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

North Carolina State University, Raleigh NC

Investigators

Abstract

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.