Li Rei-Ping, Lu Shiang-Yi, Lin Yen-Jen, Chen Chih-Yen
Department of Materials and Optoelectronic Science, National Sun Yat-Sen University, Kaohsiung 804, Taiwan.
Nanomaterials (Basel). 2022 Jun 29;12(13):2236. doi: 10.3390/nano12132236.
As extraordinary topological insulators, 2D bismuth telluride (BiTe) nanosheets have been synthesized and controlled with a few-layer structure by a facile and fast solvothermal process. The detail-oriented growth evolution of 2D BiTe in an ethylene glycol reducing solution is discovered and recorded for direct observation of the liquid-solid interactions through the use of environmental SEM. At the initial synthesis stage, Te nanowires are rapidly synthesized and observed in solution. In the next stage, Bi nanoclusters slowly adhere to the Te nanowires and react to form hierarchical Te-BiTe nanostructured materials. Additionally, the Te nanowires shorten in-plane in an orderly manner, while the BiTe nanosheets exhibit directional out-of-plane epitaxial growth. In the last procedure, BiTe nanosheets with a clear hexagonal appearance can be largely obtained. Experiments performed under these rigorous conditions require careful consideration of the temperature, time, and alkaline environment for each reaction process. In addition, the yield of a wider and thinner BiTe nanosheet is synthesized by manipulating the crystal growth with an optimal alkaline concentration, which is found through statistical analysis of the AFM results. In the UV-Vis-NIR spectroscopy results, the main peak in the spectrum tends to redshift, while the other peak in the ultraviolet range decreases during BiTe nanosheet synthesis, facilitating a rapid understanding of the trends in the morphological evolution of the BiTe materials in solution. By rationalizing the above observations, we are the first to report the success of environmental SEM, HAADF-STEM, and UV-Vis-NIR spectroscopy for confirming the BiTe nanosheet formation mechanism and the physical properties in the solvent media. This research promotes the future optimization of promising BiTe nanomaterials that can be used in the fabrication of thermoelectric and topological components.
作为特殊的拓扑绝缘体，二维碲化铋（BiTe）纳米片已通过简便快速的溶剂热法合成并控制为几层结构。通过环境扫描电子显微镜观察乙二醇还原溶液中二维BiTe的详细生长演变，以直接观察液固相互作用。在初始合成阶段，溶液中迅速合成并观察到碲纳米线。在下一阶段，铋纳米团簇缓慢附着在碲纳米线上并反应形成分级的Te-BiTe纳米结构材料。此外，碲纳米线在平面内有序缩短，而BiTe纳米片则呈现出定向的面外外延生长。在最后一步，可以大量获得具有清晰六边形外观的BiTe纳米片。在这些严格条件下进行的实验需要仔细考虑每个反应过程的温度、时间和碱性环境。此外，通过对原子力显微镜结果进行统计分析，利用最佳碱性浓度控制晶体生长，合成出了更宽更薄的BiTe纳米片。在紫外-可见-近红外光谱结果中，光谱主峰趋于红移，而在BiTe纳米片合成过程中，紫外区域的另一个峰降低，这有助于快速了解溶液中BiTe材料形态演变的趋势。通过对上述观察结果进行合理分析，我们首次报道了利用环境扫描电子显微镜、高角度环形暗场扫描透射电子显微镜和紫外-可见-近红外光谱成功证实了BiTe纳米片在溶剂介质中的形成机制和物理性质。这项研究推动了未来有望用于制造热电和拓扑组件的BiTe纳米材料的优化。
