11] and the "bottom-up method" (e.g., chemical vapor deposition and wet-chemical methods). [12][13][14][15][16] Among these methods, liquid-phase exfoliation is considered to be quite promising and powerful due to its high output, large scalability, low cost, and simplicity. [7] Moreover, this method can produce nanosheets from most layered materials provided that the solvent's surface energy matches well with that of the target nanosheets. [7,17] The limited species and quantity, as well as the lack of certain properties, of 2D layered materials have motivated extensive investigations into 2D nonlayered materials, whose bulk counterparts are nonlayered and are held together strongly by chemical bonds in all three dimensions. [5,[18][19][20][21][22][23] In comparison with 2D layered materials, 2D nonlayered materials show distinct characteristics that their layered counterparts may not possess. Specifically, the surfaces of 2D nonlayered materials have abundant dangling bonds, which are absent on the surface of the layered materials, thereby offering numerous chemically active sites and resulting in improved catalytic capacity, [24][25][26] energy storage and conversion, [27,28] carrier properties, [18,29] etc. Due to these merits, considerable efforts have been made to fabricate 2D nonlayered materials. He and co-workers demonstrated a van der Waals epitaxial method to fabricate 2D nonlayered Pb 1−x Sn x Se nanoplates. [30,31] Zhang and co-workers synthesized nanosheets from the noble metal gold via a template-directed synthesis in which graphene oxide was developed as a 2D template for the growth of nonlayered materials. [32][33][34] Inspired by the concept of 2D layered materials, Sun and co-workers reported freestanding ZnSe single Investigations into 2D nanomaterials are of considerable significance from both an academic and industrial point of view. The present work addresses, for the first time, the fabrication of 2D nonlayered ultrathin selenium through a facile liquid-phase exfoliation method. The results reveal that the asprepared 2D Se nanosheets are 40-120 nm in lateral dimension and 3-6 nm in thickness. The nanosheets exhibit a trigonal crystalline phase similar to their bulk counterpart, indicating the conservation of the crystalline features during the exfoliation procedure. The success...

2D Crystal–Based Fibers: Status and Challenges

“…Their results show that the bandgap of the prepared selenene increases from 1.98 to 2.31 eV with decreasing lateral size. In addition, they also proved that selenene does not oxidize in air and thus has good structural stability . Subsequently, Qin et al used physical vapor deposition method to fabricate high‐quality selenene with a thickness of about 5 nm and transverse size up to 30 microns.…”

“…Therefore, selenene has promising potentials for applications of thermoelectronics and photoelectronics . In addition, selenene are strongly fluorescent and thus could be useful for imaging …”

Multifunctional black phosphorus/MoS2 van der Waals heterojunction

“…As we know, MoS 2 is an n-type semiconductor with reasonably high electron mobility and a bandgap ranging from 1.2 to 1.8 eV [14,15]. Few-layer BP has a narrow bandgap of ~0.3 eV, and it is a p-type semiconductor with high carrier mobility [7,[16][17][18][19][20][21][22][23][24]. Therefore, the integration of two materials to form a heterojunction can enable a large bandgap offset achieving good rectifying characteristics.…”

2D GeP as a Novel Broadband Nonlinear Optical Material for Ultrafast Photonics

“…These as‐prepared 2D GeP nanosheets have a broad lateral dimension range from about 180 to 410 nm ( Figure a). The nonuniformity in size of the 2D materials is common in LPE preparations . Some large GeP nanosheets were also observed to exhibit low contrast, suggesting their thin feature.…”