State Key Laboratory of Applied Organic Chemistry (SKLAOC), Key Laboratory of Nonferrous Metal Chemistry and Resources Utilization of Gansu Province, College of Chemistry and Chemical Engineering, Key Laboratory of Special Function Materials and Structure Design, Ministry of Education, Lanzhou University, Lanzhou, 730000, China.
Nanoscale. 2018 Dec 7;10(45):21106-21115. doi: 10.1039/c8nr06797j. Epub 2018 Oct 16.
The rediscovery of black phosphorus (BP) has expanded the 2D family into Group 15 (Nitrogen Group) elements, among which bismuthene is the latest member with extraordinary opto-electronic, catalytic and biocompatible properties and potential as a 2D topological insulator. However, bulk Bi is not easily mechanically exfoliated as its counterpart of BP. Thus, to date, the reports on 2D Bi fabrication are rare, and investigations on its nonlinear optical properties are even less. Herein, we rationally designed a new strategy combining acid-interaction and liquid exfoliation to successfully transform metal bulk Bi into few-layer semiconductor, which resulted in unseen opto-electronic properties, such as tunable nonlinear responses all the way to the near-infrared (NIR) region. This band is critical for telecommunication and military purposes, but currently, functioning materials are extremely scarce. The origin of this strong saturable absorption was thoroughly explored through time-resolved spectroscopy spanning from the fs to μs timescale, which indicated ultrafast fs to ps carrier dynamics in the early stage and long exciton bleaching recovery up to μs. As a proof-of-concept application, the as-prepared 2D Bi was employed as a saturable absorber to mode-lock a Tm-doped fiber laser and successfully realized a 2 μm NIR-wavelength output. This study not only offers an effective and scalable method to fabricate the new 2D family member bismuthene with extraordinary stability, but also explores its strong and broad nonlinear responses extending into the NIR region and fundamental photoinduced dynamics, which demonstrate the full potential of 2D Bi for application in opto-electronic devices and nonlinear optics.
黑磷（BP）的重新发现将二维家族扩展到了第 15 族（氮族）元素，其中铋烯是最新成员，具有非凡的光电、催化和生物相容性，有望成为二维拓扑绝缘体。然而，块状 Bi 不像其 BP 那样容易机械剥离。因此，迄今为止，关于二维 Bi 制备的报道很少，对其非线性光学性质的研究就更少了。在此，我们合理设计了一种新的策略，结合酸相互作用和液相剥离，成功地将金属块状 Bi 转化为少层半导体，从而产生了前所未有的光电性质，例如可调谐的非线性响应一直到近红外（NIR）区域。这个波段对电信和军事用途至关重要，但目前，功能材料极其稀缺。通过从飞秒到微秒时间尺度的时间分辨光谱，彻底研究了这种强饱和吸收的起源，这表明在早期存在超快的 fs 到 ps 载流子动力学，以及长达微秒的长激子漂白恢复。作为概念验证应用，所制备的二维 Bi 被用作可饱和吸收体来锁模掺铥光纤激光器，并成功实现了 2 µm NIR 波长的输出。这项研究不仅提供了一种有效且可扩展的方法来制造具有非凡稳定性的新型二维家族成员铋烯，还探索了其强而宽的非线性响应扩展到近红外区域和基本光致动力学，这展示了二维 Bi 在光电设备和非线性光学中的应用潜力。
