Topologically Enhanced Raman Spectroscopy

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Various biochemical sensing techniques are governed by the interface coupling between biochemical molecules and sensor materials, in which the surface electronic states and surface atomic termination of the sensor materials play a key role. Conventional materials suffer from easily destroyable surface states derived from dangling bonds, vacancies, or doping. In contrast, topological quantum materials, a class of materials such as topological insulators and Weyl semimetals, possess unique topologically protected surface states that are robust against surface modifications, shape imperfections, and defects. Therefore, topological insulators and Weyl semimetals constitute ideal platforms to interface biochemical molecules for sensing applications. This project will explore nanostructures of topological insulators and Weyl semimetals as sensitive and low-noise platforms to interact with molecules and to produce unprecedented Raman enhancement signals for molecule sensing. This project cuts across traditional boundaries of two scientific disciplines, topological quantum physics and molecule sensing, and will open a new avenue of biochemical sensing technologies by fostering the invention of new methods and materials. The research of this project will broadly impact multiple disciplines including physical chemistry, quantum materials, biomolecular engineering, and optics. The research outcome will also constitute excellent educational materials for undergraduate and graduate students, and K-12 students, especially under-represented minorities and females. The educational and outreach activities will prepare the new generations of workforce to handle multidisciplinary tasks involving quantum science, new materials, optics, and biochemical engineering.This project will pioneer the usage of topological quantum materials in chemistry and biomedicine, develop new platforms and methods based on nanostructured topological insulators and Weyl semimetals to enable high-performance surface enhanced Raman spectroscopy sensing. The central hypothesis is that nanostructured topological insulators and Weyl semimetals can generate ultra-strong and ultra-stable surface plasmons and efficient interface coupling with molecules due to their topologically protected surface electronic states, unique to conventional materials. Nanostructured topological insulators and Weyl semimetals have highly conductive and free electron-like surface states, thus possess strong and low-loss surface plasmons. The surface electronic states are topologically protected and immune to surface defects and shape imperfection; thus Raman enhancement will be ultra-stable and low-noise. In addition, the topological surface states induce effective electronic transfer with molecules, further boosting Raman signals through chemical enhancement mechanisms. This project will develop the Raman enhancement platforms based on topological insulators and Weyl semimetals utilizing both plasmonic enhancement and chemical enhancement. Multimodal and tunable Raman sensing platforms will also be developed by integrating the electrochemical reactions and magnetic tuning of topological materials, respectively, in the Raman enhancement device. As part of the project, the educational programs proposed in this project will lead to new classroom and laboratory instructional modes, stimulate student creativity, and foster research-like classes. Graduate and undergraduate students will receive research training by participating in this project. K-12 students will participate in the outreach activities and lab tours which will be developed from the outcome of this research.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.