Hydroxyl,hydroperoxyl free radicals determination methods in atmosphere and troposphere

The hydroxyl radical(·OH)has a crucial function in the oxidation and removal of many atmospheric compounds that are harmful to health.Nevertheless,high reactivity,low atmospheric abundance,determination of hydroxyl,and hydroperoxyl radical’s quantity is very difficult.In the atmosphere and troposphere,hydroperoxyl radicals(HO_(2))are closely demanded in the chemical oxidation of the troposphere.But advances in technology have allowed researchers to improve the determination methods on the research of free radicals through some spectroscopic techniques.So far,several methods such as laser-induced fluorescence(LIF),high-performance liquid chromatography(HPLC),and chemical ionization mass spectroscopy have been identified and mostly used in determining the quantity of hydroxyl and hydroperoxyl radicals.In this systematic review,we have advised the use of scavenger as an advance for further researchers to circumvent some of these problems caused by free radicals.The primary goal of this review is to deepen our understanding of the functions of the most critical free radical(·OH,HO_(2))and also understand the currently used methods to quantify them in the atmosphere and troposphere.

The degradation pathways of contaminants by reactive oxygen species generated in the Fenton/Fenton-like systems

Reactive oxygen species(ROSs)in Fenton process are of great importance in treating contaminants in wastewater.It is crucial to understand their chemical properties,formation,and reaction mechanisms with contaminants.This review summarizes the reactive oxygen species in Fenton process,including hydroxyl radical(·OH),superoxide radical(O_(2)·-),singlet oxygen(1O_(2)),hydroperoxyl radical(HO_(2)·),and high-valent iron.·OH shows a trend to react with chemistry groups with abundant electrons through H-atom abstraction,radical adduct formation and single electron transfer.Electron transfer is discovered to be an important pathway when1O_(2)degrades organic pollutants.Ring-opening andβ-scission are proposed to be the possible ways of1O_(2)to certain contaminants.Proton abstraction,nucleophilic substitution,and single electron transfer are proposed to explain how O_(2)·-degrade pollutants.As the conjugated acid of O_(2)·-,radical adduct formation and H-atom abstraction are reported for the reaction mechanisms of hydroperoxyl radical.High-valent iron in Fenton,namely Fe(IV),reacts with certain pollutants via single-or two-electron transfer.This review is important for researchers to understand the ROSs produced in Fenton and how they react with pollutants.

Theoretical Investigations of the Catalytic Role of Water in Propene Epoxidation on Gold Nanoclusters： A Hydroperoxyl- Mediated Pathway

We report a comprehensive theoretical investigation of the catalytic reaction mechanisms of propene epoxidation on gold nanoclusters using density functional theory （DFT）. We have shown that water acts as a catalytic promoter for propene epoxidation on gold catalysts. Even without reducible supports, hydroperoxyl （OOH） and hydroxyl （OH） radicals are readily formed on small-size gold clusters from co-adsorbed H20 and 02, with energy barriers as low as 4-6 kcal/mol （1 cal = 4.186 J）. Propene epoxidation occurs easily through reactions between C3H6 and the weakened O-O bond of the OOH radicals on the surfaces of gold clusters.