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arXiv 2108.00136cond-mat.mtrl-sciphysics.chem-ph
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二维范德瓦尔斯空间中的氧化还原与分子扩散

Redox and Molecular Diffusion in 2D van der Waals Space

Haneul Kang, Kwanghee Park, Sunmin Ryu

摘要:

理解两个化学实体之间的电荷转移(CT)及其电荷密度的后续变化不仅对分子物种而且对各种低维材料都是必不可少的。由于其极高的表面原子分数,二维(2-D)材料最容易发生电荷交换,并根据其电荷密度表现出截然不同的物理化学性质。在这方面,自2004年首次报道以来,石墨烯在环境空气中的自发和不可控制的电离在实现实验再现性方面造成了许多混乱和技术困难。此外,同样的环境空穴掺杂很快在二维半导体中被观察到,这意味着一个共同的机制应该是有效的,并普遍适用于其他低维材料。在这个帐户中,我们回顾了我们在解开使用2-D晶体的隐藏CT反应的化学起源和机械要求方面的突破。我们开发了原位光学方法,使用拉曼和光致发光(PL)光谱和成像来量化电荷密度。使用气体和温度控制的原位测量,我们发现,电空穴注入的氧还原反应(ORR):$O_{2}$ + $4H^{+}$ + $4e^{-}$ $\rightleftharpoons$ $2H_{2}O$,这是独立验证的pH值依赖于HCl溶液。除了氧气和水蒸气,整个CT反应需要亲水性介电基质,这有助于样品-基质界面的水合。界面局部化反应使我们能够通过改变2-D间隙间距和引入缺陷来可视化和控制界面分子扩散和CT。在这个帐户中总结的基本电荷交换的完整机制将是必不可少的,在探索其他低维材料的材料和器件特性。

英文摘要:

Understanding charge transfer (CT) between two chemical entities and subsequent change in their charge densities is essential not only for molecular species but also for various low-dimensional materials. Because of their extremely high fraction of surface atoms, two-dimensional (2-D) materials are most susceptible to charge exchange and exhibit drastically different physicochemical properties depending on their charge density. In this regard, spontaneous and uncontrollable ionization of graphene in the ambient air has caused much confusion and technical difficulty in achieving experimental reproducibility since its first report in 2004. Moreover, the same ambient hole doping was soon observed in 2-D semiconductors, which implied that a common mechanism should be operative and apply to other low-dimensional materials universally. In this Account, we review our breakthroughs in unraveling the chemical origin and mechanistic requirements of the hidden CT reactions using 2-D crystals. We developed in-situ optical methods to quantify charge density using Raman and photoluminescence (PL) spectroscopy and imaging. Using gas and temperature-controlled in-situ measurements, we revealed that the electrical holes are injected by the oxygen reduction reaction (ORR): $O_{2}$ + $4H^{+}$ + $4e^{-}$ $\rightleftharpoons$ $2H_{2}O$, which was independently verified by pH dependence in HCl solutions. In addition to oxygen and water vapor, the overall CT reaction requires hydrophilic dielectric substrates, which assist hydration of the sample-substrate interface. The interface-localized reaction allowed us to visualized and control interfacial molecular diffusion and CT by varing the 2-D gap spacing and introducing defects. The complete mechanism of the fundamental charge exchange summarized in this Account will be essential in exploring material and device properties of other low dimensional materials.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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