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Raman Spectroscopy of Single Light-Absorbing Carbonaceous Particles Levitated in Air Using an Annular Laser Beam
Analytical Chemistry ( IF 6.7 ) Pub Date : 2017-11-22 00:00:00 , DOI: 10.1021/acs.analchem.7b03455 Masaru Uraoka 1 , Keisuke Maegawa 1 , Shoji Ishizaka 1
Analytical Chemistry ( IF 6.7 ) Pub Date : 2017-11-22 00:00:00 , DOI: 10.1021/acs.analchem.7b03455 Masaru Uraoka 1 , Keisuke Maegawa 1 , Shoji Ishizaka 1
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A laser trapping technique is a powerful means to investigate the physical and chemical properties of single aerosol particles in a noncontact manner. However, optical trapping of strongly light-absorbing particles such as black carbon or soot is quite difficult because the repulsive force caused by heat is orders of magnitude larger than the attractive force of radiation pressure. In this study, a laser trapping and Raman microspectroscopy system using an annular laser beam was constructed to achieve noncontact levitation of single light-absorbing particles in air. Single acetylene carbon black or candle soot particles were arbitrarily selected with a glass capillary connected to a three-axis oil hydraulic micromanipulator and introduced into a minute space surrounded by a repulsive force at the focal point of an objective lens. Using the developed system, we achieved optical levitation of micrometer-sized carbonaceous particles and observation of their Raman spectra in air. Furthermore, we demonstrated in situ observations of changes in the morphology and chemical composition of optically trapped carbonaceous particles in air, which were induced by heterogeneous oxidation reactions with ozone and hydroxyl radicals.
中文翻译：
使用环形激光束在空气中悬浮的单光吸收碳质颗粒的拉曼光谱
激光捕获技术是一种以非接触方式研究单个气溶胶颗粒的物理和化学性质的有力手段。但是，由于黑热或碳黑等强光吸收粒子的热排斥力比辐射压力的吸引力大几个数量级，因此很难进行光捕获。在这项研究中，构造了一个使用环形激光束的激光捕获和拉曼光谱系统，以实现空气中单个吸光颗粒的非接触悬浮。用连接到三轴油压微型操纵器的玻璃毛细管任意选择单个乙炔炭黑或蜡烛烟ot颗粒，然后将其引入物镜焦点处被排斥力包围的微小空间中。使用开发的系统，我们实现了微米级碳质颗粒的光学悬浮，并观察了它们在空气中的拉曼光谱。此外，我们现场观察了空气中被光学捕获的碳质颗粒的形态和化学组成的变化，这些变化是由与臭氧和羟基自由基的异质氧化反应引起的。
更新日期：2017-11-23
中文翻译：
使用环形激光束在空气中悬浮的单光吸收碳质颗粒的拉曼光谱
激光捕获技术是一种以非接触方式研究单个气溶胶颗粒的物理和化学性质的有力手段。但是，由于黑热或碳黑等强光吸收粒子的热排斥力比辐射压力的吸引力大几个数量级，因此很难进行光捕获。在这项研究中，构造了一个使用环形激光束的激光捕获和拉曼光谱系统，以实现空气中单个吸光颗粒的非接触悬浮。用连接到三轴油压微型操纵器的玻璃毛细管任意选择单个乙炔炭黑或蜡烛烟ot颗粒，然后将其引入物镜焦点处被排斥力包围的微小空间中。使用开发的系统，我们实现了微米级碳质颗粒的光学悬浮，并观察了它们在空气中的拉曼光谱。此外，我们现场观察了空气中被光学捕获的碳质颗粒的形态和化学组成的变化，这些变化是由与臭氧和羟基自由基的异质氧化反应引起的。
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