Xiang Limin, Zhang Peng, Liu Chaoren, He Xin, Li Haipeng B, Li Yueqi, Wang Zixiao, Hihath Joshua, Kim Seong H, Beratan David N, Tao Nongjian
Biodesign Center for Biosensors and Bioelectronics, Biodesign Institute, Arizona State University, Tempe, Arizona 85287, USA.
Lead contact.
Matter. 2020 Jul 1;3(1):166-179. doi: 10.1016/j.matt.2020.03.023. Epub 2020 Apr 20.
Water molecules can mediate charge transfer in biological and chemical reactions by forming electronic coupling pathways. Understanding the mechanism requires a molecular-level electrical characterization of water. Here, we describe the measurement of single water molecular conductance at room temperature, characterize the structure of water molecules using infrared spectroscopy, and perform theoretical studies to assist in the interpretation of the experimental data. The study reveals two distinct states of water, corresponding to a parallel and perpendicular orientation of the molecules. Water molecules switch from parallel to perpendicular orientations on applying an electric field, producing switching from high to low conductance states, thus enabling the determination of single water molecular dipole moments. The work further shows that water-water interactions affect the atomic scale configuration and conductance of water molecules. These findings demonstrate the importance of the discrete nature of water molecules in electron transfer and set limits on water-mediated electron transfer rates.
水分子可以通过形成电子耦合路径来介导生物和化学反应中的电荷转移。理解这一机制需要对水进行分子水平的电学表征。在此，我们描述了室温下单水分子电导的测量，利用红外光谱表征水分子的结构，并进行理论研究以辅助解释实验数据。该研究揭示了水的两种不同状态，对应于分子的平行和垂直取向。施加电场时，水分子从平行取向转变为垂直取向，导致电导状态从高到低切换，从而能够确定单水分子偶极矩。这项工作进一步表明，水 - 水相互作用会影响水分子的原子尺度构型和电导。这些发现证明了水分子的离散性质在电子转移中的重要性，并为水介导的电子转移速率设定了限制。
