Department of Chemistry, Stanford University, Stanford, CA 94305.
Department of Mechanical Engineering, Stanford University, Stanford, CA 94305.
Proc Natl Acad Sci U S A. 2020 Dec 8;117(49):30934-30941. doi: 10.1073/pnas.2020158117. Epub 2020 Nov 23.
It was previously shown [J. K. Lee , , 116, 19294-19298 (2019)] that hydrogen peroxide (HO) is spontaneously produced in micrometer-sized water droplets (microdroplets), which are generated by atomizing bulk water using nebulization without the application of an external electric field. Here we report that HO is spontaneously produced in water microdroplets formed by dropwise condensation of water vapor on low-temperature substrates. Because peroxide formation is induced by a strong electric field formed at the water-air interface of microdroplets, no catalysts or external electrical bias, as well as precursor chemicals, are necessary. Time-course observations of the HO production in condensate microdroplets showed that HO was generated from microdroplets with sizes typically less than ∼10 µm. The spontaneous production of HO was commonly observed on various different substrates, including silicon, plastic, glass, and metal. Studies with substrates with different surface conditions showed that the nucleation and the growth processes of condensate water microdroplets govern HO generation. We also found that the HO production yield strongly depends on environmental conditions, including relative humidity and substrate temperature. These results show that the production of HO occurs in water microdroplets formed by not only atomizing bulk water but also condensing water vapor, suggesting that spontaneous water oxidation to form HO from water microdroplets is a general phenomenon. These findings provide innovative opportunities for green chemistry at heterogeneous interfaces, self-cleaning of surfaces, and safe and effective disinfection. They also may have important implications for prebiotic chemistry.
先前有研究表明[J. K. Lee,, 116, 19294-19298 (2019)]，在没有外加电场的情况下，通过雾化大块水产生的微米级水微滴（microdroplets）中会自发产生过氧化氢（HO）。在这里，我们报告水蒸气在低温基底上逐滴冷凝形成的水微滴中也会自发产生 HO。因为过氧化物的形成是由微滴水-空气界面上形成的强电场诱导的，所以不需要催化剂或外加偏压以及前体化学物质。对冷凝微滴中 HO 生成的时程观测表明，HO 是由尺寸通常小于约 10 µm 的微滴生成的。在各种不同的基底上，包括硅、塑料、玻璃和金属上，都观察到了 HO 的自发产生。对具有不同表面条件的基底的研究表明，凝结水微滴的成核和生长过程控制着 HO 的生成。我们还发现，HO 的生成产率强烈依赖于环境条件，包括相对湿度和基底温度。这些结果表明，HO 的产生不仅发生在雾化大块水形成的水微滴中，而且还发生在水蒸气冷凝形成的水微滴中，这表明从水微滴中自发氧化水形成 HO 是一种普遍现象。这些发现为异质界面上的绿色化学、表面自清洁以及安全有效的消毒提供了新的机会。它们也可能对前生物化学具有重要意义。
