New Nonlinear Optical Approaches for Probing the Microscopic Nature of Liquids and Solutions

当我们想到化学反应时，我们通常会想象一个装满溶液的烧杯，坐在实验室的长椅上。大多数化学作用发生在溶液中，在溶液中，反应物和产物周围的液体会以意想不到的方式影响化学反应。虽然化学家们认识到溶液的复杂性已经有一段时间了，但他们通常不会考虑容器的大小。这是真的，集装箱是大的。然而，当装有溶液的容器的直径减少到几百纳米，或者说大约是人类头发直径的万分之一时，分子与容器壁的相互作用会改变溶液的性质，使问题变得更加困难。在化学系化学结构动力学和机理A(CSDM-A)计划的支持下，马里兰大学园区分校的John Fourkas教授正在开发新的实验和模拟方法，用于表征大容器和纳米限制下的溶液。从该项目中获得的见解可以促进我们对解决方案的基本理解，并使测量更准确，这两者都可能对一系列技术产生广泛的影响，如化学分离、润滑、石油回收和催化。该项目还为下一代科学家提供跨学科培训，外联活动正在促进公众对科学探索和发现的欣赏。人们正在寻求新的非线性光学光谱方法来解决液体和溶液中的重要悬而未决的问题。Fourkas教授正在与他的学生合作，将光学克尔效应(OKE)光谱与分子模拟相结合，开发出一种通用方法，用于测量纳米受限环境中液体的本征密度，这是确定液体行为的关键属性，并研究溶剂和二氧化硅表面之间的氢键相互作用。该项目还寻求大幅改进对强吸收分子和纳米材料溶液的高强度光吸收性能的测量。一种新的方法，双光束作用(2-BA)光谱仪，正在发展中，以改进多光子吸收截面的测量。2-BA光谱学允许详细和准确地描述多光子荧光团的光物理特性，并为将类似技术应用于涉及非线性吸收的广泛的其他过程奠定了基础。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

When we think of a chemical reaction, we often envision a beaker filled with a solution and sitting on a lab bench. Most chemistry takes place in solution, where the liquid surrounding the reactants and products can affect a chemical reaction in unexpected ways. While chemists have appreciated the complicated nature of solutions for some time, they do not typically consider the container's size to be a factor. This is true of the container is large. However, when the container holding the solution is reduced to just a few hundred nanometers across, or about 1/10,000 the diameter of a human hair, interaction of molecules with the walls of the container alter the solution properties, making the problem even more difficult. With support for the Chemical Structure Dynamics, and Mechanisms A (CSDM-A) Program in the Division of Chemistry, Professor John Fourkas at the University of Maryland-College Park is developing new experimental and simulation methods for characterizing solutions, both in large containers, and under nanoconfinement. Insights gained from the project could advance our fundamental understanding of solutions, as well as enable more accurate measurements, both of which could have broad implications for range of technologies such as chemical separations, lubrication, oil recovery, and catalysis. The project also provides interdisciplinary training of the next generation of scientists, and outreach activities are fostering public appreciation of scientific exploration and discovery. New nonlinear optical spectroscopic approaches are being pursued to address important outstanding problems in liquids and solutions. Working with his students, Professor Fourkas is combining Optical Kerr effect (OKE) spectroscopy with molecular simulations to develop a general approach for measuring the intrinsic density of liquids in nanoconfined environments, which is a crucial property in determining the behavior of a liquid, as well as to study hydrogen bonding interactions between solvents and silica surfaces. The project is also pursuing substantially improved measurements of the high-intensity optical absorption properties of solutions of strongly absorbing molecules and nanomaterials. A new class of methods, 2-beam action (2-BA) spectroscopies, is being developed to make improved measurements of multiphoton absorption cross sections. 2-BA spectroscopies allow for the detailed and accurate characterization of the photophysics of multiphoton fluorophores, and set the stage for the application of analogous techniques to a broad range of other processes that involve nonlinear absorption.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.