Interfacial Doping at Surfaces and in Low-Dimensional Materials

“to dope”这个词来源于荷兰语“doop”，意思是厚厚的蘸酱，所以dopen“意思是蘸”。在电子材料的上下文中，它是指将杂质（掺杂剂）引入到材料中或材料上，导致其电子特性发生变化。例如，通过测量薄膜或低维结构的电阻变化，可以容易地检测这种变化。因此，可以高精度地定量确定是否存在蘸酱或掺杂剂，例如用于气体或液体传感器。这种传感器的挑战是如何在之后去除蘸酱以重新使用该装置。我们介绍了分子开关的概念，作为薄纳米碳（或其他二维材料）薄膜的化学掺杂剂。这些分子可以在存在或不存在特定分析物的情况下在掺杂和非掺杂状态之间切换。它们赋予选择性不仅是由于它们的掺杂行为的变化，而且还通过物理地阻止分析物溶液中的其他潜在掺杂剂与导电膜相互作用。实际上，它们形成了一种可以留下来的蘸酱，因为它可以改变味道。基于这一概念，我们已经证明了饮用水的消毒剂传感器，由碳纳米管网络或涂有氧化还原可切换的低聚苯胺的无菌拉伸膜制成。该概念也可以应用于其他分析物（饮用水中的pH值，阴离子，阳离子等），但有必要更好地了解这些可切换的掺杂剂及其工作原理。 该提案旨在了解可切换掺杂剂分子与石墨烯，二硫化钼或由不同等级的碳纳米管制成的渗滤网络等二维材料的相互作用。特别地，我们将阐明分子-基底相互作用的五个方面：（1）基底化学身份的作用;（2）基底膜拓扑结构的作用（例如网络与单晶）;（3）施加外部电场以平衡和量化分子掺杂效应;（4）分子的电子结构，也考虑空间方面;（5）分子与基底膜的系链的性质（非共价对共价）和与基底中的化学缺陷的关系。 我们的传感器有可能比任何其他现有技术更强大，更简单，更可靠。消毒剂传感器已经开始商业化，用于饮用水质量控制，但我们的目标是开发和部署阴离子、阳离子、pH和消毒剂传感器，用于市政供水、原住民保护区、矿山或农田附近的地表沃茨等的水质控制，从而造福所有加拿大人的健康和他们的环境。我们的传感器还可以应用于医疗保健、研究或过程控制。

The word to dope' derives from the Dutch word doop' meaning thick dipping sauce', so doopen' means to dip'. In the context of electronic materials, it refers to introducing impurities (dopants) into or onto a material that lead to a change in its electronic properties. Such a change is easily detected, e.g. by measuring the change in resistance of a thin film or low-dimensional structure. So the absence or presence of the dipping sauce', or dopant, can be determined quantitatively with great accuracy, e.g. for use in gas or liquid sensors. A challenge for such a sensor is how to remove the dipping sauce' afterwards in order to reuse the device. We introduce the concept of molecular switches as chemical dopants for thin nanocarbon (or other two-dimensional material) films. These molecules can be switched between doping and non-doping states in the presence or absence of a particular analyte. They impart selectivity not only due to their change in doping behavior, but also by physically blocking other potential dopants in the analyte solution from interacting with the conductive film. In effect, they form a dipping sauce' that can stay on, because it can be made to change flavor. Based on this concept, we have demonstrated disinfectant sensors for drinking water fabricated from carbon nanotube networks or pencil-drawn films coated in redox-switchable oligoanilines. The concept can also be applied to other analytes (pH, anions, cations, etc. in drinking water), but it becomes necessary to better understand these switchable dopants, and how they work. This proposal aims to build an understanding of the interactions of switchable dopant molecules with 2-dimensional materials such as graphene, molybdenum disulfide or percolation networks made of different grades of carbon nanotubes. In particular, there are five aspects of the molecule-substrate interaction that we will elucidate: (1) The role of the chemical identity of the substrate; (2) The role of substrate film topology (e.g. network vs. single crystal); (3) Application of an external electric field to balance out and quantify the molecular doping effect; (4) Electronic structure of the molecules, also considering steric aspects; (5) Nature of the tether of the molecules to the substrate film (non-covalent vs. covalent) and relation to chemical defects in the substrate. Our sensors have the potential to be more robust, simple and reliable than any other available technology. The disinfectant sensors are already on their way to commercialization for drinking water quality control, but we aim to develop and deploy anion, cation, pH, and disinfectant sensors for water quality control in municipal water supplies, on first nations reserves, surface waters near mines or agricultural land, etc., thus benefitting the health of all Canadians, and their environment. Our sensors can also find applications in healthcare, research, or process control.