Hydroxyl (OH) radical is the most important reactive species produced by the plasma-liquid interactions, and the OH in the liquid phase (dissolved OH radical, OHdis) takes effect in many plasma-based applications due to its high reactivity. Therefore, the quantification of the OHdis in the plasma-liquid system is of great importance, and a molecular probe method usually used for the OHdis detection might be applied. Herein we investigate the validity of using the molecular probe method to estimate the [OHdis] in the plasma-liquid system. Dimethyl sulfoxide is used as the molecular probe to estimate the [OHdis] in an air plasma-liquid system, and the partial OHdis is related to the formed formaldehyde (HCHO) which is the OHdis-induced derivative. The analysis indicates that the true concentration of the OHdis should be estimated from the sum of three terms: the formed HCHO, the existing OH scavengers, and the OHdis generated H2O2. The results show that the measured [HCHO] needs to be corrected since the HCHO destruction is not negligible in the plasma-liquid system. We conclude from the results and the analysis that the molecular probe method generally underestimates the [OHdis] in the plasma-liquid system. If one wants to obtain the true concentration of the OHdis in the plasma-liquid system, one needs to know the destruction behavior of the OHdis-induced derivatives, the information of the OH scavengers (such as hydrated electron, atomic hydrogen besides the molecular probe), and also the knowledge of the OHdis generated H2O2.
Recombination of Geminate (OH,eaq-) Pairs in Concentrated Alkaline Solutions: Lack of Evidence For Hydroxyl Radical Deprotonation
在200 nm的光解氢氧化物水溶液和400 nm（3光子）电离的水在浓碱性溶液中产生的水合电子和羟基自由基的皮秒动力学。在亚纳秒时间尺度上没有观察到羟基自由基的去质子化，即使在1-10 M KOH溶液中也是如此。这一结果与稀碱溶液中OH自由基去质子化的动力学数据完全不一致。我们认为，在浓碱性溶液中，羟基自由基的去质子化反应大大减慢。
N-electron valence perturbation theory with reference wavefunctions from quantum computing: application to the relative stability of hydroxide anion and hydroxyl radical
