Chae Seung Hee, Kim Min Sik, Kim Jae-Hong, Fortner John D
Department of Chemical and Environmental Engineering, Yale University, 17 Hillhouse Ave., New Haven, Connecticut 06520, United States.
Department of Environmental Engineering and Soil Environment Research Center, Jeonbuk National University, Jeonju, Jeollabukdo 54896, Republic of Korea.
ACS ES T Eng. 2023 Jun 16;3(10):1504-1510. doi: 10.1021/acsestengg.3c00124. eCollection 2023 Oct 13.
Nanobubble (NB) generation of reactive oxygen species (ROS), especially hydroxyl radical (OH), has been controversial. In this work, we extensively characterize NBs in solution, with a focus on ROS generation (as OH), through a number of methods including degradation of OH-specific target compounds, electron paramagnetic resonance (EPR), and a fluorescence-based indicator. Generated NBs exhibit consistent physical characteristics (size, surface potential, and concentration) when compared with previous studies. For conditions described, which are considered as high O NB concentrations, no degradation of benzoic acid (BA), a well-studied OH scavenger, was observed in the presence of NBs (over 24 h) and no EPR signal for OH was detected. While a positive fluorescence response was measured when using a fluorescence probe for OH, aminophenyl fluorescein (APF), we provide an alternate explanation for the result. Gas/liquid interfacial characterization indicates that the surface of a NB is proton-rich and capable of inducing acid-catalyzed hydrolysis of APF, which results in a false (positive) fluorescence response. Given these negative results, we conclude that NB-induced OH generation is minimal, if at all, for conditions evaluated.
纳米气泡（NB）产生活性氧（ROS），尤其是羟基自由基（OH），一直存在争议。在这项工作中，我们通过多种方法，包括降解OH特异性靶标化合物、电子顺磁共振（EPR）和基于荧光的指示剂，对溶液中的纳米气泡进行了广泛表征，重点是ROS的产生（作为OH）。与先前的研究相比，生成的纳米气泡表现出一致的物理特性（尺寸、表面电位和浓度）。在所描述的条件下，即被认为是高O纳米气泡浓度的条件下，在纳米气泡存在的情况下（超过24小时），未观察到苯甲酸（BA）（一种经过充分研究的OH清除剂）的降解，也未检测到OH的EPR信号。虽然使用OH荧光探针氨基苯基荧光素（APF）时测量到了阳性荧光响应，但我们对该结果提供了另一种解释。气/液界面表征表明，纳米气泡的表面富含质子，能够诱导APF的酸催化水解，从而导致假（阳性）荧光响应。鉴于这些负面结果，我们得出结论，在所评估的条件下，纳米气泡诱导的OH生成极少，如果有的话。
