HIGH SENSITIVITY VAPOUR RECOGNITION AND MONITORING USING PORPHYRIN-CALIXARENE FILMS FOR A WIDE RANGE OF ANALYTES

对存在或进入大气层的污染物或污染物蒸气的识别和测量从未像今天这样重要。目前对我们环境的兴趣是因为压倒性的科学数据证实了全球变暖和相关的气候变化。此外，以犯罪手段将有毒蒸气引入我们的空气供应的恐怖主义所构成的威胁突出表明，迫切需要高响应性的传感材料，这些材料可以构成高效传感系统的活性成分。许多监测设备使用基于半导体的或电化学传感元件，但这些元件通常是非特定的，通常需要较高的工作温度。有机材料最引人注目的是电子鼻的形式，在电子鼻中，导电聚合物充当化学电阻。然而，从一批到另一批复制这些聚合物的行为的问题阻碍了它们的商业发展。我们之前的研究已经产生了一系列的卟啉，它们表现出了有用的传感材料的大部分特征，适用于广泛的分析物和低浓度(通常在0.5/10ppm)。卟啉是一种高度共轭的有机分子，具有丰富的紫外可见吸收光谱。这些转变很容易被各种气体分析物分子的吸附所改变。对吸收光谱的仔细研究表明，蒸气暴露引起的详细变化因分析物不同而不同。目前先进的、高分辨率的、便携的，最重要的是便宜的(&lt；2-3k)紫外-可见光谱仪现在意味着，即使是由于与不同分析物相互作用而产生的修改光谱中的非常微小的变化也可以很容易地检测出来。因此，通过在阵列配置中使用传感材料家族的几个成员，可以预期识别和量化特定分析物的浓度。我们的卟啉可以加工成朗缪尔-谢弗(LS)膜，尽管我们的工作表明，使用主体成分/例如脂肪酸或杯[n]芳烃酸/有助于成膜，并导致样品的高重复性。在这项拟议的研究计划中，我们希望开发一类卟啉(杯[n]芳烃)，其中，卟啉单体接枝在杯[n]芳烃羧酸环的边缘，形成一种分子，具有卟啉的蒸气/敏感官能团和杯[n]芳烃酸物种的极好的成膜性能。此外，与熔点通常在250/300oC的许多其他主体材料相比，杯[n]芳烃是一种相对热稳定的化合物。重要的是，我们希望引用杯[n]芳烃本身的相互作用性质，众所周知，杯[n]芳烃与广泛的小分子如NO2、甲苯和各种金属离子结合在一起，使得加合物的光学性质在紫外可见光区被显著改变。该计划的主要目标是实现一个分子系统，在该系统中，所得到的薄膜的光学性质受到分析物与卟啉部分和/或杯[n]芳烃腔之间的相互作用的显著影响。这些分子的双功能有望提高选择性，超越我们目前的成就，并导致非常有用的传感材料。杯芳烃载体的多种性质(结合能力、孔隙率、成膜能力、热稳定性)与卟啉的蒸气敏感性相结合，应该使我们能够开发出具有快速响应速度、高灵敏度、高识别能力(选择性/使用阵列)的敏感材料，并且最有可能显示出抑制的温度依赖性。

The identification and measurement of pollutant or contaminant vapours present in or entering the atmosphere has never been more important than today. Current interest in our environment has resulted from overwhelming scientific data confirming global warming and associated climate change. Furthermore, the threat posed by terrorism of toxic vapours introduced criminally into our air supply highlights the urgent need for highly responsive sensing materials that can form the active ingredients in efficient sensing systems. Many monitoring devices utilise semiconductor-based or electrochemical sensing elements but these are often non-specific and usually require high operating temperatures. Organic materials have most notably attracted attention in the form of the electronic nose in which conducting polymers act as chemi-resistors. However, problems with reproducing the behaviour of these polymers from batch to batch have hindered their commercial development. Our previous research has produced a family of porphyrins which exhibits most of the characteristics of useful sensing materials for application with a wide range of analytes and at low concentrations (typically in the region 0.5 / 10ppm). Porphyrins are highly conjugated organic molecules which display a rich UV-visible absorption spectrum . These transitions are readily modified by the adsorption of a wide range of gaseous analyte molecules. Close study of the absorption spectrum shows that the detailed changes resulting from vapour exposure are different from analyte to analyte. The current availability of sophisticated, high resolution, portable and, most importantly, inexpensive (<2-3k) UV-visible spectrophotometers now means that even very small variations in the modified spectra arising from interactions with different analytes can be detected easily. Thus, by using several members of a family of sensing materials in an array configuration, one can expect to identify and quantify the concentration of a particular analyte. Our porphyrins are processable as Langmuir-Schaeffer (LS) films although our work has shown that the use of a host component / for example, a fatty acid or a calix[n]arene acid / aids film formation and leads to high reproducibility of samples. In this proposed research programme, we wish to develop a family of porphyrins ( calixporphs ) in which the porphyrin monomer is grafted around the edge of a calix[n]arene carboxylic acid ring to form a molecule possessing the vapour /sensitive functionality of the porphyrin coupled to the superb film-forming properties of the calix[n]arene acid species. Furthermore, calix[n]arenes are known to be relatively thermally stable compounds compared to many other host materials with melting points usually in the range 250 / 300oC. Importantly, we wish to invoke the interaction properties of calix[n]arenes themselves which are known to bind a wide range of small molecules such as NO2, toluene and various metal ions in such a way that the optical properties of the adduct are significantly modified in the UV-visible region. The principal aim of this programme is to realise a molecular system in which the optical properties of resulting thin films are affected dramatically by the presence of interactions between the analyte and the porphyrin moieties and / or the calix[n]arene cavities. The bifunctionality of these molecules would be expected to enhance selectivity beyond our present achievements and lead to extremely useful sensing materials. The versatile properties of the calixarene carrier (binding ability, porosity, film-forming ability, thermal stability) coupled to the vapour sensitivity of the porphyrins should allow us to develop sensing materials displaying fast response rate, high sensitivity, high identification power (selectivity / with the use of arrays) and most probably materials showing suppressed temperature dependence.