Spin-labeling Electron Paramagnetic Resonance Methods for Measurements at Nanoscale Interfaces

在化学系化学测量和成像项目的支持下，北卡罗莱纳州立大学的Tatyana Smirnova和她的团队正在开发一种新的测量方法来评估界面上纳米颗粒的特性。随着颗粒变小并接近纳米尺度——通常直径为1到100纳米（比人类头发直径小数千倍）——界面特性成为颗粒与周围环境相互作用的主要因素。该项目旨在解决纳米结构界面测量的需求，通过在纳米颗粒表面以原子尺度精度定位分子探针和光谱读取界面特性。一旦开发，新的测量方法有可能产生急需的数据，这将有助于新材料的设计以及改进制造过程。研究生和本科生的直接参与将提供材料、物理和分析化学方面的专门培训。研究计划的选定要素直接整合到本科课堂实验活动中，为本科教育带来以发现为基础的方法。提出的开发新测量能力的方法是基于一系列光谱活性探针，这些探针将通过共同表面基团共价附着在纳米结构表面上，以评估界面处的局部动力学，质子浓度以及静电和介电性质。该方法利用电子顺磁共振（EPR），有望提供独特的能力来报告纳米级界面的高度局部、位点特异性异质性质。探针相对于界面的位置将通过脉冲EPR测量探针的电子自旋与表面磁性原子核之间的偶极相互作用以原子尺度精度确定。测量方法的有效性将在广泛的环境条件下进行调查，以证明该方法在材料科学，化学和生物学中感兴趣的纳米系统的广泛适用性。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。

With support from the Chemical Measurement and Imaging Program in the Division of Chemistry, Tatyana Smirnova and her group at North Carolina State University are working on developing a novel measurement methodology to assess properties of nanoparticles at interfaces. As particles become smaller and approach the nanoscale – typically 1 to 100 nm in diameter (thousands of times smaller than the diameter of a human hair) - interfacial properties become the dominant factors in interactions of the particles with their surroundings. This project aims to address the need for measurements at nanostructured interfaces by positioning molecular probes at the nanoparticle surface with atomic-scale precision and reading the interfacial properties spectroscopically. Once developed, the new measurement method has the potential to yield much needed data that will aid in the design of novel materials as well as improve manufacturing processes. Direct participation of graduate and undergraduate students will provide for specialized training in materials, physical, and analytical chemistry. Selected elements of the research plan are directly integrated in undergraduate classroom laboratory activities, bringing a discovery-based approach to undergraduate education.The proposed approach to develop a new measurement capability is based on a series of spectroscopically active probes, which will be covalently attached to nanostructured surfaces via common surface groups to assess local dynamics, proton concentration and electrostatic and dielectric properties at interfaces. The approach utilizes electron paramagnetic resonance (EPR) and is expected to provide unique capability to report on highly local, site-specific heterogeneous properties of nanoscale interfaces. The position of the probe with respect to the interface will be determined with atomic-scale accuracy from measurements of dipolar interactions between the electronic spin of the probe and the surface magnetic nuclei by pulsed EPR. The validity of the measurement approach will be investigated over a wide range of environmental conditions to demonstrate a broad applicability of the method to nanosystems of interest in materials science, chemistry, and biology.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.