Proton transport in water networks: Understanding cooperative effects in charge migration via isomer-selective vibrational spectroscopy of cold cluster ions

水网络中的质子传输：通过冷簇离子的异构体选择性振动光谱了解电荷迁移的协同效应

• 批准号: 0911199
• 负责人: Mark Johnson
• 金额: $ 48万
• 依托单位: Yale University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-09-01 至 2012-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0911199&HistoricalAwards=false
• 关键词: Proton; transport; water; networks; Understanding

In this award funded by the Experimental Physical Chemistry Program of the Division of Chemistry, Professor Mark A. Johnson of Yale University will explore the molecular-level interactions responsible for the unique properties associated with an excess proton in water. Better understanding of water-mediated proton transport is needed because this process occurs in many fields of science and technology where only a small number of water molecules are available. Examples range from trans-membrane proton pumps that mediate electrical signaling in biological systems to proton exchange membranes that conduct positive charge in fuel cells. One of the long-standing roadblocks preventing direct observation of the local environment of an excess proton in the condensed phase is that its vibrational signature is so broad that it masks the molecular-level picture of how the charge is accommodated at various stages along the transport chain. The focus of the research funded by Prof. Johnson's award is to overcome this problem by exploiting very recent advances in the preparation and photochemical manipulation of cold, size-selected water clusters in the gas phase. These methods involve Ar-cluster mediated synthesis and pump-probe vibrational spectroscopy of cluster ions using multiple stages of mass selection. The specific goal is to obtain precise spectroscopic signatures that can be analyzed to reveal how the degree of charge delocalization depends on the different network topologies of the hydrogen-bonded environment. The target systems chosen to express these effects are derived from water cluster-mediated reactions that occur naturally in the atmosphere, and indeed promise to resolve a long-standing puzzle regarding the observed deionization rate of the ambient NO+ ion in the D region of the ionosphere (80 km altitude). A new type of measurement will be developed that is capable of measuring the energetic barriers to proton transfer, and thus expose the key factors controlling proton mobility. The wide ranging implications of the basic science explored in this effort provide a natural way to engage the interest and participation of students at all levels - high school through Ph.D. candidates - with projects that connect to issues of immediate importance to the society like energy (in the case of fuel cells) and the environment (in the case of water-mediated atmospheric chemistry). Several students already involved in this research are from under-represented groups in the physical sciences, including undergraduates at Yale University.

在这个由化学系实验物理化学项目资助的奖项中，马克·A·耶鲁大学的约翰逊将探索分子水平上的相互作用，这种相互作用与水中过量质子的独特性质有关。需要更好地理解水介导的质子传输，因为这一过程发生在许多科学和技术领域，只有少量的水分子可用。 例子包括从在生物系统中介导电信号的跨膜质子泵到在燃料电池中传导正电荷的质子交换膜。 长期以来，阻碍我们直接观察凝聚相中过剩质子的局部环境的一个障碍是，它的振动特征如此之宽，以至于掩盖了电荷在传输链沿着的各个阶段是如何被容纳的分子水平图像。 由约翰逊教授的奖项资助的研究的重点是克服这一问题，利用最新的进展，在制备和光化学操纵冷，大小选定的水簇在气相中。 这些方法涉及Ar-团簇介导的合成和使用多级质量选择的团簇离子的泵浦-探测振动光谱。 具体目标是获得精确的光谱特征，可以分析，以揭示电荷离域的程度如何取决于氢键环境的不同网络拓扑结构。 选择来表达这些效果的目标系统来自于大气中自然发生的水团簇介导的反应，并且确实有望解决关于在电离层D区域（80公里高度）中观察到的环境NO+离子的去电离率的长期难题。 将开发一种新型的测量方法，能够测量质子转移的能量障碍，从而揭示控制质子迁移率的关键因素。在这项工作中探索的基础科学的广泛影响提供了一种自然的方式来吸引各级学生的兴趣和参与-高中到博士。候选人-项目涉及对社会至关重要的问题，例如能源（就燃料电池而言）和环境（就水介导的大气化学而言）。 已经参与这项研究的几名学生来自物理科学领域代表性不足的群体，包括耶鲁大学的本科生。