南京大学王伟团队报道了单个水微滴中H₂O₂自发生成的动力学。相关研究成果于2024年1月17日发表在国际顶尖学术期刊《美国化学会杂志》。

自2019年首次发现以来，在亚10微米大小的水微滴中自发产生的H₂O₂越来越受到人们的关注。另一方面，由于这些微滴的寿命短（快速蒸发），并且缺乏合适的工具来实时监测单个微滴中H₂O₂的生成，这种看似热力学上不利的过程也引发了关于H₂O₂起源及其潜在机制的激烈争论。

该文中，研究人员通过微孔约束制备了寿命长（>1小时）的水微滴，并通过延时荧光成像动态监测了单个微滴中H₂O₂的自发产生。结果表明，在所制备的水微滴中，H₂O₂是连续产生的，在H₂O₂消耗反应的存在下，H₂O₂的表观平衡浓度为～3μM。通过对这些微滴的几何形状进行工程设计，研究人员进一步揭示了单个微滴中H₂O₂的生成速率与其表面积体积比成正比例。

这也使研究人员能够在存在H₂O₂消耗反应的情况下提取出7.7 nmol m^–2 min^–1的最大H₂O₂生成率，并首次推导出界面H₂O自发转化为H₂O₂的相应概率，即在1秒内约65000个水分子中的1个。这些发现提供了强有力的证据，证明H₂O_2的自发生成确实发生在微滴表面，并为人们进一步提高水微滴中H₂O₂的产量以供未来应用提供了重要的起点。

附：英文原文

Title: Deciphering the Kinetics of Spontaneous Generation of H2O2 in Individual Water Microdroplets

Author: Kai Zhou, Hua Su, Jia Gao, Haoran Li, Shasha Liu, Xuannuo Yi, Zhibing Zhang, Wei Wang

Issue&Volume: January 17, 2024

Abstract: Spontaneous generation of H2O2 in sub-10 μm-sized water microdroplets has received increasing interest since its first discovery in 2019. On the other hand, due to the short lifetime of these microdroplets (rapid evaporation) and lack of suitable tools to real-time monitor the generation of H2O2 in individual microdroplets, such a seemingly thermodynamically unfavorable process has also raised vigorous debates on the origin of H2O2 and the underlying mechanism. Herein, we prepared water microdroplets with a long lifetime (>1 h) by virtue of microwell confinement and dynamically monitored the spontaneous generation of H2O2 in individual microdroplets via time-lapsed fluorescence imaging. It was unveiled that H2O2 was continuously generated in the as-prepared water microdroplets and an apparent equilibrium concentration of ～3 μM of H2O2 in the presence of a H2O2-consuming reaction can be obtained. Through engineering the geometry of these microdroplets, we further revealed that the generation rates of H2O2 in individual microdroplets were positively proportional to their surface-to-volume ratios. This also allowed us to extract a maximal H2O2 generation rate of 7.7 nmol m–2 min–1 in the presence of a H2O2-consuming reaction and derive the corresponding probability of spontaneous conversion of interfacial H2O into H2O2 for the first time, that is, ～1 of 65,000 water molecules in 1 s. These findings delivered strong evidence that the spontaneous generation of H2O2 indeed occurs at the surface of microdroplets and provided us with an important starting point to further enhance the yield of H2O2 in water microdroplets for future applications.

DOI: 10.1021/jacs.3c09864

Source: https://pubs.acs.org/doi/abs/10.1021/jacs.3c09864