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| Acquisition and Analysis of Raman Signals of Levitated Single Droplet by Optical Tweezers System |
| CAO Xue, ZHANG Yun-hong* |
Institute of Chemical Physics, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, China
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Abstract To overcome the limitations of traditional commercial spectroscopic detection instruments, this study focuses on measuring the evolution mechanisms of atmospheric fine particulate matter and its important physicochemical parameters. We have developed a long-duration, spatially resolved, high-sensitivity, and high-spectral-resolution optical tweezers-stimulated Raman spectroscopy device, combining new principles, technologies, and methodologies. This device integrates spontaneous and stimulated Raman scattering, as well as Rayleigh scattering, aiming to address the scientific challenges of real-time monitoring of physical and chemical processes in micron-scale levitated single droplets, as well as the observation of aerosol microdroplets reacting with trace gaseous species. Specifically, this device enables real-time detection of a levitated single droplet, allowing for the observation of reaction processes between the gas phase and the droplet while simultaneously measuring the chemical composition and evolution of both phases. A 532 nm continuous-wave laser serves as the light source for optical tweezers levitation and Raman signal excitation, facilitating the rapid capture and stable levitation of a single droplet. The relationship between the stability of the levitated droplet and the laser power has been established. Additionally, an EMCCD was employed as the detector for spontaneous and stimulated Raman signals, enabling the investigation of the reaction kinetics of an optical tweezers-levitated single droplet with trace SO2 gas under precisely controlled conditions of trace reaction gas and relative humidity. The research results reveal dynamic changes in the reaction processes within the droplet, providing quantitative data on the variation of droplet radius over time. This device effectively detects and analyzes the chemical reaction processes of aerosol microdroplets, exhibiting high temporal and spatial resolution. It not only provides a new experimental platform and methodology for understanding the evolution mechanisms of atmospheric particulate matter but also lays a foundation for detailed studies of gas-aerosol reaction processes.
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Received: 2024-12-12
Accepted: 2025-01-06
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Corresponding Authors:
ZHANG Yun-hong
E-mail: yhz@bit.edu.cn
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