We demonstrate the application of direct absorption spectroscopy to measure multiphase chemical reactions taking place in single, acoustically levitated droplets. Acidification reactions are monitored using a colored pH indicator dissolved in the droplets. The pH decrease during the uptake of dilute gas-phase carbon dioxide into an aqueous droplet is followed in real time. We show that uptake coefficients may be extracted from such measurements. The acidification is significantly suppressed when the droplet has a near-monolayer coating of 1-octanol. Such inhibition of interfacial transport by near monolayers of slightly soluble amphiphiles, which do not reside entirely at the water surface, has been previously reported for I₂ and NO₂ but not yet for CO₂.

中文翻译：

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实时测量由于多相大气化学作用而产生的单个悬浮悬浮液滴中pH值的变化

我们展示了直接吸收光谱法在测量单个声悬浮液滴中发生的多相化学反应中的应用。使用溶解在液滴中的有色pH指示剂监测酸化反应。实时跟踪在将稀的气相二氧化碳吸收到水滴中期间pH的降低。我们表明摄取系数可以从这种测量中提取。当液滴具有1-辛醇的近单层涂层时，酸化被显着抑制。先前已经报道了对于I ₂和NO ₂但尚未对于CO _2的不完全存在于水表面的难溶两亲物的近单层的这种界面运输的抑制。