Responsive surfaces: Lanthanide based Langmuir-Blodgett mono-layers for the sensing of chemical warfare agent mimics

传感器在社会中发挥着重要作用，在各种情况下都有应用，包括环境监测，临床生物学（例如疾病标志物检测），食品安全（例如污染物检测），国防（例如实时生物和化学战剂（CWA）检测，爆炸物检测），核工业（例如辐射和温度传感器）和工程/航空电子设备（例如温度和压力传感器，表面损伤传感器）仅举几例。在所有情况下，早期发现或感知变化是至关重要的。传感器发展的一个特别重要的应用是在CWA传感领域。有机膦酸盐（OP）家族神经毒剂的剧毒性质以及对军人和平民的潜在暴露构成了真正的危险。可以理解的是，对于军事人员和平民来说，明确需要足够的实时探测能力，因为提前预警将有助于防止伤亡。目前用于检测有机膦酸盐的分析技术虽然具有高灵敏度，但存在一些明显的局限性，包括仪器复杂、样品制备不方便、缺乏便携性和高成本。这些缺点在一定程度上阻碍了成本效益高的现场便携式设备的发展，这些设备很容易集成到个人防护设备（例如智能纺织品）和公共场所使用的非侵入性探测器中。为克服这些问题而开发的一种方法是通过与反应材料的相互作用来测量信号变化，反应材料在暴露于化学衍生物时发生化学、电学、光学或磁性质的变化。发光作为一种响应介质，在一般传感器的发展中受到了极大的关注，特别是在过去的5 - 10年里，一些优雅的发光超分子系统已经被开发出来，用于检测CWAs及其模拟物。其中大多数是基于溶液的传感器（这限制了设备的使用-溶液不方便存储，通常存在不稳定性，样品制备可能很麻烦-见上文），并且考虑到基于现场的应用，需要从溶液响应系统转向基于表面固定化受体报告的传感器。这代表了该领域的一个重大差距，因为发光传感为固定化传感器提供了一种有吸引力的介质，具有从简单组件开发小型便携式设备的潜力。因此，我们将使用另一种方法来克服上述一些缺点。通过利用薄膜（单层）基于镧系元素的传感器，将传感器沉积（固定）在表面上（使用Langmuir-Blodgett技术），并在暴露于低水平的CWA模拟物时经历发光特性的变化，我们将克服上述局限性。在整个研究项目中，我们将探索这种替代方法对CWA模拟物的选择性和敏感性，并最终评估其纳入功能设备的适用性。因此，我们将镧系元素优越的光物理特性与Langmuir-Blodgett技术提供的沉积控制相结合的方法将产生设计镧系元素发光传感器，这些传感器可以轻松可靠地固定，有可能改变表面分子传感领域。

Sensors play an important role in society, with applications in a variety of circumstances including environmental monitoring, clinical biology (e.g. disease marker detection), food safety (e.g. detection of contaminants), defence (e.g. real-time biological and chemical warfare agent (CWA) detection, explosives detection), the nuclear industry (e.g. radiation and temperature sensors), and engineering/avionics (e.g. temperature and pressure sensors, surface damage sensors) to name just a few. In all cases the early detection, or sensing, of change is paramount. One particularly important application of sensor development is in the field of CWA sensing. The highly toxic nature of the organophosphonate (OP) family of nerve agents and the potential for exposure to both military and civilian populations represents a real danger. Understandably, there is a clear requirement for adequate real-time detection capabilities for both military personal and civilian populations where advanced warning of exposure will help prevent casualties. Current analytical technologies for sensing organophosphonates, whilst being highly sensitive, have some clear limitations including complex instrumentation, inconvenient sample preparation, lack of portability, and high cost. These drawbacks somewhat hinder the development of cost-effective field based portable devices that are easily integrated into personal protective equipment (e.g. smart textiles) and non-invasive detectors for use in public areas.One approach that has been developed to overcome these problems is to measure signal change through interaction with responsive materials that undergo changes in chemical, electrical, optical or magnetic properties on exposure to chemical derivatives. Luminescence as a responsive medium for general sensor development has received significant attention and in particular some elegant luminescent supramolecular systems have been developed over the last 5 - 10 years for the detection of CWAs and their mimics. The majority of these have been solution based sensors (this limits the use in devices - solutions are inconvenient to store, often suffer from instability and sample preparation can be troublesome - see above), and with field based applications in mind, there is a need to move from solution responsive systems to surface immobilised receptor-reporter based sensors. This represents a significant gap in the field as luminescence sensing offers an attractive medium for immobilised sensors with potential to develop small portable devices from simple components. As such, we will use an alternative approach to overcome some of the above drawbacks. By utilising thin film (mono-layers) lanthanide based sensors where the sensor is deposited (immobilised) onto a surface (using the Langmuir-Blodgett technique) and undergoes a change in light emitting properties on exposure to low levels of CWA mimics we will overcome the limitations listed above. Throughout this research project we will explore this alternative approach for selectivity and sensitivity towards CWA mimics and ultimately assess its applicability for inclusion into functional devices. Therefore, our approach of combining the superior photophysical properties of the lanthanides, and the control over deposition afforded by the Langmuir-Blodgett technique will generate designer lanthanide luminescent sensors that can be immobilised easily and reliably, potentially transforming the field of on-surface molecular sensing.