Cremer Johannes W, Thaler Klemens M, Haisch Christoph, Signorell Ruth
Department of Chemistry and Applied Biosciences, Laboratory of Physical Chemistry, ETH Zurich, Vladimir-Prelog-Weg 2, CH-8093 Zurich, Switzerland.
Laboratory for Applied Laser Spectroscopy, Chair of Analytical Chemistry, Technical University of Munich, Marchioninistrasse 17, D-81377 Munich, Germany.
Nat Commun. 2016 Mar 16;7:10941. doi: 10.1038/ncomms10941.
Photochemistry taking place in atmospheric aerosol droplets has a significant impact on the Earth's climate. Nanofocusing of electromagnetic radiation inside aerosols plays a crucial role in their absorption behaviour, since the radiation flux inside the droplet strongly affects the activation rate of photochemically active species. However, size-dependent nanofocusing effects in the photokinetics of small aerosols have escaped direct observation due to the inability to measure absorption signatures from single droplets. Here we show that photoacoustic measurements on optically trapped single nanodroplets provide a direct, broadly applicable method to measure absorption with attolitre sensitivity. We demonstrate for a model aerosol that the photolysis is accelerated by an order of magnitude in the sub-micron to micron size range, compared with larger droplets. The versatility of our technique promises broad applicability to absorption studies of aerosol particles, such as atmospheric aerosols where quantitative photokinetic data are critical for climate predictions.
大气气溶胶液滴中发生的光化学对地球气候有重大影响。气溶胶内部电磁辐射的纳米聚焦在其吸收行为中起着关键作用，因为液滴内部的辐射通量强烈影响光化学活性物种的活化速率。然而，由于无法测量单个液滴的吸收特征，小气溶胶光动力学中与尺寸相关的纳米聚焦效应一直未被直接观测到。在此，我们表明对光学捕获的单个纳米液滴进行光声测量提供了一种直接的、广泛适用的方法，可实现阿托升灵敏度的吸收测量。我们针对一种模型气溶胶证明，与较大液滴相比，在亚微米到微米尺寸范围内光解加速了一个数量级。我们技术的多功能性有望广泛应用于气溶胶颗粒的吸收研究，例如大气气溶胶，其中定量光动力学数据对于气候预测至关重要。
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