二硫化钼(MoS₂)作为水系锌离子电池的正极材料, 受到锌离子(Zn²⁺)与主体框架之间的强静电相互作用表现出缓慢的反应动力学。并且MoS₂的层间距较窄难以嵌入大尺寸水合Zn²⁺, 导致MoS₂电极呈现出较低的放电比容量。本研究通过一种简单的氨水辅助水热法制备了NH₄⁺扩层的二硫化钼(MoS₂-N)电极, 氨水分解产生的氨气在促进硫代乙酰胺水解和提供还原性S^2-的同时, 还会产生大量NH₄⁺作为插层离子, 将MoS₂的层间距由0.62 nm扩展至0.92 nm, 进而大大降低了Zn²⁺嵌入能垒(改性电极的电荷转移电阻R_ct低至35 Ω)。当电流密度为0.1 A·g^-1时, MoS₂-N电极的初始放电比容量相比未扩层的MoS₂电极提高了1倍, 高达149.9 mAh·g⁻¹。同时在1.0 A·g^-1电流密度下放电比容量稳定在110 mAh·g^-1左右, 循环200圈后库仑效率将近100%。本研究提出的氨水辅助扩层法, 丰富了提升MoS₂电化学性能的改性策略, 为后续的正极材料开发提供了新的思路。

Miniaturized spectrometers have been widely researched in recent years, but few studies are conducted with on-chip multimode schemes for mode-division multiplexing (MDM) systems. Here we propose an ultracompact mode-division demultiplexing spectrometer that includes branched waveguide structures and graphene-based photodetectors, which realizes simultaneously spectral dispersing and light fields detecting. In the bandwidth of 1500–1600 nm, the designed spectrometer achieves the single-mode spectral resolution of 7 nm for each mode of TE₁–TE₄ by Tikhonov regularization optimization. Empowered by deep learning algorithms, the 15-nm resolution of parallel reconstruction for TE₁–TE₄ is achieved by a single-shot measurement. Moreover, by stacking the multimode response in TE₁–TE₄ to the single spectra, the 3-nm spectral resolution is realized. This design reveals an effective solution for on-chip MDM spectroscopy, and may find applications in multimode sensing, interconnecting and processing.Miniaturized spectrometers have been widely researched in recent years, but few studies are conducted with on-chip multimode schemes for mode-division multiplexing (MDM) systems. Here we propose an ultracompact mode-division demultiplexing spectrometer that includes branched waveguide structures and graphene-based photodetectors, which realizes simultaneously spectral dispersing and light fields detecting. In the bandwidth of 1500–1600 nm, the designed spectrometer achieves the single-mode spectral resolution of 7 nm for each mode of TE₁–TE₄ by Tikhonov regularization optimization. Empowered by deep learning algorithms, the 15-nm resolution of parallel reconstruction for TE₁–TE₄ is achieved by a single-shot measurement. Moreover, by stacking the multimode response in TE₁–TE₄ to the single spectra, the 3-nm spectral resolution is realized. This design reveals an effective solution for on-chip MDM spectroscopy, and may find applications in multimode sensing, interconnecting and processing.

Understanding the ultrafast carrier dynamics and the mechanism of two-dimensional (2D) transition metal dichalcogenides (TMDs) is key to their applications in the field of optoelectronic devices. In this work, a single pulse pump probe method is introduced to detect the layer-dependent ultrafast carrier dynamics of monolayer and few-layer WS2 excited by a femtosecond pulse. Results show that the ultrafast carrier dynamics of the layered WS2 films can be divided into three stages: the fast photoexcitation phase with the characteristic time of 2–4 ps, the fast decay phase with the characteristic time of 4–20 ps, and the slow decay phase lasting several hundred picoseconds. Moreover, the layer dependency of the characteristic time of each stage has been observed, and the corresponding mechanism of free carrier dynamics has been discussed. It has been observed as well that the monolayer WS2 exhibits a unique rising time of carriers after photoexcitation. The proposed method can be expected to be an effective approach for studying the dynamics of the photoexcited carriers in 2D TMDs. Our results provide a comprehensive understanding of the photoexcited carrier dynamics of layered WS2, which is essential for its application in optoelectronics and photovoltaic devices.

以石墨烯为代表的二维材料具有优异的本征性质, 例如高表面积和电导率, 但其宏观块体材料的性质仍不理想。这是由于石墨烯片层堆叠损失了有效的表面; 片层之间联结较弱导致接触电阻和热阻增大。原则上二维材料的三维化设计能避免上述问题, 将纳米尺度的优异性质传递到宏观尺度, 获得高表面积、高导电、贯通孔道和优良机械性能的块体材料。二维材料多孔块体可用于电极、吸附剂和弹性体等。发泡法工艺简单、成本低, 是近年来制备二维材料泡沫体的主要方法。本文系统总结了发泡法的基本原理, 综述了石墨烯、氮化硼等二维材料泡沫体的研究进展, 展望了二维材料泡沫体在能源、环境等方面的应用前景。