Molecular Simulation of Chemical Warfare Agent Adsorption

摘要韦恩州立大学 - 0522005基于半导体金属氧化物 (SMO) 的传感器用于检测化学战剂 (CWA) 和有毒工业材料 (TIM)，其灵敏度约为十亿分之一。 基于 SMO 的传感器在尺寸、重量和成本方面比其他化学试剂检测方法具有潜在优势。 使用基于 SMO 的传感器进行 CWA/TIM 检测的一个限制因素是这些材料是非选择性的。 也就是说，除了感兴趣的试剂之外，还有许多分子可以产生阳性检测结果。 所提出的工作重点是提高半导体金属氧化物传感器的选择性和减少误报。控制 CWA/IM 在表面上的吸附及其随后通过孔隙的扩散以及此类设备设计中的关键因素。 这可以通过预过滤方案来完成，其中混合气流通过陶瓷膜或活性炭。 孔径、形状和化学成分可以定制以选择性地吸附感兴趣的分子。 CWA/TIM在预过滤器中浓缩后，通过化学置换器或热脉冲释放并发送至SMO进行检测。 预过滤的另一种方法是使用模板形成对目标分子具有高选择性的多孔半导体金属氧化物。 在所提出的工作中，分子模拟用于确定 CWA 及其模拟物在分子筛 MCM-41 中的吸收行为。在 CWA/TIM 上进行实验的困难性质激发了计算方法的使用。 分子模拟非常适合有毒物质的研究，可用于提取有关特定分子间相互作用在吸附过程中所起作用的信息。 由于感兴趣的分子不存在适当的模型（力场），因此建议大力开发有机磷酸盐的可转移联合原子力场，包括化学战剂沙林和 VX。 分子模型的开发是使用模拟设计基于 SMO 的传感器所需的第一步。 这些分子模型将允许使用模拟来研究孔径、形状和成分对特定 CWA/TIM 多孔材料选择性的影响。 原子模拟和从头算方法用于识别特定的多孔结构（形状/尺寸），具有低误报率的 CWA/TIM 传感所需的高选择性。 更广泛的影响 最近发生的世界事件，例如沙林毒气进入东京地铁系统，以及当前对潜在对手怀疑开发和使用化学和生物战剂的担忧，凸显了为这些材料开发高度机动、精确的传感器和净化设备的重要性。 作为拟议研究的成果，PI 期望通过开发必要的计算基础设施来克服该领域当前的局限性，以便在新型模板分子识别材料的设计中使用模拟。 与其他多孔材料相比，这些模板化分子识别材料有望对化学战剂具有高选择性和敏感性。 开发对特定目标分子具有高亲和力的吸附剂预计将改进传感器、过滤器和催化材料。 这些进展预计将减少恐怖组织使用化学战剂的威胁，改善国家安全和公共卫生。 此外，描述任务分子和金属氧化物表面之间相互作用的精确力场将使其他研究小组能够使用分子模拟来设计用于其他目的的新型吸附剂和催化材料。这项研究与教育相结合。 鼓励本科生，特别是代表性不足的少数族裔和女性，参与本科生研究项目。 本科生研究经验被用作指导工具，以改善保留率历来较低的少数群体学生的招募和保留。

ABSTRACTWayne State University - 0522005Semi-conducting metal oxide (SMO) based sensors for the detection of chemical warfare agents (CWA) and toxic industrial materials (TIM) exhibit sensitivities on the order of parts per billion. SMO based sensors have potential advantages over other methods of chemical agent detection in terms of size, weight and cost. One limiting factor in the use of SMO based sensors for CWA/TIM detection is that these materials are non-selective. That is, there are many molecules, in addition to the agent of interest, which will yield positive detection results. The proposed work is focused on improving the selectivity of semi-conducting metal oxide sensors and the reduction of false positive responses.Controlling the adsorption of CWA/IM onto the surfaces and their subsequent diffusion through the pores and key factors in the design of such devices. This can be done via a pre-filtering scheme, where a mixed gas stream in passed through a ceramic membrane or activated carbon. Pore size, shape and chemical composition can be tailored to selectively adsorb the molecule of interest. After being concentrated in the pre-filter, the CWA/TIM is released by a chemical displacer or a thermal pulse and sent to the SMO for detection. An alternative approach to pre-filtering is to use templating to form porous semi-conducting metal oxides with high selectivity to the target molecule. In the proposed work, molecular simulation is used to determine the absorption behavior of CWA and their simulants in the molecular sieve MCM-41.The difficult nature of performing experiments on CWA/TIM motivates the proposed use of computational methods. Molecular simulations is well suited to the study to the toxic material and can be used to extract information on the roles specific intermolecular interactions play in the adsorption process. Because appropriate models (force fields) so not exist for the molecules of interest, significant effort is proposed on the development of transferable united-atom force fields for organophosphates, including the chemical warfare agents sarin and VX. The development of molecular models is a required first step in use of simulation for the design of SMO based sensors. These molecular models will allow for the use of simulation to investigate the effects of pore size, shape and composition on the selectivity of porous materials with respect to specific CWA/TIM. Atomistic simulations and ab initio methods are used to identify specific porous structures (shape/size) with the high selectivity necessary for the sensing of CWA/TIM with low false positives. Broader ImpactsRecent world events, such as the release of sarin gas into the Tokyo subway system and the current concern over potential adversaries suspected development and use of chemical and biological warfare agents underscore the importance of developing highly mobile, accurate sensors and decontamination equipment for these materials. As an outcome of the proposed research, the PI expects to overcome the current limitations of the field by developing the necessary computational infrastructure for the use of simulation in the design of novel templated molecular recognition materials. These templated molecular recognition materials hold the promise of high selectivity and sensitivity to chemical warfare agents compared to other porous materials. Development of adsorbents with high affinity to a specific target molecule is expected to result I improved sensors, filters and catalytic materials. Such developments are expected to reduce the threat of the use of chemical warfare agents by terrorist organizations, improving national security and public health. Furthermore, accurate force fields describing the interactions between quest molecules and metal oxide surfaces will allow other research groups to use molecular simulation as a too to design novel adsorbent and catalytic materials for other purposes.This research is integrated with education. Undergraduates, particularly underrepresented minorities and women, are encouraged to participate in undergraduate research projects. The undergraduate research experience is used as a mentoring tool to improve the recruitment and retention of students in minority groups with historically low retention rates.