跨16 nm厚细菌视紫红质多层膜的电流随距离单指数衰减特性
Mono-exponential Current Attenuation with Distance across 16 nm Thick Bacteriorhodopsin Multilayers
AI总结：
本研究针对干燥蛋白长程导电机制未解的问题，制备不同厚度的bR自组装多层膜，测得其零偏下电导率单指数衰减且衰减系数小，明确温度依赖源于界面，为揭示bR高效长程电子输运微观机制提供实验依据。
摘要：
尽管已有大量研究，天然蛋白质在干燥状态下实现长距离导电的卓越能力在很大程度上仍无法解释。在部分情况中，类似非共振隧穿输运的（弱）指数长度衰减特性，甚至能延伸至超过10 nm的厚度。本报告研究了在自组装的细菌视紫红质（bacteriorhodopsin, bR）蛋白多层膜中观测到的这类电荷输运特性。研究人员利用氨基己基膦酸和聚二烯丙基二甲基铵静电连接剂，在导电氮化钛（titanium nitride, TiN）衬底上制备了厚度约7.5 nm至15.5 nm的bR层。采用锥形共晶镓铟（EGaIn）顶电极，在零偏压下测得bR层电导率随厚度呈现奇特的单指数衰减规律，衰减系数β较小，约为0.8 nm⁻¹。通过蒸镀钛/金（Ti/Au）顶电极开展的变温测量，将数据拟合至隧穿、跳跃和载流子级联输运模型后，得到约100 meV的有效能垒。观测到的温度依赖性被归因于蛋白质-电极界面。电流密度的输运长度依赖性和温度依赖性，分别与通过蛋白质-蛋白质界面和蛋白质-电极界面的隧穿过程一致。重要的是，我们的研究结果表明需要新的理论方法，来揭示bR内部高效长程电子输运背后的微观机制。
英文摘要：
The remarkable ability of natural proteins to conduct electricity in the dry state over long distances remains largely inexplicable despite intensive research. In some cases, a (weakly) exponential length-attenuation, as in off-resonant tunneling transport, extends to thicknesses even beyond 10 nm. This report deals with such charge transport characteristics observed in self-assembled multilayers of the protein bacteriorhodopsin (bR). About 7.5 nm to 15.5 nm thick bR layers were prepared on conductive titanium nitride (TiN) substrates using aminohexylphosphonic acid and poly-diallyl-dimethylammonium electrostatic linkers. Using conical EGaIn top contacts, an intriguing, mono-exponential conductance attenuation as a function of the bR layer thickness with a small attenuation coefficient $β\approx 0.8 \space {\rm nm}^{-1}$ is measured at zero bias. Variable-temperature measurements using evaporated Ti/Au top contacts yield effective energy barriers of about 100 meV from fitting the data to tunneling, hopping, and carrier cascade transport models. The observed temperature-dependence is assigned to the protein-electrode interfaces. The transport length and temperature dependence of the current densities are consistent with tunneling through the protein-protein and protein-electrode interfaces, respectively. Importantly, our results call for new theoretical approaches to find the microscopic mechanism behind the remarkably efficient, long-range electron transport within bR.
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。
