Development of Single Droplet Interface-Specific Sum Frequency Scattering Spectroscopy

With the support of the Chemical Measurement and Imaging Program in the Division of Chemistry, Dr. Yi Rao and his students of Utah State University will develop a new nonlinear optical spectroscopy to directly probe molecular behaviors on surfaces of single droplet. Droplets play important roles in chemical reactions, biological activity, environmental pollution, and physical processes. Currently, single-droplet instrumentation is limited to overall characteristics, neglecting unique surface phenomena. With the development of the single-droplet surface spectrometer, these shortcomings will be addressed by directly studying the surface chemistry of small-volume single droplets. A broader impact of this work is to increase our understandings of surface reactivity of droplet chemistry. The work will integrate their findings to enhance teaching at the undergraduate and graduate levels and allow students to gain valuable experience in cutting-edge laser technology. Dr. Rao and his students also plan to improve science communication and host outreach events to educate and inspire the next generations of STEM students, professionals, and educators. Surface-specific single particle spectroscopy will be investigated in two scenarios: 1) Buildup and analysis of second-harmonic, electronic sum-frequency, and vibrational sum-frequency scattering spectroscopies of single droplet surfaces; 2) Investigation of adsorption of molecules onto droplet surfaces from the surrounding gas as well as the effect of physical and chemical settings on the adsorption processes. The team will advance nonlinear spectroscopy, align experiments and theory, and provide a means to precisely analyze surface chemistry at droplets in-situ. 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.