Instrument Development: Modular, Multitrack, and Multifunctional Linearly Polarized Spectrometer for Synchronized Multispectral Characterization of Molecular Assembly

在化学部化学测量和成像（CMI）项目和刺激竞争性研究（EPSCoR）既定项目的支持下，密西西比州立大学的张东茂教授及其研究小组正在开发一种多通道光谱仪，用于同时采集紫外可见和线性偏振共振同步（LPRS）光谱。 LPRS光谱学是由Zhang团队最近开发的一种新技术，其利用线偏振光进行激发和检测。 当与紫外-可见光测量结合使用时，LPRS方法可以定量测定天然和合成生物、化学和环境样品的吸收、散射和发射特性。 结合UV-vis和LPRS分析获得的光谱特征提供了关于材料的几何特征（尺寸和形状）和光学性质的指纹状信息。 然而，目前的UV-vis和LPRS分析是耗时的，并且仅适用于稳态样品，因为它需要用两种不同的仪器进行三次连续的光谱采集。因此，该补助金支持开发新的测量工具，以实现具有高时间分辨率的动态系统的同时多维光谱表征。 这些技术对许多科学技术领域至关重要，包括生物学、材料科学、清洁能源应用和环境保护。 该项目的更广泛影响还包括为来自不同背景的学生提供科学仪器，光谱学，数据采集和分析以及材料科学等跨学科领域的培训机会。 此外，Zhang团队将组织两次光谱学研讨会，为HBCU（历史上的黑人学院和大学）和PUI（主要本科院校）的学生和教师提供机会，了解该项目中开发的技术的理论和独特能力。 涉及材料动态演化的溶液相过程在化学、生物学和材料科学中普遍存在。这种系统的实例包括蛋白质聚集、分子组装和纳米颗粒合成，以及大分子、超分子组装和纳米级材料的合成后修饰。能够同时监测这些材料演变的技术不仅对于破译结构和光学性质之间的相关性至关重要，而且对于新材料的发现和优化也至关重要。 利用光与物质相互作用的光学光谱技术一直是研究这种动态系统的首选方法，因为它们具有广泛的可访问性和相对较高的时间分辨率。然而，现有的工具是有限的，因为它们不能同时解决的吸收，散射和发射过程之间的复杂的相互作用的信息内容。 组合的UV-vis和LPRS分析是非常有用的，因为这种方法能够同时实验定量材料的吸收消光光谱、散射消光光谱、散射去偏振光谱、荧光强度和去偏振光谱以及荧光量子产率。 总的来说，这些光谱特征提供了关于材料的大小、形状、分子组成和光学活性的关键见解，其中许多是以前无法获得的。 该项目中概述的科学研究旨在创建一个多通道线性偏振光谱仪，能够同时采集这些具有亚秒级时间分辨率的多维特征。 该研究小组将研究卟啉组件的形成，作为开发测量方法的模型系统，并将研究吸收，散射和发射特性在组装和拆卸过程中如何变化。 这些研究有可能揭示卟啉组装和拆卸过程中的机械途径。 为这些模型系统开发的测量和数据分析策略将可扩展到跨一系列科学学科的许多其他动态系统，并为高级学生培训和来自不同背景的研究人员的参与提供平台。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估来支持。

With support from the Chemical Measurement and Imaging (CMI) program of the Chemistry Division and the Established Program to Stimulate Competitive Research (EPSCoR), Professor Dongmao Zhang and his research group at Mississippi State University are developing a multichannel spectrometer for simultaneous acquisition of UV-visible and linearly polarized resonance synchronous (LPRS) spectra. LPRS spectroscopy is a new technique recently developed by the Zhang group that employs linearly polarized light for excitation and detection. When used in combination with UV-visible measurements, the LPRS method enables quantitative determination of the absorption, scattering, and emission properties of natural and synthetic biological, chemical, and environmental samples. The spectral signatures obtained with the combined UV-vis and LPRS analysis provide fingerprint-like information about the geometric features (sizes and shapes) and the optical properties of materials. However, the current UV-vis and LPRS analysis is time-consuming and applicable only to steady-state samples because it requires three sequential spectral acquisitions performed with two different instruments. Therefore, this grant supports the development of new measurement tools to enable simultaneous multidimensional spectroscopic characterization of dynamic systems with high temporal resolution. Such techniques are crucial for many areas of science and technology, including biology, materials science, clean energy applications, and environmental protection. The broader impacts of the project also include training opportunities for students from diverse backgrounds in the cross-disciplinary areas of scientific instrumentation, optical spectroscopy, data acquisition and analysis, and materials science. Furthermore, the Zhang group will organize two optical spectroscopy workshops to provide opportunities for HBCU (Historically Black College and University) and PUI (Predominantly Undergraduate Institution) students and faculty to learn about the theory and unique capabilities of the techniques being developed in this project. Solution-phase processes involving the dynamical evolution of materials are ubiquitous in chemistry, biology, and materials science. Examples of such systems include protein aggregation, molecular assembly, and nanoparticle synthesis, as well as post-synthetic modifications of macromolecules, supramolecular assemblies, and nanoscale materials. Technologies that are capable of concurrently monitoring the evolution of these materials are crucial not only for deciphering correlations between structure and optical properties, but also for discovery and optimization of new materials. Optical spectroscopic techniques that exploit the interaction of light and matter have been the methods of choice for studying such dynamic systems because of their broad accessibility and relatively high temporal resolutions. However, existing tools are limited in their information content because they are incapable of simultaneously resolving the complex interplay among the absorption, scattering, and emission processes. The combined UV-vis and LPRS analysis is extraordinarily informative because this approach enables concurrent experimental quantification of a material’s absorption extinction spectrum, scattering extinction spectrum, scattering depolarization spectrum, fluorescence intensity and depolarization spectra, and fluorescence quantum yield. Collectively, these spectral signatures provide critical insights, many being inaccessible before, on the sizes, shapes, molecular compositions, and optical activities of materials. The scientific investigation outlined in this project aims to create a multichannel linearly polarized spectrometer capable of concurrent acquisition of these multidimensional signatures with sub-second temporal resolution. The research team will study the formation of porphyrin assemblies as model systems for developing the measurement approach and will investigate how the absorption, scattering, and emission properties vary during assembly and disassembly. These studies have the potential to reveal mechanistic pathways in the porphyrin assembly and disassembly processes. The measurement and data analysis strategies developed for these model systems will be extensible to numerous other dynamic systems across a range of scientific disciplines, and provide a platform for advanced student training and the engagement of researchers from diverse backgrounds.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.