Rules for Ion Pairing in Aqueous Interfacial Structures

水界面结构中离子对的规则

• 批准号: 2305129
• 负责人: Paul Cremer
• 金额: $ 53.12万
• 依托单位: Pennsylvania State Univ University Park
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-09-01 至 2026-08-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2305129&HistoricalAwards=false
• 关键词: Rules; Ion; Pairing; Aqueous; Interfacial

With the support of the Macromolecular, Supramolecular, and Nanochemistry Program in the Division of Chemistry, Professor Paul S. Cremer of Pennsylvania State University will explore the rules for ion pairing at chemically treated interfaces. The surfaces of many organic-based substances are charged in water. Examples include everything from colloids in water-based paints to proteins residing in cell membranes. Negatively charged surfaces attract positively charged metal ions from the adjacent solution. This study will help determine how metal ions from salts interact with negatively charged surfaces. The answers to this question have relevance in the biological and environmental sciences on the one hand, and materials science and engineering problems on the other. This research will also train a new generation of students using a combination of experimental physical chemistry techniques that involve laser light. The students will also get experience from working with theoretical collaborators who will help model ion-pairing data. The results are expected to provide information not only on how tightly ions bind to charged surfaces but also give important details on how the chemical composition of a surface influences ion binding. The results will be applicable to a wide range of practical problems ranging from the most effective way to soften drinking water to the guidance of pharmaceutical drug manufacturing. Work will also be conducted in association with high school chemistry teachers to develop new week-long laboratories for high school students that take advantage of ion pairing to partition food coloring into salt rich liquid phases. The goal will be to create experiments that can be conducted without the need for complex equipment or expensive chemicals.Experiments will be performed using infrared-visible sum frequency vibrational spectroscopy (SFVS) to probe the interactions of Hofmeister ions with Langmuir monolayers of long chain surfactants at the air/water interface. The vibrational spectra should contain information on interfacial water structure, alkyl chain ordering and headgroup hydration. In these experiments, both positively and negatively charged headgroups will be employed. This will include studies of carboxylate, sulfate, sulfonate, phosphate, and phosphate anionic headgroups as well as amine and trimethylamine cationic headgroups. A key feature of these experiments will be to conduct measurements as a function of interfacial charge density. This will be accomplished by using long chain fatty alcohols as filler surfactants to tune the mole fraction of charged headgroups. The order of binding for counterions will be noted and equilibrium binding constants will be measured for each counterion that is employed. Special attention will also be paid to conditions that lead to contact ion pair formation as opposed to solvent-shared ion pairing. Where appropriate, complementary data in bulk solution on ion pairing will be obtained by using multicurve resolution Raman spectroscopy. These types of systematic measurements should enable the elucidation of a set of rules that govern counterion pairing at macromolecular interfaces as a function of chemical identity and interfacial structure.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

在化学系大分子、超分子和纳米化学项目的支持下，宾夕法尼亚州立大学的Paul S. Cremer教授将探索化学处理界面上离子配对的规则。许多有机物质的表面在水中是带电的。例子包括从水性涂料中的胶体到驻留在细胞膜中的蛋白质。带负电荷的表面从邻近溶液中吸引带正电荷的金属离子。这项研究将有助于确定盐中的金属离子如何与带负电荷的表面相互作用。这个问题的答案一方面与生物和环境科学有关，另一方面与材料科学和工程问题有关。这项研究还将培养新一代的学生，他们将使用涉及激光的实验物理化学技术的组合。学生们还将从理论合作者那里获得经验，他们将帮助建立离子配对数据模型。预计这些结果不仅能提供离子与带电表面结合紧密程度的信息，还能提供表面化学成分如何影响离子结合的重要细节。研究结果将适用于广泛的实际问题，从最有效的软化饮用水的方法到指导药品生产。还将与高中化学教师合作，为高中学生开发新的为期一周的实验室，利用离子配对将食用色素分解成富含盐的液相。目标将是创造出不需要复杂设备或昂贵化学品就能进行的实验。实验将使用红外-可见和频振动光谱（SFVS）来探测霍夫迈斯特离子与长链表面活性剂Langmuir单层在空气/水界面的相互作用。振动谱应包含界面水结构、烷基链有序和头基水化的信息。在这些实验中，带正电荷和带负电荷的头团都将被使用。这将包括羧酸盐、硫酸盐、磺酸盐、磷酸盐和磷酸盐阴离子头基以及胺和三甲胺阳离子头基的研究。这些实验的一个关键特征将是作为界面电荷密度的函数进行测量。这将通过使用长链脂肪醇作为填充表面活性剂来调节带电头基的摩尔分数来实现。将记录反离子的结合顺序，并测量所使用的每个反离子的平衡结合常数。还将特别注意导致接触离子对形成的条件，而不是溶剂共享离子对。在适当的情况下，将通过使用多曲线分辨率拉曼光谱获得体溶液中离子配对的补充数据。这些类型的系统测量应该能够阐明一套规则，这些规则支配着大分子界面上的对偶，作为化学特性和界面结构的函数。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。