Yang Ke, Liu Tianyu, Zhang Xiao-Dong
Department of Physics and Center for Joint Quantum Studies, School of Science, Tianjin University, Tianjin, China.
Tianjin Key Laboratory of Brain Science and Neural Engineering, Academy of Medical Engineering and Translational Medicine, Tianjin University, Tianjin, China.
Front Chem. 2021 Jun 18;9:700250. doi: 10.3389/fchem.2021.700250. eCollection 2021.
The fluorescence-based optical imaging in the second near-infrared region (NIR-II, 1,000-1,700 nm) has broad applications in the biomedical field, but it is still difficult to find new NIR-II fluorescence materials in the two dimension. As a crucial characteristic of the electronic structure, the band structure determines the fundamental properties of two-dimensional materials, such as their optical excitations and electronic transportation. Therefore, we calculated the electronic structures and optical properties of different crystalline phases (1T phase and 2H phase) of pure monolayer MoS films and found that the 1T phase has better absorption and thus better fluorescence in the NIR-II window. However, its poor stability makes the 1T-phase MoS less useful bioimaging. By introducing vacancy defects and doping with foreign atoms, we successfully tuned the bandgap of the monolayer 2H-MoS and activated it in the NIR-II. Our results show that by engineering the vacancy defects, the bandgap of the 2H phase can be tailored to around 1 eV, and there are three candidates of vacancy structures that exhibit strong absorption in the NIR-II.
基于荧光的第二近红外区域（NIR-II，1000 - 1700纳米）光学成像在生物医学领域有着广泛应用，但在二维材料中仍难以找到新型NIR-II荧光材料。作为电子结构的关键特性，能带结构决定了二维材料的基本性质，如它们的光激发和电子输运。因此，我们计算了纯单层MoS薄膜不同晶相（1T相和2H相）的电子结构和光学性质，发现1T相在NIR-II窗口具有更好的吸收，从而有更好的荧光。然而，其稳定性较差使得1T相MoS在生物成像中的用途较少。通过引入空位缺陷和用外来原子掺杂，我们成功地调节了单层2H-MoS的带隙并使其在NIR-II中被激活。我们的结果表明，通过设计空位缺陷，2H相的带隙可以调整到约1电子伏特，并且有三种空位结构候选物在NIR-II中表现出强吸收。
