CAREER: Development of Super-Resolution Scanning Probe Stimulated Raman Microscopy with Excellent Spatial Resolution

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With support from the Chemical Measurement and Imaging Program in the Division of Chemistry, Professor Xiaoji Xu of Lehigh University is developing new measurement methods that probe how light interacts with matter at the nanoscale (1000 times smaller than the diameter of a human hair). Raman spectroscopy and microscopy are popular tools for measuring properties of molecules as they enable research discoveries and chemical characterizations of value to industry, health care, and environmental monitoring. Professor Xu is improving the spatial resolution of stimulated Raman microscopy so that objects with dimensions approaching those of large molecules can be chemically characterized on a routine basis, and in a highly robust and reliable fashion. Specifically, this project examines aerosols in the atmosphere that may contain harmful substances that can impair the health of individuals by causing respiratory illness, heart failure, or even prenatal defects. Understanding the composition, origin, and transformation of aerosols is of vital importance for reducing their production or lessening their affects. In addition to studying aerosols, Dr. Xu's team is also developing an educational module that connects cutting-edge scientific research laboratories with elementary and high school students in a standard classroom setting, via immersive virtual reality experiences. A range of chemical reactions are demonstrated to elementary and high school students through virtual reality streaming, thereby promoting their curiosity for science. Furthermore, Professor Xu's educational activities are improving the effectiveness of scientific outreach for promoting science to the general public. Being able to visualize the chemical properties of matter on small length scales is a major challenge for Raman microscopy. The project is addressing this need for super-resolution Raman microscopy by combining scanning probe microscopy and coherent stimulated Raman events. Chemical sensitivity is provided by the stimulated Raman process. High spatial resolution is achieved by nanoscale probing using a scanning probe microscope tip. The project aims to achieve robust and reliable Raman imaging so as to differentiate objects separated by roughly 10 nanometers. Through integration of nanoscale infrared imaging techniques invented by the Xu group, multimodal spectroscopic and mechanical microscopy are possible for chemical, biological, and environmental samples. Professor Xu's team studies the chemical composition and physical properties of individual sub-micron-sized urban contaminant particles in the atmosphere, allowing his team to decipher their chemical origins and photochemical transformations, with identification of and control over aerosol pollutions being his team's ultimate goal. From efforts associated with the educational plan, many students in elementary and high school classrooms are connected to an advanced research instrument in a laboratory via real-time multimedia capture and streaming devices. The students experience the operation of advanced research instruments, solidifying learning outcomes. Educational activities will be shared with students in schools in the Bethlehem, PA School District.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.