Aqueous chloramine sensors based on molecules acting as switchable dopant sites on graphene-like carbon films

水对我们生存的大多数方面都是至关重要的。饮用水水质监测的重要参数之一是消毒剂的用量。如果它们的水平太低，微生物会在水中生长，这对我们的健康有害。如果消毒剂水平太高，消毒剂本身可能是有害的，或者至少对人类不舒服。在水处理厂完成一级消毒后，必须保持整个供水系统的消毒剂水平(二级消毒)。氯胺化越来越多地用于此目的，而不是氯化。虽然一氯胺的持久性在分销过程中是一种好处，但在消费者端更难检测到(它是无味的)和去除(它是稳定的)。然而，对于医疗保健、水文化、游泳池以及食品和饮料行业的应用，通过过滤完全去除氯胺是必不可少的。滤清器的寿命很难仅仅通过年龄或水量来判断，因为它更直接地是滤清器容量和污染物负荷的函数。理想情况下，过滤器后的传感器可以立即警告由于缺陷或容量耗尽而造成的漏洞。在这里，我们专注于开发一种用于点式滤水器的氯胺传感器。这项工作将建立在一种新型传感器设计的基础上，我们的研究团队最近证明该设计对检测饮用水中的游离氯有效。这一设计是基于我们的发现，即苯胺低聚物能够被水中的游离氯氧化，从而开启它们作为碳纳米管薄膜的p-掺杂剂的能力。一个简单的化学电阻结构可以定量地检测由于掺杂切换而导致的纳米碳膜的显著电导率变化，从而在整个相关范围内充当定量氧化还原传感器。初步数据表明，这些传感器还可以用来检测和区分各种氧化还原活性物种。通过使用不同的选择性可切换掺杂剂分子，同样的传感原理可以应用于pH或其他分析物。因此，我们建议为我们的工业合作伙伴3M加拿大公司开发一种能够定量检测相关应用中的氯胺的传感阵列。

Water is fundamentally important to most aspects of our existence. One of the most important monitoring parameters of drinking water quality is the level of disinfectants. If their levels are too low, microorganisms can grow in the water, which are harmful to our health. If the disinfectant levels are too high, the disinfectants themselves may be harmful, or at least unpleasant to humans. After primary disinfection at the water treatment plant is complete, disinfectant levels have to be maintained throughout the water distribution system (secondary disinfection). Chloramination is increasingly used for this purpose instead of chlorination. While its persistence is a benefit during distribution, monochloramine is harder to detect (it is odorless) and remove (it is stable) at the consumer end. For applications in health care, aqua culture, swimming pools, and in the food and beverage industry, however, complete removal of chloramines by filtration is imperative. Filter lifetime is difficult to judge just by age or water volume since it is more directly a function of filter capacity and contaminant load. Ideally, a sensor immediately after the filter could warn of breaches due to defects or exhausted capacity. Here we focus on the development of a chloramine sensor for point-of-use water filters. This work will build on a novel sensor design that our research team has recently demonstrated as effective for detecting free chlorine in drinking water. The design is based on our finding that aniline oligomers are capable of being oxidized by the free chlorine in water, thus switching on their ability to act as p-dopants for carbon nanotube films. A simple chemiresistor configuration can quantitatively detect the significant conductivity change of the nanocarbon film due to the dopant switching, and hence serve as a quantitative redox sensor across the entire relevant range. Preliminary data indicates that these sensors can also be used to detect and distinguish a variety of redox-active species. The same sensing principle can be applied to pH or other analytes by using different selectively switchable dopant molecules. Hence, we propose to develop a sensing array capable of quantitatively detecting chloramines in relevant applications for our industrial partner, 3M Canada.