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Single-Particle Optical Trapping as a Standalone Micro-Reactor for the Study of Particle Loss, Formation, and Chemical Reaction
CHUJI WANG, Yukai Ai, Haifa Alali, Yong-Le Pan, Gorden Videen, Mississippi State University
Abstract Number: 83
Working Group: Instrumentation and Methods
Abstract
From the early optical-tweezers approach, which uses a single tightly focused laser beam to levitate dielectric or absorbing micron-sized particles, to the recently developed universal optical trap, which can trap particles of arbitrary chemical and physical properties in different media, optical trapping has evolved significantly over the last decades. One of the most recent developments in optical trapping is the combination of optical trapping with advanced laser spectroscopic techniques to achieve on-trap single-particle measurements. As single particles can be trapped stably in the universal optical trap for long periods of time, temporal evolution of the chemical and physical properties of trapped particles can be monitored. We study chemical reactions of a single particle under controlled atmospheric environments. In particular, we use the universal optical trap to trap single airborne particles, such as pollen grains, fungal spores, droplets, etc., in an air-tight cell and measure time-resolved Raman spectra of the single particles exposed to different relative humidity and ozone concentrations. Chemical reactions of the single particles are revealed by time-evolutions of the Raman spectral intensity and Raman band structure. Further, we propose to use cavity ringdown spectroscopy to track concentrations of reactants and or reaction products in situ, in near-real time. Results suggest that single-particle optical trapping can serve as a standalone micro-reactor for the study of loss, formation, and chemical reaction of single particles in their near-native states.