纳米限阈下的水分子作为载体的信号转换、传导和放大

Signal conversion, transmission, and multiplication mediated by water wires within nano-confinement

通常各种信号处理器,如放大器、分流器等,都是利用电子或者光子进行信号的处理,当处理器小到纳米或分子尺度时,由于分子体系固有的复杂性,和来自热涨落和纳米尺度上区间信号的相互干扰等原因,分子层次上信号的准确传递、转换和放大常常是十分困难的.从分子层次的相互作用的角度来看,与静电相互作用的慢衰减方式和范德华作用的快速衰减方式相比,极性分子的偶极相互作用是屏蔽热噪声的影响且有效地避免分支信号间的干扰而实现分子层次上的长程信号传递的有效方法.本文回顾了如何利用限阈于特定管径的碳纳米管内的水分子单链有效地进行将单电子电量大小的电信号转换成偶极信号,并在常温热噪声的环境中实现有效地分子层次的长程信号传导,并进一步利用Y型水分子单链实现分子层次信号的放大.本文还讨论了Y型水分子单链实现分子层次信号放大的鲁棒性,并利用在水分子之外的极性小分子链——尿素分子链,再次展现这种通过偶极相互作用来实现分子层次的信息处理方式.对于人们设计新型的纳米信号传输器件、理解生物信号传递机制,这些研究具有重要的理论意义.

Signal processors such as amplifiers and diverters usually utilize electrons or photons to process signals. As their sizes decrease to nano- or molecular scale, accurate signal conversion, transmission, and multiplication at the molecular level usually become difficult, due to the intrinsic complexity in these molecular systems and the significant noises arising from thermal fluctuations as well as interferences between branch signals. From the viewpoint of molecular interactions, compared with the slow decay of electrostatic interactions and the fast decay of van der Waals interactions, the dipole-dipole interactions between polar molecules can effectively screen the thermal noises and avoid the interferences between branch signals, thus achieving accurate signal transmission at the molecular level. In this paper, we briefly review recent progress on the effective conversion of a charge signal at the single-electron level to a dipolar signal, long-range signal transmission in the presence of significant thermal noises, and molecular-scale signal multiplication, by using one-dimensional water wires confined within carbon nanotubes with appropriate diameters. We also discuss the robustness of such signal multiplication, and demonstrate the capability of polar organic molecules（using urea for illustration） for signal multiplication. These findings are expected to be helpful in design of novel nano-/molecular-based signal processors, and provide new insights into our understanding toward signal processing in biological systems.