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Acoustic devices play an increasingly important role in modern society for information technology and intelligent systems, and recently significant progress has been made in the development of communication, sensing, and energy transduction applications. However, conventional material systems, such as polymers, metals and silicon, show limitations to fulfill the evolving requirements for high‐performance acoustic devices of small size, low power consumption, and multifunctional capabilities. 2D materials hold the promise in overcoming the development bottleneck of acoustic devices aforementioned, given their atomic‐thin thickness, extensive surface area, superior physical properties, and remarkable layer‐stacking tunability. By suspending the 2D materials, mechanical and thermal disruption from substrate will be eliminated, which will enable the development of new classes of acoustic devices with unprecedented sensitivity and accuracy. In this review, the recent progress of acoustic devices based on suspended 2D materials and their composites, especially applications in the audio frequency, static pressure, and ultrasonic frequency range, is briefly summarized, emphasizing the advantageous properties of suspended 2D materials and related outstanding device performance. Together with the development of 2D membrane synthesis, transfer, as well as microelectromechanical fabrication process, suspended 2D materials will shed light on the next‐generation high‐performance acoustic devices. [ABSTRACT FROM AUTHOR]

Near‐infrared (NIR) responsive smart drug delivery systems could provide efficient osteogenesis through the synergy of heat and drugs. However, such systems are hampered by an inability to allow supersensitive drug release through mild heat. Here superior osteogenesis is demonstrated using a biocompatible dexamethasone (Dex)‐loaded MXene‐poly(N‐isopropylacrylamide)‐co‐N‐(Hydroxymethyl) acrylamide hydrogel capable of the supersensitive release of Dex at ≈42 °C upon NIR irradiation. Furthermore, the hydrogel can significantly promote bone regeneration under NIR irradiation due to the synergistic anti‐apoptosis and osteogenic differentiation of bone‐derived mesenchymal stem cells induced by the mild heat and supersensitive release of Dex. The resulting osteogenesis efficiency of hydrogels surpass efficiencies previously reported for heat and drug stimulation and their combination. The synergistic osteogenesis strategy is characterized by near‐instantaneous, noninvasive, and precise treatment through temporal NIR irradiation. [ABSTRACT FROM AUTHOR]

The toxicity of lead‐based halide perovskites hampers broad application in optoelectronics. Lead‐free perovskite Cs2AgBiBr6 is considered a promising candidate, owing to the long carrier lifetime and great stability. However, the relatively large bandgap of 1.98 eV limits its absorption in the visible region. Herein, Fe2+ is chosen as the dopant to alloy into Cs2AgBiBr6 single crystals, and results in an absorption range broadening to ≈1350 nm, which is the longest near‐infrared (NIR) response recorded among lead‐free perovskites. About 1% of Fe ions are alloyed into the Cs2AgBiBr6 lattice to cause lattice shrink age. Instead of narrowing the bandgap, Fe doping would introduce a new intermediate band inside the pristine bandgap of Cs2AgBiBr6 to strongly absorb NIR light, as confirmed by third harmonic generation results. Moreover, considerable photogenerated carriers are produced in Fe doped Cs2AgBiBr6 crystals with NIR irradiation. This work has provided a new way to extend the optical response of lead‐free perovskites for NIR photodetectors and intermediate band photovoltaics. [ABSTRACT FROM AUTHOR]

Grain Boundaries: Nanoassembly Growth Model for Subdomain and Grain Boundary Formation in 1T' Layered ReS2 (Adv. Funct. Keywords: anisotropy; grain boundary; rhenium disulfide; subdomain; superlattices Anisotropy, grain boundary, rhenium disulfide, subdomain, superlattices. [Extracted from the article]

Grain boundaries (GBs) significantly affect the electrical, optical, magnetic, and mechanical properties of 2D materials. An anisotropic 2D material like ReS2 provides unprecedented opportunities to explore novel GB properties, since the reduced lattice symmetry offers greater degrees of freedom to build new GB structures. Here the atomic structure and formation mechanism of unusual multidomain and diverse GB structures in the vapor phase synthesized ReS2 atomic layers are reported. Using high‐resolution electron microscopy, two major categories of GBs are observed in each ReS2 domain, namely, the joint GB including three structures, and the GBs formed from a reconstruction of Re4‐chains including seven different structures. Based on the experimental observations, a novel "nanoassembly growth model" is proposed to elucidate the growth process of ReS2, where three types of Re4‐chain reconstruction give rise to a multidomain structure. Moreover, it is shown that by controlling the thermodynamics of the growth process, the structure and density of GB in the ReS2 domain can be tailored. First‐principles calculations point to interesting new properties resulting from such GBs, such as a new electron state or ferromagnetism, which are highly sought after in the construction of novel 2D devices. [ABSTRACT FROM AUTHOR]

Grain boundaries (GBs) significantly affect the electrical, optical, magnetic, and mechanical properties of 2D materials. An anisotropic 2D material like ReS2 provides unprecedented opportunities to explore novel GB properties, since the reduced lattice symmetry offers greater degrees of freedom to build new GB structures. Here the atomic structure and formation mechanism of unusual multidomain and diverse GB structures in the vapor phase synthesized ReS2 atomic layers are reported. Using high‐resolution electron microscopy, two major categories of GBs are observed in each ReS2 domain, namely, the joint GB including three structures, and the GBs formed from a reconstruction of Re4‐chains including seven different structures. Based on the experimental observations, a novel "nanoassembly growth model" is proposed to elucidate the growth process of ReS2, where three types of Re4‐chain reconstruction give rise to a multidomain structure. Moreover, it is shown that by controlling the thermodynamics of the growth process, the structure and density of GB in the ReS2 domain can be tailored. First‐principles calculations point to interesting new properties resulting from such GBs, such as a new electron state or ferromagnetism, which are highly sought after in the construction of novel 2D devices. [ABSTRACT FROM AUTHOR]